Apparatus for surface mounting flip chip carrier modules

• US 5,535,526 A
• Filed: 05/25/1995
• Issued: 07/16/1996
• Est. Priority Date: 01/07/1994
• Status: Expired due to Fees

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: White, Lawrence H.
• Primary Examiner(s): Sollecito, John M.
• Assistant Examiner(s): GRAVINI, STEPHEN MICHAEL
• Application Number:
  US08/450,845
• Time in Patent Office: 418 Days
• Field of Search: 228/6.2, 228/8, 228/180.22, 29/739, 29/874, 34/77, 34/78, 34/80, 34/181, 34/202
• US Class Current: 34/78
• CPC Class Codes: H01L 21/563 Encapsulation of active face of flip-chip device, e.g. underfilling or underencapsulation of flip-chip, encapsulation preform on chip or mounting substrate
• CPC Class Codes: H01L 2224/13111 Tin [Sn] as principal constituent
• CPC Class Codes: H01L 2224/16 of an individual bump connector
• CPC Class Codes: H01L 2224/73203 Bump and layer connectors
• CPC Class Codes: H01L 2224/73253 Bump and layer connectors
• CPC Class Codes: H01L 2224/81801 Soldering or alloying
• CPC Class Codes: H01L 24/81 using a bump connector
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/01005 Boron [B]
• CPC Class Codes: H01L 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01013 Aluminum [Al]
• CPC Class Codes: H01L 2924/01019 Potassium [K]
• CPC Class Codes: H01L 2924/01029 Copper [Cu]
• CPC Class Codes: H01L 2924/01033 Arsenic [As]
• CPC Class Codes: H01L 2924/01045 Rhodium [Rh]
• CPC Class Codes: H01L 2924/0105 Tin [Sn]
• CPC Class Codes: H01L 2924/01074 Tungsten [W]
• CPC Class Codes: H01L 2924/01078 Platinum [Pt]
• CPC Class Codes: H01L 2924/01082 Lead [Pb]
• CPC Class Codes: H01L 2924/01087 Francium [Fr]
• CPC Class Codes: H01L 2924/01322 : Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/15153 : the die mounting substrate comprising a recess for hosting the device
• CPC Class Codes: H01L 2924/1517 : Multilayer substrate
• CPC Class Codes: H01L 2924/15311 : being a ball array, e.g. BGA
• CPC Class Codes: H01L 2924/15312 : being a pin array, e.g. PGA
• CPC Class Codes: H01L 2924/1532 : the connection portion being formed on the die mounting surface of the substrate
• CPC Class Codes: H01L 2924/15787 : Ceramics, e.g. crystalline carbides, nitrides or oxides
• CPC Class Codes: H01L 2924/16195 : Flat cap [not enclosing an internal cavity]
• CPC Class Codes: H05K 2201/10477 : Inverted
• CPC Class Codes: H05K 2201/10977 : Encapsulated connections
• CPC Class Codes: H05K 2201/10992 : Using different connection materials, e.g. different solders, for the same connection
• CPC Class Codes: H05K 2203/041 : Solder preforms in the shape of solder balls
• CPC Class Codes: H05K 2203/0415 : Small preforms other than balls, e.g. discs, cylinders or pillars
• CPC Class Codes: H05K 3/284 : for encapsulating mounted components H05K1/185 takes precedence
• CPC Class Codes: H05K 3/3436 : having an array of bottom contacts, e.g. pad grid array or ball grid array components
• CPC Class Codes: Y02P 70/50 : Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y10T 29/49144 : by metal fusion
• CPC Class Codes: Y10T 29/49204 : Contact or terminal manufacturing
• CPC Class Codes: Y10T 29/53174 : Means to fasten electrical component to wiring board, base, or substrate

Abstract

A process for handling and storing surface-mount, encapsulated flip-chip carrier modules to prevent the formation of amoeba-like solder bridges between the flip-chip C4 connections along the boundary between the encapsulant and the chip surface and/or between the encapsulant and the chip carrier substrate surface. The concentration of free moisture in the encapsulant is maintained below a predetermined safe limit during reflow heating used to mount the modules on a circuit board.

Claims

1. Apparatus for manufacturing an interconnect assembly, comprising:

an organic, flip-chip carrier substrate;

a flip-chip connected directly to the substrate using an array of reflow solder connections, to form a flip-chip carrier with the chip separated from the substrate by a volume around the connections;

an organic encapsulant material filling the volume between the substrate and connected flip-chip to protect the solder connections and form a finished carrier; and

means for controlling the level of moisture in the encapsulant between the flip-chip and carrier substrate to provide a sufficiently low level for subsequent solder attachment without forming solder bridges between the connections.

2. The apparatus of claim 1 in which the means for controlling the level of moisture includes means to prevent the diffusion of moisture into the encapsulant in the carrier.

3. The apparatus of claim 2 in which the means to prevent the diffusion of moisture includes means to store the finished carrier at an temperature elevated above ambient of at least about 40°

C.

4. The apparatus of claim 2 in which the means for controlling the diffusion of moisture include means to store the finished carrier in a sealed approximately air tight bag.

5. The apparatus of claim 1 in which the means for controlling the level of moisture includes means to heat the finished carrier for baking the finished carrier at a temperature of at least 100°

C.

6. The apparatus of claim 2 in which the means for controlling the diffusion of moisture includes means to assure using finished carriers within one week of their exposure to ambient atmosphere.

7. The apparatus of claim 4 in which means to store finished carrier in a sealed bag include:

a sealed plastic approximately air tight bag enclosing a multiple of finished carriers; and

containers of dessicant material exposed to an atmosphere in the plastic bag, enclosed in the plastic bag with the finished carriers.

8. The apparatus of claim 5 in which the means for baking the finished carrier includes means to heat the finished carrier to at least 125°

C.

9. The apparatus of claim 5 further including timing means to assure that the finished carrier is heated for a sufficient time.

10. The apparatus of claim 9 further including timing means to assure that the finished carrier is heated at least 12 hours.

11. The apparatus of claim 5 further including means for determining the time or temperature of baking depending on the humidity level or time of exposure to moisture.

12. The apparatus of claim 1 in which the organic substrate is a flexible laminate including layers of polyimide and copper.

13. The apparatus of claim 1 in which the substrate includes reinforcing fibers.

14. The apparatus of claim 13 in which the fibers are fiberglass and the substrate includes an epoxy filler.

15. The apparatus of claim 4 in which the bag contains dessicant.