First off, are you planning on placing these parts with your placement machine since you mentioned that you do not have an alignment system for rework? I would be leery of handplacing a BGA into paste by steady hand and craned neck alignment. Second, When you state that you are not confident in the flux on pad only method I am curious as to why not? You are not (in my opinion) going to be really be changing anything by applying paste and then reflowing exept the possibility of varying paste volumes. Have you been experiencing failures?
Anyway, I have used the microstencils and have pretty much gone away from them for the following reasons.
1. unless you have some type of holder/positioner (which is available)it is difficult to apply paste that is both registered and of consistant volume.
2. Edge clearances sometimes need to be in excess of 2.5 mm.
Finally, I am not saying the ministencils don't work because they do, but I have found that they seem to add more variables and cost unecessarily
And thats my take on the subject
Russ
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