# US 9,439,281 B2 · Method for manufacturing printed circuit board

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- Number: US 9,439,281 B2
- Document ID: US9439281B2
- Status: Granted
- Kind: B2
- Application number: 13/947,114
- Filed: 2013-07-22
- Published: 2014-03-06
- Granted: 2016-09-06
- Earliest claimed: 2012-08-29
- Assignees: Zhen Ding Technology Co., Ltd.
- Applicants: Zhen Ding Technology Co., LTd.
- Inventors: Wen-Hung Hu
- Web page: https://patentgrep.com/patent/US9439281B2

## CPC

- H05K 1/0296: {Conductive pattern lay-out details not covered by sub groups H05K1/02 - H05K1/0295 (H05K1/11 takes precedence; lay-out adapted to mounted component configuration H05K1/18)}
- H05K 3/007: {Manufacture or processing of a substrate for a printed circuit board supported by a temporary or sacrificial carrier (H05K1/187, H05K3/20 and H05K3/4682 take precedence)}
- H05K 3/4661: {Adding a circuit layer by direct wet plating, e.g. electroless plating; insulating materials adapted therefor (other insulating materials H05K3/387)}
- H05K 3/185: {by making a catalytic pattern by photo-imaging}
- H05K 3/422: {characterised by electroless plating method; pretreatment therefor}
- H05K 2203/107: Using laser light
- H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS

## Abstract

A printed circuit board includes a base, a number of conductive pads, a dielectric layer, an activated metal layer, a first metal seed layer, a second metal seed layer, and a plurality of metal bumps. The conductive pads are formed on the base. The dielectric layer is formed on a surface of the conductive pads and portions of the base are exposed from the conductive pads. The dielectric layer includes blind vias corresponding to the conductive pads, and a laser-activated catalyst. The activated metal layer is obtained by laser irradiation at the wall of the blind via. The activated metal layer is in contact with the dielectric layer. The second metal seed layer is formed on the activated metal layer and the conductive pads. Each metal bump is formed on the second metal seed layer, and each metal bump protrudes from the dielectric layer.

## Claims

### Claim 1

A method for manufacturing a printed circuit board, comprising:
providing a circuit substrate, the circuit substrate comprising a base and a plurality of conductive pads;
forming a dielectric layer on a surface of the conductive pads and a surface of the base exposed from the conductive pads, the dielectric layer comprising a laser-activated catalyst;
forming a first metal seed layer on a surface of the dielectric layer furthest from the circuit substrate;
forming a photoresist layer on a surface of the first metal seed layer furthest from the dielectric layer, the photoresist layer comprising a trace portion;
exposing the trace portion of the photoresist layer;
defining a plurality of blind vias in the photoresist layer, the first metal seed layer, and the dielectric layer using a laser, the blind vias spatially corresponding to the conductive pads, each conductive pad exposed from a corresponding blind via, the laser-activated catalyst at a wall of the blind via being activated by laser, thereby obtaining an activated metal layer;
forming a second metal seed layer on the activated metal layer, the second metal seed layer being electrically connected to the first metal seed layer;
removing the trace portion of the photoresist layer by developing to form a trace opening, and a portion of the first metal seed layer being exposed from the trace opening;
forming a metal bump in each blind via and forming a trace in the trace opening by electroplating, the metal bump protruding the surface of the dielectric layer furthest from the circuit substrate; and
removing the first metal seed layer uncovered by the trace and the photoresist layer, thereby obtaining a printed circuit board.

### Claim 2 (depends on 1)

The method of claim 1, wherein the dielectric layer is formed by printing an ink, exposing the ink, and developing the ink, and the ink comprises the laser-activated catalyst.

### Claim 3 (depends on 2)

The method of claim 2, wherein a mass percent of the laser-activated catalyst in the ink is in a range from 0.1% to 30%.

### Claim 4 (depends on 3)

The method of claim 3, wherein the laser-activated catalyst is a heavy metal mixture oxide spinel or metal salt.

### Claim 5 (depends on 4)

The method of claim 4, wherein the laser-activated catalyst is copper-chromium oxide spinel, copper sulfate, copper hydroxide phosphate, or cupric rhodanate.

### Claim 6 (depends on 1)

The method of claim 1, wherein the second metal seed layer is formed by electro-less copper plating.

### Claim 7 (depends on 6)

The method of claim 6, further comprising a step of forming a protection layer on a surface of each metal bump protruding the dielectric layer.

### Claim 8 (depends on 1)

The method of claim 1, further comprising forming a solder mask on the surface of the dielectric layer and a surface of the trace, a plurality of holes corresponding to the metal bumps defined in the solder mask, a portion of the metal bump protruding from the blind via being exposed from each corresponding hole.

### Claim 9 (depends on 8)

The method of claim 8, wherein an area of cross section of each hole is larger than an area of cross section of the metal bump in the corresponding hole.