YB-700 Thermosetting Yellowing-Resistant LED White Ink

What Is It?

YB-700 is a white, two-component thermosetting solder-mask ink developed for LED PCB and white reflective solder-mask applications where high reflectivity, yellowing resistance and high temperature tolerance are required in a single film. It is supplied as a base ink and a separate hardener that are mixed 80 : 20 by weight before use.

The cured film has a 6H pencil hardness, 100/100 adhesion on 3M tape, and survives three passes of 260 °C hot-air leveling without yellowing or losing bond. It is also fully compatible with ENIG (electroless nickel / immersion gold) and immersion tin plating, so the same white mask can be used on boards that go through both processes. The high reflectivity makes it the standard choice for LED aluminium PCB and LED FR4 panels where the white solder mask is part of the optical stack.

Key Features

• Two-component, long pot life. 80% base + 20% hardener, mixed just before use. Pot life 8 hours at room temperature — long enough for a full shift, short enough to avoid waste.
• Thermosetting cure. 150 °C for 30 minutes in a hot-air oven, or 200 °C for 4 minutes on an IR belt conveyor. The cured film is hard, glossy and fully cross-linked.
• 6H surface hardness. Hard enough to survive assembly, rework and in-field handling without scratching. Pencil test at 700 g load.
• 100/100 adhesion. Passes 3M medium-tack tape cross-hatch test after full cure. No lift, no blister.
• 260 °C solder heat resistance. Three cycles of 260 °C × 10 seconds hot-air leveling with no yellowing, no loss of bond, no loss of reflectivity.
• Good resistance to plating chemistry. Compatible with ENIG (electroless Ni / immersion Au) and immersion tin plating. The white mask survives the plating line intact and strips cleanly afterwards if rework is needed.

Process Flow

The full sequence from substrate to finished part. Exact temperatures and times depend on the application; full details are in the operating parameters table below.

Technical Specifications

Operating Parameters — Step by Step

1. Mixing. Weigh 80 parts of base ink and 20 parts of hardener into a clean container. Mix thoroughly for at least 10 minutes, scraping the sides and bottom, until the blend is completely uniform. The pot life of the mixed ink is 8 hours at room temperature — mix only what you can use in a shift.
2. Thinning. If viscosity adjustment is needed, use YB-02 ink thinner or anti-whitespirit thinner. Use the supplier-recommended dilution only; off-the-shelf generic thinners can cause scumming or haze. After thinning, rest 10–20 minutes for air to escape before printing.
3. Screen printing. Use a 77T–51T polyester screen and a polyurethane or hard-rubber squeegee at 60–70 Shore A. Print in a single pass; the wet film should be thick enough to give a fully covered, glossy surface after cure.
4. Leveling. After printing, let the panel level for 10–20 minutes. This relaxes the screen pattern and lets air bubbles rise out of the film before cure.
5. Curing. Hot-air convection oven at 150 °C for 30 minutes, or infrared belt conveyor at 200 °C for 4 minutes. Either route gives a fully cross-linked film.
6. Inspection. The cured film should be uniformly white, glossy, and free of orange peel, pinholes or unlevel areas. Adhesion and hardness can be confirmed on a test coupon with a cross-hatch tape pull and a pencil hardness test.

Typical Applications

• LED FR4 PCBs (single and double sided)
• Aluminium LED PCBs
• White reflective solder mask on lighting modules
• COB (chip-on-board) LED substrates
• Backlight panels and edge-lit LED strips
• White solder mask on any PCB where high reflectivity and yellowing resistance matter

Storage and Safety

• Storage of unmixed ink. Sealed, in a cool dry dark place below 25 °C. Shelf life of unopened base and hardener is typically 6–12 months. Do not expose to direct sunlight or extreme temperature.
• Pot life of mixed ink. 8 hours at room temperature. Do not use mixed ink that has been sitting for longer — partial cure will cause scumming, poor adhesion and loss of heat resistance.
• Mixing discipline. Use a clean container and stirrer. Contamination with other inks, dust or moisture will cause cratering, fisheyes or cure problems.
• Thinner choice. Use YB-02 or the supplier-recommended thinner only. A generic thinner can cause whitening, hazing or bond failure.
• Ventilation and PPE. Use in a well-ventilated area. Wear nitrile gloves and safety glasses. Avoid skin and eye contact; in case of contact, wash immediately with soap and water.

Quality Inspection

Each batch is checked on a production test panel before it ships. Below: typical adhesion, exposure and development results on PCB and metal substrates.