The solder mask is a coating that protects the circuit from electrical shorts and corrosion as well as providing electrical insulation, allowing higher voltage traces to be placed at a closer proximity to each other.
Once you have decided on your design of your Printed Circuit Board you need decide on options that will suit your requirements for your board. One of the options is the choice to have a solder mask and/or silkscreen legend. Why not deviate from the standard green printed circuit board and pick a color that will match your corporate logo?
It is important, even for your prototype PCB’s to have a solder mask and silkscreen legend for many reasons. Without the solder mask, your board would be plain copper, or what is known as a bare board with Tin Plating (tin, lead and usually a silver mixture). The Tin plating is placed on the bare board to allow soldering to take place and also slows down the rate of oxidation in the copper.
Today the Solder Mask application is LPI (Liquid Photo Image), which is applied to the production panel in a silkscreen printing process one side at a time. It is then dried in an oven and then the solder mask film is aligned to the pads and bared in an UV exposing machine then placed in a conveyorised developer to remove all the areas (SMT pads and holes) that will be required to have the surface finish applied later like HASL, Immersion Gold, OSP, etc.
The most important function of the solder mask is to keep the solder on the pads, which will reduce the formation of bridges or unintended connections. In some cases, such as wave soldering, solder masks are a critical element of this process whereas in other cases, it enables a more efficient and more accurate hand solder job as the solder covers the entire board except for the pads. The colour of the solder mask is not vital to the function of the board, rather providing a distinctive colour to your design and enabling better visibility to your copper connections. There is an option to have a partial solder mask that will cover a specified part of the pad, rather then exposing the entire pad. This would be ideal if there is a pad underneath a chip, leaving the pad exposed and vulnerable to solder bridges.
Exposed vias are usually covered with the solder mask and silkscreen as this will provide protection from corrosion and electrical shorts while also providing a larger surface area. If a board does not contain a solder mask, it is not an issue, it will mean that care must be taken when soldering as the solder mask reduces cost of mistakes and time taken to complete the solder and components.
We offer a range of Solder Mask colour options such as green, blue, purple, red, yellow, white, black matt and black gloss as well as the option to have no solder mask. These options apply to our FR4 (2-20 layer), Full Spectrum (1-40 layer) and Aluminum Printed Circuit Boards.
For more information on our range of solder mask solutions, please contact us via webform enquiry or by phone.
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