Is solder purity affect solder joint reliability?

Q1. Do we really need to follow the IPC J-STD-001 Solder purity? A1. Yes, you should control impurities in solder. Further information: * "Allowable concentration of contaminating elements in solder: impurities are harmless unless their level goes too high.(Wave Soldering)" Schouten, G & Diepstraten, G; Circuits Assembly; 01-MAY-07 * Soldering in Electronics, RJ Klein-Wassink, Electrochemical Publications, 2nd e, Chapter 4.4. * J-STD-006, Requirements for Electronic Grade Solder Alloys and Fluxed and Non-Fluxed Solid Solders for Electronic Soldering Applications * Coombs' Printed Circuits Handbook; Coombs, CF; McGraw-Hill [0071350160] 43.7.7 Metal Contaminants * "The Effect Of Metallic Impurities On The Wetting Properties Of Solder" D Bernier, VP, Research & Development Kester Solder Company * Contamination of Electronic Assemblies; Pecht, M et al; CRC Press 2002 [0849314836] Chapter 6 Measuring Contaminates In Substrates p.97 Q2. How to effectively balance the chemistry of Sn63/Pb37 other than adding a pure tin on the solder bath? A2. Don't let the tin oxidize. Don't let contaminants from boards, components, and other sources enter the pot.

Q3. Is this really needed to monitor in monthly basis? A3. You should monitor this on a schedule that assures that you are maintaining proper levels of impurities. Some people monitor monthly. So, that's a commonly accepted frequency. If you'd like, you might be able to demonstrate that a longer sampling rate still produces good results.

Q4. How many kgs of pure tin per percent losses in a 565 kilos solder bath? A4. Total alloy weight in the solder pot is [Yik Shing Tat Industrial]: T = W(A-B)/(100-A) Example: 500 kg(63-61.5)/(100-63) = 750/ 37 = 20.3 kg pure tin weight for adding into solder pot T: Weight of pure tin need to be added W: Total alloy weight in the solder pot A: Standard weight percentage of tin B: Actual weight percentage of tin in the solder pot

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hello Dave, thanks for the references. i will try to compare the results in 3 months interval.

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