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Viscosity Solder Paste for SMT Production

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#36214

Viscosity Solder Paste for SMT Production | 22 August, 2005

Well guys,

I just buy a brand new solder paste softener Malcom type SPS2, I've tried with this with this viscosity result. I Use Almit Solder Paste Lead Free LFM-52X

1 min : 264 pas. 2 min : 272 pas. 3 min : 277 pas. I use standard for Viscosity 200 +/- 20 pas.

So here is my question : 1. What is recommended viscosity standard? 2. Which one is better, higher viscosity or lower viscosity and what is relation of them to defect of production? 3. How Do you find better Planetary Motion Solder Paste Mixer or Belt Type? 4. I usually put a solder paste in refrigerator and take it if i want to use i let it abt 2 hour then i mix with solder paste mixer? Am I doing right?

Please help me, Thanks

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#36220

Viscosity Solder Paste for SMT Production | 22 August, 2005

First off, why do you feel you need to check paste viscosity ? I thought checking paste viscosity was a thing of the past ?? If you are having paste viscosity problems then it's time to get a new paste supplier. Any of the main paste suppliers have good robust paste chemistries that operate in many various conditions without problems.

Indium Aim Kester Multicore

If you feel you are having paste problems, I would contact your paste supplier. They will have way more resources to check chemistries than you do.

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#36225

Viscosity Solder Paste for SMT Production | 22 August, 2005

Q1. What is recommended viscosity standard? A1: There is no standard. ASTM D4040-05 "Standard Test Method for Rheological Properties of Paste Printing and Vehicles by the Falling-Rod Viscometer" is a test method that might work. For more, look here http://www.smtnet.com/forums/Index.cfm?CFApp=1&Message_ID=33796

Q2. Which one is better, higher viscosity or lower viscosity and what is relation of them to defect of production? A2: Viscosity is important. Paste that is: * Too thick (high viscosity) may lead to a bad print in the form of an insufficient volume. * Too thin (low viscosity) may lead to the paste slumping.

Q4. I usually put a solder paste in refrigerator and take it if i want to use i let it abt 2 hour then i mix with solder paste mixer? Am I doing right? A4: The typical warming or stabilization time for solder paste is four to six hours. Check with your supplier for specific recommendations.

Finally: Solder paste is a non-Newtonian fluid. Its viscosity is not only a function of temperature, but also of shear rate. Providing data for one is useless without the other. ["How Heat Generation in Stencil Printing Affects Solder Joint Quality" MHA Riedlin and NN Ekere; Surface Mount Technology (SMT) August 1999]

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