WO1999017595A1 - Solder ball placement with flux, template and laser tag - Google Patents

Solder ball placement with flux, template and laser tag Download PDF

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Publication number
WO1999017595A1
WO1999017595A1 PCT/SG1998/000056 SG9800056W WO9917595A1 WO 1999017595 A1 WO1999017595 A1 WO 1999017595A1 SG 9800056 W SG9800056 W SG 9800056W WO 9917595 A1 WO9917595 A1 WO 9917595A1
Authority
WO
WIPO (PCT)
Prior art keywords
template
solder ball
pads
balls
solder
Prior art date
Application number
PCT/SG1998/000056
Other languages
French (fr)
Inventor
Yun Sheng Cai
Tay Hock Lau
Original Assignee
Advanced Systems Automation Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Advanced Systems Automation Ltd. filed Critical Advanced Systems Automation Ltd.
Publication of WO1999017595A1 publication Critical patent/WO1999017595A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
    • H01L21/67005—Apparatus not specifically provided for elsewhere
    • H01L21/67011—Apparatus for manufacture or treatment
    • H01L21/67144—Apparatus for mounting on conductive members, e.g. leadframes or conductors on insulating substrates
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
    • H01L21/48—Manufacture or treatment of parts, e.g. containers, prior to assembly of the devices, using processes not provided for in a single one of the subgroups H01L21/06 - H01L21/326
    • H01L21/4814—Conductive parts
    • H01L21/4846—Leads on or in insulating or insulated substrates, e.g. metallisation
    • H01L21/4853—Connection or disconnection of other leads to or from a metallisation, e.g. pins, wires, bumps
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
    • H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
    • H05K3/34—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by soldering
    • H05K3/3457—Solder materials or compositions; Methods of application thereof
    • H05K3/3478—Applying solder preforms; Transferring prefabricated solder patterns
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
    • H05K2203/04—Soldering or other types of metallurgic bonding
    • H05K2203/041—Solder preforms in the shape of solder balls
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
    • H05K2203/04—Soldering or other types of metallurgic bonding
    • H05K2203/043—Reflowing of solder coated conductors, not during connection of components, e.g. reflowing solder paste
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
    • H05K2203/05—Patterning and lithography; Masks; Details of resist
    • H05K2203/0548—Masks
    • H05K2203/0557—Non-printed masks
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
    • H05K2203/10—Using electric, magnetic and electromagnetic fields; Using laser light
    • H05K2203/107—Using laser light
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
    • H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
    • H05K3/34—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by soldering
    • H05K3/3494—Heating methods for reflowing of solder

Definitions

  • the present invention relates to the use of soldering in the electrical connection between an IC device and a printed circuit board.
  • the present invention relates to the exact placement of solder balls on a ball grid array (BGA) device in the manufacturing process.
  • BGA ball grid array
  • BGA packaging of integrated circuit (IC) devices is gaining increasing importance in IC device production.
  • the IC chip is commonly mounted on a copper substrate with pads, whereon flux is applied followed by the placement of solder balls. The solder balls are then soldered onto the pads in a reflow oven.
  • the conventional method of ball placement is to use a vacuum suction head with the appropriate array of suction holes to pick up the soldering balls.
  • the balls sucked up in the proper array onto the head are then lowered onto a substrate with pre-applied flux.
  • This BGA assembly can then be conveyed to the reflow oven for soldering of the solder balls.
  • the number of interconnecting pads per chip can be as high as 1 ,000 to 2,000, compared to a low density BGA package of below 400 pads per chip for the same surface area.
  • the pitch (distance between solder balls) and solder ball size have to be reduced accordingly.
  • a low density BGA configuration of below 400 pads per chip with a pad diameter of 25 mil. and pitch of 50 mil. can use solder balls of 30 mil. diameter.
  • solder balls of 12 mil. diameter have to be used instead.
  • the first problem is placement problem. Due to the very small size and light weight of the solder balls, even a minute air turbulence or a minor warpage of the substrate might result in a displacement of the ball position. Because of the fine pitch required in high density arrays, even a slight displacement may result in bridging, which is the mixing of two soldering balls to form a connection during the process of soldering in a reflow oven. Once bridging occurs, the entire package has to be rejected. Consequently, conventional method of ball placement using the vacuum suction head results is high rejection rates due to bridging. The second problem is in the transfer of the packaging from the ball placement site to the reflow oven.
  • the present invention is a system for solder ball placement on pads of substrates of BGA packaging comprising means for template alignment, means for solder ball placement and a laser head.
  • a template is aligned with connection pads located on the surface of the substrate with pre- applied flux.
  • the aligned template allows accurate guiding of the balls onto the pads by the ball placement means.
  • One ball is dropped into each hole in the template directly onto a pad.
  • the balls positioned on the pads are then exposed for a short time to a laser via the laser head to cause partial melting of the balls. This short exposure to laser results in a gentle attachment or tagging of the balls onto the pad of the substrate. Once the balls are tagged, they can be transferred to the reflow oven without being easily displaced.
  • Figure 1 is a schematic illustration of template-guided ball placement step according to the present invention.
  • Figure 2 is a schematic illustration of the laser tagging step according to the present invention.
  • Figure 3 is a schematic diagram to show the positioning of a laser head for tagging of the solder ball.
  • Figure 4 is a flow diagram to illustrate the steps involved in the laser tagging system according to the present invention.
  • the present invention utilizes a combination of two separate techniques to the packaging of high density BGA devices. Applying either technique alone gives unsatisfactory results, but the combination of the two techniques in the proper sequence gives results that are synergistically superior to their expected additive benefits.
  • the first technique involves the use of a template to guide the release and placement of the ball from a conventional ball sucking head. Once the balls are properly placed above the substrate and within the template, the second technique of laser tagging is used, which causes localized melting of the solder balls. This results in the balls being gently attached or tagged to the substrate below. The template can then be removed and the device transferred onto the reflow oven for proper soldering. The result is BGA packaging with high quality soldering of the solder balls. Rejection due to bridging of solder balls is also minimized.
  • Figure 1 shows a schematic illustration of the first step in the ball placement process according to the present invention.
  • a template 22 of the high density array is placed over the substrate.
  • a ball sucking head 24 with solder balls in position is aligned over the substrate, using the template as a guide.
  • the ball sucking head may be a conventional one commonly used in BGA packaging, with the array adapted for high density devices.
  • the template can be a wire mesh with the mesh size of the required density.
  • the template may be made from any material which is heat tolerant such as stainless steel or aluminium.
  • a preferred material is stainless steel.
  • the wire of the mesh should be thick enough to prevent a solder ball from rolling over the wire.
  • the thickness of the wire of the mesh may be around 12 mil, to prevent the ball from rolling out of the cavity 27.
  • the surface area of the cavity should preferably be slightly larger than the diameter of the solder ball for ease of placement by the ball sucking head, and prevention of a ball getting easily attached to the wire mesh.
  • a preferred area is 15- 35% larger than the cross-sectional area of the solder ball.
  • Figure 2 illustrates how a matrix laser head is used to tag the solder balls.
  • the ball sucking head is moved away from the substrate after ball placement, and a laser head 30 is placed over the template and solder balls.
  • a short exposure of laser is given to the solder balls to cause localized melting, resulting in the tagging of the solder balls onto the substrate.
  • the laser head is preferably a gyroscope head or a matrix type head comprising of a series of optical fibers arranged in an identical array as the ball array.
  • Lasers such as neodymium.yttrium-aluminum-garnet (Nd.YAG) laser is suitable for tagging.
  • the exposure duration and intensity would depend on the size of the solder ball.
  • Figure 3 shows the alignment of the optic fibers of the laser head with the solder balls 28 placed inside the cavities 27 of the template 29 above the layer of flux 32.
  • the optical fibers are housed in a housing 34 which fixes the position of the optical fibers 36 to match the position of the pads and the solder balls.
  • the wire mesh of the template has a height 26 approximately the same as the diameter of the solder balls.
  • Figure 4 is a flow diagram to show process according to the present invention.
  • the template is aligned with the substrate followed by ball placement with the ball sucking head 42.
  • a visual check 44 is preferably performed with a camera for example a CCD (capacitor charge device) camera to ensure that the balls are placed properly, followed by laser tagging 46.
  • Steps 42-46 are preferably performed with the package stationary to minimize any disturbance to the balls once they are placed onto the substrate.
  • the last step 48 is the transfer of the package to the reflow oven for soldering of the balls.

Abstract

A system for solder ball (28) placement on BGA packaging comprising means for template alignment, means for solder ball placement and a laser head (36). A template (29) is aligned with connection pads located on the surface of the substrate with pre-applied flux. The aligned template allows accurate guiding of the balls onto the pads by the ball placement means. One ball is dropped into each hole (27) in the template directly onto the pad. The balls positioned on the pads are then exposed for a short time to a laser via the laser head to cause partial melting of the balls. This short exposure to laser results in a gentle attachment or tagging of the balls onto the pad of the substrate. Once the balls are tagged, they can be transferred to the reflow oven without being easily displaced.

Description

SOLDER BALL PLACEMENT WITH FLUX, TEMPLATE AND
LASER TAG
FIELD OF THE INVENTION
The present invention relates to the use of soldering in the electrical connection between an IC device and a printed circuit board. In particular, the present invention relates to the exact placement of solder balls on a ball grid array (BGA) device in the manufacturing process.
BACKGROUND OF THE INVENTION
Ball grid array (BGA) packaging of integrated circuit (IC) devices is gaining increasing importance in IC device production. In BGA packaging, the IC chip is commonly mounted on a copper substrate with pads, whereon flux is applied followed by the placement of solder balls. The solder balls are then soldered onto the pads in a reflow oven.
The conventional method of ball placement is to use a vacuum suction head with the appropriate array of suction holes to pick up the soldering balls. The balls sucked up in the proper array onto the head are then lowered onto a substrate with pre-applied flux. This BGA assembly can then be conveyed to the reflow oven for soldering of the solder balls.
Current trend in IC chip production is for greater IC density per chip. The higher the IC density, the greater the number of interconnects required on the same chip size. Therefore, there has been a demand for BGA packages with higher density pads and solder balls. In these high density BGA packages, the number of interconnecting pads per chip can be as high as 1 ,000 to 2,000, compared to a low density BGA package of below 400 pads per chip for the same surface area. For high density packages above 400 pads per chip, the pitch (distance between solder balls) and solder ball size have to be reduced accordingly. For example, a low density BGA configuration of below 400 pads per chip with a pad diameter of 25 mil. and pitch of 50 mil. can use solder balls of 30 mil. diameter. In the case of high density BGA configurations for example with pads diameter of 10 mil. and pitch of 20 mil., solder balls of 12 mil. diameter have to be used instead.
This reduced pitch and ball size poses a problem for the soldering process. The first problem is placement problem. Due to the very small size and light weight of the solder balls, even a minute air turbulence or a minor warpage of the substrate might result in a displacement of the ball position. Because of the fine pitch required in high density arrays, even a slight displacement may result in bridging, which is the mixing of two soldering balls to form a connection during the process of soldering in a reflow oven. Once bridging occurs, the entire package has to be rejected. Consequently, conventional method of ball placement using the vacuum suction head results is high rejection rates due to bridging. The second problem is in the transfer of the packaging from the ball placement site to the reflow oven. Even if the solder balls were placed accurately, the movement necessary to transfer the packaging to the reflow oven would cause the balls to be displaced. There is therefore a need to improve the packaging process by designing new concepts of ball placement which would prevent displacement of the solder balls and bridging. OBJECT OF THE INVENTION
It is an object of the present invention to provide a method of small solder ball placement in the packaging of BGA devices.
It is another object to reduce the occurrence of solder ball bridging in the BGA assembly process.
SUMMARY OF THE INVENTION
The present invention is a system for solder ball placement on pads of substrates of BGA packaging comprising means for template alignment, means for solder ball placement and a laser head. A template is aligned with connection pads located on the surface of the substrate with pre- applied flux. The aligned template allows accurate guiding of the balls onto the pads by the ball placement means. One ball is dropped into each hole in the template directly onto a pad. The balls positioned on the pads are then exposed for a short time to a laser via the laser head to cause partial melting of the balls. This short exposure to laser results in a gentle attachment or tagging of the balls onto the pad of the substrate. Once the balls are tagged, they can be transferred to the reflow oven without being easily displaced.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic illustration of template-guided ball placement step according to the present invention.
Figure 2 is a schematic illustration of the laser tagging step according to the present invention.
Figure 3 is a schematic diagram to show the positioning of a laser head for tagging of the solder ball.
Figure 4 is a flow diagram to illustrate the steps involved in the laser tagging system according to the present invention.
DESCRIPTION OF THE INVENTION
The present invention utilizes a combination of two separate techniques to the packaging of high density BGA devices. Applying either technique alone gives unsatisfactory results, but the combination of the two techniques in the proper sequence gives results that are synergistically superior to their expected additive benefits. The first technique involves the use of a template to guide the release and placement of the ball from a conventional ball sucking head. Once the balls are properly placed above the substrate and within the template, the second technique of laser tagging is used, which causes localized melting of the solder balls. This results in the balls being gently attached or tagged to the substrate below. The template can then be removed and the device transferred onto the reflow oven for proper soldering. The result is BGA packaging with high quality soldering of the solder balls. Rejection due to bridging of solder balls is also minimized.
Figure 1 shows a schematic illustration of the first step in the ball placement process according to the present invention. After flux is applied to the substrate 20 according to conventional methods, a template 22 of the high density array is placed over the substrate. A ball sucking head 24 with solder balls in position is aligned over the substrate, using the template as a guide. When the array in the ball sucking head is aligned with the array of the template, the vacuum on the ball sucking head is released, and the solder balls drop onto the substrate with flux. The ball sucking head may be a conventional one commonly used in BGA packaging, with the array adapted for high density devices. The template can be a wire mesh with the mesh size of the required density. The template may be made from any material which is heat tolerant such as stainless steel or aluminium. A preferred material is stainless steel. The wire of the mesh should be thick enough to prevent a solder ball from rolling over the wire. For example, for a solder ball with diameter of 12 mil, the thickness of the wire of the mesh, as indicated by reference numeral 26 of Figure 3, may be around 12 mil, to prevent the ball from rolling out of the cavity 27. In addition, the surface area of the cavity should preferably be slightly larger than the diameter of the solder ball for ease of placement by the ball sucking head, and prevention of a ball getting easily attached to the wire mesh. A preferred area is 15- 35% larger than the cross-sectional area of the solder ball.
Figure 2 illustrates how a matrix laser head is used to tag the solder balls. The ball sucking head is moved away from the substrate after ball placement, and a laser head 30 is placed over the template and solder balls. A short exposure of laser is given to the solder balls to cause localized melting, resulting in the tagging of the solder balls onto the substrate. The laser head is preferably a gyroscope head or a matrix type head comprising of a series of optical fibers arranged in an identical array as the ball array. Lasers such as neodymium.yttrium-aluminum-garnet (Nd.YAG) laser is suitable for tagging. The exposure duration and intensity would depend on the size of the solder ball.
Figure 3 shows the alignment of the optic fibers of the laser head with the solder balls 28 placed inside the cavities 27 of the template 29 above the layer of flux 32. The optical fibers are housed in a housing 34 which fixes the position of the optical fibers 36 to match the position of the pads and the solder balls. The wire mesh of the template has a height 26 approximately the same as the diameter of the solder balls.
Figure 4 is a flow diagram to show process according to the present invention. After flux application 40, the template is aligned with the substrate followed by ball placement with the ball sucking head 42. After step 42, a visual check 44 is preferably performed with a camera for example a CCD (capacitor charge device) camera to ensure that the balls are placed properly, followed by laser tagging 46. Steps 42-46 are preferably performed with the package stationary to minimize any disturbance to the balls once they are placed onto the substrate. The last step 48 is the transfer of the package to the reflow oven for soldering of the balls.
While the present invention has been described particularly with references to Figs 1 and 4, it should be understood that the figures are for illustration only and should not be taken as limitation on the invention. It is contemplated that many changes and modifications may be made by one of ordinary skill in the art without departing from the spirit and the scope of the invention described.

Claims

1. A system for solder ball placement for ball grid array packaging of an IC chip with a substrate having an array of pads comprising :
means for template alignment;
a template with an array of cavities matching said array of pads,
means for solder ball placement and
a laser module with a laser head adapted to send at least one laser beam onto said solder balls,
said system performing the sequential steps of :
aligning said cavities of said template with said array of pads having pre-applied flux;
aligning said means for solder ball placement with said substrate using said template as a guide so that an array of solder balls is aligned with said array of pads;
discharging said aligned solder balls onto said pads with pre-applied flux so that one solder ball is placed within each cavity of said template;
aligning said laser head with said substrate; and
discharging a laser beam directly onto said solder ball such that said solder balls are lightly melted and tagged onto said pad.
2. A system for solder ball placement according to claim 1 wherein said system further comprises a camera, and an additional step of visual checking is performed after solder ball placement.
3. A system for solder ball placement of ball grid array packaging according to claim 1 wherein said laser head is a matrix laser head.
4. A system for solder ball placement of ball grid array packaging according to claim 1 wherein said laser head delivers a Nd:YAG laser beam.
5. An apparatus for solder ball placement of ball grid array packaging of an IC chip with a substrate having an array of pads for interconnection comprising :
means for template alignment;
means for solder ball placement onto said pads; and
a laser head adapted to send a laser beam onto said solder balls.
PCT/SG1998/000056 1997-09-26 1998-07-06 Solder ball placement with flux, template and laser tag WO1999017595A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SG9703592-7 1997-09-26
SG1997003592A SG67424A1 (en) 1997-09-26 1997-09-26 Solder ball placement with flux template and laser tag

Publications (1)

Publication Number Publication Date
WO1999017595A1 true WO1999017595A1 (en) 1999-04-08

Family

ID=20429749

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SG1998/000056 WO1999017595A1 (en) 1997-09-26 1998-07-06 Solder ball placement with flux, template and laser tag

Country Status (3)

Country Link
SG (1) SG67424A1 (en)
TW (1) TW352351B (en)
WO (1) WO1999017595A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6412680B1 (en) * 2000-09-26 2002-07-02 Agere Systems Guardian Corp. Dual-in-line BGA ball mounter
EP1439744A2 (en) * 2003-01-15 2004-07-21 Senju Metal Industry Co., Ltd. Apparatus and method for aligning and attaching solder columns to a substrate

Non-Patent Citations (5)

* Cited by examiner, † Cited by third party
Title
1ST 1997 IEMT/IMC SYMPOSIUM, (IEEE Cat. No. 97CH36056), Published Tokyo, Japan 1997, "High Density BGA Substrates Fabricated by Laser Technology", HIRAKAWA T. et al., pages 295-298. *
DERWENT ABSTRACT, Accession No. 96-281730/29, Class L03, M23; & JP 08118005 A (MATSUSHITA DENKI SANGYO KK) 14 May 1996. *
PROCEEDINGS OF THE TECHNICAL PROGRAM, NATIONAL ELECTRONIC PACKAGING AND PRODUCTION CONFERENCE, NEPCON EAST 1994, Published STANFORD, CT, USA, "An Overview of Advancements in Surface Mount and Fine Pitch Technology", RUA R., pages 336-343. *
RECENT PROGRESS IN PRINTED CIRCUIT BOARD TECHNOLOGY, Berlin, Germany, 27-29 Jan. 1997, "Solder Ball Bumping for Printed Circuit Boards", KASULKE P. et al., page 176. *
SOLID STATE TECHNOLOGY, Vol. 39, No. 9, PENNWELL PUBLISHING USA, September 1996, "Laser Drilling Speeds BGA Packaging", LIZOTTE T. et al., pages 120-122, 124, 127, 128. *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6412680B1 (en) * 2000-09-26 2002-07-02 Agere Systems Guardian Corp. Dual-in-line BGA ball mounter
EP1439744A2 (en) * 2003-01-15 2004-07-21 Senju Metal Industry Co., Ltd. Apparatus and method for aligning and attaching solder columns to a substrate
EP1439744A3 (en) * 2003-01-15 2005-04-13 Senju Metal Industry Co., Ltd. Apparatus and method for aligning and attaching solder columns to a substrate

Also Published As

Publication number Publication date
SG67424A1 (en) 1999-09-21
TW352351B (en) 1999-02-11

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