METHOD FOR MANUFACTURING PRINTED CIRCUIT BOARDS
A method for manufacturing a PCB is related. The method includes providing a substrate with two opposite conductive layers and defining a through hole passing through the two conductive layers; forming a first electrically conductive metal layer on an inner surface of the substrate in the through hole using an electro-less plating process; forming a second electrically conductive metal layer on the first electrically conductive metal layer using an electro-plating process till the through hole being filled.
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1. Technical Field
The present disclosure generally relates to printed circuit boards, and particularly, relates to a method for manufacturing printed circuit boards (PCBs).
2. Description of Related Art
As technology progresses, microphones, portable computers and other electronic products have achieved ever greater levels of miniaturization by the use of double-sided PCBs and multilayer PCBs having via-holes and buried-holes.
Usually, a through hole metalizing process is employed in a traditional method for manufacturing double-sided PCBs or multilayer PCBs to establish electrical connection between circuits of different layers. The through hole metalizing process generally includes a step of filling electrically conductive material into a through hole of a PCB substrate having a base and two copper layers formed on opposite surfaces of the base. As such, the conductive material electrically connects the copper layers to each other.
However, the thermal expansion index of the electrically conductive material may be different from that of the copper layers. As a result, because of heating and cooling of the PCB, interspaces are formed between the conductive material and the PCB substrate. Thus, in wet etching process, etchant may be lodged into the interspaces and corrode the PCB substrate.
What is needed, therefore, is a method for manufacturing a printed circuit board to overcome the above-described problem.
Many aspects of the embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the different views.
Referring to
In step 1, as shown in
The base 13 is an insulating resin layer, and the first conductive layer 11 and the second conductive layer 12 are made of copper. For purpose of manufacturing thin electrical traces, the thickness of the first conductive layer 11 and the second conductive layer 12 is less than or equal to 10 micrometers, and the diameter of the through hole 101 is in the range from 50 micrometers to 100 micrometers. Additionally, the base 13 can be an overlapping structure of a unit including an insulating resin layer and two conductive layers disposed on two opposite surfaces of the resin layer.
In step 2, as shown in
In detail, as shown in
As shown in
In step 3, as shown in
As shown in
In the present embodiment, both the first and second electrically conductive metal layers 20, 40 are compact, and have approximate similar thermal expansion indexes to those of the two conductive layers 11, 12. Therefore, interspace is prevented from being formed between the two electrically conductive metal layers 20, 40 and the two conductive layers 11, 12, the inner surface 1011 is protected from corrosion in wet process.
Referring to
As shown in
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As showing in
Referring to
Referring to
While certain embodiments have been described and exemplified above, various other embodiments will be apparent to those skilled in the art from the foregoing disclosure. The present invention is not limited to the particular embodiments described and exemplified but is capable of considerable variation and modification without departure from the scope of the appended claims.
Claims
1. A method for manufacturing a PCB, the method comprising:
- providing a substrate including a base and two conductive layers formed on opposite surfaces of the base, the substrate defining a through hole passing through the two conductive layers;
- forming a first electrically conductive metal layer on an inner surface of the substrate in the through hole using an electro-less plating process;
- forming a second electrically conductive metal layer on the first electrically conductive metal layer using an electro-plating process filling the through hole.
2. The method as claimed in claim 1, further comprising applying a protecting layer onto outer surfaces of the substrate while exposing the through hole before forming the first electrically conductive metal layer.
3. The method as claimed in claim 1, wherein the first electrically conductive metal layer includes a first portion formed on the outer surfaces of the substrate and a second portion formed on the inner surface, the method further comprising applying a protecting layer onto the first portion of the first electrically conductive metal layer while exposing the second portion thereof before forming the second electrically conductive metal layer.
4. The method as claimed in claim 2, wherein the protecting layer is a dry photoresist film, liquid photoresist layer or binder layer.
5. The method as claimed in claim 3, wherein the protecting layer is a dry photoresist film, liquid photoresist layer or binder layer.
6. The method as claimed in claim 3, further comprising removing the protecting layer and the first portion of the first electrically conductive metal layer.
7. The method as claimed in claim 1, further comprising smoothening opposite ends of the second electrically conductive metal layer, the opposite ends thereof protruding from the two opposite conductive layers.
8. A method for manufacturing a PCB, comprising:
- providing a substrate, the substrate including a base and two conductive layers formed on opposite surfaces of the base and defining a blind hole passing through one of the two conductive layer and the base;
- forming a first electrically conductive metal layer on an inner surface of the substrate in the blind hole using an electro-less plating process;
- forming a second electrically conductive metal layer on the first electrically conductive metal layer using an electro-plating process till the through hole being filled.
9. The method as claimed in claim 8, further comprising applying a protecting layer onto outer surfaces of the substrate while exposing the blind hole before forming the first electrically conductive metal layer.
10. The method as claimed in claim 8, wherein the first electrically conductive metal layer includes a first portion formed on an outer surfaces of the substrate and a second portion formed on the inner surface, the method further comprising applying a protecting layer onto the first portion of the first electrically conductive metal layer while exposing the second portion thereof before forming the second electrically conductive metal layer.
11. The method as claimed in claim 9, wherein the protecting layer is a dry photoresist film, liquid photoresist layer or binder layer.
12. The method as claimed in claim 10, wherein the protecting layer is a dry photoresist film, liquid photoresist layer or binder layer.
13. The method as claimed in claim 10, further comprising removing the protecting layer and the first portion of the first metal layer.
14. The method as claimed in claim 8, further comprising smoothening opposite ends of the second electrically conductive metal layer, the opposite ends thereof protruding from the two opposite conductive layers.
Type: Application
Filed: Apr 19, 2009
Publication Date: Feb 25, 2010
Applicant: FOXCONN ADVANCED TECHNOLOGY INC. (Tayuan)
Inventors: CHUNG-JEN TSAI (Tayuan), YU-CHENG HUANG (Tayuan), HUNG-YI CHANG (Tayuan), CHENG-HSIEN LIN (Tayuan)
Application Number: 12/426,276
International Classification: C25D 5/02 (20060101); C25D 7/00 (20060101);