Assembly aid for mounting packaged integrated circuit devices to printed circuit boards

• US 6,084,781 A
• Filed: 06/04/1998
• Issued: 07/04/2000
• Est. Priority Date: 11/05/1996
• Status: Expired due to Term

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micro Electronics Incorporated
• Inventors: Klein, Dean A.
• Primary Examiner(s): Picard, Leo P.
• Assistant Examiner(s): Vigushin, John B.
• Application Number:
  US09/090,966
• Time in Patent Office: 761 Days
• Field of Search: 29/840, 29/843, 29/852, 174/255, 174/260, 174/261, 174/258, 174/263, 174/265, 228/180.21, 228/180.22, 228/187, 257/723, 257/724, 257/737, 257/738, 257/747, 257/748, 257/772, 257/778, 257/779, 257/780, 257/786, 257/774, 361/760, 361/772, 361/773, 361/774, 361/779, 361/782, 361/783, 361/803, 361/767, 361/768, 361/771, 361/777, 438/106, 439/68, 439/69, 439/74, 439/83, 439/179
• US Class Current: 361/771
• CPC Class Codes: H01L 2224/16235 the bump connector connecting to a via metallisation of the item
• CPC Class Codes: H01L 2224/16237 the bump connector connecting to a bonding area disposed in a recess of the surface of the item
• CPC Class Codes: H01L 2224/27438 the preform being at least partly pre-patterned
• CPC Class Codes: H01L 2224/81136 involving guiding structures, e.g. spacers or supporting members
• CPC Class Codes: H01L 2224/81191 wherein the bump connectors are disposed only on the semiconductor or solid-state body
• CPC Class Codes: H01L 2224/81801 Soldering or alloying
• CPC Class Codes: H01L 24/13 of an individual bump connector
• CPC Class Codes: H01L 24/16 of an individual bump connector
• CPC Class Codes: H01L 24/81 using a bump connector
• CPC Class Codes: H01L 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01033 Arsenic [As]
• CPC Class Codes: H01L 2924/01047 Silver [Ag]
• CPC Class Codes: H01L 2924/0105 Tin [Sn]
• CPC Class Codes: H01L 2924/01082 Lead [Pb]
• 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 2924/3511 Warping
• CPC Class Codes: H05K 2201/10424 Frame holders
• CPC Class Codes: H05K 2201/10734 Ball grid array [BGA]; Bump grid array
• CPC Class Codes: H05K 2203/0415 : Small preforms other than balls, e.g. discs, cylinders or pillars
• CPC Class Codes: H05K 2203/167 : Using mechanical means for positioning, alignment or registration, e.g. using rod-in-hole alignment
• 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 29/49165 : by forming conductive walled aperture in base

Abstract

An apparatus and method for surface-mounting ball grid array integrated circuit (IC) devices to printed circuit boards. A thin single- or multi-layer sheet of nonconductive material having a plurality of apertures corresponding to the leads of the IC device to be mounted is interposed between the ball grid array and the circuit board prior to solder processing to facilitate solder application, device alignment, and solder retention. An assembly guide is located on the top surface of the aid to assist in the orientation and placement of the IC device during assembly. In a further aspect, the disclosed assembly aid helps compensate for non-planarity in the IC device array or circuit board, and maintains a minimum standoff distance between the IC package and the circuit board to preclude undue solder joint deformation. The assembly aid also allows for reworking of the surface mount by facilitating localized placement of the solder prior to reflow processing without masking or other additional processing steps.

Claims

1. An assembly aid for mounting an integrated circuit device having connecting leads to a circuit board, comprising:

a plurality of solidified solder elements, said elements being shaped to receive respective ones of said connecting leads; and

a mounting substrate communicating at least in part with said circuit board and having at least a first layer and second layer, said first layer having a plurality of first apertures substantially corresponding to the location of said connecting leads, said first apertures further receiving said solidified solder elements therein, and said second layer having a plurality of second apertures substantially corresponding to the location of said first apertures, said second apertures being sized so as to prevent said solder elements from passing through said second apertures.

2. The assembly aid of claim 1, wherein said assembly aid, integrated circuit device, and circuit board is installed in a computer system.

3. The assembly aid of claim 1, wherein said circuit board is selected from the group consisting of a video processor card, a computer motherboard, a network interface card, a memory card, and a graphics processor card.

4. The assembly aid of claim 1, wherein said solidified solder elements are selected from the group of shapes comprising a toroid, a cylinder, a square block, a rectangular block, or a polygonal block.

5. The assembly aid of claim 1, wherein said solidified solder elements include a flux coating.

6. The assembly aid of claim 1, wherein the integrated circuit device comprises a ball grid array.

7. The assembly aid of claim 1, wherein the cross-section of said first or second apertures is selected from the group comprising a circle, square, rectangle, ellipse, or polygon.

8. The assembly aid of claim 1, wherein said solidified solder elements have holes through their thickness to receive said connecting leads.

9. An assembly aid for mounting an integrated circuit device having a plurality of leads to a circuit board, comprising:

a plurality of solidified solder elements, said elements being shaped to receive respective ones of said leads;

a mounting substrate having at least a first layer and a second layer;

said first layer having a plurality of first apertures substantially corresponding to the location of said leads, said first apertures further being sized to receive said solidified solder elements therein, said second layer having a plurality of second apertures substantially corresponding to the location of said first apertures, said second apertures being sized so as to prevent said solder elements from passing through said second apertures; and

an adhesive layer communicating with said first mounting substrate layer so as to retain said solder elements substantially within said first apertures.

10. A circuit board having an integrated circuit device with connecting leads, assembled by a process comprising the steps of:

providing a mounting substrate having a plurality of first and second apertures, the relative positions of both said first and second apertures corresponding to those of the connecting leads of the integrated circuit device, said second apertures having a smaller diameter than said first apertures and communicating therewith;

locating solder material substantially upon said mounting substrate such that said solder material communicates with selected first apertures of said substrate,

applying an adhesive layer to said mounting substrate such that said solder material is retained substantially within said first apertures;

attaching said mounting substrate to said circuit board;

positioning the integrated circuit device adjacent to said mounting substrate such that the connecting leads of the integrated circuit communicate with said first apertures and said solder material, so as to form an assembly; and

heating said assembly so as to melt said solder material to form an electrical contact between said integrated circuit and said circuit board.

11. The circuit board of claim 10, wherein said circuit board having said integrated circuit device is installed in a computer system.

12. The circuit board of claim 10, wherein said circuit board is selected from the group comprising a video processor card, a computer motherboard, a network interface card, a memory card, and a graphics processor card.

13. The assembly aid of claim 10, wherein said solder material is in the form of one or more solidified solder elements.

14. The assembly aid of claim 13, wherein the cross-section of said solder elements is selected from the group of shapes comprising a toroid, a cylinder, a square block, a rectangular block, or a polygonal block.

15. The assembly aid of claim 13, wherein said solidified solder elements include a flux coating.

16. The assembly aid of claim 10, wherein the integrated circuit device comprises a ball grid array.

17. The assembly aid of claim 10, wherein the cross-section of said first or second apertures is selected from the group comprising a circle, square, rectangle, ellipse, or polygon.

18. A computer system having a circuit board, said circuit board having an integrated circuit device with connecting leads and being assembled by a process comprising the steps of:

providing a mounting substrate having a first and second layer in substantial communication with each other, said first layer having a plurality of first apertures whose relative positions on said substrate correspond to those of the connecting leads of said integrated circuit device, said second layer having a plurality of second apertures of smaller diameter than said first apertures and communicating substantially therewith;

locating solidified solder elements substantially within said mounting substrate such that said solder elements communicate with respective first apertures of said first substrate layer;

applying an adhesive layer to said mounting substrate such that said solder elements are retained substantially within said first apertures;

attaching said mounting substrate to said circuit board;

positioning the integrated circuit device adjacent to said mounting substrate such that the connecting leads of the integrated circuit communicate with said first apertures and said solder elements, so as to form an assembly; and

heating said assembly so as to at least partially melt said solder elements to form an electrical contact between said integrated circuit and said circuit board.

19. A circuit board having an integrated circuit device with connecting leads, prepared by a process comprising the steps of:

providing a mounting substrate having a plurality of first and second apertures, the relative locations of both of said first and second apertures corresponding to that of the connecting leads of the integrated circuit device, said second apertures having a smaller diameter than said first apertures and communicating therewith;

attaching said mounting substrate to said circuit board via a first adhesive layer;

locating solder material substantially within said mounting substrate such that said solder material communicates with selected first apertures of said substrate,

applying a second adhesive layer to said mounting substrate such that said solder material is retained substantially within said first apertures;

positioning the integrated circuit device adjacent to said mounting substrate such that the connecting leads of the integrated circuit communicate with said first apertures and said solder material, so as to form an assembly; and

heating said assembly so as to melt said solder material to form an electrical contact between said integrated circuit and said circuit board.