PCB bake

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Hi, Can anyone help explain the benefits/disadvantages of... - Jan 17, 2002 by ianchan

Ianchan, baking as being part of pre-heating is obviously s... - Jan 18, 2002 by Wolfgang Busko

Thanks for the tips... found out the ex-employee guy, had... - Jan 19, 2002 by ianchan

ianchan

#18680

PCB bake | 17 January, 2002

Hi,

Can anyone help explain the benefits/disadvantages of bareboard pcb baking, as part of the pre-heat conditioning, before the bareboard pcb use in SMT production run?

The pcb board is 200mm x 240mm panelized pcb board, and has 28 smaller pcb boards inside the entire panelized pcb. pcb thickness is 0.6mm, and has gold plated pads, typical pad footprint size is for 0402 SMD.

we currently bake the bareboard pcb at 90deg-C for 1h, as this was previously set by a now ex-employee engineer; internally, we were wondering is this a compulsary baking process that must be followed?

If it is adviable for us to continue this bareboard pcb baking process before the SMT run, do we need to wash the pcb bareboards using our Electrovert Aquastorm 90?

Any feedback shared is really appreciated. Thanks.

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Wolfgang Busko

#18682

PCB bake | 18 January, 2002

Ianchan, baking as being part of pre-heating is obviously sensless cause the PCB will not maintain any of that heat till soldering. Common reason for prebaking PCB�s is getting the moisture out to prevent outgassing, warpage and maybe other defects. One big known disadvantage of this is a negative effect on solderability, ah you know, oxides and all that stuff .... ( don�t think that you are baking with nitrogen ) Performing any process step should be based upon insight in it�s usefulness for the whole enterprise and the process parameters should be set that the desired effect is obtained. (Or should I better have said "shall").

If it�s advisable to continue with this especially with 90�C for 1 h is up to you once you know and understand what it�s there for. Washing bare boards before further processing isn�t something very common. I suspect this might be one possible reason for that prebaking !Drying! action, don�t you think so ?

Better find out what all this is (was) good for, look if it�s still necessary or if it was performed only for a special batch of PCB`s for what ever reason. I wouldn�t be happy either with processes I don�t know what they are good for. You may also try the search function on "pebaking" and find some information on this topic.

- Do what you know and know why you do -

still have a nice day

Wolfgang

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ianchan

#18686

PCB bake | 19 January, 2002

Thanks for the tips...

found out the ex-employee guy, had pre-bake conditioning put into the process flow, as this pcb is made of polymide material, that is reputed to have historical patterns in thermal sensitivity. To avoid "thermal damaging" the pcb, we decided to stick with the pre-heat baking process...

PS: polymide is akin to the common materials makeup of BIB/backplane PCB

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