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Staging Time Between Soldering and Cleaning
What is the maximum staging time permissible for PCBA's between wave soldering and cleaning? Is there an industry standard?
Phil Zarrow, ITM Consulting With over 35 years experience in PCB assembly, Phil is one of the leading experts in SMT process failure analysis. He has vast experience in SMT equipment, materials and processes.
Jim Hall, ITM Consulting A Lean Six-Sigma Master Blackbelt, Jim has a wealth of knowledge in soldering, thermal technology, equipment and process basics. He is a pioneer in the science of reflow.
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You definitely want to wait until the post wave/reflow board temperature is below the temperature of the first wash stage. This will prevent porous components taking on moisture during contraction.
K.D.
C'mon Fellas! Time between soldering and cleaning depends upon more than just the process delays. This has to be considered as a two-part question.
First part is no-cleans. If you're going to clean no-clean fluxes, it depends upon the wash water temperature and the chemistry of the cleaning solution. Saponafiers and other solvents allow you an extended rest period between soldering and wash depending upon the wash temperature and aggressiveness of the cleaning solution. The longer you wait, the harsher and hotter the solution needs to be.
Organic acids on the other hand are a bit more insidious than their no-clean counterparts. The longer they sit, the more corrosion damage they do to the metals on the assembly and the further they creep into porous substrates making them almost impossible to remove completely.
You also forgot to mention that the longer OA's sit, the physically harder the flux gets, changing the chemistry of the wash required to remove the residues. What was once an easy removal in hot DI water becomes a difficult proposition to remove with chemicals, up to the point that they cannot be removed. Did I mention that they stay corrosive even after they harden?
An no mention of cleanliness testing to validate the cleaning process? Omegameter or Ionograph testing will tell you if the boards have been cleaned or if another pass or more aggressive chemistries are required. Ion chromatography is not optimum for routine testing since it is site and ion specific and all you need is a general idea of whether or not the boards meet the specific cleanliness requirements for the assembly.
Sunstone Circuits, has released the newest version of their design software, PCB123. Bottom line, the design process just got easier. Sunstone Circuits
Multicore TFN700B is a no-clean, halide-free tacky flux formulated to address the challenging requirements of package-on-package applications. Henkel Corporation
Once you have made the decision to package your electronics with rigid flex, it makes sense to pick a production partner who can build it right. Printed Circuits, Inc.
Once you have made the decision to package your electronics with rigid flex, it makes sense to pick a production partner who can build it right. Printed Circuits, Inc.
Components encapsulated in plastic or organic compounds are susceptible to moisture damage. So are PCBs, all can cause early field failures. Control MSDs per IPC J-Std-033b.1 and 1601. Super Dry®
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Use the form below to submit a comment.
K.D.
First part is no-cleans. If you're going to clean no-clean fluxes, it depends upon the wash water temperature and the chemistry of the cleaning solution. Saponafiers and other solvents allow you an extended rest period between soldering and wash depending upon the wash temperature and aggressiveness of the cleaning solution. The longer you wait, the harsher and hotter the solution needs to be.
Organic acids on the other hand are a bit more insidious than their no-clean counterparts. The longer they sit, the more corrosion damage they do to the metals on the assembly and the further they creep into porous substrates making them almost impossible to remove completely.
You also forgot to mention that the longer OA's sit, the physically harder the flux gets, changing the chemistry of the wash required to remove the residues. What was once an easy removal in hot DI water becomes a difficult proposition to remove with chemicals, up to the point that they cannot be removed. Did I mention that they stay corrosive even after they harden?
An no mention of cleanliness testing to validate the cleaning process? Omegameter or Ionograph testing will tell you if the boards have been cleaned or if another pass or more aggressive chemistries are required. Ion chromatography is not optimum for routine testing since it is site and ion specific and all you need is a general idea of whether or not the boards meet the specific cleanliness requirements for the assembly.
J.W.