U.S. patent application number 11/817961 was filed with the patent office on 2010-08-19 for pins for transferring material.
This patent application is currently assigned to AURIGIN TECHNOLOGY PTE LTD. Invention is credited to Ee Lim, Thian Loo, Boon NG.
Application Number | 20100209674 11/817961 |
Document ID | / |
Family ID | 37115409 |
Filed Date | 2010-08-19 |
United States Patent
Application |
20100209674 |
Kind Code |
A2 |
NG; Boon ; et al. |
August 19, 2010 |
PINS FOR TRANSFERRING MATERIAL
Abstract
A pin for allowing material having adhesive properties to adhere
thereon, the pin comprising: a shaft having a longitudinal axis, a
distal end and a proximal end opposite to the distal end; and a
first tapered portion disposed on the longitudinal axis of the
shaft, the tapered portion tapering from a first circumference to a
second smaller circumference in a direction toward the proximal end
of the shaft.
Inventors: |
NG; Boon; (Singapore,
SG) ; Loo; Thian; (Singapore, SG) ; Lim;
Ee; (Singapore, SG) |
Correspondence
Address: |
SEED INTELLECTUAL PROPERTY LAW GROUP PLLC
701 FIFTH AVE
SUITE 5400
SEATTLE
WA
98104
UNITED STATES
206-622-4900
206-682-6031
|
Assignee: |
AURIGIN TECHNOLOGY PTE LTD
Blk 4010 Ang Mo Kio Ave 10, #07-09, Techplace 1
Singapore
SG
569626
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20090035531 A1 |
February 5, 2009 |
|
|
Family ID: |
37115409 |
Appl. No.: |
11/817961 |
Filed: |
April 19, 2005 |
PCT Filed: |
April 19, 2005 |
PCT NO: |
PCT/SG2005/000127 |
371 Date: |
October 24, 2008 |
Current U.S.
Class: |
428/195.1;
118/200; 427/58 |
Current CPC
Class: |
B23K 3/082 20130101;
H01L 24/743 20130101; B23K 1/203 20130101; H05K 2203/0195 20130101;
Y10T 428/24802 20150115; H05K 3/3489 20130101 |
Class at
Publication: |
428/195.1;
427/058; 118/200 |
International
Class: |
B32B 3/10 20060101
B32B003/10; B05D 5/12 20060101 B05D005/12; B05C 1/00 20060101
B05C001/00 |
Claims
1. A pin for allowing flux material having adhesive properties to
adhere thereon, the pin comprising: a shaft having a longitudinal
axis, a distal end and a proximal end opposite to the distal end;
and a first tapered portion disposed on the longitudinal axis of
the shaft, the tapered portion tapering from a first circumference
to a second smaller circumference in a direction toward the
proximal end of the shaft, wherein the taper angle of said first
tapered portion is chosen for at least partially inhibiting flux
creep on said shaft in the direction of the proximal end.
2. A pin as claimed in claim 1, comprising: a second tapered
portion disposed on the longitudinal axis of the shaft between said
first tapered portion and the proximal end, the second tapered
portion tapering from a third circumference to a fourth smaller
circumference in a direction toward the distal end of the
shaft.
3. A pin according to claim 1, wherein in use, the taper angle of
the first tapered portion at least partially inhibits material
creep on the shaft in the direction of the proximal end.
4. A pin according to claim 2, wherein in use, the taper angle of
the first tapered portion relative to the taper angle of the second
tapered portion at least partially inhibits material creep on the
shaft beyond the first tapered portion.
5. A pin according to claim 1, further comprising a third tapered
portion disposed on the longitudinal axis of the shaft between said
first tapered portion and said distal end.
6. A pin according to claim 5, wherein the third tapered portion
tapers from a fifth circumference to a sixth smaller circumference
in a direction toward the proximal end of the shaft.
7. A pin according to claim 6, wherein the sixth circumference of
the third tapered portion is less than the second circumference of
the first tapered portion.
8. A pin according to claim 6, wherein the first circumference of
the first tapered portion is greater than the fifth circumference
of the third tapered portion.
9. A pin according to claim 2, wherein the second circumference of
the first tapered portion is the same as the fourth circumference
of the second tapered portion.
10. A pin according to claim 2, wherein the taper angles of the
first and second tapered portions are the same.
11. A pin according to claim 2, wherein the taper angles of the
first and second tapered portions are different.
12. A pin according to claim 2, wherein the taper angle of the
second tapered portion is less than the taper angle of the first
tapered portion.
13. A pin according to claim 2, wherein the taper angle of the
second tapered portion is in the range selected from the group
consisting of about 0.5.degree. to about 40.degree.; about
0.5.degree. to about 35.degree.; about 0.5.degree. to about
30.degree.; about 0.5.degree. to about 25.degree.; about
0.5.degree. to about 20.degree.; about 0.5.degree. to about
15.degree.; about 0.5.degree. to about 10.degree.; about
0.5.degree. to about 5.degree.; about 0.75.degree. to about
40.degree.; about 1.degree. to about 40.degree.; about 1.5.degree.
to about 40.degree.; about 2.degree. to about 40.degree.; and about
2.degree. to about 5.degree..
14. A pin according to claim 1, wherein the taper angle of the
first tapered portion is in the range selected from the group
consisting of about 0.5.degree. to about 60.degree.; about
0.5.degree. to about 50.degree.; about 0.5.degree. to about
40.degree.; about 0.5.degree. to about 35.degree.; about
0.5.degree. to about 30.degree.; about 0.5.degree. to about
25.degree.; about 0.5.degree. to about 20.degree.; about
0.5.degree. to about 15.degree.; about 0.5.degree. to about
10.degree.; about 0.5.degree. to about 5.degree.; about
0.75.degree. to about 60.degree.; about 1.degree. to about
60.degree.; about 1.5.degree. to about 60.degree.; about 2.degree.
to about 60.degree.; and about 2.degree. to about 5.degree..
15. A pin according to claim 1, wherein the distal end of the pin
comprises a wear portion at the end face of the distal end.
16. A pin according to claim 5, wherein the first tapered portion,
the second tapered portion and the third tapered portion form an
integral structure with the shaft.
17. A flux imprint apparatus for imprinting flux on a substrate,
the flux imprint apparatus comprising: a support; and an array of
pins mounted to the support, wherein each of said pins comprises: a
shaft having a longitudinal axis, a distal end and a proximal end
opposite to the distal end; and a first tapered portion disposed on
the longitudinal axis of the shaft, the tapered portion tapering
from a first circumference to a second smaller circumference in a
direction toward the proximal end of the shaft.
18. A flux imprint apparatus according to claim 17, wherein each of
the pins comprises a second tapered portion disposed on the
longitudinal axis of the shaft between said first tapered portion
and the proximal end, the second tapered portion tapering from a
third circumference to a fourth smaller circumference in a
direction toward the distal end of the shaft.
19. A flux imprint apparatus according to claim 17, wherein in use,
the taper angle of the first tapered portion at least partially
inhibits flux creep on the shaft in the direction of the proximal
end.
20. A pin according to claim 18, wherein in use, the taper angle of
the first tapered portion relative to the taper angle of the second
tapered portion at least partially inhibits adhesion of the flux
beyond the first tapered portion.
21. A flux imprint apparatus according to claim 17, further
comprising biasing means disposed between the support and the
proximal ends of said array of pin shafts.
22. A flux imprint apparatus according to claim 21, wherein the
biasing means is at least one spring.
23. A flux imprint apparatus according to claim 17, wherein each of
the pins further comprise a third tapered portion disposed on the
longitudinal axis of the shaft between said first tapered portion
and said distal end.
24. A flux imprint apparatus according to claim 23, wherein the
third tapered portion tapers from a fifth circumference to a sixth
smaller circumference in a direction toward the proximal end.
25. A flux imprint apparatus according to claim 24, wherein the
fifth circumference of the third tapered portion is less than the
first circumference of the first tapered portion.
26. A flux imprint apparatus according to claim 18, wherein the
second circumference of the first tapered portion is the same as
the fourth circumference of the second tapered portion.
27. A flux imprint apparatus according to claim 18, wherein the
taper angles of the first and second tapered portions are the
same.
28. A flux imprint apparatus according to claim 18, wherein the
taper angles of the first and second tapered portions are
different.
29. A flux imprint apparatus according to claim 18, wherein the
taper angle of the second tapered portion is less than the taper
angle of the first tapered portion.
30. A flux imprint apparatus according to claim 18, wherein the
taper angle of the second tapered portion is in the range selected
from the group consisting of about 0.5.degree. to about 40.degree.;
about 0.5.degree. to about 35.degree.; about 0.5.degree. to about
30.degree.; about 0.5.degree. to about 25.degree.; about
0.5.degree. to about 20.degree.; about 0.5.degree. to about
15.degree.; about 0.5.degree. to about 10.degree.; about
0.5.degree. to about 5.degree.; about 0.75.degree. to about
40.degree.; about 1.degree. to about 40.degree.; about 1.5.degree.
to about 40.degree.; about 2.degree. to about 40.degree.; and about
2.degree. to about 5.degree..
31. A flux imprint apparatus according to claim 17, wherein the
taper angle of the first tapered portion is in the range selected
from the group consisting of about 0.5.degree. to about 60.degree.;
about 0.5.degree. to about 50.degree.; about 0.5.degree. to about
40.degree.; about 0.5.degree. to about 35.degree.; about
0.5.degree. to about 30.degree.; about 0.5.degree. to about
25.degree.; about 0.5.degree. to about 20.degree.; about
0.5.degree. to about 15.degree.; about 0.5.degree. to about
10.degree.; about 0.5.degree. to about 5.degree.; about
0.75.degree. to about 60.degree.; about 1.degree. to about
60.degree.; about 1.5.degree. to about 60.degree.; about 2.degree.
to about 60.degree.; and about 2.degree. to about 5.degree..
32. A flux imprint apparatus according to claim 17, wherein the
distal ends of the pins each comprise a wear portion at the end
face of the distal end.
33. A flux imprint apparatus according to claim 23, wherein the
first tapered portion, the second tapered portion and the third
tapered portion form an integral structure with the shaft.
34. A method of imprinting flux using a flux imprint apparatus
comprising a support; and an array of pins mounted to the support,
wherein each of said pins comprises: a shaft having a longitudinal
axis, a distal end and a proximal end opposite to the distal end;
and a first tapered portion disposed on the longitudinal axis of
the shaft, the tapered portion tapering from a first circumference
to a second smaller circumference in a direction toward the
proximal end of the shaft; the method comprising the steps of: (a)
contacting the array of pins with flux material; (b) removing the
array of pins from the flux material while at least some of the
flux material adheres to at least the first tapered portion of the
pins; and (c) depositing flux material on a substrate by contacting
the distal ends of the pins on the substrate.
35. A method according to claim 34, wherein the step of contacting
the array of pins with flux material comprises inserting the array
of pins into the flux material.
36. A method according to claim 34, wherein the step of depositing
comprises pressing the pins onto the substrate.
37. A method according to claim 34, wherein the method further
comprises the step of removing the pins from the substrate.
38. A flux material, deposited on a substrate by a method as
claimed in claim 34.
39. A pin according to claim 5, further comprising a fourth tapered
portion disposed on the longitudinal axis of the shaft between said
first tapered portion and said third tapered portion.
40. A pin according to claim 39, wherein the fourth tapered portion
tapers from a seventh circumference to an eighth smaller
circumference in a direction toward the distal end of the shaft.
Description
BACKGROUND
[0001] 1. Technical Field
[0002] The present invention generally relates to pins for
transferring material.
[0003] 2. Description of the Related Art
[0004] In the manufacture of semiconductor devices, it is often
necessary to connect multiple components of the semiconductor
device together with an electrically conductive connector so that
an electrical connection can be formed therebetween in use.
[0005] The conductive connector may be formed using ball grid array
(BGA) technology, which involves depositing solder balls onto a
substrate of an electronic component. The solder balls are
subjected to soldering to thereby form conductive connectors to
conduct electricity.
[0006] Prior to the deposition of solder balls onto the substrate,
it is necessary to also deposit a flux material on the substrate so
that the solder balls can adequately adhere to the substrate.
[0007] Current BGA technology uses a pin block to dispense solder
flux onto the substrate. A known pin block and method of use is
disclosed in U.S. Pat. No. 5,816,481. A disadvantage with the
method disclosed in U.S. Pat. No. 5,816,481 is that an insufficient
quantity of flux material is often deposited by the pins at the
soldering site of the substrate. An insufficient quantity of flux
material leads to inadequate soldering. This may cause the
semiconductor device to fail in use.
[0008] The pins disclosed in U.S. Pat. No. 5,816,481 also have the
disadvantage of depositing an excess of flux material onto the
substrate. An excess of flux results in flux residue accumulating
on the substrate after soldering. Excess flux residue may result in
post-soldering cleaning problems.
[0009] Another problem associated with excess flux is that solder
balls may merge with neighbouring solder balls. This results in an
uneven ball size distribution on the substrate causing coplanarity
problems at the conductive solder ball connectors, which may result
in failure of the semiconductor device.
[0010] Accordingly, it is important for a precise amount of flux
material to be deposited on the substrate at soldering sites.
[0011] Referring to FIGS. 1A to 1D, there is shown a schematic
diagram of a known flux imprinting process. In the known flux
imprinting process, the flux material is imprinted on the substrate
using a flux imprinting device. This device comprises an array of
flux pins 10 which are mounted within a chamber 12. An enlarged
view of one of the flux pins 10 in FIGS. 1A to 1D is shown in FIG.
1. Referring to step 1 of FIG. 1A, the array of flux pins 10 are
mounted within a moveable chamber 12 comprising a housing 14, in
which reside proximal ends 16 of the pins 10. Each of the pins 10
is biased by springs 18 in a direction shown by arrow 20 toward the
distal ends 22 of the pins 10. The distal ends 22 of the pins 10
are immersed in the flux material 24 in tray 26 to coat the distal
ends 22 with the flux material 24.
[0012] In step 2 of FIG. 1B, the pins 10 are removed from the flux
material 24 and the distal ends 22 of the pins 10 are coated with
the flux material 24.
[0013] In step 3 of FIG. 1C, the pins 10 are lowered onto a
substrate 28 in a direction shown by arrow 32 to deposit the flux
material 24 thereon. The substrate 28 includes a plurality of
recesses 30 on which the flux material 24 is to be deposited.
[0014] In step 4 of FIG. 1D, the pins 10 are released from the
substrate 28 in a direction shown by arrow 34.
[0015] Referring now in particular to FIG. 1B, it can be seen that
a flux bridge 24a is formed between the pins 10a and 10b due to
flux creep over prolonged use of the flux imprinting device.
[0016] The contributing factors for flux creeping or crawling on
the pin 10 is due to the surface energy of the cylindrical surface
23 being constant along the longitudinal axis 21. This constant
surface energy causes flux to spread out along the cylindrical
surface 23 to achieve equilibrium. The surface energy of the taper
surface 25 increases with its circumference along the longitudinal
axis 21 and encourages flux to move towards the larger
circumference.
[0017] The accumulation of flux on the pins, after successive
dipping in flux material, results in the flux material 24 tending
to creep up the shafts of the pins 10 in a direction toward the
proximal ends of the pins 10. This is known as "flux creep" or
"flux crawl".
[0018] The formation of flux bridges 24a results in an uneven
deposition of the flux material 24a on the substrate 28 as shown by
arrow 38 in FIG. 1D.
[0019] A further problem with flux creep is that it causes a
reduced amount of flux that is adhered on the distal end 22 because
the bulk of the flux is `pulled` up the pin shaft. The reduced
amount of flux deposited on the distal end 22 results in a reduced
amount of flux being deposited on the substrate. This causes an
unequal amount of flux deposition on the substrate which may result
in defective soldering. This phenomena is particularly pronounced
when a flux having a low viscosity is used.
[0020] Accordingly, it would be an advantage if embodiments of the
invention provided pins which could overcome or at least ameliorate
one or more of the disadvantages described above.
BRIEF SUMMARY
[0021] According to a first aspect of the invention, there is
provided a pin for allowing flux material having adhesive
properties to adhere thereon, the pin comprising:
[0022] a shaft having a longitudinal axis, a distal end and a
proximal end opposite to the distal end; and
[0023] a first tapered portion disposed on the longitudinal axis of
the shaft, the tapered portion tapering from a first circumference
to a second smaller circumference in a direction toward the
proximal end of the shaft, wherein the taper angle of said first
tapered portion is chosen for at least partially inhibiting flux
creep on said shaft in the direction of said proximal end.
[0024] In one embodiment of the first aspect, the pin comprises a
second tapered portion disposed on the longitudinal axis of the
shaft between said first tapered portion and said proximal end, the
second tapered portion tapering from a third circumference to a
fourth smaller circumference in a direction toward the distal end
of the shaft.
[0025] Advantageously, in use, the taper angle of the first tapered
portion relative to the taper angle of the second tapered portion
at least partially inhibits adhesion of the material on the second
tapered portion.
[0026] Advantageously, material creep or crawl is substantially
prevented from occurring on the shaft of the pin beyond the first
tapered portion.
[0027] In one embodiment, there is provided a pin for allowing
material having adhesive properties to adhere thereon, the pin
comprising:
[0028] a shaft having a longitudinal axis, a distal end and a
proximal end opposite the distal end; and
[0029] a first tapered portion disposed on the longitudinal axis of
the shaft, the tapered portion tapering from a first circumference
to a second smaller circumference in a direction toward the
proximal end of the shaft, and wherein the taper angle of the first
tapered portion is in the range selected from the group consisting
of about 0.5.degree. to about 60.degree..
[0030] Also disclosed herein is a pin for allowing material having
adhesive properties to adhere thereon, the pin comprising:
[0031] a shaft having a longitudinal access, a distal end and a
proximal end opposite to the distal end; and
[0032] a first tapered portion disposed on the longitudinal axis of
the shaft, the tapered portion tapering from a first circumference
to a second smaller circumference in a direction toward the
proximal end of the shaft.
[0033] According to a second aspect of the invention, there is
provided a flux imprint apparatus for imprinting flux on a
substrate, the flux imprint apparatus comprising:
[0034] a support; and
[0035] an array of pins mounted to the support, wherein each of
said pins comprises: a shaft having a longitudinal axis, a distal
end and a proximal end opposite to the distal end; and
[0036] a first tapered portion disposed on the longitudinal axis of
the shaft, the tapered portion tapering from a first circumference
to a second smaller circumference in a direction toward the
proximal end of the shaft.
[0037] In one embodiment of the second aspect, each of the pins
comprises a second tapered portion disposed on the longitudinal
axis of the shaft between said first tapered portion and said
proximal end, the second tapered portion tapering from a third
circumference to a fourth smaller circumference in a direction
toward the distal end of the shaft.
[0038] According to a third aspect of the invention, there is
provided a method of imprinting flux using a flux imprint apparatus
comprising:
[0039] a support; and
[0040] an array of pins mounted to the support, wherein each of
said pins comprises: a shaft having a longitudinal axis, a distal
end and a proximal end opposite to the distal end; and
[0041] a first tapered portion disposed on the longitudinal axis of
the shaft, the tapered portion tapering from a first circumference
to a second smaller circumference in a direction toward the
proximal end of the shaft; the method comprising the steps of:
[0042] (a) contacting the array of pins with flux material;
[0043] (b) removing the array of pins from the flux material while
at least some of the flux material adheres to at least the first
tapered portion of the pins; and
[0044] (c) depositing flux material on a substrate by contacting
the distal ends of the pins on the substrate.
[0045] In said method of said third aspect, said at least some flux
material adheres to the distal ends of the pins while the first
tapered portions at least partially inhibit creeping of flux
towards the proximal end.
[0046] In one embodiment of the third aspect, each of the pins
comprises a second tapered portion disposed on the longitudinal
axis of the shaft between said first tapered portion and said
proximal end, the second tapered portion tapering from a third
circumference to a fourth smaller circumference in a direction
toward the distal end of the shaft.
DEFINITIONS
[0047] The following words and terms used herein shall have the
meaning indicated:
[0048] The term `taper angle` as used herein refers to the angle of
tapering between a first circumference to a second smaller
circumference of a tapered portion relative to the longitudinal
axis of a shaft on which the tapered portion is disposed.
[0049] The terms "flux", "flux material" and variations thereof,
refer to any substance that aids, induces, or otherwise actively
participates in fusing, flowing, and/or preventing the oxidation of
a solder ball to a substrate during a soldering process. The flux
may also de-oxidise and/or clean the pads on the substrate during
soldering. Exemplary flux material is disclosed in U.S. Pat. No.
4,419,146, U.S. Pat. No. 4,360,392, U.S. Pat. No. 4,342,607, and
U.S. Pat. No. 4,269,870.
[0050] Unless specified otherwise, the terms "comprising" and
"comprise", and grammatical variants thereof, are intended to
represent "open" or "inclusive" language such that they include
recited elements but also permit inclusion of additional, unrecited
elements.
[0051] As used herein, the term "about", in the context of
concentrations of components of the formulations, typically means
+/-5% of the stated value, more typically +/-4% of the stated
value, more typically +/-3% of the stated value, more typically,
+/-2% of the stated value, even more typically +/1% of the stated
value, and even more typically +/-0.5% of the stated value.
[0052] Throughout this disclosure, certain embodiments may be
disclosed in a range format. It should be understood that the
description in range format is merely for convenience and brevity
and should not be construed as an inflexible limitation on the
scope of the disclosed ranges. Accordingly, the description of a
range should be considered to have specifically disclosed all the
possible sub-ranges as well as individual numerical values within
that range. For example, description of a range such as from 1 to 6
should be considered to have specifically disclosed sub-ranges such
as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6,
from 3 to 6 etc., as well as individual numbers within that range,
for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the
breadth of the range.
BRIEF DESCRIPTION OF DRAWINGS
[0053] The accompanying drawings illustrate a disclosed embodiment
and serve to explain the principles of the disclosed embodiment. It
is to be understood, however, that the drawings are designed for
purposes of illustration only, and not as a definition of the
limits of the invention.
[0054] FIG. 1 is a schematic diagram of a prior art pin being used
in a flux imprinting device;
[0055] FIGS. 1A to 1D respectively show schematic diagrams of Steps
1 to 4 of a prior art method for imprinting flux material on a
substrate: FIG. 1A shows an array of prior art pins of a flux
imprinting device being immersed in flux material; FIG. 1B shows
the prior art pins loaded with the flux material and positioned
above a substrate to be imprinted; FIG. 1C shows the prior art pins
imprinting flux material on the substrate; and FIG. 1D shows the
prior art pins being removed from the substrate after flux
imprinting.
[0056] FIG. 2A shows a side view of a pin in accordance with an
embodiment of the invention;
[0057] FIG. 2B shows an end view of the pin of FIG. 2A;
[0058] FIG. 2C shows a close-up view of a distal end of the pin of
FIG. 2A;
[0059] FIG. 3 shows a flux imprint device having an array of the
pins disclosed in FIG. 2A;
[0060] FIG. 3A is a close-up of one of the pins of FIG. 3 loaded
with flux material;
[0061] FIGS. 4A to 4D respectively show schematic diagrams of a
method for imprinting flux material on a substrate in accordance
with an embodiment of the invention: FIG. 4A shows the array of
pins in accordance with an embodiment of the invention being
immersed in flux material; FIG. 4B shows the pins in accordance
with an embodiment of the invention being loaded with flux material
and positioned above a substrate to be imprinted; FIG. 4C shows the
pins in accordance with an embodiment of the invention imprinting
flux material on the substrate; and FIG. 4D shows the pins in
accordance with an embodiment of the invention being removed from
the substrate after flux imprinting.
DETAILED DESCRIPTION
[0062] Exemplary, non-limiting embodiments of a pin for allowing
material having adhesive properties to adhere thereon will now be
disclosed.
[0063] The pin comprises a shaft having a longitudinal axis, a
distal end and a proximal end. The pin also comprises a first
tapered portion disposed on a longitudinal axis of the shaft. The
first tapered portion tapers from a first circumference to a second
smaller circumference in a direction toward the proximal end of the
shaft. The pin may also comprise a second tapered portion disposed
on the longitudinal axis of the shaft between said first tapered
portion and said proximal end. The second tapered portion tapers
from a third circumference to a smaller fourth circumference in a
direction toward the distal end of the shaft.
[0064] Advantageously, in use, the taper angle of the first tapered
portion relative to the taper angle of the second tapered portion
at least partially inhibits flux creeping past the second tapered
portion. Advantageously, material creep or crawl is substantially
prevented from occurring on the shaft of the pin beyond the first
tapered portion.
[0065] In one embodiment, the pin comprises a third tapered portion
disposed on the longitudinal axis of the shaft between said first
tapered portion and said distal end. The third tapered portion
tapers from a fifth circumference to a sixth smaller circumference.
In one embodiment, the third tapered portion tapers in a direction
toward the proximal end of the shaft.
[0066] There may be a non-tapered section between the third tapered
portion and the first tapered portion.
[0067] There may be a non-tapered section between the first tapered
portion and the second tapered portion.
[0068] In one embodiment, the pin comprises a fourth tapered
portion disposed on the longitudinal axis of the shaft between said
third tapered portion and said first tapered portion. The fourth
tapered portion tapers from a seventh circumference to an eighth
smaller circumference. In one embodiment, the fourth tapered
portion tapers in a direction toward the distal end of the
shaft.
[0069] The sixth circumference of the third tapered portion and the
eighth circumference of the fourth tapered portion may be the
same.
[0070] In one embodiment, the fifth circumference of the third
tapered portion is less than at least one of the first
circumference of the first tapered portion and the third
circumference of the second tapered portion. In one embodiment, the
second circumference of the first tapered portion is the same as
the fourth circumference of the second tapered portion.
[0071] In one embodiment, the sixth circumference of the third
tapered portion is less than at least one of the second
circumference of the first tapered portion and the fourth
circumference of the second tapered portion.
[0072] The taper angles of the first and second tapered portions
may be the same or different. In one embodiment, the taper angle of
the second tapered portion is less than the taper angle of the
first tapered portion.
[0073] In one embodiment, the taper angle of the second tapered
portion is in the range selected from the group consisting of about
0.5.degree. to about 40.degree.; about 0.5.degree. to about
35.degree.; about 0.5.degree. to about 30.degree.; about
0.5.degree. to about 25.degree.; about 0.5.degree. to about
20.degree.; about 0.5.degree. to about 15.degree.; about
0.5.degree. to about 10.degree.; about 0.5.degree. to about
5.degree.; about 0.75.degree. to about 40.degree.; about 1.degree.
to about 40.degree.; about 1.5.degree. to about 40.degree.; about
2.degree. to about 40.degree.; and about 2.degree. to about
5.degree..
[0074] In one embodiment, the taper angle of the first tapered
portion is in the range selected from the group consisting of about
0.50 to about 60.degree.; about 0.5.degree. to about 50.degree.;
about 0.5.degree. to about 40.degree.; about 0.5.degree. to about
35.degree.; about 0.5.degree. to about 30.degree.; about
0.5.degree. to about 25.degree.; about 0.5.degree. to about
20.degree.; about 0.5.degree. to about 15.degree.; about
0.5.degree. to about 10.degree.; about 0.5.degree. to about
5.degree.; about 0.75.degree. to about 60.degree.; about 1.degree.
to about 60.degree.; about 1.5.degree. to about 60.degree.; about
2.degree. to about 60.degree.; and about 2.degree. to about
5.degree..
[0075] In one embodiment, the distal end of the pin may comprise an
end portion for providing a wear face at the end face of the distal
end. The end portion may be non-tapered. Advantageously, the end
portion may increase the life of the pin by providing a contact
surface that is subjected to wearing in use.
[0076] The tapered portions may form an integral structure with the
shaft. In other embodiments, the tapered portions may not be
integral formed with the shaft but may be attached to the
shaft.
[0077] In one embodiment, the shaft is circular shape when viewed
in cross-section transverse to the longitudinal axis. In other
embodiments, the shaft may be any shape, such as oval, square or
hexagonal etc, when viewed in a cross-sectional view transverse to
the longitudinal axis.
[0078] A proximal end of the shaft, opposite to the distal end, may
be mounted to a support. A biasing means may be provided between
the support and the proximal end to bias the pin along the
longitudinal axis in a direction toward the distal end.
[0079] The support may comprise a housing having a chamber. The
pins may partially extend into the chamber through a series of pin
holes provided in the housing. In one embodiment, the proximal ends
of the pins comprise a flange. The biasing means may be disposed
between the flanges of the pins and a wall of the chamber. The
flange may be used to abut the pin holes provided in the housing to
prevent the pins from moving when under the bias force.
[0080] In one embodiment, the biasing means is at least one spring.
In another embodiment, a spring may abut each of the pin
flanges.
[0081] In other embodiments, the biasing means comprises a plate
and one or more springs that bias the plate toward the flanges of
the pins. Other embodiments may comprise a rubber membrane backed
by a larger spring or sponge, or a rubber membrane biased by
pressurised air.
[0082] In one embodiment, there is provided a flux imprint
apparatus for imprinting flux material on a substrate. The flux
imprint apparatus comprises a support and an array of the pins
mounted to the support.
[0083] In one embodiment, there is also provided a method of
imprinting flux on a substrate using the flux imprint apparatus.
The method of imprinting flux material comprising the steps of:
[0084] (a) contacting the array of pins with flux material; and
[0085] (b) removing the array of pins from the flux material while
at least some flux material adheres to at least the first tapered
portion of the pins; and
[0086] (c) depositing flux material on a substrate by contacting
the distal ends of the pins on the substrate.
[0087] Advantageously, while the tapered portions at least
partially inhibit flux creep up the shaft, beyond the first tapered
portion.
[0088] The contacting step may comprise the step of inserting the
array of pins into flux material.
[0089] The depositing may comprise pressing the pins, having said
flux adhered to said distal ends of said pins, onto the substrate.
The method may comprise removing the pins from the substrate.
[0090] Non-limiting examples of the invention, including the best
mode, and a comparative example will be further described in
greater detail by reference to specific examples, which should not
be construed as in any way limiting the scope of the invention.
[0091] Referring to FIG. 2A there is shown a pin in accordance with
one exemplary embodiment of the invention. The pin 50 comprises a
longitudinal body in the form of shaft 52 having a proximal end
section 54 and a distal end section 56. The shaft 52 is circular
when viewed in cross section as shown by the end view of FIG. 2B. A
longitudinal axis 58 is shown by line 58 extending through the
shaft 52.
[0092] The pin 50 comprises a first tapered portion in the form of
tapered portion 68 that is disposed between distal end section 56
and proximal end section 54 of the shaft 52. The tapered portion 68
tapers in a direction toward the proximal end section 56 from a
first circumference 60C to a second smaller circumference 60B. The
pin 50 also comprises a second tapered portion in the form of
tapered portion 60 that is disposed between the proximal end
section 54 and tapered portion 68. The tapered portion 60 tapers in
a direction toward the distal end section 56 from circumference 60A
to a smaller circumference 60B.
[0093] The pin 50 also comprises a third tapered portion 74, which
can be seen in FIG. 2B. The third tapered portion 74 has a smaller
circumference when viewed from an end view than the circumference
of the tapered portions 60 and 68. The third tapered portion 74
tapers in a direction toward the tapered portion 68 from
circumference 74A to 74B.
[0094] The pin 50 also comprises a fourth tapered portion 75, which
can be seen in FIG. 2C. The fourth tapered portion 75 tapers in a
direction toward the third tapered portion 74 from circumference
68B to 74B.
[0095] The third tapered portion 74 also includes a wear portion in
the form of an end portion 76. The end portion 76 is provided at
the end face of the distal end section 56 to provide extra material
for wear and tear of the pin when in use. Accordingly, the end
portion 76 increases the working live of the pin.
[0096] The pin 50 is made by turning out on a lathe to form the
shape shown in FIG. 2A. The metal in this embodiment is stainless
steel. It should be noted that in other embodiments, the pins may
be made by placing molten metal in a mould to form the shape show
in FIG. 2A.
[0097] Referring now to FIG. 2C there is shown an enlarged view of
the distal end section 56 and the region approximate to the distal
end section 56. The enlarged view of FIG. 2C clearly shows the
tapered angles in this particular embodiment of the tapered
portions 60 and 68.
[0098] As can be seen in FIG. 2C, the tapered angle A of the
tapered portion 68 is larger than the tapered angle B of the
tapered portion 60. In this particular embodiment, the tapered
angle A is 4.degree. while the tapered angle B is 3.5.degree.. The
dimensions (which are exemplary) are as follows: diameter of the
shaft 52 is 0.4 mm; diameter of the circumference 60B is 0.16;
diameter of the circumference 60C is 0.23 mm; and diameter of the
circumference 74A is 0.16 mm.
[0099] The flux material has an inherent stickiness or tackiness
which results in the flux adhering to the tapered portion 68. The
shape of the flux on the pins is determined by its surface tensile
forces as well as the geometrical features of the pins.
[0100] Without being bound by theory, it is thought that flux
material, being liquid or quasi-liquid, will establish a stable
state shape by moving to or spreading over a solid region with
sufficient surface energy to stabilise itself with its own surface
tensile energy.
[0101] Flux will spread out along the conical surface of tapered
portion 68 to achieve equilibrium. The surface energy of the
tapered surface 68 increases with its circumference. As such, it
will tend to retain the flux towards the larger circumference and
thereby limit or inhibit flux creep toward the proximal ends
54.
[0102] The tapered portions (68,60) in FIG. 2C provide a changing
surface energy along the longitudinal axis 58 with larger
circumferences having larger surface energy. The relative angle of
the tapered portion 60 to the tapered portion 68 produces a
different rate of change in surface energy on the tapered surfaces
60 and 68 along its longitudinal axis 58. Because the taper angles
are in opposite directions, an opposing rate of change in surface
energy is formed along the longitudinal axis 58. The higher surface
energy on tapered surface 68 as opposed to the weaker surface
energy on tapered surface 60 limits the tendency for the flux to
creep beyond the tapered portion 68 towards tapered surface 60.
Accordingly, the profile created by the combination of the second
tapered portion 60 and the first tapered portion 68, achieves an
advantageous effect in that the flux material 88 that is deposited
thereon, and any residual flux material 88 on the distal ends 56 of
the pins 50, does not tend to creep beyond the first tapered
portion 68 towards the proximal ends 54 of the pins 50.
[0103] Referring now to FIG. 3, there is shown a flux imprint
device 80. The flux imprint device 80 comprises a support in the
form of pin housing 82 for mounting and supporting an array of pins
50. The proximal ends 54 of the pins 10 are mounted within a
chamber 84 of the pin housing 82. The pin housing 82 comprises a
plurality of pin conduits for allowing the pins 50 to be located
therein. The pins 50 are each biased by a set of springs 86 in the
direction of arrow 85. The springs 86 allow the pins 50 to be
subjected to a compressive force during loading of the flux and
during imprinting. The springs 86 also enable the array of pins 50
to conform to the contours of the surfaces on which the flux
material 88 is to be imprinted.
[0104] FIG. 3A illustrates a flux material 88 loaded distal end 56
of the pin 50. The contour shape of the distal end section 56
provided by the tapered portion 68 enables a "tear-drop" shape
droplet to be formed thereon. The attainment of such a shape
facilitates transfer of the droplet of flux material 88 from the
pin 50 to a substrate, leaves behind minimal residual flux material
at the distal end 56. Furthermore, it will be appreciated that flux
material does not creep up substantially past the tapered portion
68 due to the opposing force that is imparted by the tapered angle
B of the tapered portion 60.
[0105] Referring now to FIG. 4, there is shown a schematic diagram
of the various steps for imprinting flux material on a substrate.
The process involves lowering of the pins 50 into the flux material
88 provided in a flux tray 90 such that the distal ends 56 are
immersed in the flux material 88 as shown in FIG. 4A. The flux
material 88, due to its inherent adhesive properties, adheres to
the distal ends 56 when the pins are elevated from the flux tray
90. The springs 86 allow the pins to be movable so that any
excessive forces imparted to the springs 86 during the loading step
are dissipated by the springs 86.
[0106] The pins 50, loaded with the flux material 88 on the distal
ends 56 are then place over a substrate 92 which has a series of
recesses 94 for allowing the deposition of the flux material 88 as
shown in FIG. 4B.
[0107] The pins 50 are brought into contact with the recesses 94 of
the substrate 92 as shown in FIG. 4C. The array of pins 50 are
subsequently elevated from the substrate 92 and the flux material
88 imprinted thereon as shown in FIG. 4D.
[0108] Referring in particular to FIG. 4D, after imprinting, the
residual flux material 88 resides around the first tapered portions
68 at the distal ends 56 of the pins 50. The flux material 88 does
not creep upwards beyond the first tapered portion 68 and toward
the second tapered portion 60 and the shaft 52. Accordingly, the
pin in accordance with the embodiment, prevents material creep or
crawl from occurring on the shaft 52 of the pin 50 beyond the first
tapered portion 68.
[0109] As described above, the loading of the flux material 88 at
the distal end 56 of the pin 50 in the configuration of a
"tear-drop" shape droplet minimises the amount of residual flux
material 88 residing at the distal end 56 after imprinting.
Accordingly, bridging of the flux material 88 between the array of
pins 50 does not occur which could otherwise result in an uneven
deposition of the flux material 88 on the substrate 92.
[0110] It should be appreciated that the pins 50 may be used to
transfer not only flux material but other types of material that is
capable of adhering to the pin surface. Exemplary materials include
chemicals for genomics research using microarray printing.
[0111] It will be appreciated that the pins 50 provide a precise
amount of flux material to be deposited on the substrate at
soldering sites. This avoids the problems associated with prior art
pins. In particular, the pins 50 inhibit or prevent the
accumulation of flux on the pins, beyond the tapered portion 68
after successive dipping in flux material. Accordingly, pins 50
avoid or prevent creep up the shafts 52 in a direction toward the
proximal end section 54.
[0112] By avoiding flux creep, the pins 50 avoid the formation of
flux bridges forming there between and thereby avoid uneven
formation of small flux at the distal ends. The `tear-drop` shape
and size of the flux formed on the pins reduced and/or inhibits
flux creep so that flux deposition is much more consistent across
pins 50. The pins 50 therefore provide an even deposition of the
flux material on the substrate 92.
[0113] It will be apparent that various other modifications and
adaptations of the invention will be apparent to the person skilled
in the art after reading the foregoing disclosure without departing
from the spirit and scope of the invention and it is intended that
all such modifications and adaptations come within the scope of the
appended claims.
* * * * *