Systems and methods for reducing overhang on electroplated surfaces of printed circuit boards
View Patent ↗Systems and methods for reducing overhang on electroplated surfaces of printed circuit boards are described. One such method includes applying a first resist layer on a substrate having a first copper layer, applying a first image to the first resist layer, developing the first resist layer in accordance with the first image, applying a second copper layer on the first copper layer, electroplating a first metallic layer on the second copper layer, removing the first resist layer, etching a portion of the first copper layer, removing the first metallic layer, depositing a third copper layer on a surface of the assembly, applying a second resist layer on the third copper layer, applying a second image to the second resist layer, developing the second resist layer in accordance with the second image, electroplating a preselected metal layer on the third copper layer, removing the second resist layer, and etching a portion of the third copper layer.
1. A method for manufacturing a printed circuit board assembly, the method comprising:
applying a first resist layer on at least one part of a substrate having a first copper layer formed on a first surface of the substrate;
applying a first image to at least one part of the first resist layer;
developing the first resist layer in accordance with the first image;
applying a second copper layer on a surface of the first copper layer;
electroplating a first metallic layer on at least a portion of a surface of the second copper layer;
removing the first resist layer;
etching at least a portion of the first copper layer;
removing the first metallic layer;
depositing a third copper layer that contacts and covers at least a portion of the second copper layer, at least a portion of the first copper layer, and at least as portion of the substrate of the printed circuit board assembly;
applying a second resist layer on the third copper layer;
applying a second image to at least one part of the second resist layer;
developing the second resist layer in accordance with the second image;
electroplating a preselected metal layer on at least a portion of the third copper layer;
removing the second resist layer; and
etching the third copper layer from at least a portion of the second copper layer not covered by the preselected metal layer, the at least a portion of the first copper layer, and the at least portion of the substrate.
2. The method of claim 1 , wherein the electroplating the preselected metal layer on the at least the portion of the third copper layer comprises:
electroplating a nickel layer on at least a portion of the third copper layer; and
electroplating a gold layer on the nickel layer.
3. The method of claim 1 , wherein the first metallic layer comprises tin.
4. The method of claim 1 , wherein the first metallic layer comprises tin and lead.
5. The method of claim 1 , wherein the applying the second image to the at least one part of the second resist layer comprises aligning the second image along the second resist layer in accordance with a location of the first image.
6. The method of claim 5 , wherein the aligning the second image along the second resist layer in accordance with the location of the first image comprises at least some mis-alignment between a location of the second image and the location of the first image.
7. The method of claim 1 , wherein a width of the second image is less than a width of the first image.
8. The method of claim 1 , wherein a width of the second image is greater than a width of the first image.
9. The method of claim 1 , wherein the developing the second resist layer in accordance with the second image comprises sanding the second resist layer in accordance with the second image.
10. The method of claim 1 , wherein the first resist layer comprises a resist selected from the group consisting of a liquid photoresist, a dry film resist, a positive photoresist, and a negative photoresist.
11. The method of claim 1 , wherein the applying a second resist layer on the third copper layer comprises using a process selected from the group consisting of an ink jet process, a screen print process, a spray coat process, a roller coat process, a dip coat process, a roll laminate process, and an electroplating process.
12. The method of claim 1 , wherein the electroplating the preselected metal layer on the at least a portion of the third copper layer comprises wrapping at least a portion of the preselected metal layer along a side wall formed by the first copper layer and the second copper layer.
13. The method of claim 1 , wherein the etching the at least the portion of the third copper layer comprises using a copper etching solution selected from the group consisting of ammoniacal etch, persulfate etch, and sulfuric peroxide etch.
14. The method of claim 1 , wherein the depositing the third copper layer on the surface of the printed circuit board assembly comprises using a deposition process selected from the group consisting of electroless deposition, sputter deposition, spray coating deposition, and chemical vapor deposition.
15. The method of claim 1 , wherein a width of the second image is about equal to a width of the first image.