Réponse rapide : Buyers choosing a photoinitiator for PCB solder mask should usually separate three different screening paths before they start comparing names: a mainstream PCB photoresist and solder-mask route, a darker or more opaque long-wave route for harder-to-cure films, and a LED-oriented package-design route that depends on a co-initiator. In Longchang’s current product positioning, Photo-initiateur 907 deserves early attention when the project is directly about PCB photoresist, solder mask ink, low yellowing, and pigment-tolerant free-radical curing. Photoinitiateur 369 moves up when the mask is darker, more opaque, or harder to cure through and the team wants the long-wave absorption and solder-mask relevance already supported on the company page. Photoinitiateur DETX becomes more relevant when the line is moving toward 385 to 420 nm LED-capable package design, thicker films, or colored systems, and the formulator is ready to build the route correctly with a co-initiator such as a tertiary amine.
That is the practical split. PCB solder mask is not judged by cure speed alone. Buyers usually care about pigment burden, cure completeness, line wavelength, insulation-protection reliability, and whether the package still behaves well once the film is no longer an easy clear UV ink.
Why PCB solder mask needs a tighter shortlist than general UV inks
Solder mask is a permanent protective layer on the PCB. In practical board manufacturing, it is expected to help protect copper circuitry, maintain electrical isolation, and survive downstream process stress. That means a weak photoinitiator choice can create problems well beyond simple surface tack.
- Pigment burden matters: solder mask is often not a clear easy-cure film, so light penetration can become a real bottleneck.
- Cure reliability matters: a mask that looks acceptable on the surface can still leave deeper undercure risk in the film.
- LED transition matters: some lines are still conventional UV-first, while others are screening longer-wave or LED-capable routes.
- Package design matters: not every useful route is a simple one-product answer, especially once the formulator moves into Type II logic.
That is why a generic “photoinitiator for UV ink” answer is too loose. A better shortlist starts by deciding whether the project is mainly a mainstream PCB solder-mask screen, a darker or more opaque long-wave screen, or a LED-oriented package-design problem.
For the broader electronics branch, see Photoinitiator for Electronic Coatings.
Quick comparison table: 907 vs 369 vs DETX
| Produit | Best first fit | Why buyers shortlist it | When it is not the first option |
|---|---|---|---|
| 907 | Mainstream PCB photoresist and solder-mask screening where low yellowing and pigment tolerance matter | Longchang directly lists PCB photoresist and solder mask ink, plus rapid UV decomposition in the 250 to 390 nm range, low yellowing, and compatibility with pigmented systems | When the team already knows the film is darker, more opaque, or better served by a longer-wave or LED-oriented route |
| 369 | Darker, more opaque, or deeper-curing solder mask and photoresist routes needing stronger long-wave response | Longchang directly lists solder mask inks and photoresist, highlights long-wave absorption around 350 to 380 nm, and positions 369 for dark-color systems and deeper curing | When the buyer wants the simplest mainstream PCB benchmark or does not need the stronger long-wave and deeper-cure logic |
| DETX | LED-oriented or thicker-film package design with colored-system pressure and co-initiator support | Longchang positions DETX for electronic materials and electronic coatings, peak absorption near 385 nm, response at 405 and 420 nm LEDs, and stronger performance in colored systems and thicker films | When the team needs a direct one-product PCB benchmark instead of a Type II route that must be built with a co-initiator package |
When 907 is the better fit
907 deserves the first screen when the project is still close to a mainstream PCB solder-mask or photoresist route and the team wants a supported benchmark before moving into more specialized packages.
- PCB relevance is explicit: Longchang directly lists PCB photoresist et solder mask ink as core applications.
- The UV range is practical for common screening: the company page describes rapid radical generation with primary absorption in the 250 to 390 nm range.
- Appearance-sensitive work benefits: Longchang highlights low yellowing, which is useful in lighter-color or appearance-sensitive systems.
- Pigment tolerance is already supported: the product page also notes good compatibility with pigmented systems, which matters because solder mask is not always an easy optical film.
If the buyer wants a practical first benchmark for PCB solder mask before moving into harder-cure or LED-oriented routes, 907 is usually the cleanest place to begin.
When 369 is the better fit
369 moves up when the mask stops behaving like an easy benchmark and the team needs a route Longchang already supports for solder mask inks, photoresist, darker systems, and deeper curing.
- Solder-mask relevance is direct: Longchang explicitly lists solder mask inks et photoresist under electronics applications.
- Long-wave response is stronger: the current page highlights absorption in the 350 to 380 nm region.
- Darker-system logic is already supported: Longchang positions 369 as particularly suitable for dark-color systems and for situations where deeper or pigmented cure matters.
- LED discussion stays plausible: the company page also notes adaptation for new UV LED light sources, which helps when the line is not purely conventional UV anymore.
If the real problem is pigment burden, deeper cure, or a film that is not curing comfortably under a simpler benchmark route, 369 usually deserves earlier attention than a routine mainstream candidate.
When DETX is the better fit
DETX belongs in a different decision path because the package logic changes. It becomes more relevant when the formulator wants a longer-wave or LED-capable route and is ready to build a proper Type II package.
- Electronics relevance is already supported: Longchang positions DETX for electronic materials et electronic coatings.
- LED-oriented wavelength fit is stronger: the current page gives DETX a peak near 385 nm and response to 405 nm and 420 nm LEDs.
- Thicker-film and colored-system value is explicit: Longchang also frames DETX as stronger in colored systems et thicker films.
- Package discipline matters: the company page makes clear that DETX is a Class II route that needs a co-initiator such as a tertiary amine to generate radicals efficiently.
That means DETX should not be treated as a drop-in substitute for every PCB solder-mask package. It is better understood as a deliberate design choice when LED fit, penetration, or longer-wave behavior is part of the real process constraint.
How buyers should choose before requesting samples
1. Start with the real film difficulty
Do not assume a lighter, easier-curing mask and a darker or more opaque mask should start with the same first shortlist.
2. Keep wavelength fit visible early
907 fits mainstream UV screening well, 369 moves the discussion toward stronger long-wave support, and DETX becomes more relevant when the line is leaning toward 385 to 420 nm LED-capable package design.
3. Separate one-product benchmarking from package design
If the team wants the cleanest mainstream first pass, 907 usually belongs early. If the real issue is difficult cure-through, 369 moves up. If the line needs a Type II longer-wave route, DETX only makes sense when the co-initiator package is built intentionally.
4. Keep the first sample round tight
A useful first screen is often one mainstream PCB route, one darker-film long-wave route, and one LED-oriented package-design route if that path is genuinely under review. That usually gives cleaner signal than comparing too many similar products.
5. Use related cluster pages to narrow the decision tree
If the project is closer to broad electronics protection rather than a dedicated solder-mask problem, continue with Electronic Coatings. If the line is really a photoresist-first question, review Photoinitiator for Negative Photoresist.
Recommended Longchang product and article paths
- Mainstream PCB solder-mask route: Photo-initiateur 907
- Darker or more opaque long-wave route: Photoinitiateur 369
- LED-oriented package-design route: Photoinitiateur DETX
- Broader electronics article: Photoinitiator for Electronic Coatings
- Photoresist article: Photoinitiator for Negative Photoresist
- Related printing application page: Photoinitiator for UV Screen Ink
- Broader family guide: How to Choose a Photoinitiator for UV Curing
FAQ
Which photoinitiator is the best starting point for PCB solder mask?
In Longchang’s current product positioning, 907 is usually the strongest first benchmark when the project is directly about PCB photoresist or solder mask ink and the team wants a mainstream free-radical route.
When should I choose 369 instead of 907?
Choose 369 earlier when the mask is darker, more opaque, or harder to cure through and the process needs stronger long-wave support plus a route Longchang already positions for solder mask inks and photoresist.
When does DETX belong in the shortlist?
DETX belongs in the shortlist when the project is moving toward a 385 to 420 nm LED-capable route, thicker films, or colored-system pressure, and the formulator is ready to build a proper Type II package with a co-initiator.
Are 907, 369, and DETX interchangeable in PCB solder mask?
No. They may all enter UV-curing discussions, but Longchang’s supported application paths and cure logic are different enough that buyers should shortlist them by PCB fit, film difficulty, wavelength window, and package design rather than by name alone.
Need a tighter PCB solder-mask shortlist?
If your board process is being limited by pigment burden, weak cure-through, a move toward LED curing, or uncertainty about package design, define the real bottleneck first and then compare only the most relevant Longchang routes. That usually produces a cleaner sample plan than treating all photoinitiators as interchangeable.