What is UV solder resist ink? How to choose the corresponding photoinitiator?
Printed circuit board on the copper circuit made, the board surface in addition to solder joints, the rest of the board need to cover a layer of solder resist to ensure that the board through the wave soldering, only solder joints at the solder, the rest of the line graphics part not stained with solder. In the screen printing method on the solder resist is used in the solder resist ink. Because of the different curing methods, solder resist ink also has two kinds of heat-set and light-set, at present, mainly with light-set solder resist ink. Solder resist graphics are also formed by the ink through the screen leakage printing after curing, because it is a permanent coating on the printed circuit board, so to have excellent electrical properties and physical mechanical properties, but also to be able to resist 260 ℃ (military products to resist 288 ℃) high temperature.
UV solder resist ink oligomer mainly choose good heat resistance, good insulation, good adhesion with copper resin, such as bisphenol A – epoxy acrylate, phenolic epoxy acrylate and polyurethane acrylate, currently commonly used is phenolic epoxy acrylate. The reactive diluent is polyfunctional acrylate with monofunctional hydroxyl ester, photoinitiator is mainly used 907 or DETX. the previous pigment is mainly phthalocyanine green, but now the coloring pigment has black, gold and other options, and can add more fillers, which is beneficial to improve heat resistance and reduce volume shrinkage. In order to improve the adhesion of ink and copper, you also need to add a little adhesion promoter, such as phosphorus methacrylate mono- or di-ester.
When preparing UV solder resist inks, photoinitiators need to be carefully selected. In addition to 907 and DETX mentioned above, the widely spread 784 and 369 are suitable for this system.
UV Photoinitiator Same series products