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Date: | Fri, 19 Nov 2010 22:24:54 +0100 |
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John,
we have seen this a number of times,and I've been looking at some of these
cases.You can start with some brief examinations:
1. are there any solder remnants on the board pads. If so, how does it look
like? Randomly spread or ring formed along the pad's circumperifery?
2.apply a solder etchant that does not etch Nickel to get an opinion about
the solder wetting
3. apply a nickel etchant that does not etch solder to get an opinion about
the nickel covering, skip plating, IMC s
4. dispens a 50-100 micrometer solder paste on the failing board pads and
run through your oven.Wetting, dewetting or non-wetting.
You need a experienced person to do the tests and to interprete the results.
In right hands, often better than pages and pages of EDAX analysis.
Inge
---- Original Message -----
From: "John Parsons" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, November 19, 2010 9:31 PM
Subject: [TN] BGA Falling off PCA
>I am not seeing a lot of the usual Friday quiz traffic so I know you
> guys-n-gals are just itching for some real work :o).
>
>
>
> We are a PCB fabricator and one of our customers has returned some
> assemblies to us for feedback. What they noticed when someone
> accidentally
> dropped an assembly is that the BGA (352 pin Cirrus Logic EP9312-CBZ)
> popped
> off the board. They then proceeded to drop a few more from a height of
> about a foot with the same results. All the other components on this
> Pb-free assembly stay fast.
>
>
>
> We have received three PCA's and 5 BGA's. On one of the BGA's a single
> ball
> has remained on the PCB. The rest of them all the balls have broken
> cleanly
> from the PCB leaving a very flat (under x10 magnification) dull gray
> surface. I sure wish that I could take photo's but lighting is critical
> and
> I don't think that I have the resources to get photo's that would do
> justice
> to what the naked eye is seeing.
>
>
>
> Also of note is that the BGA lands are mask defined with a 31mil circuit
> pad
> and 26mil solder mask relief.
>
>
>
> Does anyone have any ideas as to how we can determine the root cause of
> this
> failure. This part has been built for some time but previously the
> surface
> finish on the PCB was a solder finish. This is the first run of the
> boards
> that has an ENIG finish. This doesn't look to me like a raw board issue
> but
> that is where everyone looks first isn't it ;o).
>
>
>
> Regards
>
>
>
> John Parsons
>
>
>
>
>
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