High-density circuit and method of its manufacture

• US 5,624,708 A
• Filed: 10/31/1994
• Issued: 04/29/1997
• Est. Priority Date: 01/05/1988
• Status: Expired due to Term

• Current Assignee: Max Levy Autograph, Inc. (Coherent Corp.)
• Original Assignee: Max Levy Autograph, Inc. (Coherent Corp.)
• Inventors: Sedberry, Donald C.
• Primary Examiner(s): UTECH, BENJAMIN L
• Application Number:
  US08/331,854
• Time in Patent Office: 911 Days
• Field of Search: 427/126.2, 427/314, 427/376.2
• US Class Current: 427/126.2
• CPC Class Codes: B41J 2/345 characterised by the arrangement of resistors or conductors
• CPC Class Codes: B41J 2/355 Control circuits for heating-element selection
• CPC Class Codes: H05K 1/0306 Inorganic insulating substrates, e.g. ceramic, glass
• CPC Class Codes: H05K 3/0017 Etching of the substrate by chemical or physical means
• CPC Class Codes: H05K 3/107 by filling grooves in the support with conductive material H05K3/045, H05K3/101, H05K3/1258 and H05K3/465 take precedence
• CPC Class Codes: H05K 3/4644 by building the multilayer layer by layer, i.e. build-up multilayer circuits making via holes in the insulating layers H05K3/0011; special circuit boards as base or core whereon the multilayer is built H05K3/4602

Abstract

The present invention is a high-density circuit, wherein the circuit conductors, and the spaces between conductors, are preferably less than about 0.005 inches wide, and wherein the lines are disposed over a relatively large area. The circuit is defined by a pattern of grooves in a dielectric substrate, and a conductive material is deposited in the grooves, and heated so as to form a tight bond with the substrate. The resulting circuit is stable, rugged, and capable of withstanding a wide range of adverse environmental conditions. The invention includes the circuit itself, as well as processes used in its manufacture. The invention also includes a high-density print head, for a thermal or electrostatic printer, made from the circuit described. The rugged, high-density circuit of the present invention can generate a set of very closely-spaced conductors which are then used to produce a high-density image. The invention also includes a multi-layered version of the circuit, and a method of making the circuit with multiple layers. The invention permits the production of black and white or color halftone images having very large numbers of grey scale levels, and exceptional resolution.

Claims

1. A method of making a substrate for an electronic circuit, the method comprising the steps of:

a) selecting a ceramic material for use as a base material for the substrate,

b) grinding and polishing the ceramic material,

c) cleaning the ceramic material,

d) selecting a dielectric material which has a melting temperature greater than about 850°

C., the dielectric material including organic impurities, and coating the ceramic material with a layer of the dielectric material,

e) heating the ceramic and dielectric materials to a first temperature sufficient, and for a time sufficient, to drive off the organic impurities in the dielectric material,

f) heating the ceramic and dielectric materials to a second temperature sufficient to allow the dielectric material to flow, the second temperature being greater than the first temperature, and

g) cooling the ceramic and dielectric materials to form a product which has a smooth surface having a deviation of not more than about 5 microns per inch, which is capable of accepting a thin film layer, and which is capable of being etched with a line density of at least about 200 lines per inch.

2. The method of claim 1, wherein step (d) is selected from the group consisting of screening the dielectric material onto the ceramic material and spraying the dielectric material onto the ceramic material.

3. The method of claim 1, wherein step (e) comprises heating the ceramic and dielectric material to a temperature of at least about 500°

C., for about two hours.

4. The method of claim 3, wherein step (f) comprises heating the ceramic and dielectric material to a temperature of at least about 1200°

C., for at least about one hour.

5. The method of claim 1, wherein the ceramic material has two sides, and wherein step (d) includes coating both sides of the ceramic material with dielectric material.

6. A method of making a substrate for an electronic circuit, the method comprising the steps of:

a) providing a ceramic material for use as a base material for the substrate,

b) selecting a dielectric material which has a melting temperature greater than about 850°

C., the dielectric material including organic impurities, and coating the ceramic material with a layer of the dielectric material,

c) heating the ceramic and dielectric materials to a first temperature sufficient, and for a time sufficient, to drive off the organic impurities in the dielectric material,

d) heating the ceramic and dielectric materials to a second, higher temperature, sufficient to allow the dielectric material to flow, the second temperature being greater than the first temperature, and

e) cooling the ceramic and dielectric materials to form a product which has a smooth surface having a deviation of not more than about 5 microns per inch, which is capable of accepting a thin film layer, and which is capable of being etched with a line density of at least about 200 lines per inch.

7. The method of claim 6, wherein step (b) is preceded by the step of grinding and polishing the ceramic material.

8. The method of claim 6, wherein step (b) is preceded by the step of cleaning the ceramic material.

9. The method of claim 6, wherein step (b) is followed by the step of drying the dielectric material by heating it.

10. The method of claim 6, wherein steps (c) and (d) comprise heating the ceramic and dielectric materials to at least about 500°

C. for about two hours, and then heating the ceramic and dielectric materials to at least about 1200°

C. for about one hour.

11. The method of claim 6, wherein the ceramic material has two sides, and wherein step (b) includes coating both sides of the ceramic material with dielectric material.

12. A method of making a substrate for a high-density electronic circuit, the method comprising the steps of:

a) providing a ceramic material for use as a base material for the substrate,

b) coating the ceramic material with a layer of dielectric material, the dielectric material having organic impurities,

c) heating the ceramic and dielectric materials to a temperature of at least about 500°

C., for about two hours, so as to drive off the organic impurities in the dielectric material,

d) heating the ceramic and dielectric materials to a temperature of at least about 1200°

C., for about one hour, so as to allow the dielectric material to flow and to define a smooth surface having a deviation of not more than about 5 microns per inch, and

e) cooling the ceramic and dielectric materials.