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baking out pcbs after reflow process

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#66757

baking out pcbs after reflow process | 5 July, 2012

I need help with how long do I need to bake out double sided PCB's that have been cleaned. The units will not be reworked but instead will be moved on to hand stuffing. I have looked in IPC CH-65B and J-STD-033C. I get information for parts if I am reworking the boards but nothing concerning the actual assembly themselves. I have been in the industry for a long time and have really never run into a company that bakes boards other then my current employer before they are moved on to the hand stuff area. I need some help because currently my company wants to bake the borads for 3 days. To me that seems like non value added time which is a reason I am un able to meet shipping numbers. Please help.

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#66769

baking out pcbs after reflow process | 5 July, 2012

Probably they had a problem with a certain product, tried baking, the problem went away and ever since there stuck with this money loosing process. So, ... * Write up a plan to split a couple of batches, bake a portion of each batch, don't bake the other portion, hand solder both batches and some sort of post-hand solder assessment. * Get buy-off from your quality people. * Execute the plan. * Move on.

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#66771

baking out pcbs after reflow process | 6 July, 2012

..... that's very strange. If there were any risk of de-lamination then it would of occurred during the reflow process, surely. Unless the through hole department are using heat guns or wave sodler?

I doubt if the sales or planning team are happy if you have an extra 3 days lead time due to baking...... If you can find out the reason behind this process change then I might be able to make some suggestions.... don't fret...its Friday

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TMS

#66773

baking out pcbs after reflow process | 6 July, 2012

All i used to do was blow them with an airline to remove the excess moisture then bake them for 15/20 min at 100' in an oven and that seems to work fine, i did get the info from a 4 stage cleaning guide for the actual cleaning solution we used but it was a long time ago and i cant remember what it was called.

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#66809

baking out pcbs after reflow process | 11 July, 2012

Why cannot reply????

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#66811

baking out pcbs after reflow process | 11 July, 2012

It is correct to remove moisture in PCB by baking. But I think the time and temperature is too little. According to our experience, it should be more than 60min at 120 centigrade degrees.

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#66812

baking out pcbs after reflow process | 12 July, 2012

Check also the specs / recommendations of your PCB manufacturer. We bake boards 4h/120°C before reflow and after automated cleaning (it´s not FR4!) and also if we have to rework with the autometd rework- stations (massive IR underheating ,..).

Regards, Thorsten

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#66817

baking out pcbs after reflow process | 12 July, 2012

You might try to complete all your soldering within a 72 hour or less time frame. For all intents treat your board like a moisture sensitive component after you have baked and completed SMT reflow. Wash, blow dry, and go direct to stuffing and complete your soldering within 72 hours, as though your assembly were, say, an MSL level 3. Any PCBs beyond 72 hours in assembly time would be rebaked for 4 hours at 120C in this model. As Dave mentioned, separate out two lots and subject one to the altenate process. Evaluate. Now go spend the 3 days making $$ instead of baking boards. 'hege

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#66822

baking out pcbs after reflow process | 13 July, 2012

I appreciate all the feedback. The reason I was asking the question is because we have an internal documnet that states we need to bake for 16 hours after the boards are cleaned. This just seemed to long for what little moisture is really removed. I did some digging and found the number was just pulled out of the air. No real testing was done to get this number. I have done some early testing and found that if we bake for an hour or 16 the amount of moisture is about the same so I am leaning towards a shorter time. Thanks again for your help.

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