Sheet welding preventing method

Abstract

The invention relates to a sheet welding preventing method, which comprises the following operation flow: (1) performing copper plate pre-treatment on a circuit board; (2) screen printing a first face by using a gas-guide base plate, standing, pre-baking the first face and cooling; (3) screen printing a second face by using a waste film as a cushion, standing and pre-baking the second face; and (4) aligning, developing and post-baking. Compared with the conventional sheet welding preventing method, the sheet welding preventing method has the innovation that: the first face is screen printed by adopting the gas-guide base plate and the second face is screen printed by using the waste film as the cushion, so that working staff can better control the hole-pass inking amount in a production process and control hole blockage to be at a rational level of approximate 80 percent; the method is simple in operation, high in efficiency and high in operability; when used for manufacturing a sheet, the method can obviously improve the hole blockage effect and can effectively improve the gas exhaust effect of hole passing when blocking and printing are carried out at the same time during singleface manufacturing and avoid the phenomenon that copper is exposed from a circuit; and the traditional time-wasting nail bed screen printing is obviated, so that the printing quality of the circuit board is greatly improved and the production efficiency of sheets is improved.

Description

technical field [0001] The invention relates to the technical field of PCB thin plate manufacturing, in particular to a thin plate anti-soldering method. Background technique [0002] In the circuit board manufacturing process, after the outer circuit is manufactured, the outer circuit must be protected against soldering to prevent the outer circuit from being oxidized or short-circuited by welding. Advanced welding process, save solder, prevent circuit short circuit, at the same time play a role in protecting copper wire and preventing welding misalignment of parts. In the past, the solder mask method used more in the industry is to pre-treat the copper surface of the circuit board, and then print a layer of solder mask ink on the circuit board by screen printing, and then go through pre-baking, exposure, development and post-processing in sequence. After baking and other processes, the anti-soldering treatment of the circuit board is completed. This traditional anti-sold...

AI Technical Summary

Problems solved by technology

This traditional anti-soldering method is widely used in the production process of circuit boards with a board thickness > 0.4mm, and the technology is relatively mature, and the output circuit board products meet the quality requirements of the market, but the silk screen thickness of the board using this anti-soldering method is ≤ However, there are many problems when using a thin plate of 0.4mm, for example: (1) Due to the small thickness of the thin plate, if a bed of nails is used for printing, it is necessary to ensure that the nails are dense and uniform, which requires a lot of labor and material costs, but it is very easy. The thickness of the ink is uneven, which affects the appearance of the circuit board and is prone to tinning or even short-circuit quality hazards during hot air leveling and SMT; if the aluminum sheet is used to plug holes first and then make one side, the ink is easy to contaminate the back, affecting the quality of the circuit board. Appearance and more time-consuming; if single-sided production with plugs and printing is used, because the board and the machine are close together, the exhaust effect is not good, the fullness of the plug holes cannot be guaranteed, and false copper exposure defects in via holes are likely to occur , During hot air leveling, due to the plug hole is not full, tin beads are hidden in the via holes, and the tin beads dissolve when passing through SMT, causing short circuits in other parts of the connection, which affects product performance

(2) When making single-sided pre-baking, due to the small thickness of the thin plate and the long pre-baking time, it is easy to develop uncleanly during exposure and development. If the time is short, the bridge oil ability will decrease and the ink will be easily stained when printing on the second side , during alignment, the ink will stick to the exposure film due to insufficient drying, resulting in copper exposure

This anti-soldering method overcomes the above-mentioned technical problems to a certain extent, but there is a problem that the amount of plug holes is not easy to control, so that the printing quality of the circuit board cannot be guaranteed