I recognize the issue. It's not a trifle. This is what I believe: The
nickel layer was too thick and too hard. When the leads were bent, the
nickel cracked, not as many microcracks, but in one or two deep 'trenches'.
When you soldered the parts, there was bad wetting in the crack zone, which
was so wide, that the capillary forces were not enough to overbridge the
crack, thus the ditch on your picture. The product may well live for decades
in an office ambient, but not in harsh mechanical environment. I would never
accept such solderings for MIL.
Take some parts directly from stock, bend the leads (not exceeding minimum
allowed radius) and inspect the result. If you get deep cracks that exposes
the base material, it's a cause for rejection.
Too often, leads are bent with too sharp an angle. People are not informed
about the nature of the lead finish. A very common problem and it seems to
go on. If we had experienced and active QAs, that would never happen. But
most of these guys are on the other side now...
Inge
----- Original Message -----
From: "Lum Wee Mei" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, September 17, 2010 7:15 PM
Subject: Re: [TN] Crack and oxidisation on IC leads
The ICs are already formed when purchased, the contractor just need to mount
them in.
I have the same sentiment with the concern.
Thanks and Regards,
~ Wee Mei ~
_____
From: TechNet on behalf of Steve Gregory
Sent: Sat 9/18/2010 12:00 AM
To: [log in to unmask]
Subject: Re: [TN] Crack and oxidisation on IC leads
Hi Wee Mei,
I got your pictures, however the photo of the oxidation is really out of
focus and hard to recognize anything.
But your photo of the cracked knee is pretty clear. It's here:
http://stevezeva.homestead.com/Cracked_Knee.jpg
Were these cut and formed by them? I think it's a little more than just a
minor crack. If it were me, I'd be concerned.
Steve Gregory
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Friday, September 17, 2010 9:23 AM
To: [log in to unmask]
Subject: Re: [TN] Crack and oxidisation on IC leads
Wee Mei,
You can send the photo to me and I will post it on my web page for all to
see...
Steve Gregory
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Lum Wee Mei
Sent: Friday, September 17, 2010 8:07 AM
To: [log in to unmask]
Subject: [TN] Crack and oxidisation on IC leads
Importance: High
Dear All,
During PCBA inspection, we noticed cracked line across the entire IC lead
width at the knee location. It happen to the whole row on one side of the IC
and we consider it a reject. However, our production subcontractor do not
concur the component as reject. They said that the crack is only fine line
and is unlikely to cause any major physical issue to the leads itself.
In another IC, we noticed a small area of oxidation on one of the lead of
about 1 - 1.5mm in size. Again the subcontractor do not accept our decision
that it is a reject. The reason given by them is that although the corrosion
exposed the base metal it is acceptable because the exposed surface is not
part of the required solder fillet.
I have tried to upload the photo on IPC Technet but not successfully. Hope
from your experience, you can provide some opinions.
Thanks and Regards,
~ Wee Mei ~
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