What is UV solder resist ink? How to choose the corresponding photoinitiator?
Quick answer: For practical formulation work, photoinitiator screening starts with the light source and film build, then checks yellowing, adhesion, and cure completeness under real production conditions.
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
A practical selection route for photoinitiator-related projects
When technical buyers or formulators screen photoinitiators, the most useful decision frame is usually cure quality plus application fit: which package cures reliably, keeps appearance acceptable, and still works under the lamp, film thickness, and substrate conditions of the actual process.
- Match the package to the lamp first: mercury lamps, UV LEDs, and visible-light systems can rank the same photoinitiators very differently.
- Check depth cure and surface cure separately: a film that feels dry on top can still be weak underneath.
- Balance yellowing with reactivity: the strongest deep-cure route is not always the best commercial choice if color or migration risk becomes unacceptable.
- Use the final formula as the benchmark: pigment load, monomer package, and film thickness can all change the apparent ranking of the same initiator.
Recommended product references
- CHLUMINIT 819: Useful when a formulation needs stronger absorption and deeper cure support.
- CHLUMINIT 1173: A practical comparison point for classic short-wave UV initiation.
- CHLUMINIT ITX: A useful long-wave support route in many printing-ink packages.
- CHLUMINIT CQ: A direct reference for visible-light and color-sensitive curing discussions.
FAQ for buyers and formulators
Why are blended photoinitiator packages so common?
Because one product may control yellowing or lamp fit well while another improves cure depth or line-speed performance, so the full package is often stronger than any single grade.
Should incomplete cure always be solved by adding more initiator?
Not automatically. The real limitation may be the lamp, film thickness, pigment shading, or the rest of the reactive system rather than simple under-dosage.