METHOD OF FABRICATING MULTILAYER CIRCUITS

• US 3,770,529 A
• Filed: 08/25/1970
• Issued: 11/06/1973
• Est. Priority Date: 08/25/1970
• Status: Expired due to Term

• Current Assignee: Leslie C. Anderson
• Original Assignee: Leslie C. Anderson
• Inventors: Anderson, Leslie C.
• Primary Examiner(s): Lesmes, George F.
• Assistant Examiner(s): Epstein, Henry F.
• Application Number:
  US05/066,776
• Time in Patent Office: 1,169 Days
• Field of Search: 156/89,272,380 174/68.5 219/121L,384 264/154,22-23 117/8,8.5,38,93.3 330/4.3 331/94.5
• US Class Current: 164/10
• CPC Class Codes: H01L 21/486 Via connections through the substrate with or without pins
• CPC Class Codes: H05K 3/101 by casting or moulding of conductive material
• CPC Class Codes: Y10S 148/069 Green sheets
• CPC Class Codes: Y10T 29/49163 with sintering of base
• CPC Class Codes: Y10T 29/49165 by forming conductive walled aperture in base

Abstract

Multiple level ceramic circuit structures are formed after the individual ceramic '"'"''"'"''"'"''"'"'green'"'"''"'"''"'"''"'"' sheets are machined using beams of radiation. Vias and channels are formed simultaneously in the individual '"'"''"'"''"'"''"'"'green'"'"''"'"''"'"''"'"' sheets by exposure of the sheet through a mask having apertures with predetermined dimensions. The method of fabricating the vias and channels recognizes the relationship between the size of the mask aperture and the depth of the machining in the '"'"''"'"''"'"''"'"'green'"'"''"'"''"'"''"'"' sheet by the beam of radiation. After stacking, registering and laminating the '"'"''"'"''"'"''"'"'green'"'"''"'"''"'"''"'"' sheets, they are sintered to a unitized state and only then metallized.

Claims

2. In the method of claim 1, wherein the paths are filled with the molten conductor only after the ceramic is sintered to a dense state.

3. In the method of claim 2, wherein filling of said paths occurs by capillary flow of the molten conductor through the via holes and channels.

4. In the method of claim 2, wherein filling of said paths occurs by applying a vacuum to said ceramic board to draw the molten conductor through the via holes and channels. Pg,19

5. A method for manufacturing a multilayer ceramic circuit board having conductors disposed in and interconnecting different layers, said method comprising the steps of:

preparing a plurality of '"'"''"'"''"'"''"'"'green'"'"''"'"''"'"''"'"' ceramic sheets of ceramic material dispersed in a heat volatile binder, individually positioning each of the '"'"''"'"''"'"''"'"'green'"'"''"'"''"'"''"'"' sheets in juxtaposed relationship with one of a plurality of masks, each mask having a predetermined pattern of apertures therein, the dimensions of the various portions of the aperture pattern in the mask conforming to the desired via hole and channel personality for the juxtaposed '"'"''"'"''"'"''"'"'green'"'"''"'"''"'"''"'"' sheet, and individually exposing each of the '"'"''"'"''"'"''"'"'green'"'"''"'"''"'"''"'"' sheets through the pattern of apertures in the juxtaposed mask to laser radiation of constant power level in the range of 0.01 to 0.1 joules per 25 square mils of area exposed to the radiation for a given time of 1 millisecond to form simultaneously the via holes and channels in that '"'"''"'"''"'"''"'"'green'"'"''"'"''"'"''"'"' sheet, the depth of the formed holes and channels being determined by the dimensions of the apertures of the various portions of the pattern in the juxtaposed mask, stacking said sheets one upon another in registry such that patterns on and holes in different sheets are superposed in a desired circuit pattern, laminating said sheets, heating said laminated sheets at a temperature high enough to drive off said binders and sinter said ceramic to a dense state with continuous paths through the densified ceramic as defined by the locations for the via holes and channels of said circuit pattern, and filling said paths with a molten conductor to complete said circuit pattern.