Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – With contact or lead
Reexamination Certificate
1999-02-16
2004-07-06
Graybill, David E. (Department: 2827)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
With contact or lead
C257S700000, C257S737000, C257S738000
Reexamination Certificate
active
06759738
ABSTRACT:
FIELD OF THE INVENTION
The fields of this invention are the production of flip-chips, the reflow solder attachment of flip-chips to chip carriers to form modules, the making of chip carriers, modules, and other components including surface mount components, especially surface-to-surface attachment components such as ball grid array (BGA) modules, and especially the deposition of solder on terminals of these surface mount components (SMC's), reflow solder attachment of such components to circuit-boards, use of resulting assemblies in manufacturing information handling systems, print screening, screen printing machines, production of printing screens, production of solder preforms, and deposition of solder paste and solder preforms onto substrates especially reflow transfer from an applicay.
The following background along with the other parts of this application enables those skilled in the art in utilizing the inventions of this application without undo experimentation and is not an admission regarding priority or claim that a search has been performed.
BACKGROUND OF THIS INVENTION
Solder bump connections have been used for mounting IC's (integrated computer chips) using the C4 (controlled collapse chip connection) technology since first suggested in U.S. Pat. No. 3,401,126 and 3,429,040 by Miller. In
Packaging Electronic Systems
by Dally (McGraw-Hill 1990 p. 113) “Chip bond pads are deployed in an area array over the surface of the chip. . . . These bonding pads are 5 mil in diameter on 10 mil centers. Matching bonding pads are produced on a ceramic substrate so that the pads on the chip and the ceramic coincide. Spheres of solder 5 mil in diameter are placed on the ceramic substrate pads . . . and the chip is positioned and aligned relative to the substrate. The assembly is heated until the solder spheres begin to soften and a controlled collapse of the sphere takes place as the solder simultaneously wets both pads. A myriad of solder structures have been proposed for mounting IC chips as well as for interconnection to other levels of circuitry and electronic packaging.”
Reflow transfer of solder from decals has been developed for depositing eutectic solder for attaching flip chips to metal pads on organic substrates. Stainless steel decals are coated with a thin layer of photoresist which is photo-developed to provide windows in the same pattern as C
4
connectors on a flip chip. A thick layer of eutectic Pb/Sn solder is electroplated onto the decals at the windows. The decal is positioned on an organic carrier aligned with connection pads and heated to reflow transfer the solder from the decal onto the pads on the carrier. Then a flip chip is placed on the carrier with C4 pads on the solder and reflow:heated to connect the chip to the pads.
Use of epoxy encapsulants to enhance fatigue life of flip-chip connection is suggested in U.S. Pat. Nos. 4,999,699; 5,089,440, and 5,194,930 mall to Christie. U.S. Pat. No. 4,604,644 to Beckham suggests materials and structures for encapsulating C4 connections. U.S. Pat. No. 4,701,482 to Itoh and U.S. Pat. No. 4,999,699 of Christie et al. disclose epoxies and provide guidance in selecting epoxies for electronic applications.
“Ball grid arrays: the hot new package” by Terry Costlow and “Solder balls make connections” by Glenda Derman both in Electronic
Engineering Times
Mar. 15, 1993, suggest using solder balls to connect ceramic or flexible chip carriers to circuit-boards. Ball grid array modules include components with plastic (organic), ceramic, and tape carrier substrates known as PBGA, CBGA, and TBGA molues respectively.
Fabrication of multi-layer ceramic chip carriers is suggested in U.S. Pat. Nos. 3,518,756; 3,988,405; and 4,202,007 as well as “A Fabrication Technique For Multi-Layer Ceramic Modules” by H. D. Kaiser et al.,
Solid State Technology,
May 1972, pp. 35-40 and “The Third Dimension in Thick-Films Multilayer Technology” by W. L. Clough,
Microelectronics,
Vol. 13, No. 9 (1970), pp. 23-30. Common ceramic materials for electronic packaging substrates include alumina, beryllia, and aluminum nitride. “Pinless Module Connector” by Stephans in
IBM Technical Disclosure Bulletin
Vol. 20, No. 10, March 1978, suggests a ceramic ball grid array module with copper balls. U.S. Pat. No. 5,118,027 to Braun suggests placing solder balls in an alignment boat, vacuum holding the balls while eutectic solder is deposited on the balls, aligning the boat with conductive pads on a substrate, reflowing in an oven and then removing the boat. EP 0,263,222 A1 to Bitaillou suggest attaching solder balls to vias in a ceramic substrate to form a ball grid array module.
U.S. Pat. No. 4,914,814 to Behun, suggests casting columns onto pads to form ceramic column grid array modules, a graphite plate is drilled with through-holes corresponding to metal pads on the bottom of a chip carrier substrate, then preforms of 3/97 Sn/Pb solder are placed in the holes. Then the plate and carrier substrate are heated to melt the preforms to connect liquid solder to the pads, then the plate and carrier substrate are cooled and the plate is moved away from the carrier leaving the columns cast to the pads.
U.S. Pat No. 4,752,027 to Gschwend suggests methods of bumping printed circuit boards for attaching modules, including screening solder paste, reflowing the paste to form bumps, and using:rollers to flatten the solder bumps. U.S. Pat No. 4,558,812 to Bailey suggests using a vacuum plate to simultaneously deposit an array of solder balls on a substrate.
Fabrication of multi-layer rigid organic circuit-boards is suggested in U.S. Pat Nos. 3,554,877; 3,791,858; and 3,554,877. Thin film Techniques are suggested in U.S. Pat. No. 3,791,858.
Flexible film chip carriers (known in the art as Area Tape Automated Bonding (ATAB) modules or TBGA modules) are suggested in U.S. Pat Nos. 4,681,654 and 5,159,535 and 4,766,670. In ATAB a flexible circuit-board chip carrier is mounted on a circuit-board using solder ball connect. U.S. Pat. No. 5,057,969 to Ameen, and U.S. Pat. Nos. 5,133,495, 5,203,075, and 5,261,155 to Angulas suggests using solder balls to connect TBGA modules to circuit boards.
U.S. Pat No. 5,261,593 to Casson suggests providing solder paste on a plurality of contact pads on a flexible printed circuit substrate (polyimide); placing flip-chips on the substrate with solder bumps of the flip-chip in registration with the pads; and heating to reflow the paste to electrically connect the bumps to the pads. According to Casson bumped flip-chips are un-packaged meaning they have no plastic shells nor metallic leads. Casson describes bumping chips (C4) by sputtering titanium/tungsten to promote adhesion to a passivation layer; sputtering copper; applying and developing a photoresist; electroplating copper and then 3/97 to 10/90 Sn/Pb or 63/35/2 Pb/Sn/Ag solder; removing the photoresist; and wet etching the exposed copper and titanium/tungsten to form 9 mil diameter bumps about 4.5 mil high (60 mils
3
). He also suggests producing flexible Novaclad® (polyimide film with sputtered copper by E. I Du Pont de Nuemers) circuit substrates; optical alignment of stencils with substrates; screening 63/37 Sn/Pb solder paste through a 4 mil stencil with 14 mil openings with a round squeegee of 90 durometer at 1.5 inches/second and 22 psi pressure to provide 6E-7 in
3
deposits on pads of flexible substrates; self alignment during reflow heating using vapor phase or in IR or convection ovens; and epoxy chip encapsulation.
U.S. Pat No. 3,781,596 suggests a single layer interconnection structure of metallic conductors on a polyimide film (e.g. KAPTON. by E. I. DuPont de Numers). U.S. Pat No. 3,868,724 suggests metallic conductors sandwiched between polyimide film, which projects through the film. U.S. Pat No. 5,112,462 to Swisher suggests producing adhesivless flexible substrates of polyimide film and copper sputtered and then electroplated onto the film.
Floropolymer based films have been proposed for flexible circuit-boards such as PTFE filled with ceramic, or glass par
Fallon Kenneth Michael
Le Coz Christian Robert
Pierson Mark Vincent
Graybill David E.
International Business Machines - Corporation
Pivnichny John R.
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