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Printing micro-vias for BGA placement

Pc

#19864

Printing micro-vias for BGA placement | 10 May, 2002

Does anyone know a surefire way to print micro-vias which are centered on BGA pads and also reduces solder ballooning? Would you design a process around two stencils? -- one for the vias themselves and one for the pads. Could you fill all of the vias then reflow - then print the pads, place the parts and reflow again? Thanks, Paul.

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#19869

Printing micro-vias for BGA placement | 10 May, 2002

First off what bone-head designer put them there in the first place. Vias in solder lands is a big time no no. I had this problem at a CEM I worked at. I had the customer change the design but had to run the 6 samples they supplied. I ended up filling them with SMT adhesive, curing it, then printing. It was successful but I would not recommend doing it in a production mode. One thing is the check with the PCB fab house to see if they can fill them from the bottom side with soldermask. It may not be feasable on your design but worth a look, if the design cannot be changed to move the vias off the solder lands. Filling them from the bottom side still has its problems because the mask will not fill the barrel and you can get out-gasing. Good Luck.

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Pc

#19870

Printing micro-vias for BGA placement | 10 May, 2002

Pete, thanks for the input. These are microvias and dont go through the pcb -- they are laser cut to various depths into the board and are .006" dia. on gold plated pads. Paul.

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#19873

Printing micro-vias for BGA placement | 10 May, 2002

I don't know �solder ballooning� from a shoebox. So, rather than let this degrade solely into a rant about the evils of via in pad, please get me up-to-speed in jargon.

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