Stenil printing adhesive

Sirs,

What are the issues involved when a stencil printer is used for printing solder paste and adhesive?

UV-curing of adhesive appears to help reduce slump and spread by forming a tough skin on the adhesive blob deposited on the PCB. Is this process fairly common? Does someone have further inputs on this procedure?

Thanks, have a nice day.

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Sanjay: Keys to successful adhesive printing are: 1. Understanding the flow behavior of the adhesive under constant shear stress 2. Stencil design, i.e. stencil aperture opening 3. PWB Footprint 4. Stencil printing parameters Optimizing all these factors require experimentation. If you call me at (423) 461-2050, we can talk about specifics of this process.

To answer your other question, I believe most of the assembly houses in the SMT field are using heat curable adhesives though I do see the UV curable adhesives occasionally. I like UV curable adhesives because the process is real fast. Other than this there is no special advantage. After all, polymerization (crosslinking of monomers) is pretty much the same whether it is triggered by heat or UV.

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Dear Sanjay, An important issue involved when stencil printing adhesives vs. solder paste is: How do you clean the stencils after printing? Do you need two machines? Two chemistries? Two waste streams? What are the potential environmental impacts and user hazards?

Smart Sonic has a Stencil Cleaner that will resolve both solder paste and adhesive cleaning issues, the Model 2003 has two separate wash tanks, one operates at ambient temperature for safe cleaning all types of solder paste and one tank is heated to 120 degrees F. for cleaning all types of SMD adhesives. No potential cross contamination of adhesive residue onto a solder paste stencil. Both use the same non-hazardous chemistry, 440-R SMT Detergent. And, the process is certified environmental and user safe and effective by the EPA and AQMD!

Visit the Smart Sonic Web Site for more info: www.smartsonic.com Any questions, please call me. 1(805)499-7440 Regards, Bill Schreiber

| Sirs, | | What are the issues involved when a stencil printer is used for printing solder paste and adhesive? | | UV-curing of adhesive appears to help reduce slump and spread by forming a tough skin on the adhesive blob deposited on the PCB. Is this process fairly common? Does someone have further inputs on this procedure? | | Thanks, have a nice day. |

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