Problems with Dynamask 5000 (Dry Film Solder Mask)

[farrell]

I'm been trying to get it working right, but always end up with bubbles.

I etch (sodium persulphate) and tin plate (MG Chemicals Liquid Tin) my board. I wash it thoroughly, then dry it thoroughly (including a little hot air to evaporate anything hidden.) Then I cut a piece of mask to size, peel off the dull side, and stick it down to one end of the board. I run it through my laminator and make sure the mask only meets the PCB at the rollers. I've got that down to where I don't get wrinkles.

This is where the problems start. I run the board through the laminator a few times, each time in a different direction, and the mask starts to adhere to the board better each time. After the third or fourth pass bubbles appear and the green material clumps under the bubbles. If I only do two passes, the mask isn't stuck down very well (I can see many places where the mask isn't stuck to the PCB by looking at the back side of my single-sided board...)

My laminator only has two "temperatures" labeled 5mil and 10mil. 5mil mode seems to work best. If I use the 10mil mode it gets really hot and the green film starts to ooze out after just two passes. In 5mil mode it takes about five passes to get the green film to ooze out. I'm fairly sure that's a bad thing

Is my lamintor just too hot? Or maybe something else? I've watched a few YouTube clips of people using this stuff and it seems almost idiot-proof. I'm stumped.

On a side note, all the video clips I've seen result in a high-gloss solder mask. Mine come out semi-glossy after I develop them. I've tried playing with the water/sodium carbonate ratio, and the exposure time, but they doesn't seem to have an effect. The mask is functional, but doesn't look like a typical solder mask.

Thanks,
-Farrell