I am late into this discussion, since I have been on holidays, but did
anyone consider the possibility that the layers were stacked together in
the wrong order internally?  I have seen colour changes like that on one
batch that was made wrong.  If the internal copper plane layer is closer
to one surface than it normally should be, it would appear darker on one
side and lighter on the other than normal, which is what I see with the
ring. 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dan Skweres
Sent: July 30, 2010 10:59 AM
To: [log in to unmask]
Subject: Re: [TN] PCB Discoloration

Looks almost like one is FR-4 and the other is Polyimide. There was
mention that they are from different lots. Call the supplier and see.
Perhaps they (the board supplier) messed up and pulled one sheet of
Polyimide and figured that it would be okay to send based on the fact it
met or exceeded requirements per print.
Dan S.
----- Original Message -----
From: "Steve Gregory" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, July 29, 2010 9:34 PM
Subject: Re: [TN] PCB Discoloration


> Hi Linda!
>
> While discoloration in itself is not a defect, I would be a little 
> worried about these seven boards. Especially since the rest of the lot

> are not discolored like this:
>
>
> http://stevezeva.homestead.com/PCB_Discoloration1.jpg
>
>
>
> I don't see any delamination in the photos, but it sure looks like the

> boards got pretty toasty. I wonder if it was because the boards were 
> sitting over a preheater or hot plate too long. From the looks of the 
> components on the board, most of it was probably hand soldered (those 
> PTH caps converted to SMT couldn't have taken reflow), and I imagine 
> that the solid plane on on the backside of the board was a real
heatsink.
> Preheating the board would have helped with soldering the PEM nuts for

> sure, but maybe the preheater was set too high. I know a Hakko IR 
> preheater can smoke a board if you're not careful (not that I've ever 
> done that, but I know a friend of a friend who did. Hehehehe).
>
>
>
> Anyways, those seven boards saw more heat than the rest of them did 
> based on the appearance in the photos. I don't think I'd buy off on
them...
>
>
>
> Steve
>
>
>
>
>
>
>
> From: Linda Langley [mailto:[log in to unmask]]
> Sent: Thursday, July 29, 2010 1:42 PM
> To: Steve Gregory
> Subject: FW: PCB Discoloration
>
>
>
> Hi Steve,
>
>
>
> Here I go again asking for help from my experts! Can you please post 
> these pictures? So I don't have to bother the whole forum, would you 
> know the name of the board guru that could answer my questions?
>
>
>
> I am not sure if the discoloration is a defect, is this a form of 
> delaminating? Why would only seven boards turn this color? They are 
> all from the same lot.
>
>
>
> Any information will be greatly appreciated.
>
>
>
>
> Linda Langley CIT
>
> Training Specialist
>
> Jabil Circuit
>
> 248-292-6176


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