Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.

Water Soluble Paste Woes

Rich Z


Water Soluble Paste Woes | 28 September, 2000


We are experiencing extreme difficulties in printing with a water soluble paste. We have tried two major brands of w/s paste and we are seeing the same problems with both. The main issue is the paste is sticking to the blades. We have tried different lot codes, mixing thoroughly, slowing print speeds, squeege up times, attack angles of blades, & squeege height off stencil. All without success. Yet sometimes we can get an hour or so of decent printing. The MPM is a Ultra Print 3000 series. Room Temp. is 73 degrees @ 42% RH. The MPM fans are not blowing directly on the stencil. We are using nickel plated blades. Permalex blades maybe a solution. Speedline as well as reps from the two paste manufacturers are mystified. Please help!!!!!!!

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Re: Water Soluble Paste Woes | 28 September, 2000

what mfg paste are you having problems with. We went through a time that we had some similar paste problems and looked at a lot of different paste types.

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Re: Water Soluble Paste Woes | 28 September, 2000

We had the same problem and after watching it run for a while we noticed the paste always pulled up on the blade that made the first stroke. We got rid of the problem by using less paste (about a finger width) and flattening the paste out before the initial stroke. When the paste is piled up the first stroke has paste ride way up on the blade before it starts rolling, then every stroke after has paste chasing up the blade.

sounds simple but it helped us, good luck

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Re: Water Soluble Paste Woes | 29 September, 2000

5 Paste sticking to squeegee: Squeegee is heavily magnetized Some pastes stick more than ... Plastic squeegees stick more than metal Old metal squeegees stick more than new Paste needs to be worked Paste needs to be at room temperature Some flux formulations are very sensitive to humidity Need enough paste for thumb sized roll. Too little & it won't fall off. Temperature in your screen printer needs to stable. Paste suppliers say that 1� C change can affect paste viscosity by about 10%.

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Re: Water Soluble Paste Woes | 30 September, 2000

Hi Maybe you have too small apertures in stencil. Good apertures size is 90% from pad. And one thing what you can try is that you cut your stencils(blades) aperture corners round (i mean like a oval). I hope that these advices can help you.

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