U.S. patent application number 12/657394 was filed with the patent office on 2011-07-21 for method for making circuitized substrates having photo-imageable dielectric layers in a continuous manner.
Invention is credited to John M. Lauffer, Voya R. Markovich, James J. McNamara, JR., Peter A. Moschak.
Application Number | 20110173809 12/657394 |
Document ID | / |
Family ID | 37187358 |
Filed Date | 2011-07-21 |
United States Patent
Application |
20110173809 |
Kind Code |
A1 |
Lauffer; John M. ; et
al. |
July 21, 2011 |
METHOD FOR MAKING CIRCUITIZED SUBSTRATES HAVING PHOTO-IMAGEABLE
DIELECTRIC LAYERS IN A CONTINUOUS MANNER
Abstract
Apparatus and method for making circuitized substrates using a
continuous roll format in which a layer of conductor is fed into
the apparatus, layers of photo-imageable dielectric are applied to
opposite sides of the conductor layer, thru-holes are formed
through the composite, and then metal layers are added over the
dielectric and then patterns (e.g., circuit) are formed therein.
Several operations are performed in addition to these to form the
final end product, a circuitized substrate (e.g., printed circuit
board), all while the conductor layer of the product is retained in
a solid format, up to the final separation from the continuous
layer.
Inventors: |
Lauffer; John M.; (Waverly,
NY) ; Markovich; Voya R.; (Endwell, NY) ;
McNamara, JR.; James J.; (Vestal, NY) ; Moschak;
Peter A.; (Chenango Forks, NY) |
Family ID: |
37187358 |
Appl. No.: |
12/657394 |
Filed: |
January 20, 2010 |
Current U.S.
Class: |
29/846 ;
29/852 |
Current CPC
Class: |
H05K 3/462 20130101;
H05K 3/4641 20130101; H05K 2201/096 20130101; H05K 2201/09536
20130101; H05K 2203/068 20130101; Y10T 29/49165 20150115; H05K
2201/10378 20130101; H05K 2203/0143 20130101; Y10T 29/49126
20150115; H05K 2203/1572 20130101; H05K 3/445 20130101; H05K 3/44
20130101; Y10T 29/49155 20150115; H05K 3/4069 20130101; H05K
2203/1545 20130101; H05K 3/427 20130101; H05K 3/064 20130101; H05K
2201/0355 20130101; Y10T 29/49128 20150115 |
Class at
Publication: |
29/846 ;
29/852 |
International
Class: |
H05K 3/42 20060101
H05K003/42; H05K 3/02 20060101 H05K003/02; H05K 3/46 20060101
H05K003/46 |
Claims
1. A method of making a plurality of circuitized substrates, said
method comprising: providing a first conductive layer on a roll,
said first conductive layer having first and second opposing
surfaces; forming holes within said first conductive layer which
extend through the thickness of said first conductive layer;
depositing photoimageable dielectric material on said first and
second opposing surfaces of said first conductive layer and within
said holes extending through said thickness of said first
conductive layer; forming first and second patterns within said
photoimageable dielectric material on said opposing surfaces of
said first conductive layer, respectively, each of said patterns
including openings therein which align with said holes within said
first conductive layer; providing electrically conductive material
within said openings and on selected parts of the external surfaces
of said photoimageable material on said first and second opposing
surfaces of said first conductive layer, respectively, to render
said openings electrically conductive and to form circuit patterns
on said selected parts of said surfaces of said photoimageable
material; and thereafter segmenting said first conductive layer,
said photoimageable material on said opposing surfaces of said
first conductive layer, and said circuit patterns on said
photoimageable material to define a plurality of circuitized
substrates each having a pattern of conductive thru-holes therein,
all of said steps being performed while said first conductive layer
is in the form of a continuous, solid member unwound from said
roll.
2. (canceled)
3. The method of claim 1 wherein said forming of said holes within
said first conductive layer is accomplished using etching.
4. The method of claim 3 further including inspecting said holes
within said first conductive layer following said etching.
5. The method of claim 1 wherein said photoimageable dielectric
material is deposited in liquid form.
6. The method of claim 1 wherein said photoimageable dielectric
material is deposited in dry film form.
7. The method of claim 1 wherein said forming of said first and
second patterns within said photoimageable dielectric material is
accomplished using photolithographic processing.
8. The method of claim 1 wherein said providing of electrically
conductive material within said openings and on said selected parts
of said surfaces of said photoimageable material is accomplished
using a plating process.
9. The method of claim 8 further including seeding said openings
prior to implementation of said plating process.
10. The method of claim 1 wherein said segmenting is accomplished
using a shearing process.
11. (canceled)
12. A method of making a plurality of circuitized substrates, said
method comprising: providing a first conductive layer on a roll,
said first conductive layer having first and second opposing
surfaces; forming holes within said first conductive layer which
extend through the thickness of said first conductive layer;
depositing photoimageable dielectric material on said first and
second opposing surfaces of said first conductive layer and within
said holes extending through said thickness of said first
conductive layer; forming first and second patterns within said
photoimageable dielectric material on said opposing surfaces of
said first conductive layer, respectively, each of said patterns
including openings therein which align with said holes within said
first conductive layer; providing electrically conductive material
within said openings of said photoimageable material; and
thereafter segmenting said first conductive layer and said
photoimageable material on said opposing surfaces of said first
conductive layer having said electrically conductive material
within said openings thereof to define a plurality of circuitized
substrates each having a pattern of conductive thru-holes therein,
all of said steps being performed while said first conductive layer
is in the form of a continuous, solid member unwound from said
roll.
13. The method of claim 12 wherein said providing of said
electrically conductive material within said openings of said
photoimageable material comprises positioning a quantity of
conductive paste within said holes.
Description
TECHNICAL FIELD
[0001] This invention relates to the manufacture of circuitized
substrates such as printed circuit boards, chip carriers, and the
like. The invention particularly relates to the manufacture of such
substrates in which conductive thru-holes are provided therein, and
more particularly to those which utilize photo-imageable dielectric
material for one or more of the substrate's dielectric layers.
BACKGROUND OF THE INVENTION
[0002] The conventional manufacture of circuitized substrates such
as printed circuit boards and chip carriers, especially those of
the multi-layered type, involves many individual processes such as
etching, plating, lamination, drilling, testing, inspection, etc.
Typically, these processes are performed at different locations
within the manufacturing facility, requiring shipment of partially
completed substrates from one station to another at such different
locations. Such transfer is costly and time-consuming, especially
when involving multi-layered products, the most common of boards
sold today in view of increased operational demands for the
products (e.g., computer servers, mainframes, etc.) in which such
boards are implemented. In these boards, the board typically
consists of parallel, planar, alternating inner layers of
insulating substrate material and conductive metal. The exposed
outer sides of the laminated structure are often provided with
circuit patterns, as with double-sided boards, and the metal inner
layer or layers typically contain circuit patterns, or, in the case
of internal power planes, layers that are substantially solid.
These latter layers also often include clearance openings or other
openings if desired.
[0003] In multilayer printed circuit boards, it is necessary to
provide conductive interconnections between the various conductive
layers or sides of the board. This is commonly achieved by
providing metallized, conductive thru holes in the board which
communicate with the sides and layers requiring electrical
interconnection. For some applications, it is desired that
electrical connection be made between all or almost all of the
conductive layers. It is often desired to also provide electrical
connection between the circuitry on one face of the board and one
or more of the inner circuit layers. In those cases, "blind vias",
passing only part way through the board, are provided. In still
another case, such multilayered boards often require internal
"vias" which are located entirely within the board's structure and
covered by external layering, including both dielectric and
conductive. Such internal "vias" are typically formed within a
sub-part structure of the final board and then combined with other
layers during final lamination of the board. The term "conductive
thru-hole" as used in the art may thus include both thru holes that
pass entirely through the board (also referred to in the printed
circuit field as plated thru holes or PTH's), "blind vias" which
extend from an external surface of the board into a specified
conductive layer of the board, as well as an "internal via" which
is internally "captured" by the board's outer layers.
[0004] To provide the desired circuit pattern on the substrate, a
variety of even more manufacturing processes are required, examples
being those which fall into the broad categories of "subtractive"
or "additive" techniques. Common to subtractive processing is the
need to etch away (or subtract) metal to expose substrate surface
in areas where no circuitry is desired. Additive processes, on the
other hand, begin with exposed substrate surfaces (or thin
commoning metallization layers for additive electroplate) and build
up thereon of metallization in desired areas, the desired areas
being those not masked by a previously-applied pattern of plating
resist material (e.g., called photo-resist in the printed circuit
board field). In conventional manufacture, such plating occurs in a
separate department or location of the facility.
[0005] Typically, thru-holes are drilled (including mechanically or
more recently using lasers) or punched into or through the
substrate at desired locations. Drilling or punching provides newly
exposed interior surfaces including via barrel surfaces and via
peripheral entry surfaces. The dielectric substrate, comprising a
top surface, a bottom surface, and at least one exposed via hole
surface, consisting partly or entirely of insulating material, is
then metallized, generally by utilization of electroless metal
depositing techniques, albeit other deposition processes are also
known in the field. The formation of such thru-holes also typically
occurs at a separate, different location within the manufacturing
facility.
[0006] In the manufacture of circuitized substrates such as printed
circuit boards, one or more dielectric sheets are employed for the
substrate. These are typically of an organic material, such as
fiberglass-reinforced epoxy resin (also referred to in the field
as, simply, "FR4"), polytetrafluoroethylene (e.g., Teflon, a
trademark of E.I. DuPont deNemours Company), Driclad material
(Driclad is a trademark of the assignee of this invention, Endicott
Interconnect Technologies, Inc.), etc. It is also known to utilize
photo-imageable materials for such dielectric layers. Typically,
when the dielectric materials for the structure are of a
photo-imageable material, the material is photo-imaged or
photo-patterned, and developed to reveal the desired circuit
pattern, including the desired opening(s) as defined herein, if
required. The dielectric material may be curtain-coated or
screen-applied, or it may be supplied as dry film. Final cure of
the photo-imageable material provides a toughened base of
dielectric on which the desired electrical circuitry is formed. An
example of a particularly useful photo-imageable dielectric is
ASMDF (Advanced Soldermask Dry Film). This composition, which is
further described in U.S. Pat. No. 5,026,624, which issued Jun. 25,
1991, and U.S. Pat. No. 5,300,402, which issued Apr. 25, 1994,
includes a solids content of from about 86.5 to about 89%, such
solids comprising: about 27.44% PKHC, a phenoxy resin; 41.16% of
Epirez 5183, a tetrabromobisphenol A; 22.88% of Epirez SU-8, an
octafunctional epoxy bisphenol A formaldehyde novolac resin; 4.85%
UVE 1014 photo-initiator; 0.07% ethylviolet dye; 0.03% FC 430, a
fluorinated polyether nonionic surfactant from 3M Company; 3.85%
Aerosil 380, an amorphous silicon dioxide from Degussa to provide
the solid content. A solvent is present from about 11 to about
13.5% of the total photo-imageable dielectric composition. When
such photo-imageable dielectric materials are used, these also are
applied typically at a separate station within the manufacturing
facility, often distant from the others. As indicated above, this
invention relates particularly to substrates which utilize one or
more photo-imageable dielectric layers as part thereof.
[0007] Since the dielectric substrate is nonconductive, in order to
plate on the substrate, the substrate is typically "seeded" and one
of the above two plating processes then occurs. Typically, these
sheets are provided as individual, thin layers of rectangular shape
and "stacked" with other layers, including conductive layers, to
form the multi-layered final structure, except in the case, of
course, of when photo-imageable materials are used in which case
these are coated onto the desired sub-composite and, when
completed, also stacked up with others sub-composites to form the
final multi-layered structure.
[0008] Still further manufacturing steps include the
afore-mentioned inspection and testing operations. Often,
inspections mandate the use of highly precise equipment such as
programmed television cameras, in addition to manual inspection,
while testing typically is accomplished with complex test apparatus
requiring a skilled professional to operate. Both of these
operations are also usually performed at different locations in the
facility from other manufacturing operations such as defined
above.
[0009] Examples of methods of making boards, including providing
same with such thru holes, are shown and described in the following
U.S. Letters Patents, as are examples of various types of boards
produced by such methods (including those with photo-imageable
dielectric layers as part thereof):
TABLE-US-00001 6,015,520 Method For Filling Holes in Printed Wiring
Boards 6,073,344 Laser Segmentation of Plated Through-Hole
Sidewalls To Form Multiple Conductors 6,175,087 Composite Laminate
Circuit Structure And Method Of Forming The Same 6,188,027
Protection of a Plated Through Hole From Chemical Attack 6,204,453
Two Signal One Power Plane Circuit Board 6,349,871 Process For
Reworking Circuit Boards 6,388,204 Composite Laminate Circuit
Structure And Methods Of Interconnecting The Same 6,479,093
Composite Laminate Circuit Structure And Methods Of Interconnecting
The Same 6,493,861 Interconnected Series of Plated Through Hole
Vias and Method of Fabrication Therefore 6,495,239 Dielectric
Structure And Method Of Formation 6,521,844 Through Hole In A
Photoimageable Dielectric Structure With Wired And Uncured
Dielectric 6,626,196 Arrangement and Method For Degassing
Small-High Aspect Ratio Drilled Holes Prior To Wet Chemical
Processing 6,628,531 Multi-Layer and User-Configurable
Micro-Printed Circuit Board 6,630,630 Multilayer Printed Wiring
Board and Its Manufacturing Method 6,630,743 Copper Plated PTH
Barrels and Methods For Fabricating 6,631,558 Blind Via Laser
Drilling System 6,631,838 Method For Fabricating Printed Circuit
Board 6,638,690 Method For Producing Multi-Layer Circuits 6,638,858
Hole Metal-Filling Method 6,750,405 Two Signal One Power Plane
Circuit Board
[0010] Various attempts have been made to manufacture at least some
parts of circuit boards using what might be referred to as a
continuous process. Examples of some of these processes are
described below.
[0011] In U.S. Pat. No. 4,372,800, issued Feb. 8, 1983, there is
described a "continuous" process for producing reinforced resin
laminates comprising the steps of impregnating a fibrous substrate
with a liquid resin (allegedly free of volatile solvent and capable
of curing without generating liquid and gaseous by-products),
laminating a plurality of the resin-impregnated substrates into a
unitary member, sandwiching the laminate between a pair of covering
sheets, and curing the laminate between said pair of covering
sheets, without applying appreciable pressure. The patent discusses
adjusting the final resin content in the resin impregnated
substrate at 10 to 90% by weight, based on the total weight of the
impregnated substrate.
[0012] In U.S. Pat. No. 4,557,784, issued Dec. 10, 1985, there is
described a metal clad laminate produced in "continuous" manner by
impregnating a plurality of fibrous substrate with a curable liquid
resin, combining the plurality of substrates together and
simultaneously laminating a metal foil onto at least one side of
said substrates, and curing the laminate. This patent discusses the
steps of applying an adhesive onto the metal foil to form a film
and heating the film in situ continuously prior to step of the
laminating of said metal foil.
[0013] In U.S. Pat. No. 4,579,612, issued Apr. 1, 1986, there is
described the formation of an "electro-laminate" made of a core of
insulating material webs with a high purity electrolytic copper
foil on at least one side of the core, for use as a circuit board
in electronic equipment. The web of insulating material and the
copper foil are led from supply rolls to a laminating machine in
out-of-contact relation. Prior to its introduction into the
laminating machine, the copper foil is heated to the temperature of
the laminating operation so that it is at its maximum thermally
expanded length when it contacts the insulating material webs.
Further, dust is removed from the copper foil as it enters the
laminating machine. The webs and copper foil are moved at the same
speed through the laminating machine. After pressing the
electro-laminate in the laminating machine, it is moved through a
cooling device. Subsequently, the electro-laminate can be wound in
a roll or cut into individual lengths.
[0014] In U.S. Pat. No. 4,659,425, issued Apr. 21, 1987, there is
described a "continuous" method wherein a coating of a solvent-free
thermosetting resin is applied to the surface of a metal foil. This
resin-coated foil is advanced into contact with a reinforcing cloth
sheet layer to form a foil/cloth assembly. The assembly is
continuously conveyed between a pair of endless belts revolving in
opposite directions with mutually facing surfaces, the belts being
heated to the curing temperature of the resin whereby the belts are
pressed against the assembly to continuously compact the assembly
and cure the resin to form a composite product which can then be
circuitized. This partial process does not include many of the
essential steps such as defined above which are necessary for
boards of more complex construction, especially those needing
conductive thru-holes as part thereof.
[0015] In U.S. Pat. No. 4,902,610, issued Feb. 20, 1990, there is
described a process for forming a multilayer printed circuit board
comprising providing a non-conductive carrier having a circuit
pattern over at least one of its surfaces, applying a first
permanent photo dielectric coating over the circuit pattern,
exposing the permanent photo dielectric coating to activating
radiation in an image pattern comprising an array of openings at
locations where interconnections are desired and developing the
imaged photo dielectric coating to provide photo-formed openings,
selectively providing an electro-less plating catalyst within the
photo-formed openings and plating electro-less copper onto the
plating catalyst to render the photo-formed openings conductive,
applying a permanent photo mask over the metallized layer of
interconnections, exposing the permanent photo mask to activating
radiation in an image pattern comprising an array of conductors and
interconnections at desired locations, developing the imaged photo
mask to provide photo-formed conductor lines where conductors are
desired and photo-formed openings where interconnections are
desired and selectively providing an electro-less plating catalyst
within the photo-formed openings and plating electro-less copper
onto the electro-less plating catalyst to render the photo-formed
openings conductive and repeating the process sequentially until
the desired number of layers are formed.
[0016] In U.S. Pat. No. 5,153,986, issued Oct. 13, 1992, there is
described a method of fabricating a multilayer electronic circuit
package. The multilayer circuit package has at least one layer that
is a circuitized, polymer encapsulated metal core. According to the
method of the invention a metal foil is provided for the metal core
of the layer. This metal core foil may be provided as a single unit
or in a roll to roll, process. The thru holes are drilled, etched,
or punched through the metal foil. An adhesion promoter is then
applied to the perforate metal foil for subsequent adhesion of
polymer to the foil. The dielectric polymer is then applied to the
perforate metal foil core by vapor depositing, chemical vapor
depositing, spraying or electrophoretically depositing, a thermally
processable dielectric polymer or precursor thereof onto exposed
surfaces of the perforate metal foil including the walls of the
thru holes. The dielectric polymer or precursor thereof is then
thermally processed to form a conformal dielectric, polymeric
coating on surfaces of the perforate metal foil, including the
interior surfaces of the thru holes. This dielectric, polymeric
coating may then be circuitized, and coated with an adhesive for
lamination to the next adjacent layer. After lamination, one or
more chips are attached to the completed package.
[0017] In U.S. Pat. No. 6,388,202, issued May 14, 2002, there is
described a high density multi-layer printed circuit board formed
by building additional dielectric and metallization layers over a
central core of conventional laminate construction. The central
core has a metallization pattern on at least one surface. A
photo-imaged dielectric layer is deposited on one side of the
central core and overlies the metallization pattern. Vias are
formed in this dielectric layer using a photo-imaging process, and
an additional metallization pattern on this layer is electrically
connected to the underlying metallization pattern through the vias.
A non-photo-imageable dielectric layer is deposited on the other
side of the central core. Vias are formed in this dielectric layer
by a laser drilling process, and an additional metallization
pattern on this layer is electrically connected to an underlying
metallization pattern through these laser drilled vias.
[0018] In U.S. Pat. No. 6,391,210, issued May 21, 2002, there is
described a process for the manufacture of a multi-level circuit
board having a first-level circuitry pattern on at least one side.
The process comprises applying a permanent photo-imageable
dielectric over the first-level circuitry pattern; exposing the
permanent photo-imageable dielectric to radiation; laminating a
conductive metal layer to the dielectric; making holes in the
conductive metal layer and dielectric by mechanical drilling or by
laser or plasma ablation; and making a second-level circuitry
pattern and filling the holes with a conductive material to
electrically connect the first and second layers of circuitry. A
further process described comprises making a prototype having the
above structure in which the holes are manufactured by mechanical
drilling or by laser or plasma ablation, evaluating the prototype,
and then manufacturing a commercial board having essentially the
same structure and materials of construction as the prototype, but
wherein the holes are manufactured using photo-imaging
processes.
[0019] In U.S. Pat. No. 6,500,349, issued Dec. 31, 2002, there is
described a "continuous" process for forming multilayer circuit
structures which includes applying and curing a film forming
polymer onto the matte side of a copper foil. The opposite (shiny)
side of the foil is cleaned, and applied with a photoresist which
is then dried. The photo-resist is exposed, and developed to remove
the non-image areas, while leaving the image areas. The foil under
the removed non-image area is then etched to form a copper pattern,
and the remaining photo-resist is removed. The foil is then cut
into sections, and then punched with registration holes. The copper
pattern is then treated with a bond enhancing treatment, inspected
for defects, and laminated onto a substrate to form a multilayered
circuit structure.
[0020] The present invention represents a new and unique method of
forming circuitized substrates having conductive thru holes
therein, in comparison to those above and other processes known in
the art. Significantly, the method as defined herein involves the
making of a circuitized substrate beginning from providing layers
of conductor and dielectric material on through circuitizing, all
on a continuous format, and then segmenting the circuitized
elements to produce individual substrates. Such substrates can then
be bonded, e.g., laminated, to other similar substrates to form a
larger, multi-layered structure. It is believed that such a method
will represent a significant advancement in the art.
OBJECTS AND SUMMARY OF THE INVENTION
[0021] It is, therefore, a primary object of the present invention
to enhance the circuitized substrate art by providing a new and
unique method of producing such substrates in which photo-imageable
dielectric materials are used.
[0022] It is another object of the invention to provide such a
process in which several conductive thru holes are formed to
interconnect various conductive layers of the substrate.
[0023] It is still another object of the invention to provide such
a process which can be implemented using conventional printed
circuit board technologies.
[0024] According to one aspect of the invention, there is defined a
method of making a plurality of circuitized substrates comprising
providing a first conductive layer having first and second opposing
surfaces, forming holes within said first conductive layer which
extend through the thickness of the first conductive layer,
depositing photo-imageable dielectric material on the first and
second opposing surfaces of the first conductive layer and within
the holes extending through the thickness of the first conductive
layer, forming first and second patterns within the photo-imageable
dielectric material on both opposing surfaces of the first
conductive layer, respectively, each of these patterns including
openings therein which align with the first conductive layer's
holes, providing electrically conductive material within the
openings and on selected parts of the external surfaces of the
photo-imageable material to render these openings electrically
conductive and to form circuit patterns on the selected parts of
the surfaces of photo-imageable material, and thereafter segmenting
the first conductive layer, photo-imageable material on the
opposing surfaces of the first conductive layer, and the circuit
patterns on the photo-imageable material to define a plurality of
circuitized substrates each having a pattern of conductive
thru-holes therein, all of these steps being performed while the
first conductive layer is in the form of a continuous, solid
member.
[0025] According to another aspect of the invention, there is
defined a method of making a plurality of circuitized substrates
comprising providing a first conductive layer having first and
second opposing surfaces, forming holes within the first conductive
layer which extend through the thickness of the first conductive
layer, depositing photo-imageable dielectric material on the first
and second opposing surfaces of the first conductive layer and
within the holes extending through the thickness of the first
conductive layer, forming first and second patterns within the
photo-imageable dielectric material on both opposing surfaces of
the first conductive layer, respectively, each of these patterns
including openings therein which align with the first conductive
layer's holes, providing electrically conductive material within
the openings to render these openings electrically conductive, and
thereafter segmenting the first conductive layer and
photo-imageable material on the opposing surfaces of the first
conductive layer having the conductive material within the openings
thereof to define a plurality of circuitized substrates each having
a pattern of conductive thru-holes therein, all of these steps
being performed while the first conductive layer is in the form of
a continuous, solid member.
[0026] According to yet another aspect of the invention, there is
provided an apparatus for making a plurality of circuitized
substrates, the apparatus comprising a device for feeding a first
conductive layer having first and second opposing surfaces, a
device for forming holes within the first conductive layer which
extend through the thickness of the first conductive layer, a
device for depositing photo-imageable dielectric material on the
first and second opposing surfaces of the first conductive layer
and within the holes extending through the first conductive layer,
a device for forming first and second patterns within the
photo-imageable dielectric material on both of the opposing
surfaces of the first conductive layer, respectively, each of these
patterns including openings therein which align with respective
ones of the holes within the first conductive layer, a device for
providing electrically conductive material within the openings and
on selected parts of the external surfaces of the photo-imageable
material to render these openings electrically conductive and to
form circuit patterns on the selected parts of the surfaces of
photo-imageable material, and a segmenting device for segmenting
the first conductive layer, the photo-imageable material on said
opposing surfaces of said first conductive layer, and the circuit
patterns on the photo-imageable material to define a plurality of
circuitized substrates each having a pattern of conductive
thru-holes therein, all of the steps being performed while the
first conductive layer is in the form of a continuous, solid member
(excluding of course when it has the formed holes therein).
[0027] According to still another aspect of the invention, there is
provided an apparatus for making a plurality of circuitized
substrates, the apparatus comprising a device for feeding a first
conductive layer having first and second opposing surfaces, a
device for forming holes within the first conductive layer which
extend through the thickness of the first conductive layer, a
device for depositing photo-imageable dielectric material on the
first and second opposing surfaces of the first conductive layer
and within the holes extending through the first conductive layer,
a device for forming first and second patterns within the
photo-imageable dielectric material on both of the opposing
surfaces of the first conductive layer, respectively, each of these
patterns including openings therein which align with respective
ones of the holes within the first conductive layer, a device for
providing electrically conductive material within the openings to
render these openings electrically conductive and a segmenting
device for segmenting the first conductive layer, the
photo-imageable material on said opposing surfaces of the first
conductive layer having the conductive material within the openings
thereof to define a plurality of circuitized substrates each having
a pattern of conductive thru-holes therein, all of the devices
performing these steps while the first conductive layer is in the
form of a continuous, solid member (excluding of course when it has
the formed holes therein).
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIGS. 1A and 1B illustrate an apparatus for forming a
circuitized substrate in a continuous format according to one
aspect of the invention, the apparatus also illustrating the steps
of making such a substrate;
[0029] FIGS. 2-4 illustrate enlarged, partial views of various
parts of the continuously formed circuitized substrate during the
method of manufacture thereof using the apparatus in FIGS. 1A and
B;
[0030] FIG. 5 is a partial view of an apparatus for forming a
circuitized substrate according to an alternative embodiment of the
invention; and
[0031] FIG. 6 is an exploded view, on a much enlarged scale over
the above FIGS., illustrating the step of bonding various
circuitized substrates formed using the apparatus and method taught
herein together to form a larger, multi-layered circuitized
substrate.
BEST MODE FOR CARRYING OUT THE INVENTION
[0032] For a better understanding of the present invention,
together with other and further objects, advantages and
capabilities thereof, reference is made to the following disclosure
and appended claims in connection with the above-described
drawings. It is understood that like numerals will be used to
indicate like elements from FIG. to FIG.
[0033] By the term "continuous" as used herein when defining a
process is meant a process in which all of the steps to manufacture
a circuitized substrate having at least one conductive layer and
two dielectric layers are performed with the at least one
conductive layer being in the form of a continuous layer, up to
final segmenting to define the final substrate's dimensions. All
steps are performed while the conductive layer remains as provided
from its original source (e.g., a roll), without segmenting
occurring until the last step.
[0034] By the term "circuitized substrate" as used herein is meant
to include substrates having at least two (and preferably more)
dielectric layers comprised of photo-imageable material and at
least one (and preferably more) metallurgical conductive layer(s).
The dielectric layers taught herein may be typically about 2 mils
to about 4 mils thick, but also thicker or thinner if desired.
Examples of circuitized substrates include printed circuit boards
(or cards) and chip carriers.
[0035] In FIGS. 1A-1B, there is shown an apparatus 21 for making a
circuitized substrate according to one aspect of this invention. As
indicated herein, apparatus 21 is able to make this substrate in a
continuous manner, meaning that at least one conductive layer of
the final substrate remains in the form of a continuous,
substantially solid member (excluding the provision of holes
therein as described) throughout the entire processing thereof, up
to the final segmenting step when individual substrates are removed
from the continuous line. One of the most significant features of
this invention is the ability to provide various layers of the
substrate using photo-imageable materials while also forming large
numbers of high density patterns of holes within the substrate line
in patterns associated with each of the final substrates being
produced. This combination of processes is attainable while also
performing other, individual processes (if required) such as
etching, exposure, testing, and the like as needed.
[0036] In FIG. 1A, first and second dielectric layers 23 and 25 are
provided from individual roll members 27 and 29, respectively, to a
first bonding station 31. As part of this feeding operation, a
conductive layer 33 is also fed, also from a roll member 35 such
that it will be sandwiched between the upper and lower dielectric
layers 23 and 25. Preferably, these three layers are provided to a
first set of feed rollers 37 which draw the layers together and
feed these into the bonding station 31. In a preferred embodiment,
the bonding station 31 includes at least one pair of opposed,
heated rollers 39 and 41. Each of these rollers is preferably
heated to a predetermined temperature (in one embodiment, to a
range of from about 75 degrees Celsius (C) to about 130 degrees C.)
and are comprised of rubber coated steel cored drums. Various means
may be utilized to heat the rollers 39 and 41, the preferred means
being electrical resistive heaters contained within the steel core
of the roller. Each of the rollers 39 and 41 are shown as being
positioned within a housing 45, but this is not a necessary
requirement. The rollers exert a force within the range of from
about 10 pounds per square inch (p.s.i.) to about 80 p.s.i. on the
three layers as these pass there-through. As a result, each of the
outer dielectric layers 23 and 25 is firmly bonded to the interim,
common conductive layer 33.
[0037] In a preferred embodiment, each of the dielectric layers is
comprised of a conventional photo-resist, a preferred example being
Riston EtchMaster photo-resist, available from E.I. DuPont de
Nemours and Company. Each layer preferably possesses a thickness
within the range of from about 0.6 mils to about 2.0 mils. The
corresponding interim conductive layer is preferably copper and has
a thickness of from about 0.5 mils to about 3 mils. Significantly,
this conductive layer will remain as a solid, integral member
(except when holes are provided therein as part of this processing)
through-out the entire method defined herein, up to the final
severance of it and associated dielectric and conductive layers (if
any) from the continuous format shown.
[0038] Once compression (lamination) of the three layers has
occurred, a bonded structure now results and is now passed on to
the next station 32. At station 32, the bonded structure comprised
of these three layers (with the photo-resist forming the outer
layers) is subjected to an exposure step in which the photo-resist
material is exposed to define a specific hole pattern therein.
These holes (59, in FIG. 2, in which the structure is shown as it
departs station 32) are to eventually define the pattern of the
clearance holes within the interim copper layer, such clearance
holes necessary to allow connection through the conductive layer
from at least one additional conductive layer to another, if
desired. It is necessary to define the hole 59 patterns in the
outer photo-resist layers to define the copper layer's pattern, as
the photo-resist is primarily used for this purpose and will be
eventually discarded (stripped away). The exposure operation
conducted at station 32 is performed using known exposure lamps,
shown by the numerals 47, it being understood that various masking
structure (not shown) is also required and well within the
knowledge of one skilled in the art.
[0039] Following the exposure, the composite structure is moved to
station 51 in which development of the photoresist and etching of
the clearance holes within the composite is performed. Development
is accomplished using a conventional developer known in
photolithographic processing, the developer deposited on the
external surface and thus serving to remove the corresponding
portions of the photoresist material and expose the desired
clearance hole locations thereunder. During the etch procedure, a
conventional etchant (preferably cupric chloride) is sprayed onto
the composite using spray devices 53 and 55. The structure so
formed, including the holes 59 and now etched openings 57, is
partially illustrated in FIG. 3. The corresponding photoresist 23
and 25, having the developed (removed) holes 59, is also shown. As
mentioned, FIG. 2 illustrates the structure of the composite
following the photoresist material removal to define these openings
59 and prior to the etching to form the holes 57.
[0040] Although etching is defined as the means of providing
clearance holes 57, the invention is not limited thereto because
other procedures, including mechanical or laser drilling and
punching are possible, these methods not requiring the use of
photo-resist layers 23 and 25.
[0041] Following this, the composite is further advanced to optical
test device 61 in which highly precise television cameras inspect
the formed apertures, now found only within the common conductive
layer 33. As part of the aforementioned develop and etch process,
the outer dielectric layers 23 and 25 have been entirely removed
(stripped) from the copper conductive layer such that only the
copper layer is now advanced. Following optical inspection, the
conductive layer 33 is continuously advanced to the next station 63
during which an adhesion treatment procedure is performed. This
optional procedure is utilized to prepare the outer surface of the
copper layer for subsequent bonding to the subsequent
photo-imageable dielectric layers being applied. In a preferred
embodiment, this treatment at station 63 involves the exposure of
these surfaces to an oxide material (e.g. sodium chlorite,
typically used in combination with other chemicals) or to what is
known as a BondFilm procedure in which a known material (called
BondFilm) is applied and the exterior surfaces roughened to an
extent necessary to enhance the subsequent bonding. Such material
is currently available on the marketplace under this name from
Atotech Deutschland GmbH, an international company having a U.S.A.
business address at 1750 Overview Drive, Rock Hill, S.C., During
this procedure, the copper layer is exposed to the treatment
material for a period of from about 5 seconds to about 2 minutes
while the material is at a temperature of from about 20 degrees C.
to about 40 degrees C.
[0042] The treated conductive layer 33 is then passed to station 71
in which photo-imageable dielectric material 73 is deposited on
opposite sides of layer 33, including within the formed holes 57.
Deposition is accomplished using opposed dispensing apparatus 75,
preferably containers 77 with suitable nozzles thereon which direct
the liquid photo-imageable material in the direction intended.
Notably, the lower container projects liquid material upwardly,
which liquid then maintains contact with the undersurface of layer
33 on to subsequent processing. The preferred photo-imageable
material applied at station 71 is advanced solder mask (also known
simply as "ASM") material available under the name DynaVia, from
the Rohm and Haas Company. Other photo-imageable materials include
those sold under the trade names PSR4000 BN and PSR4000-AUS703,
available from Taiyo. This deposition occurs within the housing at
station 71 at a temperature within the range of from about 20
degrees C. to about 30 degrees C., with the photo-imageable
material at a viscosity of about 30 to about 110 pascal-seconds
(pa-s). As stated, the material also enters the holes 57 of the
copper layer and substantially fills same. Once applied at station
71, and when moving on to the next station (101), the
photo-imageable material has a thickness of about 1 mil to about 3
mils on each opposing side of layer 33.
[0043] In an alternative embodiment, it is possible to apply the
photo-imageable material in dry film form, rather than liquid as
shown. If the case, the film is provided from individual roll
members (similar to roll members 27 and 29), each film dispensed
from a roll member on either the upper or lower side of layer 33,
much as the dry film dielectric materials 23 and 25 are provided.
This pair of roll members would be located adjacent the shown feed
rollers 81 and would feed their respective films to station 71
similarly to the feed of dielectric layers 23 and 25. In this case,
however, station 71 will include compression rollers similar to
rollers 39 and 41 at station 31. Similar pressures and temperatures
would be utilized, and, as with the liquid version, portions of the
dry film material will penetrate within the openings 57. These feed
roll members and compression rollers are not shown for ease of
explanation, but are understood from the above description and
associated roll structures.
[0044] In either the preferred or alternative embodiments described
above, it is understood that additional operations might be
required in processing of the photo-imageable dielectric material,
depending on the material that is used. These additional operations
could include drying operations or post expose bakes. These drying
and bake operations could be performed with in-line convection or
infrared ovens, which are not shown in the FIGS.
[0045] The next step in the operation, performed at the
aforementioned station 101, involves the exposure and development
of patterns within each of the opposing photo-imageable layers,
each of these patterns including openings 103 which align with
respective holes 57 in interim layer 33. Exposure and development
of these opposing patterns is performed using lamps 105, much the
same as lamps 47 served to expose photo-resist 23 and 25. Following
exposure, a developer solution (not shown) is dispensed from
container 107 to remove exposed (or non-exposed, depending on
whether negative or positive photo-imaging occurs) portions of the
photo-imageable material to thus define openings 103. It is now
seen in FIG. 1B that the aligned holes 57 in layer 33 and the
openings 103 in the outer photo-imageable layers 73 define a
plurality of holes which extend entirely through the thickness of
the three-layered structure as it leaves station 101. Notably, some
of the photo-resist material will remain on the internal walls of
holes 57, to provide electrical insulation between the eventual
conductive material(s) to be deposited in these holes and the
conductive layer. That is, such insulation assures that the
conductive thru-holes to be formed in this structure do not
electrically couple to layer 33, as this layer is preferably to be
used as a power layer in one embodiment of the final product
provided herein. This is not meant to limit the invention, of
course, as it is possible to use layer 33 as a signal layer and
couple selected ones of the formed thru-holes to same.
Alternatively, it is also possible to use layer 33 as a ground
layer and selectively couple some of the thru-holes thereto should
it be desirable in the end product to ground the layer (e.g.,
signal lines) to which the thru-hole is also coupled. Various other
possibilities are also within the scope of this invention, as
understood by one of skill in this art. Further description is not
considered necessary.
[0046] In one example, a total of 20,000 holes may be provided at
station 101 for each of the circuitized substrates being formed,
each of these holes including a diameter of only from about 1 mil
to about 8 mils, and provided at spacings from one another as
little as 5 mils. It is to be understood that one of the most
important aspects of this invention is the ability to provide such
large numbers of holes in such close patterns all in a continuous
process in which other important steps are also being performed. Of
further significance, the use of photo-imageable materials and
photolithographic processing (exposure, development, etc.) thereof
avoids the necessity of using mechanical drills or even lasers to
provide the holes at this location of apparatus 21.
[0047] Following the photolithographic processing at station 101,
the apertured, three-layered structure is moved by advance rollers
111 to the next station 113, at which the holes are seeded with a
conventional seed material known in the art (e.g., one example
being a solution of stannous chloride and palladium chloride) to
enhance subsequent metal application. Following seed, the holes are
flash plated using an electro-less copper plating solution. Plating
may continue with conventional plating procedures, two preferred
examples being full build electro-less copper and electrolytic
copper. The plating device is represented, generally, by numeral
115 at station 113. During the plating operation, the preferred
plated metal is copper, deposited at a thickness of from about 0.2
mils to about 1.5 mils. Significantly, plated conductive material
is also deposited on the upper and lower surfaces of the
three-layered structure at station 115, thereby producing a
five-layered structure as it leaves station 113, with the outer
conductive layers (117) being substantially solid. Each outer
conductive layer has a thickness of about 0.2 mils to about 1.5
mils. It is understood that these outer conductors will serve as a
conductive layer in the final product, perhaps as signal layers or
even possibly as ground or power, depending on the operational
requirements for the end product.
[0048] Following plating, the composite structure is advanced to
the next station, 121, during which the final outer circuit
patterns 119 will be defined within the external conductive layers
117. In a preferred embodiment, this is accomplished using known
photolithographic processing such as performed earlier in the
process. If so, a second photo-resist (not shown) is supplied
(i.e., using nozzles 123), followed by exposure (i.e., using lamps
125), and subsequent development and etch (i.e., using etching
apparatus 127). The preferred photo-resist and etchants may be the
same as used at stations 31 and 51. Following this operation, a
final optical test, again using precise television cameras, is
performed at station 131.
[0049] Finally, the respective circuitized substrates, represented
by the numeral 133 and also seen in larger detail in FIG. 4, are
separated (preferably using a shearing device in which opposing
blades 135 are used). In one example, each of the circuitized
substrates possesses a width of about 18 inches and a length of 24
inches. Each includes the described common interim conductive layer
33, having its clearance holes therein such that the thru-holes as
plated in station 113 are used and which are electrically isolated
from the clearance holes to interconnect the opposite, formed
circuit patterns now within the outer conductive layers 75, unless
the foregoing alternative connections are desired.
[0050] Although it is shown in FIGS. 1A and 1B to apply only one
pair of conductive and dielectric layers to the opposite sides of
copper layer 33, the invention is not so limited. Specifically, it
is also within the scope of this invention to add additional
photo-imageable dielectric and conductive layers at subsequent
stations, depending on the operational requirements of the end
product. If the case, the initial layers shown at station 121 will
be processed as defined and a second photo-imageable dielectric
layer will then be applied, using a similar structure as shown at
station 71. This added deposition would occur immediately following
inspection at station 131, following which exposure and
development, similar to that defined above, would occur. Following
this, added conductive layers would be provided on the
photo-imageable third and fourth layers, and in any holes formed
therein, the conductive layers forming, in one embodiment, circuit
patterns having designated line and hole patterns. The apparatus to
perform these added operations is preferably similar to that used
above, so further description is not necessary. The thru-holes
formed at station 101 could also be provided through the complete,
now several layered structure, the initial grouping provided in the
three layered structure at station 101 not being provided until
this final phase. That is, the thru holes which extend entirely
through the multi-layered structure will not be provided until all
dielectric and conductive layers are bonded and circuitized. Only
one hole formation process for such entire grouping of thru-holes
is thus necessary (or desired).
[0051] It is understood that one of the unique teachings of the
present invention is the ability to not only provide several
similar circuitized substrates 133, each having the same hole
pattern and conductive circuit patterns on the exterior surfaces
thereof, but also to provide circuitized substrates with different
clearance holes and external circuit patterns thereon. This is
accomplished by appropriate software to coordinate the respective
hole-forming operations and circuit pattern forming steps.
[0052] In FIG. 5, there is shown an alternative embodiment of
making circuitized substrates in accordance with the teachings of
this invention. In FIG. 5, the composite structure as passed
through station 101 passes to a new station 141 rather than
directly into station 113, new station 141 designed to deposit
electrically conductive paste 143 within the provided holes in the
composite. (In one embodiment, it is preferred to clean these holes
of any possible photo-imageable material residue, in which case
such cleaning occurs using conventional hole-cleaning equipment
(not shown)) In a preferred embodiment, paste 143 is provided using
a conventional squeegee, as represented by the numerals 145, and
applied from opposite surfaces of the structure as shown. In a
preferred embodiment, the conductive paste as deposited may be a
silver, copper, gold or tin filled polymer such as that available
from National Starch and Chemical Company under the product name
Ablestick 8175, or that provided by E.I. duPont deNemours &
Company under product name CB100. This may also be an
organo-metallic paste such as Ormelink paste available from Ormet
Circuits, Inc. Although the structure removed from station 101
includes holes that are preferably clear of contaminants, it is
also within the scope of the invention to seed and plate these
holes prior to the deposition of the defined electronic paste.
Should this be desired, the same metals as described above with
respect to station 113 are provided, preferably at the thicknesses
defined.
[0053] Following paste deposition, the three-layered composite is
moved next to inspection station 131 (shown in FIG. 1B) and then to
severance, preferably using shearing devices 135, as was done for
the substrate in FIGS. 1A-1B.
[0054] It is thus understood that in the latter embodiment (paste
version), the resulting structure in its simplest version will
comprise the common, interim copper layer 33, the two outer
photo-imageable layers, and the paste, the latter filling the
thru-holes which extend entirely through the thickness of the
substrate. In one embodiment, the resulting circuitized substrate
will serve as an interconnector structure, specifically designed
for interconnecting conductors of opposing, other circuitized
substrates such as printed circuit boards, chip carriers and the
like, including other substrates as produced using the teachings
herein.
[0055] FIG. 6 represents much enlarged examples of the circuitized
substrates which can be produced using the teachings of this
invention. In FIG. 6, the upper and lower substrates 133' are
similar to those provided using the apparatus in FIGS. 1A-1B.
Specifically, each includes a common conductive layer 33' having
the defined clearance openings 57' therein. Each further includes
the outer photo-imageable layers 73', in addition to conductive
thru-holes 161, shown much clearer here than in previous FIGS. The
thru-holes extend entirely through the thickness of the substrate
to couple the outer conductive layers to one another. It is noted
that in FIG. 6, each of these circuitized substrates 133' includes
two conductive layers 117' (similar to layers 117 defined above)
and 118' on the outer surfaces thereof. This may be accomplished
using the teachings of the invention by providing only partial
removal of the copper outer layer having the defined. As further
seen in FIG. 6, each of these external circuit patterns also
include individual conductive elements 163 which may, in the final
structure, serve as signal lines.
[0056] Also seen in FIG. 6 is an example of the circuitized
substrate, represented by the numeral 133'' as produced from the
embodiment shown in FIG. 5. This structure also includes the common
conductive layer 33' and its corresponding clearance holes 57, as
well as the external photo-imageable layers 73'. However, the
circuitized substrate 133'' in FIG. 6, as mentioned, does not
include the above-defined external conductive patterns thereon, but
instead only includes a series of holes having the described
conductive paste 143 therein.
[0057] In FIG. 6, the three illustrated circuitized substrates are
aligned in the manner shown such that the conductive paste as shown
aligns with corresponding opposing pairs of thru-holes. The
composite structure is then laminated using conventional lamination
processing and a composite structure formed, of a multi-layered
configuration having the defined seven conductive layers therein
with respective conductive layers being coupled through the interim
circuitized substrate 133'' by the conductive paste. In one
example, the lamination procedure to bond these three substrates
was conducted at a temperature of about 190 degrees C. and a
corresponding pressure of about 500 p.s.i. The resulting structure,
in one example of the invention, possessed an overall thickness of
only about 15 mils. It may also possess width and length dimension
similar to those described for the individual substrates defined
above, this resulting structure being a combination of same aligned
in a vertical orientation.
[0058] Although it is shown in FIG. 6 that the conductive
thru-holes are not physically coupled to one or both of the interim
conductive layers 33', it is possible that this be accomplished,
e.g., should the interim conductive layer function as a ground and
it is desired to ground one or more of these thru-holes and the
remaining conductive element (e.g., a signal line) which is
electrically coupled thereto.
[0059] Thus there has been shown and described a new and unique
method of making a circuitized substrate in which the substrate is
formed during a continuous process in which the substrate's
conductive layer remains a solid sheet (except when defined
patterns of holes or openings are provided therein) throughout the
entire operation. Additional conductive layers are also possible.
Significantly, the final structures are provided during which
precise hole formation is possible using photo-imageable materials
as the substrate's dielectric, in addition to other precise
operations such as circuit pattern formation and the like. This
method, and the defined apparatus for accomplishing same, thus
represents a significant advancement in the art.
[0060] While there have been shown and described what are at
present the preferred embodiments of the invention, it will be
obvious to those skilled in the art that various changes and
modifications may be made therein without departing from the scope
of the invention as defined by the appended claims.
* * * * *