Method of manufacturing multilayer printed wiring board

• US 5,826,330 A
• Filed: 12/18/1996
• Issued: 10/27/1998
• Est. Priority Date: 12/28/1995
• Status: Expired due to Term

• Current Assignee: Hitachi AIC, Inc. (Resonac Holdings Corp.)
• Original Assignee: Hitachi AIC, Inc. (Resonac Holdings Corp.)
• Inventors: Isoda, Satoshi, Noguchi, Koichi, Okamura, Toshiro, Iwasaki, Yasuhiro, Yokoyama, Hiroyoshi, Matuda, Youiti, Fukuzato, Kenshirou, Zama, Tsutomu
• Primary Examiner(s): ARBES, CARL J
• Application Number:
  US08/768,426
• Time in Patent Office: 678 Days
• Field of Search: 29/852, 219/121.7, 219/121.71, 219/121.74, 219/121.76, 427/97
• US Class Current: 29/852
• CPC Class Codes: B23K 26/389 of fluid openings, e.g. nozzles, jets laser machining of inkjet nozzles B41J2/1634
• CPC Class Codes: H05K 2201/0195 Dielectric or adhesive layers comprising a plurality of layers, e.g. in a multilayer structure
• CPC Class Codes: H05K 2201/0236 Plating catalyst as filler in insulating material
• CPC Class Codes: H05K 2201/09518 Deep blind vias, i.e. blind vias connecting the surface circuit to circuit layers deeper than the first buried circuit layer
• CPC Class Codes: H05K 2201/09827 Tapered, e.g. tapered hole, via or groove
• CPC Class Codes: H05K 2201/09845 Stepped hole, via, edge, bump or conductor
• CPC Class Codes: H05K 2203/0207 Partly drilling through substrate until a controlled depth, e.g. with end-point detection
• CPC Class Codes: H05K 2203/0554 Metal used as mask for etching vias, e.g. by laser ablation
• CPC Class Codes: H05K 3/0035 of blind holes, i.e. having a metal layer at the bottom
• CPC Class Codes: H05K 3/387 for electroless plating H05K3/4661 takes precedence
• CPC Class Codes: H05K 3/421 Blind plated via connections H05K3/422, H05K3/423 and H05K3/425 take precedence
• CPC Class Codes: H05K 3/4661 Adding a circuit layer by direct wet plating, e.g. electroless plating; insulating materials adapted therefor other insulating materials H05K3/387
• CPC Class Codes: Y10T 29/49165 by forming conductive walled aperture in base

Abstract

In a method of manufacturing a multilayer printed wiring board including an internal wiring circuit formed on a board, an insulating resin layer formed on the internal wiring circuit, a blind hole formed in the insulating resin layer and communicating with the internal wiring circuit, and a conductive portion formed on an inner wall of the blind hole and connected to the internal wiring circuit, the blind hole is formed by using a short-pulse CO₂ laser.

Claims

1. A method of manufacturing a multilayer printed wiring board including an internal wiring circuit formed on a board, an insulating resin layer formed on the internal wiring circuit, a blind hole formed in the insulating resin layer and communicating with the internal wiring circuit, and a conductive portion formed on an inner wall of the blind hole and connected to the internal wiring circuit, the method comprising the steps of:

forming the blind hole by using a short-pulse CO₂ laser;

preparing at least two internal wiring circuits which are isolated from each other by an insulating layer in a direction of thickness;

forming one land portion, which has a hole formed in correspondence with the blind hole, on one of the two internal wiring circuits which is on an upper surface side;

forming the other land portion on the other internal wiring circuit on a lower surface side in correspondence with a bottom portion of the blind hole so as to have a diameter larger than that of the hole of said one land portion;

forming the blind hole by using a laser beam from a short-pulse CO₂ laser which has a diameter smaller than the diameters of the two land portions and larger than the diameter of the hole of said one land portion; and

,

performing through hole plating.

2. A method according to claim 1, wherein an oscillation frequency of the short-pulse CO₂ laser is set to 10⁴ to 10⁴ Hz.

3. A method according to claim 1, further comprising forming an external wiring circuit on the insulating resin layer, the external wiring circuit being connected to the conductive portion of the blind hole.

4. A method according to claim 1, further comprising forming the insulating resin layer by using epoxy resin containing no glass cloth.

5. A method according to claim 4, wherein the insulating resin layer contains a plating catalyst.

6. A method according to claim 3, further comprising forming the insulating resin layer by using a plurality of layers, and arranging a layer of the plurality of layers cut by a laser beam on the external wiring circuit side, and a layer of the plurality of layers cut by a laser beam on the internal wiring circuit side.

7. A method according to claim 6, further comprising forming the insulating resin layer by using a first layer cut by a laser beam at 120 to 80 μ

m/shot, a second layer cut by a laser beam at 90 to 50 μ

m/shot, and a third layer cut by a laser beam at 70 to 30 μ

m/shot, the first to third layers being arranged from the external wiring circuit side to the internal wiring circuit side, and using a short-pulse CO₂ laser having an oscillation frequency of 10⁴ to 10⁸ Hz to irradiate a laser beam from the first layer side, thereby forming a blind hole such that an angle defined by an upper edge and wall surface of the blind hole is set to not less than 90°

.

8. A method according to claim 1, wherein an irradiation range of the short-pulse CO₂ laser is expanded to a portion adjacent to the internal wiring circuit on the insulating resin layer.