How to manage wave solder alloy contamination - …

1 How to manage wave solder alloy contaminationsGerjan Diepstraten & Harry TripCobar Europe BVBalver ZinnContent SnPb solder and impurities Lead-free solder change Pb contaminations in lead-free Measure solder composition Sample interval Recommendations Wave soldering versus selectiveSnPb impuritiesLimits according to IPC-J-STD001 EScores from >1500 solder pot analysisOut of specification:Copper contamination in SnPbMaximum 0,3%Remove at 190 C with stainless steel strainerExchange solderProcedure:1. Empty solder pot2. Clean all parts3. Refill pot with pure Sn (wash Sn)4. Run solder pumps for > 0,5 hour4. Empty solder pot5. Refill solder pot with lead-free solderSolder exchange Sn washPercentage of Pb after lead-free refillUse wash Sn to get low Pb impuritiesSpectro analysis1.

2 Sample: flowing solder middle of the wave2. Preparation sample3. OES AnalysisErosion solder potLead-free: Higher solder temperatures Higher Ag & Sn content Lack of Pb lubricationErosionPotential alternatives:TitaniumCast ironChrome carbid Ag-less alloysFe contamination FeSn2needles SAC alloys sensitive for erosion Co or Ni doping to minimize erosionFe Max. Values 0,02 %SPC Chart Fe contaminationFeSn2needles: Melting point >500 C In areas where there is no flow Bridging potentialsHard to define iron erosion by analyzing solder samplesFeSn2 Needles Selective SnPbAlso in SnPb alloys there is steel flow impurity historical graphCopper leachingSAC305 SnPbSN100 CSPC: Cu content in solder Nitrogen wave solder process (full tunnel)(identical machines, same customer).

3 Automotive, Medical products (SnPb)Industrial (lead-free)SnPBSN100 CNi additiveCu6Sn5 IMCat ~ 3 % Ni in (Cu,Ni) + (Cu,Ni)6Sn5 Fluidity and Ni ContentFluidity LengthIMC growthThe Ni in the IMC has the effect of stabilizing the hexagonal crystal structure of the Cu6Sn5and slowing down total IMC growthNi SPC-chart SN100 CNi content is consistent over the solder bars Ni contentUniform eutectic structurePrimary (Cu,Ni)6Sn5 CrystalsEutectic between crystals600 PPM>1000 PPMSN100 CImpact of Ag on fluiditySAC 305 elements contentsSelective soldering processCu drifts more due:1. Leaching2. SnAg or SAC barsSilver/copper content in SAC305 Higher melting range: Fast solidification of solder Bridging Spikes GermaniumGe acts as an antioxidant and surface active minutes ramp up to 340 C - 30 minutes cooling K Watling, A Chandler, K Nogita.

4 A Dahle, University of QueenslandSnCuNiSnCuNiGeDross and GermaniumLess Ge results in more of P Phosphorus in lead-free solder (SAC) increases stainless steel erosion. P acts like a P to SnCuNi destroys the beneficial effect of + + + Ni benefit goneSAC alloys out of specNumber of Pb defects is decreasingNi is less criticalSampling intervalTrend 0,032%/weekTrend 0,29%/week10x more RecommendationsIPC J-STD-001 Echapter solder Purity Maintenance: If contamination exceed limits, intervals between the analyses, replacement or replenishment shall [N1D2D3] be shortened. The frequency of analysis should be dertermined on the basis of historical data or montly analysis. DrossAfter running 20 hours(no maintenance) solder (wave) continuous running.

5 solder temperature 260 dross Use Nitrogen blanket Reduce solder fall height Ge tablets Wave formerSnPb wave versus selectiveAutomotive line (identical products)One year average scoresPeriodic tablePrCeGdLaSmNdHalogensRare Earth elementsRoHSAnti-oxidants(Vitamins)Concl usions: Lead-free soldering requires more alloy analyses. Copper contents in lead-free solder alloys should be monitored on a frequently basis. (Minimal 12 x /year for selective soldering) Lead impurities are decreasing in lead-free alloys . Metal erosion ( solder pot parts) is hard to identify by solder analysis. Check during Balver Lab Nihon Superior