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Circuit Board Moisture Sensitivity and Baking
Talk concerning IPC's new guideline for handling and storage of PCB's covering moisture sensitivity and baking.
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.
Comments» Use the form below to submit a comment.
Responding to comments by Jeff Yearly March 28, 2011
Misconceptions concerning the proper handling of MSD's is virtually universal. You seem to be more knowledgeable than most.
The issues of drying requirements with MBB's and dry cabinets is presented in Section 4.1 of J-Std 033 (the "Bible" for assemblers handling MSD's.) Our general advise is that someone in any organization handling MSD's must get a copy of this spec and spend the time (the
whole spec is only 15 pages long) to understand it completely. THEN decide what the best program is for your manufacturing environment.
On the inconsistent MSL spec from component manufacturers, we are not surprised. Is there intelligent life in these companies.
Jim Hall & Phil Zarrow, ITM Consulting
I am a component Engineer at Libra Industries in Mentor, Ohio. I enjoy listening to your board talk segments, and I was fortunate to attend Phil's lecture at a SMTA meeting in Ohio recently "Low Volume-High Mix SMT Manufacturing."
Topics of MSD are of interest to me because I am working on improving our current system for storing moisture sensitive devices. I am wondering if you ever came across the situation I am facing right now. I have a Infineon component (QFN 160) SAB82538H-10 V3.2 that we bought and it came in marked as MSL 3 and when we bought more of the same part for our next build approx. a month or two later, that very same MPN came to us marked as MSL 5.
Between MSL 3 and 5 there is a significant difference in the allotted floor time. This has happened numerous other times with multiple types of components from different manufacturers. I have contacted the manufacturers to try to get some answers of why this is happening and I never seem to get a straight answer; answers like "it depends on the type of material we used for that particular lot." To be safe I have been treating these suspect components as if they are the higher MSL rated device (MSL 5).
With the example I shared with you on the Infineon component we were unknowingly processing the parts as if they were MSL 3 not knowing they came in again marked as MSL 5. This part was falling off the board during reflow and the popular answer at my company was to secure the part down with epoxy prior to being reflowed. I stepped in and noticed the part had an ever so slightly bulge on the bottom of the device. I baked the parts at the recommended bake times and temps and the problem has left.
Also we have McDry storage cabinets, and I heard Phil state that by putting MSD components back in the dry cabinets that it stops the clock on moisture absorption. Does this process ever reset the clock so to speak? I hear from others in our company and from the manufacture of the cabinets that over a period of time the dry cabinets will draw out any moisture, I would imagine if this were true then the parts would definitely need to be out of the bags right? (I’m not talking about sealed bags but the parts being put back in the bags that are left open.) Are either of you aware of such claims? Or is baking the only real true way to reset the clock?
Jeff Yeary, CIT, Libra Industries
Phil and Jim, with reference PCB MSD and baking. You said that IPC 1601 is in final draft. However I use IPC HDBK-001 with amendment 1 and 2, page 97, section 7.3.2 and table 7-1. PCB bake out.
120 C (248 F) 3.5 - 7 hrs
100 C (212 F) 8 - 16 hrs
80 C (176 F0 18 - 48 hrs
What is your take on this? Thanks for all your help and recommendations.
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Use the form below to submit a comment.
Misconceptions concerning the proper handling of MSD's is virtually universal. You seem to be more knowledgeable than most.
The issues of drying requirements with MBB's and dry cabinets is presented in Section 4.1 of J-Std 033 (the "Bible" for assemblers handling MSD's.) Our general advise is that someone in any organization handling MSD's must get a copy of this spec and spend the time (the
whole spec is only 15 pages long) to understand it completely. THEN decide what the best program is for your manufacturing environment.
On the inconsistent MSL spec from component manufacturers, we are not surprised. Is there intelligent life in these companies.
Jim Hall & Phil Zarrow, ITM Consulting
Topics of MSD are of interest to me because I am working on improving our current system for storing moisture sensitive devices. I am wondering if you ever came across the situation I am facing right now. I have a Infineon component (QFN 160) SAB82538H-10 V3.2 that we bought and it came in marked as MSL 3 and when we bought more of the same part for our next build approx. a month or two later, that very same MPN came to us marked as MSL 5.
Between MSL 3 and 5 there is a significant difference in the allotted floor time. This has happened numerous other times with multiple types of components from different manufacturers. I have contacted the manufacturers to try to get some answers of why this is happening and I never seem to get a straight answer; answers like "it depends on the type of material we used for that particular lot." To be safe I have been treating these suspect components as if they are the higher MSL rated device (MSL 5).
With the example I shared with you on the Infineon component we were unknowingly processing the parts as if they were MSL 3 not knowing they came in again marked as MSL 5. This part was falling off the board during reflow and the popular answer at my company was to secure the part down with epoxy prior to being reflowed. I stepped in and noticed the part had an ever so slightly bulge on the bottom of the device. I baked the parts at the recommended bake times and temps and the problem has left.
Also we have McDry storage cabinets, and I heard Phil state that by putting MSD components back in the dry cabinets that it stops the clock on moisture absorption. Does this process ever reset the clock so to speak? I hear from others in our company and from the manufacture of the cabinets that over a period of time the dry cabinets will draw out any moisture, I would imagine if this were true then the parts would definitely need to be out of the bags right? (I’m not talking about sealed bags but the parts being put back in the bags that are left open.) Are either of you aware of such claims? Or is baking the only real true way to reset the clock?
Jeff Yeary, CIT, Libra Industries
120 C (248 F) 3.5 - 7 hrs
100 C (212 F) 8 - 16 hrs
80 C (176 F0 18 - 48 hrs
What is your take on this? Thanks for all your help and recommendations.
Tom Blackmon, CEM ltd