Printed wire circuit board and its method of manufacture

• US 4,791,248 A
• Filed: 01/22/1987
• Issued: 12/13/1988
• Est. Priority Date: 01/22/1987
• Status: Expired due to Fees

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Oldenettel, Jayne L.
• Primary Examiner(s): Nimmo, Morris H.
• Application Number:
  US07/006,823
• Time in Patent Office: 691 Days
• Field of Search: 174/685, 427/97
• US Class Current: 174/265
• CPC Class Codes: H05K 1/056 the metal substrate being covered by an organic insulating layer
• CPC Class Codes: H05K 2201/0323 Carbon
• CPC Class Codes: H05K 2201/068 wherein the coefficient of thermal expansion is important
• CPC Class Codes: H05K 2201/0959 Plated through-holes or plated blind vias filled with insulating material
• CPC Class Codes: H05K 2203/0191 Using tape or non-metallic foil in a process, e.g. during filling of a hole with conductive paste
• CPC Class Codes: H05K 2203/143 Treating holes before another process, e.g. coating holes before coating the substrate
• CPC Class Codes: H05K 3/0094 Filling or covering plated through-holes or blind plated vias, e.g. for masking or for mechanical reinforcement
• CPC Class Codes: H05K 3/445 having insulated holes or insulated via connections through the metal core

Abstract

Thermal shock tolerance is achieved in conductive core printed wire circuit boards, especially those having graphite or copper-Invar-copper cores for heat removal and expansion control, by filling the oversized through-holes with glass-filled, m-diallyl phthalate resin and plating on the inner surface of a bore drilled through the resin. Meta-diallyl phthalate has a coefficient of thermal expansion that is lower than epoxy and that is closer to that of the core. It creates a substantially void free, dielectric collar between the plating and the core to insulate the two electrically. Its use temperature is higher than epoxy while its curing temperature is lower than polyimide. The boards can be made by molding of the thermosetting resin in a peel ply process that avoids milling of the board and reduces waste.

Claims

1. A conductive core printed wire circuit board, comprising:

(a) a printed wire circuit board having a conductive core and at least one oversized through-hole extending through the core;

(b) a dielectric collar in the through-hole, the collar being a cured filled resin substantially free of voids, having a coefficient of thermal expansion closer to that of the core than the coefficient of thermal expansion of epoxy, and having a central bore drilled into the collar and

(c) a conductive plating on the inner surface of the bore forming a plated-through-hole, the plating providing electrical connection between one side of the board and the other side but being electrically insulated from the core by the collar.

2. A conductive core printed wire circuit board, comprising:

(a) a printed wire circuit board having a conductive core and at least one oversized tnrough-hole extending through the core;

(b) a dielectric collar in the through-hole, the collar being a cured, filled resin substantially free of voids, having a coefficient of thermal expansion closer to that of the core than the coefficient of thermal expansion of epoxy, and having a central bore drilled into the collar wherein the resin is m-diallyl phthalate; and

(c) a conductive plating on the inner surface of the bore forming a plated-through-hole, the plating providing electrical connection between one side of the board and the other side but being electrically insulated from the core by the collar.

3. The board of claim 2 wherein the core is selected from the group consisting of aluminum, graphite, or copper-Invar-copper.

4. The board of claim 2 wherein the resin is filled with fiberglass.

5. The board of claim 2 wherein the resin has a use temperature higher than epoxy and a curing temperature lower than polyimide.

6. The board of claim 5 wherein the resin has a glass transition temperature of above about 200°

C.

7. The board of claim 2 wherein the plated-through-hole is copper.

8. The board of claim 2 wherein the resin is injection moldable and thermosetting.

9. A conductive core printed wire circuit board, comprising:

(a) a printed wire circuit board having a conductive core to remove heat and to control expansion, the core being selected from the group consisting of aluminum, graphite, or copper-Invar-copper, and having at least one oversized through-hole extending through the core from one side of the board to the otherside;

(b) a dielectric collar adhered to the surface of the through-hole, the collar being a resin composite including fiberglass reinforcement, the resin having a use temperature higher than epoxy and curing temperature lower than polyimide, the resin also having a glass transition temperature in excess of about 200°

C. and a coefficient of thermal expansion lower than epoxy/glass and polyimide/glass, the filler having a central bore and being substantially free of voids; and

(c) a conductive plating forming a plated-through-hole on the inner surface of the bore, the plating providing electrical connection between one side of the board to the other side but being electrically insulated from the core of the board by the filler.

10. The board of claim 9 wherein the resin includes diallyl phthalate.

11. The board of claim 10 wherein the core is graphite.

12. The board of claim 10 wherein the core is copper-Invar-copper.

13. A printed wire circuit board having a conductive core, a m-diallyl phthalate dielectric collar through the core, and a plated-through-hole on the inner surface of the collar, the collar insulating the plated-through-hole from the core.

14. A conductive core printed wire circuit board, comprising:

(a) a conductive core;

(b) a dielectric layer having a first surface in contact with at least a portion of the conductive core; and

(c) a conductive plating on a second surface of the dielectric layer and being electrically isolated from the conductive core.

wherein the dielectric layer is m-diallyl phthalate so that the layer and core have a smaller mismatch in coefficients of thermal expansion than the core would have with epoxy.