We perform very low volume / high mix Class 3 PCB assembly.  Our PCB 
assemblies include both ceramic and plastic parts.  Our plastic parts come 
on tape and reel, as well as matrix trays, (or, if  people get sloppy, loose 
in an ESD bag...).

I understand the Level 1 - 6 ratings for plastic parts with respect to 
moisture absorption.  Now I am looking for an effective means of 
implementing controls in my factory.  Two possible options are as follows. 
 Both have serious drawbacks.  I am looking for a sanity check as to how 
others in this situation have approached the challenge.

1) BAKE EVERYTHING BEFORE USE:

a) What is the effect on tape and reel parts?  (Will plasticizers in tape 
degrade solderability?  Will the adhesive on the release strip be adversely 
effected?)

b) How many times can you bake out a part before you do more harm than good 
(solderability, etc)?

c) What a nuisance to pull every reel off the machine for rebaking...  Plus 
the cycle time...

2) KEEP EVERYTHING DRY:

a) Everything should be coming in sealed in bags.  I can keep them that way 
until they hit the floor.  But once on the machine, it will be a nuisance to 
track each part for how much exposure they have had.

b) Since I will never use a whole reel in my low volume process run, I could 
pull the reel after the run and place back into a desiccator box.  Again, 
tracking and labor...

What is the rest of the industry doing here?

Thanks,

Michael Lang

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