Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Carlos Palacios

#10368

Is baking PCB necessary before solder process? | 28 July, 1999

Currently, we are baking any PCB before process on SMT, the 'reason' is to dry any possible humidity that could be inner the PCB, it does not matter if the PCB is multilayer or not. We bake PCB's at 107C for 4 hrs and the board must be process into next 8 hours, if not, the PCB needs to be reconditioned again. Evenmore, nobody can tell me if this conditioning is a requirement or not, we just baked as a 'good practice'. Could someone tell me if there is any requirement to bake PCB before processing? Where is that documment? What may be affected if PCB's are not longer baked? Any comment will be welcome !

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#10369

Re: Is baking PCB necessary before solder process? | 28 July, 1999

| Currently, we are baking any PCB before process on SMT, the 'reason' is to dry any possible humidity that could be inner the PCB, it does not matter if the PCB is multilayer or not. We bake PCB's at 107C for 4 hrs and the board must be process into next 8 hours, if not, the PCB needs to be reconditioned again. Evenmore, nobody can tell me if this conditioning is a requirement or not, we just baked as a 'good practice'. Could someone tell me if there is any requirement to bake PCB before processing? Where is that documment? What may be affected if PCB's are not longer baked? Any comment will be welcome ! | | | Carlos: Baking boards is a lousey practice. It increases the oxidation on the solderable surfaces and that makes it more difficult for you flux to do a good job.

There is no requirement that you bake boards.

I worked in shops that baked boards, because they bought boards:

* By the boat-load and stored them in a humid environment for months. Boards are hydroscopic and will absorb moisture. The moisture will tend to boil-off during soldering operations. * With less than 1 mil barrel plating thickness. Thin plating allows moisture in the board to escape through the trough holes and cause very messy and ugly solder connections. This is a result of poor fabrication processes. Our old freind Bob Willis has a procedure for evaluating plating thickness on his site, which is listed in the archives some where.

I say:

* Find better suppliers * Get control of your board inventory * Store boards properly ( see previous threads in the archive) * Stop baking your boards.

My 2�

Dave F

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ScottM

#10370

Re: Is baking PCB necessary before solder process? | 29 July, 1999

| Currently, we are baking any PCB before process on SMT, the 'reason' is to dry any possible humidity that could be inner the PCB, it does not matter if the PCB is multilayer or not. We bake PCB's at 107C for 4 hrs and the board must be process into next 8 hours, if not, the PCB needs to be reconditioned again. Evenmore, nobody can tell me if this conditioning is a requirement or not, we just baked as a 'good practice'. Could someone tell me if there is any requirement to bake PCB before processing? Where is that documment? What may be affected if PCB's are not longer baked? Any comment will be welcome ! | | | Sounds like the last place I worked... you work in Anahiem? or do you do Military work? Baking boards back in the 70s, when multilayer boards were so bad, became a "standard" process so much so that they got written into the MIL-STDs. Gov't contractors don't like change for fear of wrath from their customer, don't fix/change/touch it. God will strike you down if you bring up the use of other fluxes rather than RMA. Sigh...

If you are in the above situation may God have pitty on your soul...

I don't bake boards, oxidizes the surface -- nasty problem. I do over 40,000 boards a month and I've had one maybe two delaminations in the last two years. I got an overage from the vendor and rebuilt the board, they'd rather do that than fight on who's fault is the delamination (IF you've established a good relationship). Saves time and reduces other assembly problems. Follow Dave's advice.

Scott

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#10371

Re: Is baking PCB necessary before solder process? | 29 July, 1999

| Currently, we are baking any PCB before process on SMT, the 'reason' is to dry any possible humidity that could be inner the PCB, it does not matter if the PCB is multilayer or not. We bake PCB's at 107C for 4 hrs and the board must be process into next 8 hours, if not, the PCB needs to be reconditioned again. Evenmore, nobody can tell me if this conditioning is a requirement or not, we just baked as a 'good practice'. Could someone tell me if there is any requirement to bake PCB before processing? Where is that documment? What may be affected if PCB's are not longer baked? Any comment will be welcome ! | | | Although I agree with Scott and Dave that assembly shouldn�t bake PCBs, some suppliers in germany keep telling us to prevent warpage during reflow we should bake our PCBs prior to assembly. I�ve seen boards that snapped in salatbowl like shapes during reflow actually shooting parts around (they are hard to get out of a vapourphase). But still I don�t see any sense in it if there is proper manufacturing, shipping, storage and handling of PCBs. How many ovens do you need if you handle a lot of that stuff�

Just try it without

Wolfgang

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