Solder bonding printed circuit boards

• US 6,013,877 A
• Filed: 03/12/1998
• Issued: 01/11/2000
• Est. Priority Date: 03/12/1998
• Status: Expired due to Term

• Current Assignee: RPX Corporation
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Degani, Yinon, Tai, King Lien
• Primary Examiner(s): Kincaid, Kristine
• Assistant Examiner(s): PATEL, DHIRUBHAI R
• Application Number:
  US09/041,157
• Time in Patent Office: 670 Days
• Field of Search: 174/261, 174/264, 228/180.22, 257/738, 257/778, 257/780, 257/772, 257/774, 361/760, 361/772, 361/773, 361/777, 361/779, 29/830, 29/840
• US Class Current: 174/264
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/32225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45099 Material
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48227 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/48465 the other connecting portion not on the bonding area being a wedge bond, i.e. ball-to-wedge, regular stitch
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2224/85399 Material
• CPC Class Codes: H01L 23/49827 Via connections through the substrates, e.g. pins going through the substrate, coaxial cables H01L23/49822, H01L23/49833, H01L23/4985, H01L23/49861 take precedence
• CPC Class Codes: H01L 24/48 of an individual wire connector
• CPC Class Codes: H01L 24/73 Means for bonding being of different types provided for in two or more of groups H01L24/10, H01L24/18, H01L24/26, H01L24/34, H01L24/42, H01L24/50, H01L24/63, H01L24/71
• 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 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01078 Platinum [Pt]
• CPC Class Codes: H01L 2924/01322 Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/15311 being a ball array, e.g. BGA
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 2924/207 Diameter ranges
• CPC Class Codes: H05K 2201/09572 : Solder filled plated through-hole in the final product
• CPC Class Codes: H05K 2201/10666 : Plated through-hole for surface mounting on PCB
• CPC Class Codes: H05K 2201/10992 : Using different connection materials, e.g. different solders, for the same connection
• 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: H05K 3/3463 : Solder compositions in relation to features of the printed circuit board or the mounting process
• CPC Class Codes: Y02P 70/50 : Manufacturing or production processes characterised by the final manufactured product

Abstract

The specification describes techniques for attaching double sided circuit boards having plated through holes to interconnection substrates using solder bump arrays. The through holes are filled with a high melting point solder which allows solder bumps to be located directly on the through hole thus saving board area and reducing the interconnection length.

Claims

1. Method for the assembly of multiple interconnection substrates in which at least one of said multiple interconnection substrates is a double sided circuit board with plated through holes extending through said double sided circuit board, the method comprising applying a first solder material to at least one of said interconnection substrates and bonding said interconnection substrates together by melting said first solder material, the method characterized by the step of filling said through holes with a second solder material prior to the step of bonding said interconnection substrates together, said second solder material having a solidus point at least 20°

C. higher than a liquidus point of said first solder material, and melting said first solder material at a temperature lower than the solidus point of said second solder material.

2. The method of claim 1 in which the said interconnection substrates are bonded together using solder bumps.

3. A method for attaching a double sided circuit board with a top side and a bottom side to an interconnection substrate wherein said double sided circuit board has at least one first interconnection site on the top side of said double sided circuit board interconnected to a circuit on the top side of said double sided circuit board, and at least one second interconnection site on the bottom side of said double sided circuit board, and a plated through hole extending through said double sided circuit board interconnecting said first interconnection site to said at least one second interconnection site, the method comprising the steps of:

a. filling said plated through hole with a first solder material, and

b. attaching said double sided circuit board to said interconnection substrate using an array of solder bumps of a second solder material wherein one of said array of solder bumps is attached to said at least one second interconnection site of said double sided circuit board, and wherein a solidus temperature of said first solder material is at least 20°

C. higher than a liquidus temperature of said second solder material.

4. The method of claim 3 in which the step of filling said through hole comprises applying the first solder material to the bottom side of the double sided circuit board.

5. An interconnection assembly comprising a double sided circuit board having a top side and a bottom side attached to an interconnection substrate by an array of solder bumps wherein said double sided circuit board has at least one first interconnection site on the top side of said double sided circuit board interconnected to a circuit on the top side of said double sided circuit board, and at least one second interconnection site on the bottom side of said double sided circuit board, and a plated through hole extending through said double sided circuit board interconnecting said first interconnection site to said at least one second interconnection site, the interconnection assembly characterized in that the through hole is filled with a first solder material, and one of said array of solder bumps is attached to said second interconnection site of said double sided circuit board, and further characterized in that a solidus temperature of said first solder material is at least 20°

C. higher than a liquidus temperature of the solder bump attached to said second interconnection site.

6. The assembly of claim 5 in which the said first interconnection site is an I/O pad of the circuit on the top side of the circuit board.

7. An interconnection assembly comprising a double sided circuit board having a top side and a bottom side with at least one first interconnection site on the top side of said circuit board and at least one second interconnection site on the bottom side of said circuit board, and at least one plated through hole extending through said circuit board interconnecting said at least one first interconnection site to said at least one second interconnection site, the interconnection assembly characterized in that the plated through hole is filled with a solder material, said solder material having a solidus temperature of at least 200°

C.

8. The assembly of claim 7 in which the said first interconnection site is an I/O pad of the circuit on the top side of the circuit board.

9. An interconnection assembly comprising a double sided circuit board having a top side and a bottom side with at least one first interconnection site on the top side of said double sided circuit board and at least one second interconnection site on the bottom side of said double sided circuit board, and at least one plated through hole extending through said double sided circuit board interconnecting said first interconnection site to said second interconnection site, and an array of solder bumps attached to the bottom side of said double sided circuit board said solder bumps comprising a first solder material, the interconnection assembly characterized in that the through hole is filled with a second solder material, the interconnection assembly further characterized in that a solidus temperature of said second solder material is at least 20°

C. higher than a liquidus temperature of said first solder material.

10. The assembly of claim 9 in which the said first interconnection site is an I/O pad of the circuit on the top side of the circuit board.

11. The assembly of claim 9 in which the first solder material has a liquidus temperature below 190°

C.

12. The assembly of claim 11 in which the second solder material has a solidus temperature above 220°

C.

13. The assembly of claim 9 in which the solder bumps are solder balls and the assembly is a ball grid array.

14. The assembly of claim 9 wherein the solder bumps are attached to said double sided circuit board with solder pads.

15. The assembly of claim 14 wherein the solder pads are located on said at least one plated through hole.