U.S. patent application number 11/160067 was filed with the patent office on 2006-03-16 for method of manufacturing double-sided printed circuit board.
Invention is credited to Shing-Fun Ho, Hung-En Hsu, Binwei Wang.
Application Number | 20060054588 11/160067 |
Document ID | / |
Family ID | 36032781 |
Filed Date | 2006-03-16 |
United States Patent
Application |
20060054588 |
Kind Code |
A1 |
Hsu; Hung-En ; et
al. |
March 16, 2006 |
Method of Manufacturing Double-Sided Printed Circuit Board
Abstract
The present invention provides a method of manufacturing a
double-sided printed circuit board. An insulation substrate is
first formed by creating a plurality of through holes on a Copper
Clad Laminate (CCL) whose copper foil surface has been removed.
Next, an electro-less copper layer is plated on the substrate for
forming a plurality of plated through holes. After a wire pattern
is formed on the substrate, a solder preventive layer is formed on
top of the wire pattern. Next, a plurality of openings is created
in between the solder preventive layer for exposing the contact
pads. Finally, a protective layer is plated on top of the contact
pads.
Inventors: |
Hsu; Hung-En; (Taipei City,
TW) ; Wang; Binwei; (Taipei City, TW) ; Ho;
Shing-Fun; (Taipei City, TW) |
Correspondence
Address: |
NORTH AMERICA INTELLECTUAL PROPERTY CORPORATION
P.O. BOX 506
MERRIFIELD
VA
22116
US
|
Family ID: |
36032781 |
Appl. No.: |
11/160067 |
Filed: |
June 7, 2005 |
Current U.S.
Class: |
216/13 ; 216/37;
216/41; 29/846 |
Current CPC
Class: |
H05K 3/108 20130101;
H05K 2203/1152 20130101; H05K 3/0032 20130101; H05K 3/426 20130101;
H05K 3/181 20130101; H05K 3/28 20130101; Y10T 29/49155 20150115;
H05K 3/243 20130101; H05K 3/381 20130101 |
Class at
Publication: |
216/013 ;
216/041; 216/037; 029/846 |
International
Class: |
H01B 13/00 20060101
H01B013/00; C23F 1/00 20060101 C23F001/00; H05K 3/02 20060101
H05K003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 10, 2004 |
TW |
093127598 |
Claims
1. A method of fabricating a double-sided printed circuit board,
the method comprising: providing a copper clad laminate (CCL),
wherein the CCL comprises an insulating substrate and at least one
copper clad disposed on the surface of the insulating substrate;
performing an etching process for removing the copper clad on the
surface of the insulating substrate; performing a drilling process
for forming a plurality of through holes in the insulating
substrate; disposing a chemical copper layer on the insulating
substrate and the sidewall of the through holes for forming a
plurality of plated through holes; forming a wire pattern on the
surface of the insulating substrate, wherein the wire pattern
includes at least one contact pad; forming a solder resistant layer
on the surface of the insulating substrate and forming at least one
opening in the solder resistant layer for exposing the contact pad;
and coating a protective layer on the surface of the contact
pad.
2. The method of claim 1, wherein the drilling process is a laser
drilling process.
3. The method of claim 1, wherein a surface treatment is performed
on the insulating substrate for increasing the adhesiveness of the
insulating substrate and the chemical copper layer before the
chemical copper layer is disposed.
4. The method of claim 3, wherein the surface treatment is a
surface coarsening process.
5. The method of claim 1, wherein the formation of wire pattern
further comprises: transferring a photoresist pattern to the
surface of the insulating substrate; forming an electroplating
copper layer on the surface of the insulating substrate and the
sidewall of the through holes; performing a photoresist removing
process; and performing an etching process on the insulating
substrate for removing the exposed chemical copper layer.
6. The method of claim 5, wherein the photo removing process is a
photo stripping process.
7. The method of claim 1, wherein the protective layer is comprised
of nickel (Ni).
8. The method of claim 1, wherein the protective layer is comprised
of gold (Au).
9. A method of fabricating a printed circuit board, the method
comprising: providing an insulating substrate; performing a
drilling process of forming a plurality of through holes in the
insulating substrate; disposing a chemical copper layer on the
insulating substrate and the sidewall of the through holes for
forming a plurality of plated through holes; and forming a wire
pattern on the surface of the insulating substrate, wherein the
wire pattern includes at least one contact pad.
10. The method of claim 9, wherein the drilling process is a laser
drilling process.
11. The method of claim 9, wherein a surface treatment is performed
on the insulating substrate for increasing the adhesiveness of the
insulating substrate and the chemical copper layer before the
chemical copper layer is disposed.
12. The method of claim 11, wherein the surface treatment is a
surface coarsening process.
13. The method of claim 9, wherein the formation of wire pattern
further comprises: transferring a photoresist pattern to the
surface of the insulating substrate; forming an electroplating
copper layer on the surface of the insulating substrate and the
sidewall of the through holes; performing a photo removing process;
and performing an etching process on the insulating substrate for
removing the exposed chemical copper layer.
14. The method of claim 13, wherein the photo removing process is a
photo stripping process.
15. The method of claim 9 further comprising the following steps
after the wire pattern on the surface of the insulating substrate
is formed: forming a solder resistant layer on the surface of the
insulating substrate and forming at least one opening in the solder
resistant layer for exposing the contact pad; and coating a
protective layer on the surface of the contact pad.
16. The method of claim 15, wherein the protective layer is
comprised of nickel (Ni).
17. The method of claim 15, wherein the protective layer is
comprised of gold (Au).
18. The method of claim 9, wherein the insulating substrate is a
copper clad laminate (CCL) with copper clad removed.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method of fabricating a
double-sided printed circuit board, and more particularly, to a
method of fabricating a double-sided circuit board with superfine
circuits and high density circuits.
[0003] 2. Description of the Prior Art
[0004] In recent history, printed circuit boards (PCBs) have been
widely used for carrying various electronic components and devices.
As there is demand for electronic products to be lighter, smaller,
and portable, research and development of printed circuit boards is
unavoidably moving toward a direction of miniaturization, higher
integration, lower thickness, and the use of multiple layers.
[0005] In general, printed circuit boards having circuit layouts on
both sides of the circuit boards have been widely used in numerous
electrical apparatuses such as air-conditioners, telephones, and
fax machines. Nevertheless, it is essential to have a "bridge", or
otherwise referred to as through holes, for communicating between
the circuits and electrical wires on both sides of the board. The
useable area of a typical double-sided printed circuit board is
often twice that of a typical single-sided printed circuit board,
and in contrast to a single-sided printed circuit board, the
double-sided printed circuit board is more suitable to be used for
products with complex circuits.
[0006] Please refer to FIG. 1. FIG. 1 is a perspective diagram
showing a double-sided printed circuit board after a laser drilling
process is performed according to the prior art. In the past, laser
drilling processes have always been performed on a substrate 30
covered with a copper clad 32 (together referred to as a copper
clad laminate, CCL). In order to drill through the copper clad 32
and the substrate 30, enormous time and effort have to be spent.
Consequently, the drilling will increase the diameters of the
through holes 34, thereby reducing the amount of useful space.
Moreover, the thickness of the substrate 30 will also increase
significantly if additional patterns need to be added. Hence it
becomes a major disadvantage for the traditional method to
fabricate printed circuit boards with superfine wires and circuits
with higher integration.
SUMMARY OF THE INVENTION
[0007] It is therefore an objective of the present invention to
provide a method of fabricating a double-sided printed circuit
board for obtaining a printed circuit board with superfine circuits
and increased circuit density.
[0008] According to the preferred embodiment of the present
invention, a method of fabricating a double-sided printed circuit
board comprises: providing a copper clad laminate (CCL) with copper
clad removed or an insulating substrate; performing a drilling
process for forming a plurality of through holes in the insulating
substrate; disposing a copper layer on the insulating substrate and
the sidewall of the through holes for forming a plurality of plated
through holes; forming a wire pattern on the surface of the
insulating substrate, wherein the wire pattern includes at least
one contact pad; forming a solder resistant layer on the surface of
the insulating substrate and forming at least one opening in the
solder resistant layer for exposing the contact pad; and coating a
protective layer on the surface of the contact pad.
[0009] By performing a drilling process on a CCL with the removed
copper clad, the present invention is able to reduce the amount of
time and effort required for a typical drilling and etching
process, and decrease the diameter of the through holes, thereby
producing printed circuit board with superfine wires and increasing
the overall wire integration.
[0010] These and other objectives of the present invention will no
doubt become obvious to those of ordinary skill in the art after
reading the following detailed description of the preferred
embodiment that is illustrated in the various figures and
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a perspective diagram showing a double-sided
printed circuit board after a laser drilling process is performed
according to the prior art.
[0012] FIG. 2 to FIG. 8 are perspective diagrams showing the method
of fabricating a double-sided printed circuit board according to
the present invention.
DETAILED DESCRIPTION
[0013] Please refer to FIG. 2 to FIG. 8. FIG. 2 to FIG. 8 are
perspective diagrams showing the method of fabricating a
double-sided printed circuit board according to the present
invention. First, a copper clad laminate (CCL) is provided, in
which the CCL comprises an insulating substrate and at least one
copper clad disposed on the surface of the insulating substrate. As
shown in FIG. 2, a copper clad 52 is formed on both top and bottom
surface of the insulating substrate 50. Next, an etching process is
performed for removing the copper clad 52 on the surface of the
insulating substrate 50, as shown in FIG. 3. Alternatively, the CCL
can be substituted with an insulating substrate without the
additional copper clad layer for saving an extra step of removing
the copper clad.
[0014] As shown in FIG. 4, a laser drilling is performed on the
insulating substrate 50 for forming a plurality of through holes 54
in the insulating substrate 50. Alternatively, vias can be formed
instead for connecting different layers of the printed circuit
board.
[0015] As shown in FIG. 5, a coarsening process is performed on the
surface of the insulating substrate 50 and the through holes 54 for
increasing the surface roughness of the insulating substrate 50 and
each through hole 54, thereby increasing the adhesion ability of
chemical copper to each surface. Next, a chemical copper layer 56
is disposed on the insulating substrate 50 and the sidewall of each
through hole 54 for forming a plurality of plated through holes
57.
[0016] As shown in FIG. 6, a photoresist pattern 58, serving as
photo mask, is then transferred to both sides of the insulating
substrate 50. Next, an electroplating process is performed for
forming an electroplating copper layer 60 on the surface of the
insulating layer 50 not covered by the photoresist pattern 58 and
the sidewall of each through hole 54. The copper layer 60, also
serving as the electrical circuit, comprises at least one contact
pad 65.
[0017] As shown in FIG. 7, a photo stripping process is performed
for removing the photoresist pattern 58. Next, an etching process
is performed on the insulating substrate 50 for removing the
exposed chemical copper layer 56. In general, the thickness of the
copper clad 52 is approximately 10-12 .mu.m whereas the thickness
of the chemical copper layer 56 is only 0.1-1 .mu.m. According to
the present invention, the copper clad 52 is first removed, leaving
the remaining chemical copper layer 56. As a result, the surface
and sidewall of the electroplating copper layer 60 can be etched at
the same time during an etching process. In order words, by
reducing the thickness of the entire copper layer formed on the
surface of the insulating substrate 50, only the remaining chemical
copper layer 56, which is much smaller in thickness compared to the
copper clad 52, is etched by the etching process, thereby. By
decreasing the etching thickness of the electroplating copper layer
60, the process is able to fabricate printed circuit boards that
are not only smaller in size, but also with much finer wire layout
and higher circuit integration.
[0018] As shown in FIG. 8, a solder resistant layer 62 is then
formed on the insulating substrate. Next, an opening 64 is formed
in the solder resistant layer 62 directly above the contact pad 65
for exposing the contact pad 65. Eventually, a protective layer 66
is formed on the surface of the contact pad 65, in which the
protective layer 66 is comprised of materials including nickel,
gold, or organic solder preservative (OSP).
[0019] In addition to the fabrication stated above, the present
invention can also be utilized in multilayer printed circuit board
fabrication by removing the copper clad from the upper-most layer
and the lower-most layer, and stacking the boards on top of one
another.
[0020] In contrast to the prior art, the present invention provides
a method of fabricating a double-sided printed circuit board by
performing a drilling process on a CCL with the removed copper clad
or an insulating substrate. By using substrates that are much
thinner than the traditional CCL, the present invention is able to
reduce the amount of time and effort required for a typical
drilling and etching process, decrease the diameter of the through
holes, and eventually produce printed circuit boards with superfine
wires and increase the overall wire integration.
[0021] Those skilled in the art will readily observe that numerous
modifications and alterations of the device and method may be made
while retaining the teachings of the invention. Accordingly, the
above disclosure should be construed as limited only by the metes
and bounds of the appended claims.
* * * * *