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March 2013

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Subject:
From:
"Tontis, Theodore" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Tontis, Theodore
Date:
Thu, 21 Mar 2013 14:48:10 -0400
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Pete,

"the assembly vendor decided to change the power inductor we specified " 

If it is NOT on your BOM, approved vendor list or they have an approved deviation the assembly house is on the hook for using a non-approved part. 

I believe a majority of assembly houses state what IPC610 assembly class they default too, the standard is class II. If they do not post that information on their website or it is not part of the purchase agreement you will need to stick to your guns and hold them to the fire.

Ted T.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Thursday, March 21, 2013 1:32 PM
To: [log in to unmask]
Subject: Re: [TN] Explaining why pretty solder joints arn't good solder joints

Well, a whole bunch more really smart people got together from all sorts of industry-leading, highly-successful companies and designed a Biggie-sized O-ring for the Space Shuttle. They all sat in a room and agreed it was absolutely perfect. Even when there were indications that it could fail they said "No way". They kept saying that until the Space Shuttle was one more thing that went BOOM in the night. Nobody put their names on the front of that document.

So, if I were you, Pete, I would stick by my guns. Even if your assembly vendor states "look - it fits on the board and they even got solder on the outside of the leads!" I would simply state, "So what. It does not meet IPC 610 requirements". Kevin is correct, a whole bunch of smart people did determine the optimum solder joint pads for given component lead geometries that were in-turn JEDEC-standardized. Then these were qualified every which way. Then they were published. And all of this was done for Sn63 solder only. The pad designs were NOT qualified for leads hanging over the edges. Nor were they qualified for lead-free solder. So if the vendor wants you to believe that the soldered pads hanging over the edge are going to be perfectly reliable based on their say-so, well they might, and they might not, but if not the supplier will not be liable, the responsibility will be yours. Do you really want to be in that position?

Remember, perfect quality (ie, all solder joints meet IPC-610) does not guarantee that good reliability is built-in. 

But it sure is a damn good place to start. 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Glidden, Kevin
Sent: Thursday, March 21, 2013 12:51 PM
To: [log in to unmask]
Subject: Re: [TN] Explaining why pretty solder joints arn't good solder joints

Because a whole BUNCH of REALLY smart people sat in a room for MANY MANY hours at a time over many years to develop and document acceptable solder joint inspection criteria, based on real world experiences and testing.  That document is called IPC-A-610.  And it, my friends, says thou shalt not have ANY end overhang of a chip component (ref IPC-A-610E section 8.3.2.2).  This is for even Class 1 product (Teddy Ruxpin's and Xbox's).   And, btw, a partial listing of that group of super-smart people is listed right at the front of the document, from all sorts of industry leading, highly successful companies.

Just my 2 cents.

What are the contractual obligations for acceptance criteria?

Another option is to turn the tables.  IPC-610 brings evidence this is NOT acceptable.  Make them PROVE it if they think it is.


-----Original Message-----
From: Pete [mailto:[log in to unmask]]
Sent: Thursday, March 21, 2013 9:41 AM
To: [log in to unmask]
Subject: [TN] Explaining why pretty solder joints arn't good solder joints

We have a product on which the assembly vendor decided to change the power inductor we specified.  The part they used is close to the same size, but even at nominal, the leads overhand the pads on 3 sides under the body.  I raised a concern that these stress points create a risky solder joint.  The engineering group running this project keeps sending me pictures:  "look - it fits on the board and they got solder on the outside of the leads!"  I pointed out that the 3 sides of the joint they can't see are stress points.  Any tips on explaining the risk here?

Pete

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