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BGA Voids

C.K.

#4979

BGA Voids | 16 January, 2001

Okay, so I've been battling voids > 10% on various BGA packages.

I checked the profile and we are getting "ideal" reflow conditions (~ 60 sec. T.A.L.). Ramp rates, temperature deltas before spike zone, and cooling rates are ideal too.

I don't believe it's a profile, print, or paste issue - these have all been checked and verified. What could other causes be?

Could they be moisture related? Is the moisture entrapment from the part outgassing during reflow? Any help would be appreciated.

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C.K.

#4980

...and yes, I checked the archives | 16 January, 2001

...but with this new version of SMTNet, none of the links on archived messages work!!! It keeps saying "parameter incorrect."

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Brian Doyle

#4981

...and yes, I checked the archives | 16 January, 2001

what was the error message you were receiving? I just did a search for BGA in the forum using the search on the gray bar at the top and it yielded 71 results. I didn't have any errors when I clicked on them. Email me if you have continued troubles.

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#4986

BGA Voids | 16 January, 2001

Yanno what's interesting on that topic? A small number of voids make the solder connection of a BGA stronger than no voids. Moral of the story ... don't get too anal about voids.

You should check the archives ;-) [har har har] we've discussed this before. For you, we'll do it again!!!

Two questions for yall ...

1 What's your criteria for accepting / rejecting BGA connections for voids?

Our criteria are:

1 Voids 1a Voids in soldered balls shall be less than 20% of the diameter of the solder ball. 1b No void shall show on the exterior of a solder connection. 1c. Multiple voids may sum to less than 20% of the diameter of the solder ball.

2 What's the pattern of your voiding rejections? Is it board, component, ball location, er what related?

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C.K.

#4994

...and yes, I checked the archives | 17 January, 2001

I'm using Netscape browser. When I click on the archive links, it opens another window which says "parameter incorrect."

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#5041

BGA Voids | 22 January, 2001

IPC-7095 - Design & Assembly Process Implementation for BGA's Implementing Ball Grid Array (BGA) and Fine-Pitch Ball Grid Array (FBGA) technology presents some unique challenges for design, assembly, inspection and repair personnel. This document delivers useful and practical information to anyone who is currently using BGAs or considering a conversion to area array packaging formats. In addition to providing guidelines for BGA inspection and repair, IPC-7095 also addresses reliability issues associated with BGAs. The effect of BGA and FBGA on current technology and component types is also discussed. 88 pages. Released August 2000.

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Dason C

#5043

BGA Voids | 22 January, 2001

I had my experience when I run the Motorola BGA and I am not sure the voiding was created due to the incompatible flux residue.

Rgds. Dason.

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#5044

BGA Voids | 22 January, 2001

3 BGA voiding:

3a Materials

Paste suppliers matter. Considering "material factors" that drive void formation, solder paste formulation is the most critical.

Pad finish, in least void producing order: Ni/Au, HASL, OSP one reflow, Ni/Pd, Ni/Pd with Au flash.

Paste particle size: Voiding increases with decreasing particle size.

Paste solvent loss: Void formation is not due to solvent evaporation.

Paste metal loading: Voids increase with metal loading.

3b Methods

Print volume: Higher volume of paste increased voids.

Paste exposure time: Time between print and reflow is critical.

Paste coverage: Voids can not escape when covered with the BGA.

Reflow profile, in order of lowest void content: Soak for 2.5 min or greater, a 205C peak, time above liquidous. Soak temperature has little impact when soak time is 2.5 min or great and peak is 205C.

3c Environment

Moisture level in PCB: No impact.

Reflow atmosphere: Voiding frequency for joints reflowed in >50 ppm oxygen was on half joints reflowed in air.

3d Human factors

PCB pad cleanliness: Handling of bare board pads creates excessive voiding.

Print rejection: Cleaning of OSP pads with acetone or isopropanol increases voiding.

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oscar mendez

#6470

BGA Voids | 3 May, 2001

Does any one experienced problems on BGA voids related to height of chip (placement), and also another question, Does any one has some statistical process control for the BGA soldering process? if the answer is yes, I'd like to have advice from you. Thanks!

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