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What is Solder Resist?

What is Solder Resist?

Solder resist is an insulating ink that covers the surface of printed wiring boards and protects the circuit pattern.

One of the main roles of solder resist is to prevent solder from adhering to unnecessary parts when components are mounted on the board. At the same time, solder resist also acts as a permanent protective coating, protecting the circuit pattern from dust, heat, and moisture as well as insulating the board's circuitry.

Main Roles

Main Roles

1. Preventing solder from adhering to unnecessary areas

Solder resist prevents solder from adhering to areas other than electrical contacts and thereby causing short circuits when various components are soldered onto a printed wiring board.

2. Protecting the circuit pattern from dust, heat, and moisture

Solder resist protects circuit patterns from the affects of dust, heat, and moisture, ensuring that electronic devices will work for a long time.

3. Maintaining electrical insulation between circuit patterns

With the miniaturization of electronic devices, circuit patterns on the average board are now in the region of 50 to 150 µm, and are even thinner on package boards. Solder resist ensures that the circuit pattern remains insulated, and prevents shorting.

Photos of Solder Resist

  • Board surface after solder resist patterning

    Board surface after solder resist patterning

    Board surface after solder resist patterning

    Solder resist is the green area

  • Solder resist is the green area

    Solder resist is the green area

Types of Solder Resist

Solder resists are categorized by their film forming methods as alkaline developable solder resist, UV curable solder resist and thermally curable solder resist.

Alkaline Developable Solder Resist

This resist ink can shape a precise circuit pattern onto a PWB by exposing a negative film with the circuit pattern onto a PWB that is fully coated with solder resist via a screen print, spray coat or curtain coat.

UV Curable Solder Resist

A type of solder resist that hardens under UV light. It used for pattern printing via a screen print method.

Thermally Curable Solder Resist

A type of solder resist that hardens when heat is applied. It used for pattern printing via a screen print method.

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