What is a solder mask made of?

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And function?

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Alina 5 years 1 Answer 324 views 0

Answer ( 1 )

  1. Miki
    0
    December 20, 2019 at 11:28 AM

    Solder mask or solder mask or solder mask is a thin lacquer-like polymer layer that is usually applied to the copper traces of a printed circuit board (PCB) to protect against oxidation and to prevent the formation of solder bridges between closely spaced solder pads. A solder bridge is an unintentional electrical connection between two conductors using a small solder blob. PCBs use solder masks to prevent this. The solder mask is not always used for hand-soldered assemblies but is required for mass-produced circuit boards that are automatically soldered using reflow or solder bath techniques. After application, openings must be made in the solder mask wherever components are soldered, which is achieved by photolithography. The solder mask is traditionally green but is now available in many colors.

    The solder mask is available in different media depending on the requirements of the application. The cheapest solder mask is an epoxy liquid that is sifted through the pattern onto the circuit board. Other types are LPSM or LPI (Liquid Photo Imageable Lot Mask) and DFSM (Dry Film Photo Imageable Lot Mask). LPSM can be screen printed or sprayed onto the circuit board, exposed to the pattern, and developed to provide openings in the pattern for parts to be soldered to the copper pads. DFSM is vacuum laminated onto the circuit board, then exposed and developed. All three processes usually go through thermal curing after defining the pattern, although LPI solder masks are also available for UV curing.

    In automating electronic design, the solder mask is treated as a layer on the circuit board and like any other layer, e.g. B. the copper and screen printing layer, described as a Gerber file. Typical names for these layers are tStop / bStop (EAGLE), LSMVS / LSMRS (WEdirekt) or GTS / GBS (Gerber and many others).

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