James

Pin holes can occur with out a fracture (in the normal sense) in the
copper barrel. These pin holes are usually caused by air bubbles at
electroless copper. Glass boundless extending into the barrel will also
cause this problem as the copper seal around these bundles is usually
poor.

Best regards

Lee



-----Original Message-----
From: James Hofer [mailto:[log in to unmask]]
Sent: Friday, September 10, 2004 3:53 PM
To: TechNet E-Mail Forum; Lee Parker
Subject: Re: [TN] Blow Holes -- Where the heck does the moisture come
from anyway?

However, Were this the case you would see fracturing or voiding of the
via.


James Hofer
Director of Operations
Accurate Circuit Engineering
3019 S. Kilson Dr.
Santa Ana Ca. 92707-4202
714-546-2162 work
714-473-6127 cell
[log in to unmask]
----- Original Message -----
From: "Lee Parker" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, September 10, 2004 12:31 PM
Subject: Re: [TN] Blow Holes -- Where the heck does the moisture come
from
anyway?


> Carrie
>
> If you cross section the vias, remove the solder from the hole and
look
> at the copper barrels at very high magnification (use and SEM if
> possible)you may see pin holes in the copper or glass bundles
protruding
> into the hole. This coupled with moisture in the dielectric which is
> normal can create the mechanism. When the board is quickly heated in
> assembly (reflow or wave solder) the moisture is pressurized and flows
> out through the pin holes into the barrels blowing the molten solder
in
> the barrels out onto the board.
>
> Best regards
>
> Lee
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Morse, Carrie
> Sent: Friday, September 10, 2004 2:33 PM
> To: [log in to unmask]
> Subject: [TN] Blow Holes -- Where the heck does the moisture come from
> anyway?
>
> Just wondering a few things here at 2:30 on Friday Afternoon:
>
> 1.  What else causes Blow Holes at wave on TH comps?  Is it primarily
> moisture?
> 2.  Where does the moisture come from?
> 3.  Are certain board materials more likely to sponge up the moisture
in
> the air?
> 4.  Can hole wall quality play a part in contributing to blow holes?
>
> -Carrie
>
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