Soldering-inhibiting method for printed circuit board

Abstract

A welding-prevention method for printed circuit board is to coat a layer of half-solid welding-preventing material with a same expansion coefficient with the circuit board base material on one or twosurfaces of the circuit board and a metal foil covering on the said resin material, to apply a predetermined pressure onto it and to be baked for a predetermined time for solidification, then to remove the metal foil on the copper surface to be exposed by etching with chemical solvent, to remove the to-bo-exposed solid welding material above the copper surface with electric etching for exposing the above mentioned copper surface, and at least to remove the remained metal foil and dry film covered on the material with chemical solvent to finish the welding-prevention operation of the circuit board.

Description

technical field [0001] The present invention relates to a method for manufacturing a printed circuit board (PCB), in particular to a method for solder masking a printed circuit board. Background technique [0002] Generally, in the production of printed circuit boards, after the production of the outer layer circuit is completed, the outer layer circuit must be protected against soldering to avoid oxidation or soldering short circuit of the outer layer circuit. [0003] And the anti-soldering treatment method of known printed circuit board is to be coated on the board surface of this circuit board with poly-soldering green paint by screen printing, roller type coating, curtain coating or electrostatic spraying etc., first through pre-drying After cooling, use the method of exposure, imaging and development to remove the green paint that does not need to be retained, and finally bake at high temperature to completely harden the resin in the remaining green paint to form a pro...

AI Technical Summary

Problems solved by technology

[0005] 1. To apply solder resist green paint to printed circuit boards by means of screen printing or roller coating, multiple screen printing or roll printing procedures are required to accumulate the green paint to the required thickness. more complicated

[0006] 2. During the high-temperature baking process of the printed circuit board, since the expansion coefficient of the resin material in the solder resist green paint is different from that of the circuit board base material, internal stress is easily generated between the resin material and the circuit board , causing the board to flex

[0007] 3. The thickness of the solder resist green paint layer is not easy to control, resulting in electrical instability of the circuit board

[0008] 4. In the process of coating the solder mask green paint on the circuit board, it is easy to infiltrate air bubbles, resulting in poor reliability of the solder mask, and the formed solder mask has a short life

[0009] 5. The method of coating the solder resist green paint on the circuit board cannot make the solder resist green paint fill the through holes on the circuit board. Therefore, before coating, the through holes are usually filled with insulating filler and brushed After leveling, the coating of solder resist green paint is carried out, thus increasing the time and cost of making printed circuit boards

[0010] 6. When coating the solder resist green paint on the circuit board, it is difficult to form a coating layer on the copper foil circuit, and the bonding degree between them is poor

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