Edge connectors for printed circuit boards comprising conductive ink

• US 6,821,555 B2
• Filed: 12/21/2001
• Issued: 11/23/2004
• Est. Priority Date: 11/20/1998
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: 3Com Corporation (HP Inc.)
• Inventors: Jean, Denis
• Primary Examiner(s): Talbot, Brian K.
• Application Number:
  US10/036,704
• Publication Number:
  US 20020086146A1
• Time in Patent Office: 1,068 Days
• Field of Search: 427/205, 427/118, 427/123, 427/96, 427/180, 427/197, 427/201
• US Class Current: 427/96.1
• CPC Class Codes: H01B 1/22 the conductive material comprising metals or alloys
• CPC Class Codes: H01B 1/24 the conductive material comprising carbon-silicon compounds, carbon or silicon
• CPC Class Codes: H05K 1/095 for polymer thick films, i.e. having a permanent organic polymeric binder
• CPC Class Codes: H05K 3/06 the conductive material being removed chemically or electrolytically, e.g. by photo-etch process semi-additive methods H05K3/108
• CPC Class Codes: H05K 3/249 comprising carbon particles as main constituent
• CPC Class Codes: Y10S 428/901 Printed circuit
• CPC Class Codes: Y10T 428/24917 including metal layer
• CPC Class Codes: Y10T 428/31681 Next to polyester, polyamide or polyimide [e.g., alkyd, glue, or nylon, etc.]

Abstract

Disclosed are edge contacts for printed circuit boards comprising a copper lead coated with conductive ink comprising a binder and graphite powder, carbon black, and silver flakes. Also disclosed are printed circuit boards containing the contacts and methods for manufacturing the contacts and circuit boards.

Claims

1. A method of manufacturing edge connectors on a printed circuit board where the maximum resistance across the edge connector is about 70×

10<sup>−

3</sup>Ω

comprising applying a conductive ink that provides a sheet resistivity of about 0.1 to 0.5 Ω

/sq/15 μ

m over a copper conductor terminating at an edge of the circuit board, the conductive ink comprising a thermoset epoxy binder, graphite powder, carbon black, and silver flakes, wherein the silver flakes have an average size not greater than about 10 μ

m.

2. A method according to claim 1, wherein the sheet resistivity is about 0.2 to 0.3 Ω

/sq/15 μ

m.

3. A method according to claim 1, wherein the sheet resistivity is about 0.25 Ω

/sq/15 μ

m.

4. A method according to claim 3, wherein the thermoset epoxy binder comprises an epoxy resin containing phenolic monomers.

5. A method according to claim 4, where the ink further comprises methanol and diethylene glycol.

6. A method according to claim 5, wherein the ink comprises

(a) from about 20 to 40% of an epoxy resin comprising phenolic monomers;

(b) from about 3 to 10% of carbon black;

(c) from about 8 to 20% of graphite powder;

(d) from about 10 to 50% of silver flakes having an average grind size not greater than about 10 μ

m.

7. A method according to claim 5, where the ink comprises

(a) from about 20 to 40% of an epoxy resin comprising phenolic monomers;

(b) from about 3 to 10% of carbon black;

(c) from about 8 to 20% of graphite powder;

(d) from about 10 to 50% of the silver flakes having an average grind size not greater than about 10 μ

m;

(e) up to about 30% thinner and

(f) up to about 8% methanol.

8. The method of claim 1 wherein the conductive ink provides a contact resistance of about 50×

10<sup>−

3</sup>Ω

.

9. The method of claim 2, wherein the edge connector has a contact resistance of about 35×

10<sup>−

3</sup>Ω

.

10. The method of claim 3 wherein the conductive ink provides a contact resistance of about 30×

10<sup>−

3</sup>Ω

.