U.S. patent number 3,731,377 [Application Number 05/173,186] was granted by the patent office on 1973-05-08 for method for handling beam-lead and odd-shaped semi-conductor devices.
Invention is credited to William L. Muckelroy.
United States Patent |
3,731,377 |
Muckelroy |
May 8, 1973 |
METHOD FOR HANDLING BEAM-LEAD AND ODD-SHAPED SEMI-CONDUCTOR
DEVICES
Abstract
An apparatus and method for manipulating monolithic
microelectronic dice are provided. The apparatus comprises a
probe-like electromagnet which uses a variety of different shaped
tips to change the configuration of the magnetic field. The
magnetic field at the tip is further adjusted by reversing the
polarity of the electricity in the electromagnet windings and
controlling the power applied to these windings. The core of the
electromagnet is maintained in a demagnetized state by switching
the electrical polarity of the windings. The method comprises the
steps of applying a magnetically permeable substance to the dice,
attaching each of the dice to the electromagnet using the force of
the magnetic field, moving the attached die to a preferred location
and orientation and releasing said die. Said magnetically permeable
substance may comprise a fluid adhesive with a magnetically
permeable insulated powder mixed therein, a permeable metal formed
in beam-leads, or a permeable metal formed into bumps on the
surface of flip-chips.
Inventors: |
Muckelroy; William L.
(Washington, DC) |
Family
ID: |
22630880 |
Appl.
No.: |
05/173,186 |
Filed: |
August 19, 1971 |
Current U.S.
Class: |
29/834; 294/65.5;
228/212; 228/180.21 |
Current CPC
Class: |
H01L
21/68778 (20130101); Y10T 29/49133 (20150115) |
Current International
Class: |
H01L
21/687 (20060101); H01L 21/67 (20060101); H05k
003/30 () |
Field of
Search: |
;294/65.5 ;117/8,239,235
;29/471.1,624,626,628,493,589,590 ;214/1BT,1BH,1BV |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lazarus; Richard Bernard
Claims
What is claimed is:
1. A method for manipulating monolithic microelectronic die
comprising the steps of
a. applying a magnetically permeable and electrically insulated
powder substance to a surface of a monolithic microelectronic die
said surface having exposed electrical terminals;
b. contacting said die with the attracting pole of an electromagnet
such that when a magnetic field is generated at said pole, said
field produces sufficient force to cause said die to adhere
thereto;
c. moving said electromagnet with said die attached thereto to a
location and decreasing said magnetic field such that said die is
released from said pole.
2. A method according to claim 1 further comprising the step of
subjecting said magnetically permeable substance to an elevated
temperature for a time period sufficient to cause said substance to
spread over said surface.
3. A method according to claim 1 further comprising the step of
demagnetizing said electromagnet by reversing the electrical
polarity of said windings and controlling the electrical power to
said windings.
4. A method according to claim 1 further comprising the step of
adjusting the magnetic field strength at said pole by reversing the
electrical polarity of said windings and controlling the amount of
electrical power supplied to said windings.
5. A method for manipulating monolithic microelectronic die
comprising the 5. of
a. applying a magnetically permeable substance to a surface of a
monolithic microelectronic die;
b. contacting said die with the attracting pole of an electromagnet
such that when a magnetic field is generated at said pole, said
field produces sufficient force to cause said dice to adhere
thereto;
c. moving said electromagnet with said die attached thereto to a
location and decreasing said magnetic field such that said die is
released from said pole; and
d. removing said substance from said surface of said die by
flushing with a solvent, said die having been attached to
microcircuit substrate prior to this step.
6. A method according to claim 5 further comprising the step of
dissolving said substance with a solvent prior to flushing said die
with a solvent said die having been attached to a microcircuit
substrate prior to these steps.
7. A method according to claim 2 wherein said substance is a
mixture which further comprises a solidifiable adhesive fluid.
8. A method according to claim 6 wherein said electromagnet
comprises a probe having a magnetically permeable core, a tip
protruding from one end thereof, a plurality of conductive windings
located around said core, means for supplying electric current to
said windings, and means for housing said core.
9. A method according to claim 8 wherein said core comprises a
paramagnetic material and a ferrimagnetic material.
10. A method according to claim 8 wherein said core comprises a
diamagnetic material and a plastic.
11. A method according to claim 1 wherein said location is at least
one bonding pad on a microcircuit substrate to which said die is
interjoined.
12. A method according to claim 1 wherein said location is a
plurality of bonding pads on a microcircuit substrate to which the
electrical exits to said die are interjoined.
13. A method according to claim 8 wherein said electromagnet
further comprises a plurality of interchangeable tips for changing
the shape of the magnetic field.
Description
RIGHTS OF THE GOVERNMENT
The invention described herein may be manufactured, used, and
licensed by or for the United States Government for governmental
purposes without the payment to the inventor of any royalty
thereon.
BACKGROUND OF THE INVENTION
This invention relates generally to the assembly of microelectronic
circuitry using substrates as bases onto which various types of
components in the form factor of a die are mounted. Specifically
this invention relates to a magnetic handling apparatus and method
for manipulation of all types of die involved in the assembly
microelectronic circuitry.
Among the many types of die to which this invention may be applied
are eutectic monolithic chips, flip-chips,
leadless-inverted-devices (LID's), beam-leaded devices, and
monolithic ceramic capacitors, monolithic resistors, and monolithic
inductors. The invention is particularly applicable to beam-leaded
devices for these are not cubic as the other types of dice.
Instead, they have beveled or truncated edges which makes this type
of dice extremely difficult to handle by tweezers or any other
means by which the sides are mechanically clamped.
Heretofore microelectronic dice were handled and manipulated by two
primary means of applying force. The first of these means where
tweezers. Tweezers were used to clasp and manipulate all types of
die. The other method and apparatus of the prior art involved the
use of vacuum supplied to an orifice in a pointed tool. The vacuum
supplied the force necessary to attach the die to the tool and
thereby permit manipulation. This means of manipulating
microelectronic dice is not discriminatory and therefore other
objects and debris in the vicinity of the die to be manipulated may
also be sucked into the orifice. These orifices are usually less
than 15 mils in diameter and are easily clogged. The tips for these
tools, because of the small orifice required, are quite expensive.
Furthermore, if debris is sucked to the tip at the same instance as
the die, contamination of the die as well as the tip may result.
Moreover, further difficulty is experienced with this method in
controlling the amount of force to be applied to the die. One way
is to control the power to the vacuum pump supplying vacuum to the
orifice. However, this is not wise because vacuum pumps are not
designed for operation at lower than rated power levels and such
operation may result in irrepairable damage. Another way is to
control the size of the air passage or orifice. This is a
cumbersome and impractical solution for the size of the orifice
would have to be increased or a vent connected to the passageway in
order to diminish the suction force. Thus, many inherent
disadvantages exist in the early methods and apparatus of this
art.
The invention described herein overcomes all of the disadvantages
of the foregoing methods.
It is an object of this invention to provide a new and novel method
for manipulating monolithic microelectronic die and a new apparatus
for effecting same.
It is yet another object of this invention to provIde a new and
novel apparatus and method for manipulating monolithic
microelectronic dice which utilizes magnetic fields as a means of
attachment.
It is yet an additional object of this invention to provide a new
and novel apparatus and method for manipulating monolithic
microelectronic dice which involves the application of a
magnetically permeable substance to a surface of said die, said
substance being compatible with the normal cleaning operations to
which the assembled substrate is subjected.
It is still an additional object of this invention to provide a new
and novel apparatus and method for manipulating monolithic
microelectronic die wherein said substance may be removed in the
cleaning operation of the assembled substrate by flushing with a
solvent.
Yet another additional object of this invention is to provide a new
and novel apparatus and method for manipulating monolithic
microelectronic dice wherein the force means used to attach and
move said die is completely variable between prescribed limits.
Still an additional object of this invention is to provide a new
and novel apparatus and method for manipulating monolithic
microelectronic dice wherein the manipulating tool comprises a
plurality of interchangeable tips for changing the shape of the
magnetic field.
These and other objects of the present invention will become more
fully apparent with reference to the following specification and
drawings which relate to several variations of a preferred
embodiment of the present invention.
SUMMARY
In accordance with this invention a new and novel apparatus and
method for manipulating monolithic microelectronic dice utilizing
the force of a magnetic field for attachment of said die is
provided which descriminates in the application of the attachment
force, against all non-magnetic contaminants and debris in the
vicinity of said die. The method is based on the use of a
probe-like tool comprising an electromagnet and propagating a
magnetic field from its tip, a magnetically permeable substance
applied to a surface of the die, and means for controlling and
varying the force of the magnetic field from said tool. The method
comprises the steps of applying a magnetically permeable substance
to a surface of a monolithic microelectronic die, contacting said
die with the attracting tip of said tool such that when a magnetic
field is generated at the tip, the field produces sufficient force
to cause the die to adhere thereto, moving the tool with the die
attached to it to a location and decreasing the magnetic field such
that the die is released from the pole. In this method the magnetic
field force at the tip is adjusted by reversing the polarity of the
electricity in the windings and controlling the amount of electric
power applied to the windings. In addition the core of the
electromagnet is maintained in a demagnetized state by reversing
the electrical polarity of the windings periodically and applying
and controlling the appropriate amount of electrical power to the
windings to accomplish this objective.
BRIEF DESCRIPTION OF THE DRAWINGS
The specific nature of the invention as well as other objects,
aspects, uses, and advantages thereof will clearly appear from the
following description and from the accompanying drawings, in
which:
FIG. 1a is a flow chart of the method for manipulating
microelectronic monolithic dice.
FIG. 1b is a flow chart of a method for manipulating
microelectronic monolithic dice using a liquid magnetic
adhesive.
FIG. 2 is a cross-section of the manipulating tool.
FIG. 3a is a drawing of a cylindrical electrical contactor.
FIG. 3b is a drawing of the strip electrical contactor in the
plastic housing.
FIG. 4 is a perspective drawing of the strip electrical
contactor.
FIG. 5 is a block diagram of the electrical operation of the
manipulating apparatus.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The method of the present invention will be easily understood in
its broad aspects by reference to FIG. 1a wherein there is shown a
flow diagram of the steps thereof. First a magnetically permeable
substance is applied to the surface of a die in a particular die
matrix. In the next step, the coated die is contacted with the tip
of a tool comprising an electromagnet, said tool being illustrated
in FIG. 2. Once the die is contacted by the manipulating tool the
core of the electromagnet is energized by supplying electricity to
the windings in the required amount necessary to generate
sufficient force at the tip to hold said die to said tool. Once the
force necessary to attach the die to the tool is attained the die
may then be relocated to the bonding site or other site necessary
to perform an assembly operation upon the die. Once relocated the
die is detached by diminishing the power to the electromagnet
windings. This is done by adjusting a power transformer 203 (See
FIG. 5) connected to the windings of the tool. The above steps are
considered essential to the application of this method for
manipulation of microelectronic monolithic dice.
In particular, one type of magnetic substance may comprise a
polyvinyl chloride adhesive with a magnetically permeable insulated
powder mixed therein. The adhesive should have similar properties
with reference to solubility as that of polyvinyl chloride glue. In
order to insure compatibility with production cleaning methods used
in the manufacture of hybrid microelectronic circuitry the adhesive
must at least be soluble in acetone, trichloroethylene, or ketone.
This type composition of the magnetically permeable substance
permits removal of the substance once manipulation is no longer
necessary and the die has been permanently attached to the
substrate. A magnetically permeable insulated powder such as 2-81
permalloy is best because this insures against electrical shorting
of the microminiature conductive paths on the substrate by a
conglomeration and adherence of several of the magnetically
permeable powder granules used in the composition. This may occur
due to insufficient flushing and cleansing of the substrate after
attachment operations are completed. In other words, the magnetic
powder may form an electrical bridge from one microminiature
conductive path to another. Magnetically permeable powder is
described and specified in the referable art. It is to be
understood that the magnetically permeable substance described
herein is not to be limited to this particular composition and may
consist of other forms of matter such as thin films of magnetically
permeable metals or poly-crystalline coatings. It is also to be
understood that magnetically permeable material may be deposited by
several means and is not to be limited by the method described
herein.
Turning to FIG. 1b, the magnetic material is loaded into a
dispensing means comprising, for example, a syringe and hypodermic
needle. The dispensing means is used to place a microdrop of the
magnetically permeable material onto the top surface of the
monolithic microelectronic die. The material is dispensed onto each
of the die in a particular matrix as it is received from the
manufacturer in the manufacturer's package. Once the microdrops of
material are deposited, the matrix is either placed in an oven or
exposed to infrared heat lamps. This step serves to warm the
mixture and cause the drop to spread over the top surface of the
die forming a smooth even coating of the material. Once coated the
adhesive is permitted to dry. Note that only one face of the die is
coated and that face is the face opposite the face to be juxtaposed
to the substrate and on which the die is resting. After drying, the
matrix of dice is located at the work station at which the die are
needed. Once this is done the manipulating tool is placed in the
vicinity of one of the die to be picked up and removed to a bonding
location, or to be picked up and bonded using the manipulating
tool.
Referring to FIG. 2 the manipulating tool 200 comprises an
electromagnet in the shape of a pencil structure with a means for
energizing the windings 60 of the electromagnet placed or
incorporated into the tool itself. This energizing means is a
normally open switch which may be actuated by depression of button
110 with one or more fingers of the hand. To continue the method,
the electromagnet in the manipulating tool is energized and the
resultant field produced at the tip 85 of the tool causes the
magnetic material in the coating on the top of the die to be
attracted and attached to said tip 85. The force of attraction is
controlled by a variable transformer 203 which controls the power
to the windings of the electromagnet housed in the manipulating
tool (See FIG. 5). The tool with the die attached is then moved to
the bonding site for the die. Either the tool may act, in addition,
as a bonding means or the die may be transferred to location such
that a bonding tool contacts said die at that location and applies
energy to the die in such a manner that is becomes attached to
metalization or other electrical conducting means incorporated onto
a substrate at that location. Alternately, the die may be
maintained at the location of said tip of the manipulating tool and
the manipulating tool used as a means for transferring energy to
the die, such energy being sufficient to cause the die to become
rigidly attached at the bonding site. These steps may be effected
and accomplished by numerical controlled machinery without human
intervention. Once the die is attached by the manipulating tool the
force of the magnetic field is diminished or reduced prior to
withdrawal of the tool from the die. This step may also be
incorporated into the logic circuitry of a numerically controlled
bonding apparatus.
In some cases, such as in the production of a laboratory prototype
model of a hybrid circuit, it is desirable to relocate a particular
monolithic microelectronic die to a substrate site and at that time
to cause the die to move to another location. This is accomplished
by reducing the magnetic field generated at the tip of the tool and
locating said tool underneath the substrate and moving said tool
along the underside of the substrate in the vicinity of the
monolithic die thus causing the die to assume a similar movement
along a similar path. In this manner, minute movements of
microelectronic die may be obtained in order to get precise
positioning of said die.
Turning again now to FIG. 2, there is shown a cross-section of the
manipulating tool required in the method. The tool is essentially
the same size as that of a hand held pencil-like soldering iron.
The manipulating tool comprises a plastic cylindrical hollow member
95, said member having openings, 84 and 83, at both ends thereof,
said member having an opening 92 on the side thereof, and said
member having threads 94 in the opening 93 at one end thereof (See
FIG. 3b). Returning to FIG. 2, opening 92 in the side of said
plastic member 95 is provided to accommodate a switching means for
supplying electricity to said manipulating tool. Core 80 is
inserted through opening 84 at one end of said housing 95 and is
held rigidly by mound 82, in said housing 95. Said core 80 is
cylindrical in shape and is inserted through the unthreaded opening
84 of plastic housing 95. The last one-half inch of the core 80 at
the unthreaded end of the plastic housing 95 has a diameter
approximately twice that of the remainder of said cylindrical core.
This last one-half inch has a hole 90 which is threaded and
centered along the axis of the core 80. This threaded portion is
for the insertion of a permeable magnetic tip 85 the inserted
portion of which is threaded and screwed into the hole 90 in said
core 80. The greater diameter at the end of the core rests upon
circular mound 82 formed into the plastic housing 95. This mound 82
forms an interference for the larger diameter portion of the core
thus preventing said core from being pushed completely through the
inner space of the housing 95. Around said core 80 is a plurality
of conductive windings 60. One of the terminations of the
conductive windings 60 is connected to screw 125. This screw 125 is
in turn connected to strip contactor member 100 (See FIG. 4) which
extends in a groove 181 (See FIG. 3b) approximately 1/8 of an inch
in width down an inner side of the plastic housing chamber 95 to an
opening 92 at the side of the housing 95. Returning to FIG. 2, the
second contactor member 15 is in the form of a cylinder (See FIG
3a). Second contactor member 65 comprises a conductive metal 75
embedded in a plastic material 65 shaped in the form of a cylinder
with a lip 78 at one end thereof, threads 56 being formed at the
outer periphery of said lip 78. The conductive cylinder 75 extends
beyond the plastic material in which it is embedded at the
unthreaded end thereof. Returning to FIG. 2, this portion of the
conductive cylinder 75 which is exposed is inserted into the inner
chamber of plastic housing 95 and screwed in threaded hole 55 until
the unexposed portion of said conductive cylinder 75 is opposite
the end of first contactor member 100. Returning to FIG. 3a, a tab
79 of conductive cylinder 75 extends up and beyond the lip 78 of
the plastic coating 65 on said conductive cylinder 75. This tab 79
is approximately 1/8 inch by 1/8 inch and is bent onto the upper
surface of the lip 78 of said member 15. Said tab 79 further
comprises a hole 76 and under said hole is a threaded hole 50 (See
FIG. 2). The second termination of the conductive windings is
attached to a screw 51 inserted into hole 50 and said screw 51
serves as a binding post in order to connect a power lead 18 from
an outside source. Screw 125 connected to contactor member 100
serves as a binding post for power lead 17. The small diameter end
of said core is held rigidly in place by means of a screw 40
inserted through cap 45 and fastened into the end of said core 80.
Another hole 42 in housing cap 45 serves as a inlet through which
power cord 130 is inserted. Returning to FIG. 3a, plastic contactor
15 has a notch 77 therein such that when it is screwed into hole 55
said notch 77 is positioned directly above contactor 100 permitting
screw 125 to be inserted into the hole 64 below the tab 66 of said
contactor 100. Contactor 100 is pressed against contactor conductor
portion 75 by means of a button 110 attached to contactor 100 and
inserted through an opening 92 in the side of housing 95. The
contact is designed to remain normally open by means of a spring
and washer assembly, 115 and 105, respectively. The button 110 is
cylindrical in shape and comprises two diameters, one diameter
approximately three times that of the second diameter, the smaller
diameter of which has inserted and formed into it, a screw 120.
screw 120 is attached to first contactor means 100. Washer 105 fits
firmly around the smaller diameter of button 100 and between the
washer and the larger diameter of button 110 is inserted spring
115. The force exerted by spring 115 against button 110 and washer
105 serves to force contactor 100 away from exposed cylindrical
contactor 75.
A permanently polarized magnetic material may be demagnetized by
immersion in a rapidly reversing magnetic field. Therefore, when
the tip of the manipulating tool herein indicates a degree of
magnetic polarization this may be eliminated by rapidly switching
the polarity of the electricity supplied to the windings around the
core of said tool. Referring to FIG. 5, the manipulating tool leads
are connected to a polarity switch 201 which in turn is connected
to a AC to DC converter 202 which in turn is connected in series to
a variable alternating transformer 203 and the variable alternating
transformer is connected to an alternating current power source
204. By switching the polarity switch 201 the polarity of the
magnetic field in the core manipulating tool 200 may be reversed.
By varying the setting of the transformer 203 value, the intensity
of the magnetic field at the tip of the manipulating tool 200 may
be controlled. By switching the polarity switch 201 several times
and setting the variable alternating transformer 203 to the proper
level any permanent polarization in the tip of the manipulating
tool 200 may be eliminated. This ensures that the tool only
attaches die when the button switch 110 on the side of the
manipulating tool is depressed.
Another useful embodiment and operation system for the manipulating
tool is to use a plastic material with a diamagnetic material
embedded in said plastic material as a core. In this combination
the windings around said core may be polarized in a direction
opposite to that of diamagnetic material. Knowing that a
diamagnetic material repels magnetically permeable materials such
as applied to the surfaces of the die, by increasing the field
strength of the windings to the value that exactly opposes the
value of the magnetic field permanently in the core and at the tip
and then minutely adjust the value of the field of the windings,
the tip may be made either to repel or attract a die coated with
said substance.
Referring again to the magnetic permeable substance, this material
may be applied during the regular processing steps for this
particular type of die. That is, the bumps on the exit termination
flip-chip dice may be formed using a magnetically permeable
material instead of applying the material after all of the
processing steps are terminated. The magnetically permeable
substance may also be used in the formation of beam-leads during
their normal formation process. Furthermore, in the case of
leadless-inverted-devices (LID's) a permanent layer of permeable
magnetic material may be placed on the under side or top side of
the ceramic carrier by vacuum deposition, silk screening, or other
means available in the art of hybrid microelectronics. In
consideration of the foregoing the manipulating tool used to handle
beam-lead, flip-chip, or LID devices may also be used to apply
energy to these die to accomplish permanent bonding of the die to
the intended substrate.
It is to be understood that the inventor does not desire to be
limited to the exact details of construction shown and described,
for obvious modifications will occur to a person skilled in the
art.
* * * * *