Printed circuit board assembly having adhesive joint

• US 6,384,339 B1
• Filed: 03/12/2001
• Issued: 05/07/2002
• Est. Priority Date: 04/30/1998
• Status: Expired due to Term

• Current Assignee: Flex, Ltd.
• Original Assignee: Sheldahl, Inc.
• Inventors: Neuman, David
• Primary Examiner(s): Cureo, Kamand
• Assistant Examiner(s): NORRIS, JEREMY C
• Application Number:
  US09/804,132
• Time in Patent Office: 421 Days
• Field of Search: 174/254, 174/259, 174/261, 174/255, 361/749-751
• US Class Current: 174/254
• CPC Class Codes: H05K 2201/10977 Encapsulated connections
• CPC Class Codes: H05K 2203/101 Using electrical induction, e.g. for heating during soldering
• CPC Class Codes: H05K 3/305 Affixing by adhesive
• CPC Class Codes: H05K 3/3473 Plating of solder
• CPC Class Codes: H05K 3/3494 Heating methods for reflowing of solder using integral heating means H05K1/0212
• CPC Class Codes: H05K 3/361 Assembling flexible printed circuits with other printed circuits
• CPC Class Codes: H05K 3/363 by soldering
• CPC Class Codes: H05K 3/386 by the use of an organic polymeric bonding layer, e.g. adhesive
• CPC Class Codes: Y10T 29/49126 Assembling bases
• CPC Class Codes: Y10T 29/49144 by metal fusion
• CPC Class Codes: Y10T 29/49149 by metal fusion bonding

Abstract

A new process for electrically and mechanically joining arrays of conductors on flexible printed circuits and other flexible conductors including collated flat, flexible cables (FFCs). An array of flat copper conductors on a flexible dielectric sheet is electroplated with tin-lead solder. Surface insulation is locally omitted or removed from conductor surfaces. A second circuit or cable is overlapped in competent electrical communication and the solder plating fused by inductively heating the copper to join the two conductor arrays. An adhesive placed between conductors is also thermally activated to bond the film on the two cable arrays together. This insulates the electrical connections and seals them from attack by moisture and chemical pollutants.

Claims

1. An assembly of electrically connected printed circuit boards, comprising:

a first printed circuit board including a substrate and an electrically conductive layer bonded to the substrate with an insulating adhesive, the conductive layer having a first plurality of solder covered electrically conductive leads disposed on the substrate with adhesive present between the first plurality of electrically conductive leads;

a second printed circuit board including a substrate and an electrically conductive layer bonded to the substrate with an insulating adhesive, the conductive layer bonded to the substrate with an insulating adhesive, the conductive layer having a second plurality of solder covered electrically conductive leads disposed on the substrate with adhesive present between the second plurality of electrically conductive leads; and

wherein inductive heat applied to the solder covered leads causes the first plurality of leads to be electrically and mechanically connected to the second plurality of leads, and an adhesive bond is formed between the adhesive between the first plurality of leads and the adhesive between the second plurality of leads thereby insulating the electrically connected leads from one another.

2. The article of claim 1 wherein the adhesives of the first and second boards are thermally activated adhesives.

3. The article of claim 1 wherein the substrate of the first board is rigid and the substrate of the second board is flexible.

4. The article of claim 1 wherein the substrate of the first board is flexible and the substrate of the second board is flexible.

5. The article of claim 1 wherein the substrate of the first board is polyester film.

6. The article of claim 5 wherein the substrate of the second board is polyester film.

7. The article of claim 5 wherein the polyester film is between about 20 and 175 microns thick.

8. The article of claim 7 wherein the adhesive is between about 10 and 75 microns thick.

9. The article of claim 1 wherein the substrate of the first board is polyester film and the substrate of the second board is polyimide film.

10. The article of claim 1 wherein the second plurality of leads is not covered by solder.

11. The article of claim 1 wherein the copper layer is between about 20 and 200 microns thick.

12. Claim 1 wherein the circuit is a printed circuit.

13. An assembly of electrically connected leads, comprising:

a first circuit board including a substrate and an electrically conductive layer bonded to the substrate with an insulating adhesive, the conductive layer having a first plurality of solder covered electrically conductive leads disposed on the substrate with adhesive present between the first plurality of electrically conductive leads;

a second component including an insulative support and a second plurality of electrically conductive leads on the support;

a coating of solder on one of said first plurality of leads and said second plurality of leads;

wherein inductive heat applied to one of said first plurality of leads and said second plurality of leads causes the first plurality of leads to be electrically and mechanically connected to the second plurality of leads, and an adhesive bond is formed between the adhesive between the first plurality of leads and the area between the second plurality of leads thereby insulating the electrically connected leads from one another.

14. An assembly of electrically connected circuit boards, comprising:

a first circuit board including a substrate and a first plurality of electrical conductors bonded to the substrate with an insulating adhesive, said first plurality of conductors terminating at a first plurality of leads defining a first plurality of sections of said first substrate between said first plurality of leads;

a second circuit board including a substrate and a second plurality of electrical conductors bonded to the substrate with an insulating adhesive, said second plurality of conductors terminating at a second plurality of leads defining a second plurality of sections of said second substrate between said second plurality of leads;

a layer of solder disposed on one of said first plurality of leads and said second plurality of leads;

wherein inductive heat applied to one of said first plurality of leads and said second plurality of leads causes the first plurality of leads to be electrically and mechanically connected to the second plurality of leads, and a bond is formed between said first plurality of sections of the first substrate and said second plurality of sections of the second substrate.