Hi Jack,
I concur with Dave.
Understanding what he is explaining landed me a Quality Engineer
position at PCC in Woburn Mass years ago. If you are not within 25% of
the center of the PTH plating thickness, sizes of defects, get
significantly exaggerated. The "depth" of the defect is not exaggerated
but the width is greatly exaggerated as you approach tangency to the
edge of a feature. Something along those lines is what I believe you had
posted. The edge of the line width is just too shallow to be a classic
etch out due to lifted resist and the wrong shape for resist residue
that degraded during etching.
Good explanation Dave.
Sincerely,
Paul Reid
Program Coordinator
PWB Interconnect Solutions Inc.
235 Stafford Rd., West, Unit 103
Nepean, Ontario
Canada, K2H 9C1
613 596 4244 ext. 229
Skype paul_reid_pwb
[log in to unmask] <mailto:[log in to unmask]>
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: Friday, February 08, 2008 8:12 AM
To: [log in to unmask]
Subject: Re: [TN] FAB: Thin Trace Failures
Hi Jack! I have a pretty good visual to explain cross section artifacts
that I use to assist my co-op students with the phenomena. Take a sheet
of paper and draw a view of a plated thru hole in a top down view point,
making sure that you have both the internal and external diameters drawn
such that your plated thru hole wall has some reasonable thickness (i.e.
like a half inch!). Now draw a line across the centerline of the plated
thru hole and a second line that 25% of the distance between the hole
centerline and the hole ID. Now use a ruler and measure the hole wall
thickness at the centerline and at the 25% distance - the 25% pth
distance is going to appear to be "thicker" as an artifact of where you
are cross sectioning the pth (the true pth wall thickness is skewed by
position)!
The location and orientation of where your cross section dissects the
sample can cause some confusion. Hope this helps.
Dave Hillman
Rockwell Collins
[log in to unmask]
Jack Olson <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
02/07/2008 05:43 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Jack Olson <[log in to unmask]>
To
[log in to unmask]
cc
Subject
Re: [TN] FAB: Thin Trace Failures
I may owe the group an apology...
For the curious, I'll answer the questions people asked me:
- the product has been in production for a long time with no problems.
- product must operate at 125C, so after ICT we do a "hot" functional
test.
- all at once we had massive fallout, ICT okay, hot NOT.
- failures in random locations, unpredictable
- same vendor, all boards from same same date code
- bare-board vendor on chinese holiday, no response yet
We sent a few failed assemblies out to be analyzed, and the
picture I provided in the link below was the first thing we got back,
but with no analysis
Since then we have found cracked via barrels, which seems
to be a more likely culprit. (but I'm no expert)
If I asked for help without waiting for enough supporting info,
I'm sorry.
but I would like to know more about "cross section artifacts"?
Where can I learn about that?
I can't visualize how the cross section could be a normal beginning
or an ending of a trace, but maybe I'm showing my ignorance
willing to learn,
Jack
.
On 2/7/08, [log in to unmask] <[log in to unmask]>
wrote:
>
> Beware of cross section artifacts. If this is not the sites you were
> aiming for it may not be a defects. Could the beginning of a trace
or
> the ending. I see this often.
>
>
> Victor,
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Jack Olson
> Sent: Thursday, February 07, 2008 9:33 AM
> To: [log in to unmask]
> Subject: [TN] FAB: Thin Trace Failures
>
> Has anyone ever seen a cross-section like this?
>
> http://www.frontdoor.biz/PCBportal/opentrace.jpg
>
> (ignore the words on the pic, just a guess)
>
> Can you point me in the right direction for cause?
>
> thanks,
> Jack
>
>
>
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