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Looking under a BGA

S. Evers


Looking under a BGA | 8 January, 2000

Hi all, Best Thing Since Sliced Bread? No doubt many of you have seen Phil Zarrow's "over-the-top" review in Circuits Assembly of the new Ersa scope, a device that allows viewing a really neat close up a side view of the component substrate interface of a BGA...

The question I have is why would you want to limit your inspection to here? Does this method of examining the edge connections of a BGA have any real merrit over xray due to the fact that the perimeter balls mask the interior ball interfaces from inspection. I know the effect of hypnotic paralax when driving by a cornfield isn't a perfect analogy here, but even the skeptic has to admit that the individual rows and columns of corn are hardly visible from such a cursary perimeter view (even with backlighting). I know from the xray images I've seen that the areas where shorts can occur are as random as the chaos theory; so what are you really looking at (or for) when you look at this particular view?

Solder quality? Solder balls? Collapse? Perimeter shorts and opens? Voids? (don't think so)

Sure you can get pretty unique pictures here using prisms, fiber optics and mirrors and the software that interfaces to your PC allows you to measure, compare, framegrab etc... but why would you want to look at BGA's in such a tedious yet limited fashion anyway?

Am I missing something?

I have noticed similar products springing up from: Has anyone here bought the Ersa system and care to comment? Has anyone tried the inexpensive version of a newly patented BGA edge device viewer from pcbvideo? Does anybody want to?

S. Evers

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Re: Looking under a BGA | 11 January, 2000

There is no way like the X-Ray. I wouldn't trust my balls to just any old inspection. Is there really any other way? I don't think so!! Spending the extra money on a X-Ray machine will save you money down the road.


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Re: Looking under a BGA | 12 January, 2000

I had the opportunity to spend time with a demo and one on one with the inventor of the Ersa scope inhouse a few months ago. I see the scope complimenting X-ray inspection but not as a substitue. It allows you to view attributes of a solder joint that you normally cannot determine with 2D X-ray. I haven't purchased this sytem but I see it's benefits. I think it's strongest application is in process development. With X-ray, it is very difficult to determine the attributes such as fillet wetting angle, feathering, and surface texture etc... that defines good solerability as outlined in IP610. Having the opportunity to view these attributes can only help us engineers in determining the effects of inputs. As far as the ERSA system goes, I believe it's very cost competitive. The capabilities are outstanding. I especially liked the ability to do linear measurements i.e. to verify complete ball collapse. Also the ability to save images to a database was a pluse. The optics were very good. I was able to view all solder bumps on a 250 I/O CSP with with great definition. I haven't seen any of the competition, they may be just as good. I would suggest getting a demo setup to see the benefits that an optical system can offer you first hand.

Good luck!

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