Method for manufacturing an ultra-thin metal layer printed circuit board

Abstract

The present invention discloses a method for manufacturing a printed circuit board having an ultra-thin metal layer. The method discharges alkaline aliphatic amine gas and the nitrogen bubbled in the cupric sulfate solution via capacitive coupling in a vacuum, to generate low temperature plasma. The polyimide film and the epoxy resin board coated with fiberglass cloth are etched and the surface is treated to graft active groups, so as to increase the surface roughness and chemical activity. Subsequently, sputtering copper plating or chemical copper plating is directly conducted. The electroplating is conducted to thicken the copper film to a required thickness. The method of the invention not only does not need adhesive (adhesive free), but also has a high peeling strength. It can be used for the preparation of the flexible PCB, the rigid PCB, the multi-layer PCB, and rigid-flex PCB, having an ultra-thin metal layer.

Claims

1. A method for manufacturing a printed circuit board having an ultra-thin metal layer, wherein the method comprises steps as below: (1) providing a material to be etched in a chamber of a vacuum capacitive coupling discharge plasma generator; conducting a modification treatment on a surface of the material to be etched by a first plasma and a second plasma to obtain an etched material; wherein the first plasma is generated by discharging gaseous aliphatic amine via capacitive coupling in a vacuum, and the second plasma is generated by discharging nitrogen bubbled in a cupric sulfate solution via capacitive coupling in the vacuum; the modification treatment includes etching, and grafting active groups including amino, hydroxyl, and/or sulfonic acid radical on the surface of the material to be treated; and (2) fully or partially forming a copper film on the surface of the etched material by an electroless copper deposition or a sputtering copper deposition.

2. The preparation method of a printed circuit board having an ultra-thin metal layer of claim 1, wherein the method further comprises steps as below: (3) thickening the copper film obtained from the step (2) by electroplating, or selectively covering the copper film obtained from the step (2) and thickening an uncovered copper film by electroplating.

3. The method for manufacturing a printed circuit board having an ultra-thin metal layer of claim 2, wherein a specific process of step (3) includes: pressing a cover layer on the copper film obtained from the step (2), to expose a part of the copper film, and thickening the uncovered copper film by electroplating.

4. The method for manufacturing a printed circuit board having an ultra-thin metal layer of claim 1, wherein when the modification treatment is conducted on the surface of the material to be etched by the first plasma and the second plasma, an atmospheric pressure range of the discharging via capacitive coupling in the vacuum is 30-80 Pa.

5. The method for manufacturing a printed circuit board having an ultra-thin metal layer of claim 1, wherein the aliphatic amine includes methylamine, primary amine, or secondary amine; wherein the number of carbon atoms of the aliphatic amine is less than 7; and a treating time of the first plasma is 5-20s.

6. The method for manufacturing a printed circuit board having an ultra-thin metal layer of claim 1, wherein a ratio of cupric sulfate to water in the cupric sulfate solution is more than 1:2; and a treating time of the second plasma is 10-30s.

7. The method for manufacturing a printed circuit board having an ultra-thin metal layer of claim 1, wherein the surface of the material to be etched is made of polyimide material or epoxy resin material.

8. The method for manufacturing a printed circuit board having an ultra-thin metal layer of claim 2, wherein when the modification treatment is conducted on the surface of the material to be etched by the first plasma and the second plasma, an atmospheric pressure range of the discharging via capacitive coupling in the vacuum is 30-80 Pa.

9. The method for manufacturing a printed circuit board having an ultra-thin metal layer of claim 2, wherein the aliphatic amine includes methylamine, primary amine, or secondary amine; wherein the number of carbon atoms of the aliphatic amine is less than 7; and a treating time of the first plasma is 5-20s.

10. The method for manufacturing a printed circuit board having an ultra-thin metal layer of claim 2, wherein a ratio of cupric sulfate to water in the cupric sulfate solution is more than 1:2; and a treating time of the second plasma is 10-30s.

11. The method for manufacturing a printed circuit board having an ultra-thin metal layer of claim 2, wherein the surface of the material to be etched is made of polyimide material or epoxy resin material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a technical solution diagram of the PI film treatment in the present invention; wherein, 11 plasma chamber; 12 polyimide film; 13 unwinding; 14 winding; 15 positive electrode; 16 negative electrode.

(2) FIG. 2 is a technical solution diagram of treating a plurality of PP films at the same time in the present invention; wherein, 21 plasma chamber; 22 PP films; 23 positive electrode; 24 negative electrode.

(3) FIG. 3 is a diagram of a new selective plating process of two-layer flexible board; wherein, 31 polyimide (PI) film; 32 copper film; 33 drilling hole; 34 exposure, development, circuit etching; 35 electroless copper plating; 36 press film; 37 drilling hole and plating copper; 38; removing the film, and then micro-etching/electroless copper plating.

(4) FIG. 4 is a diagram of preparing the four-layer flexible printed circuit board by build-up process; wherein, 41 PI film; 42 copper film; 43 groove etching; 44 CL; 45 through via; 46 chemically deposited film; 47 electroplated copper film; 48 groove etching.

(5) FIG. 5 is a diagram of preparing the four-layer rigid printed circuit board by build-up process; wherein, 51 epoxy resin board coated with fiberglass cloth; 52 double-sided plating copper film; 53 groove etching; 54 PP; 55 through via; 56 chemically deposited copper film; 57 electroplated copper film; 58 groove etching.

(6) FIG. 6 is a diagram of preparing the rigid-flex printed circuit board by build-up process and new selective plating process; wherein, 60 PI film; 61 electroplated copper film; 62 groove etching; 63 PP; 64 CL; 65 through via; 66 copper deposition on the surface; 67 electroplated copper film; 68 dry film; 69 etched surface; 70 groove etching.

(7) FIG. 7 is a technical solution diagram of the preparation of the rigid-flex high density interconnection board and new selective plating process; wherein, 71 polyimide film (PI); 72 double-sided plated copper film; 73 groove etching; 74 CL; 75 PP; 76 blind via; 77 through via; 78 copper deposition on the surface; 79 electroplated copper film; 80 dry film; 81 etched surface; 82 groove etching.

DETAILED DESCRIPTION OF THE INVENTION

(8) The embodiments of the present invention are shown as below, and they are only used for explaining the present invention, rather than limiting the present invention.

(9) Referring to FIG. 1, the present invention uses the method as below to manufacture a single-sided or double-sided printed circuit board laminate having a PI substrate:

(10) (1) Providing a polyimide (PI) film roll on the winding device in a chamber of a low vacuum plasma generator. Vacuumizing the chamber to a vacuum level less than 20 Pa, and then feeding aliphatic amine gas (e.g., methylamine, ethylamine, primary amine, secondary amine etc.), to discharge and generate plasma to etch and graft the polyimide (PI) film. The winding device speed is controlled to ensure that the treatment time for the polyimide (PI) film passing through the plasma discharge region is 5-20s. The roughness of the surface of the polyimide (PI) film is increased by means of the plasma etching effect. At the same time, amino NH2 is grafted on the surface of the polyimide (PI) film.

(11) (2) Stopping supply of the aliphatic amine gas and pumping till the vacuum level is below 20 Pa, feeding the nitrogen bubbled by the cupric sulfate solution (Cupric sulfate: Deionized water 1:2) to conduct a plasma discharge treatment for 10-30s. Stopping the device and feeding the air, taking out the polyimide (PI) film.

(12) (3) Forming a copper film on the surface of the substrate by electroless copper plating or sputtering copper plating to meet the electroplating condition.

(13) (4) Thickening the copper film by electroplating to complete the manufacturing of a single-sided or double-sided laminate of the flexible printed circuit board.

(14) (5) Preparing the printed circuit board.

(15) Referring to FIG. 2, the present invention uses the method as below to prepare a single-sided or double-sided printed circuit board laminate having a PP substrate:

(16) The epoxy resin (PP) board coated with fiberglass cloth is suspended and provided between a positive electrode and a negative electrode of the low vacuum plasma generator. The single-sided or double-sided printed circuit board laminate having a PP substrate is prepared according to above steps of the first solution.

Embodiment 1

(17) Referring to FIG. 3, this embodiment mainly related to a selective plating method of two-layer flexible board, including:

(18) A. preparing a two-layer flexible board laminate including a polyimide (PI) film and a double-sided electroplated copper film;

(19) B. drilling a through via mechanically or by a laser;

(20) C. exposing, developing, and circuit etching;

(21) D. after intensively removing the adhesive by plasma, and etching to increase the roughness and the active groups of the PI surface, performing electroless copper deposition;

(22) E. pressing the dry film, exposing and developing;

(23) F. selectively electroplating only at the drilled through via;

(24) G. micro-etching/chemical copper plating, and proceed to the next procedure.

(25) The objective of selective electroplating is to plate copper at the through via, without plating copper on the flexible board laminate, to make the flexible board region more torsion resistant.

Embodiment 2

(26) Referring to FIG. 4, this embodiment mainly relates to a method of manufacturing a four-layer flexible printed circuit board (FPCB) by build-up process.

(27) A. preparing a two-layer flexible board laminate including the polyimide (PI) film and double-sided plated copper film;

(28) B. exposing, developing and etching two-layer circuits;

(29) C. pressing a cover layer, wherein the cover layer is heated and pressed in a vacuum without covering a copper foil;

(30) D. drilling a through via, removing the adhesive residue after drilling, plasma etching to increase the surface roughness and the active groups;

(31) E. chemical copper plating;

(32) F. thickening the copper layer by plating;

(33) G. exposing, developing, and etching the print circuits, to complete the preparation of the four-layer flexible printed circuit board, and then proceeding to the testing procedure.

Embodiment 3

(34) Referring to FIG. 5, this embodiment discloses a method of manufacturing a four-layer rigid printed circuit board by build-up process.

(35) A. preparing a two-layer rigid board laminate including a dielectric plate made of the epoxy resin (PP) coated with fiberglass cloth, and a double-sided electroplated copper film;

(36) B. exposing, developing and etching print two-layer circuits;

(37) C. heating and pressing the epoxy resin (PP) coated with fiberglass cloth in a vacuum, without covering a copper foil;

(38) D. drilling a through via, removing the adhesive residue after drilling, plasma etching to increase the surface roughness and the active groups;

(39) E. forming a copper film by electroless copper plating;

(40) F. thickening the copper film obtained from the last step by plating;

(41) G. exposing, developing and etching the print circuits, to complete a preparation of a four-layer rigid printed circuit board, and then proceeding to the testing procedure.

Embodiment 4

(42) Referring to FIG. 6, this embodiment discloses a method for manufacturing a rigid-flex printed circuit board by build-up process and a new selective plating process.

(43) A. providing a two-layer flexible board laminate (also called a double-sided copper clad laminate-CCL) including a polyimide (PI) film and a double-sided electroplated copper film, wherein the two-layer flexible board laminate is prepared by the first technical solution of the present invention;

(44) B. exposing, developing and etching circuits;

(45) C. directly pressing the cover layer and the epoxy resin (PP-Prepreg) coated with fiberglass cloth in a high temperature and a vacuum, without copper foil;

(46) D. laser or mechanical drilling a through via;

(47) E. after intensively removing the adhesive by plasma, increasing the roughness and the grafted active groups on the PI surface, performing electroless copper deposition;

(48) F. thickening the copper layer by electroplating;

(49) G. pressing the dry film;

(50) H. exposing, developing, and exposing the etched surface;

(51) I. etching, and removing the film to complete the preparation of the rigid-flex printed circuit board and then proceeding to the testing procedure.

Embodiment 5

(52) Referring to FIG. 7, this embodiment mainly relates to a method for manufacturing a rigid-flex high-density interconnection board and a new selective plating process.

(53) A. providing a two-layer flexible board laminate including a polyimide (PI) film and a double-sided electroplated copper film, wherein the two-layer flexible board laminate is prepared by the first technical solution of the present invention;

(54) B. exposing, developing and etching circuits;

(55) C. pressing the cover layer and the epoxy resin (PP) in a high temperature, a high pressure and a vacuum, without a copper foil;

(56) D. drilling a blind via by laser;

(57) E. mechanical drilling a through via;

(58) F. after intensively removing the adhesive by plasma, increasing the roughness and the grafted active groups on the PI surface, performing electroless copper deposition;

(59) G. filling the blind via 86 and thickening the copper layer by electroplating;

(60) H. attaching dry film;

(61) I. exposing, developing, and exposing the etching surface

(62) J. etching, and removing the film to complete the preparation of the rigid-flex high-density interconnection board and then proceeding to the testing procedure.

(63) The adhesive free flexible printed circuit board (FPCB) laminate having an ultra-thin polyimide (PI) and the adhesive free rigid printed circuit board laminate having an ultra-thin metal layer can be produced by the method of the present invention. Further, the method of the present invention can also be used for manufacturing multi-layer printed circuit board, blind via, and buried via by build-up process, and the selective plating process. The obtained built-up electroplated copper layer is thin, and can be used to produce the thinner circuits.

(64) The above description is just for the preferred embodiments of the present invention, and is not intended to limit the present invention. Any modifications, equivalent replacements, simple improvements etc. within the substantial contents of the present invention, fall in the scope of the present invention.