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BGA Via Tenting

Dreamsniper

#31784

BGA Via Tenting | 17 December, 2004

I goy this issue:

Voids in almost every ball of my BGA's prcessed since we changed our BGA via tenting to double tenting. The tenting is done with a dry film application to fill the via from the solder side then apply LPI Mask on the surface of the (solder side) PWB. Then same process on the component side. Dry film first to fill the vias the LPI.

Will that be a possible source of my BGA voids. We do not have this problem prior to switching to this Via tenting process.

Thanks for your help.

Dreamsniper

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Dreamsniper

#31785

BGA Via Tenting | 17 December, 2004

I got this issue:

Voids in almost every ball of my BGA's processed since we changed our BGA via tenting to double tenting. The tenting is done with a dry film application to fill the via from the solder side then apply LPI Mask on the surface of the (solder side) PWB. Then same process on the component side. Dry film first to fill then vias the LPI.

Will that be a possible source of my BGA voids. We do not have this problem prior to switching to this Via tenting process.

Thanks for your help.

Dreamsniper

reply »

#31804

BGA Via Tenting | 21 December, 2004

It's very possible.

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T2

#31842

BGA Via Tenting | 26 December, 2004

Dreamsniper

What is the rationale for the double plugging? And why from both sides?

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Bob R.

#31948

BGA Via Tenting | 9 January, 2005

I'm just thinking out loud here with no experience to back it up, but I could see where you're trapping air or solvent filled voids inside the via by tenting from both sides. When you go through a heat cycle like reflow or wave solder you could be expanding the gas in those vias and forcing them up into the joint.

I'd cross-section some vias on un-populated boards and have a look to see if you're getting complete fill or voids.

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Board House

#32206

BGA Via Tenting | 21 January, 2005

I work for a board house and our proceedure for this process is the following,

We cover the via pads leaving the hole open and then apply the surface finish and then go back and Cover the Via with a second operation. By doing this you do not entrap chemicals in the hole causing contamination or leaching or blown holes while it is going through a baking or hot air process.

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Dreamsniper

#32210

BGA Via Tenting | 21 January, 2005

Hi T2, The purpose of this is that we want to make our rework robust. Whenever we rework BGA's we have solder getting trapped into those 1 sided tented vias and bet yah...they are hard to desolder! And during BGA resoldering these trapped solder will rise up from the vias and become solder ball.

With the double tenting process this problem was eliminated.

regards, dreamsniper

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