YB-800 Liquid Photosensitive Solder-Resist Ink

What Is It?

YB-800 is a two-component liquid photosensitive solder-mask ink for fine-line printed circuit boards. It is mixed 3 : 1 (base : hardener) by weight, screen-printed, pre-baked, exposed through a phototool on a 21-step exposure scale, developed in 1% sodium carbonate, and post-cured. The cured film gives a hard, glossy green solder mask that survives lead-free hot-air leveling, ENIG plating and immersion tin plating without lift, blister or chemical attack.

The standard grade is formulated to meet EU RoHS requirements. For customers who need a halogen-free solder mask, the same YB-800 is available in a halogen-free variant. YB-800 is one of the workhorse liquid photoimageable solder masks used in the Chinese PCB industry and is the right choice for multilayer and fine-line boards where 3 mil (75 µm) green-oil bridges and BGA via plugging are routine.

Key Features

• Two-component, photoimageable. 3 : 1 base : hardener mix ratio. Liquid photosensitive — develop in 1% Na₂CO₃, no organic solvent. Standard phototool workflow on a 21-step exposure scale.
• 3 mil green-oil bridge, BGA via plugging. Resolution down to 3 mil (75 µm) green-oil bridge between pads. Built for BGA — fully supports via plugging on the same line.
• Compatible with lead-free HASL, ENIG, immersion tin. Cured film survives 260 °C lead-free hot-air leveling, electroless nickel / immersion gold plating, and immersion tin plating. No lift, no blister, no chemical attack on the mask.
• RoHS standard, halogen-free variant. Standard grade meets EU RoHS. Halogen-free variant available for medical, automotive and other demanding applications.
• Aqueous development, no organic solvent. Develop in 1% Na₂CO₃ solution at 30 °C. The line does not need a solvent develop / strip section, which simplifies the equipment and the waste treatment.
• Compatible with existing exposure and develop lines. Fits any standard 21-step exposure unit and a 1% Na₂CO₃ spray developer. The pre-bake and post-cure temperatures (75 °C and 150 °C) are within the range of any commercial PCB oven.

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. Substrate preparation. Acid-clean or mechanical scrub the copper surface. A clean, micro-roughened copper surface is essential for full adhesion and to prevent resist lift during plating or HASL.
2. Mixing. Weigh 3 parts base and 1 part hardener into a clean container. Add thinner if needed for the chosen mesh. Stir or shake for 5–10 minutes until the base and hardener are completely blended.
3. Rest. Let the mixed ink stand 10–20 minutes. Air bubbles introduced during mixing will rise and clear, and the viscosity will stabilize.
4. Screen printing. Use a 43T mesh for standard PCB, 36T mesh for lead-free HASL, ENIG or immersion tin boards. Print the solder side first, then the component side. A single wet pass with a sharp squeegee is the standard.
5. Rest after print. 10–40 minutes. Thicker copper needs a longer rest, but never more than 4 hours.
6. Pre-bake. Hot-air convection oven at 75 °C. First side 15–20 minutes, second side 25–30 minutes if printed separately. If both sides are printed and baked together, 25–40 minutes total.
7. Cool and rest. At least 20 minutes to cool below 30 °C, but not more than 24 hours before exposure.
8. Exposure. 21-step exposure scale, sensitivity 9–13 grid. Use a fine-line test strip to confirm correct exposure for your lamp, phototool and copper thickness.
9. Rest after exposure. At least 10 minutes. This allows the photoinitiated reaction to complete before development.
10. Develop. 1 wt% Na₂CO₃ aqueous solution, 30 °C ± 2, spray pressure 2.0–2.5 kg/cm², 40–90 seconds. The unexposed film washes away; the image appears sharply with no scumming.
11. Post-cure. 150 °C for 60 minutes (HASL), 50 minutes (ENIG / immersion tin). For plugged vias, run a two-stage cure: 75 °C for 120 minutes, then 150 °C for 60 minutes.

Typical Applications

• Multilayer and double-sided PCB (consumer electronics, industrial control, automotive)
• Lead-free HASL boards
• ENIG (electroless nickel / immersion gold) boards
• Immersion tin (ImSn) boards
• BGA — fine-pitch and via plugging
• Medical, aerospace and other high-reliability boards (halogen-free variant)

Storage and Safety

• Storage of unmixed components. Sealed, in a cool dry dark place below 25 °C. Shelf life of unopened base and hardener is typically 6–12 months.
• Pot life of mixed ink. The mixed ink begins to thicken gradually; use within the same shift. Do not store mixed ink overnight — partial cure will cause scumming and poor resolution.
• Developer handling. 1% Na₂CO₃ is mildly alkaline. Wear nitrile gloves and safety glasses. Wash skin with water if contact occurs.
• Ventilation. Pre-bake and post-cure ovens should be vented to outside air. Cured film is inert; uncured components should not be heated in an enclosed space.
• Disposal. Cured scrap can be disposed of as non-hazardous industrial waste. Uncured ink and developer solution should be treated as chemical waste and disposed of through a licensed contractor.

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.