Method for manufacturing high-density multilayer printed circuit boards

• US 6,119,338 A
• Filed: 03/19/1998
• Issued: 09/19/2000
• Est. Priority Date: 03/19/1998
• Status: Expired due to Fees

• Current Assignee: Transpacific IP I Limited (Transpacific IP Group Limited)
• Original Assignee: Industrial Technology Research Institute
• Inventors: Chen, Man-Lin, Chiou, Chuang-Shin, Ding, Pei-Wen, Chan, Ming-Shun, Wang, Tsung-Hsiung
• Primary Examiner(s): Young, Lee
• Assistant Examiner(s): Trinh, Minh
• Application Number:
  US09/044,969
• Time in Patent Office: 915 Days
• Field of Search: 29/852, 29/848, 29/830, 29/832, 29/847, 174/264, 174/258, 174/262, 174/261, 156/150, 156/151, 361/792, 361/795
• US Class Current: 29/852
• CPC Class Codes: H05K 2201/0347 Overplating, e.g. for reinforcing conductors or bumps; Plating over filled vias reinforcing the conductive pattern H05K3/24
• CPC Class Codes: H05K 2201/0355 Metal foils
• CPC Class Codes: H05K 2201/0394 Conductor crossing over a hole in the substrate or a gap between two separate substrate parts
• CPC Class Codes: H05K 2201/09509 Blind vias, i.e. vias having one side closed
• CPC Class Codes: H05K 2201/0959 Plated through-holes or plated blind vias filled with insulating material
• CPC Class Codes: H05K 2201/096 Vertically aligned vias, holes or stacked vias
• CPC Class Codes: H05K 2203/0554 Metal used as mask for etching vias, e.g. by laser ablation
• CPC Class Codes: H05K 2203/085 Using vacuum or low pressure
• CPC Class Codes: H05K 3/0035 of blind holes, i.e. having a metal layer at the bottom
• 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 3/045 by making a conductive layer having a relief pattern, followed by abrading of the raised portions
• CPC Class Codes: H05K 3/4069 for via connections in organic insulating substrates
• CPC Class Codes: H05K 3/421 Blind plated via connections H05K3/422, H05K3/423 and H05K3/425 take precedence
• CPC Class Codes: H05K 3/4602 characterized by a special circuit board as base or central core whereon additional circuit layers are built or additional circuit boards are laminated
• 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
• CPC Class Codes: Y10T 29/49126 Assembling bases
• CPC Class Codes: Y10T 29/4913 Assembling to base an electrical component, e.g., capacitor, etc.
• CPC Class Codes: Y10T 29/49156 with selective destruction of conductive paths
• CPC Class Codes: Y10T 29/49165 by forming conductive walled aperture in base

Abstract

A method for making high-density multilayer printed circuit boards is disclosed. It includes the steps of: (a) forming a pair of first conductive layers on top and bottom sides of a dielectric substrate; (b) forming first via holes through one of the first electrically conductive layers; (c) forming a blind hole through the dielectric substrate using a conformal laser drilling technique and filling the blind hole with an electrically conductive material; (d) forming a circuit pattern from the first electrically conductive layer; (e) forming a first electrically insulating layer on the first electrically conductive layer; (f) forming second via holes through the first electrically insulating layer using a non-conformal laser drilling technique; (g) forming a second electrically conductive layer covering the top surface of the circuit pattern, the first electrically insulating layer, and the side surface of the second via holes by electroplating; (h) forming a second electrically insulating layer on the first electrically conductive layer and filling the second via hole with the same electrically insulating material; (i) removing the second electrically insulating layer and the second electrically conductive layer above the second via hole; (j) forming a third electrically conductive layer on the first electrically insulating layer, wherein the third electrically conductive layer is in contact with the top edges of the second electrically conductive layer remaining on the cylindrical surface of the second via; (k) forming another circuit pattern on the third electrically conductive layer. Steps(e) through (k) can be repeated for more circuit patterns.

Claims

1. A method for making high-density multilayer printed circuit boards comprising the following steps:

(a) forming a pair of first electrically conductive layers on top and bottom sides of a dielectric substrate;

(b) forming at least one first via hole through one of said first electrically conductive layers;

(c) forming at least one blind hole through said dielectric substrate in alignment with said through hole using a conformal laser drilling technique and filling said blind hole with an electrically conductive blind hole filling material;

(d) forming a circuit pattern from said first electrically conductive layer;

(e) forming a first electrically insulating layer on said first electrically conductive layer;

(f) forming at least one second via through said first electrically insulating layer using a non-conformal laser drilling technique to expose a top surface of said circuit pattern;

(g) conformally coating a second electrically conductive layer covering said top surface of said circuit pattern, a side surface of said second via hole, and a top surface of said first electrically insulating layer, by electroplating;

(h) forming a second electrically insulating layer on said second electrically conductive layer and, at the same time, filling said second via hole with the same electrically insulating material;

(i) removing said second electrically insulating layer and said second electrically conductive layer above said second via hole to cause said second electrically conductive layer to assume the shape of a cup and expose top edges of said second electrically conductive layer;

(j) forming a third electrically conductive layer on said first electrically insulating layer, wherein said third electrically conductive layer is in contact with said top edges of said second electrically conductive layer so that it is electrically connected to said circuit pattern;

(k) forming another circuit pattern from said third electrically conductive layer; and

(l) repeating steps (e) through (k) if one or more electrically conductive conductive patterns are needed.

2. The method for making high-density multilayer printed circuit boards according to claim 1 wherein said blind hole is formed using a conformal carbon dioxide laser drilling technique.

3. The method for making high-density multilayer printed circuit boards according to claim 1 wherein said via holes in the dielectric layers are formed using a non-conformal carbon dioxide laser, a YAG laser or an excimer laser.

4. The method for making high-density multilayer printed circuit boards according to claim 1 wherein said electrically conductive layer is a copper layer.

5. The method for making high-density multilayer printed circuit boards according to claim 1 wherein said dielectric substrate is an epoxy resin, a polyimide resin, a bismaleimide triazine resin, or a cyanate ester.

6. The method for making high-density multilayer printed circuit boards according to claim 1 wherein said dielectric substrate is a glass fiber reinforced epoxy resin, a polyimide resin, a bismaleimide triazine resin, or a cyanate ester.

7. The method for making high-density multilayer printed circuit boards according to claim 1 wherein said electrically conductive blind hole filling material is an organic material, an inorganic material, or a metal-based gelatinous material.

8. The method for making high-density multilayer printed circuit boards according to claim 1 wherein said circuit pattern on said electrically conductive layer is formed using a combination of a lithophotographic technique and etching.

9. The method for making high-density multilayer printed circuit boards according to claim 8 wherein said lithophotographic technique utilizes a positive or negative photoresist.