Technical Article
Solder Wetting ( in μN / mm ) at given Times
Flux TCA 0.70s 1.00s 2.00s 3.00s 4.00s 5.00s
Stainless Steel Flux 0.34 167 226 250 251 251 251
Zinc Chloride Free Solder paste
Zinc Chloride Based Solder paste
2.60 -129 7 213 255 256 253
1.26 -159 -107 143 247 263 261
Flux TCA 0.70s
Stainless Steel Flux 253 1094
Zinc Chloride Free Solder paste 218 -73
Zinc Chloride Based Solder paste 282 762
Table 1 : Solderability Test Results : Comparison of Standard Liquid Stainless Steel Flux to Best Stainless Steel Soldering Pastes
Figure 6 . Solderability test results .
Figure 5 . Description of how to read solderability testing results .
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To evaluate the results , the height of the curve within the immersion time of the solderability test dip is measured in terms of wetting force . The wetting force is a measure of the extent of solder flow . Greater solder flow will result in better soldering .
Solderability Test Terms
Time To Cross Axis ( TCA ) - Time , in seconds , needed to achieve positive solder wetting . This is the measure of how fast the solder will start to spread on a surface .
Solder Wetting ( in µ N / mm ) at Given Times - Wetting force expressed in micronewtons / millimeter (µ N / mm ) at the time indicated in the solderability curve .
Maximum Wetting ( MW ) - Maximum force ; expressed in micronewtons / millimeter (µ N / mm ), in the positive solder wetting region of the solderability curve . This is a measure of how far the solder will spread on a surface .
Integrated Area Under The Curve ( IA ) - The area between the curve and the x-axis during the entire immersion cycle . The area is recorded in units of micronewtons / mil- limeter-seconds (µ N / mm-sec ). This measure combines the effects of both maximum wetting and time to cross axis to give a single performance value .
Conclusions
As a result of the testing described in this article there is now a better soldering paste for soldering stainless steel available . The new zinc chloride-based solder paste Has faster positive solderability than the previous zinc chloride-free solder paste used for this application , and , equally impressively , the new solder paste has maximum wetting like that of the strong stainless steel liquid flux .
The new zinc chloride-based solder paste has the advantage of being much more like the highly active corrosive liquid fluxes typical of this application . Unlike the earlier zinc chloride-free solder paste used for this application , this new soldering paste can withstand torch heating and long oven heating processing . This new solder paste works on 316 stainless steel and all other easier to solder steels and metals .
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About the Authors
William Avery is Metal Joining Specialist at Superior Flux and Mfg . Co . with expertise in solderability testing , evaluating solder joint quality , and product development of innovative flux and soldering solutions for hardto-solder metals for the electronic and industrial soldering industries . He graduated from the State University of New York at Buffalo . reNTals , rePaIrsrs, solUTIoNs .
Dr . Baskin is the president of Superior Flux .
Rebecca Zronek has been a chemist with Superior Flux for over 20 years .
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