TECHNET Archives

April 2017

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
"Upton, Shawn" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Upton, Shawn
Date:
Wed, 26 Apr 2017 14:01:55 +0000
Content-Type:
text/plain
Parts/Attachments:
text/plain (1 lines)
I have to wonder why the plane was pulled back.  Looks like a DB9, so I'm thinking, low speed signals, possible RS232.  But it could be some high impedance circuit where capacitive loading is a big problem.  Perhaps not.  Perhaps the pullback was done not to limit capacitive effects on the traces on that DB9, just a pullback to prevent coupling, as a plane wasn't required.  Just guessing, so as to not impact circuit performance.  



If low capacitance is required, it might be a bit more work than just adding a split plane or thieving, as it couldn't be added under the traces--but it could be brought "near" for the desired effect.  But if it was just a "we don't need a plane here, just remove it" then a split plane should be easy enough to use, with a full or crosshatched pour.



Shawn Upton

Section Head, Test Engineering

Sensors Business Unit

Allegro MicroSystems, LLC

[log in to unmask]

603.626.2429/fax: 603.641.5336





-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Carl Van Wormer

Sent: Wednesday, April 26, 2017 9:51 AM

To: [log in to unmask]

Subject: [TN] PCB delamination at area with ground-plane cutout



We received pictures from our contract manufacturer, marked to show delamination occurring in 2 areas on our 6-layer boards.  The delamination areas were at the electrically isolated communication interfaces that were made with no copper on the power and ground planes to reduce capacitive coupling.  The response from the PCB manufacturer is:



​​​​​1)defect reason: we used our stock boards to run the thermal shock test, we see the de-lam is only taking place in the two areas without copper (pic 1.jpg),

    There is insufficient glue in this area that happened during lamination and that is why the de-lam is happening when the customer is assembling under the high temp, 2)correction action:  if the customer needs us to remake, we suggest to modify the design a little, pls see pic 2.jpg, we will fill the marked area with solid copper .

Please confirm if a remake is needed, we will arrange right away.



Steve Gregory has posted the pictures at:

http://stevezeva.homestead.com/Carl1.jpg (board cut open for evaluation at board house)



http://stevezeva.homestead.com/Carl2.jpg (picture showing where they want to add copper)



(and 2 pictures of the delaminated areas) http://stevezeva.homestead.com/Delamination_-_is_it_caused_by_missing_ground_plane__1_.jpg

http://stevezeva.homestead.com/Delamination_-_is_it_caused_by_missing_ground_plane__2_.jpg





Question to the group:  Will adding copper on the electrically isolated open areas eliminate this type of delamination?  We could add the copper, but not connect it to the system ground.



Thanks,

Carl













Carl B. Van Wormer, P.E., AE7GD

Senior Hardware Engineer

Cipher Engineering LLC

    21195 NW Evergreen Pkwy Ste 209

    Hillsboro, OR  97124-7167

    503-617-7447x303

    [log in to unmask]<mailto:[log in to unmask]>     http://cipherengineering.com<http://cipherengineering.com/>



This message may contain confidential and/or proprietary information, and is intended for the person/entity to whom it was originally addressed. Any use by others is strictly prohibited.  If I sent this to you by mistake, please be nice and delete it, and then tell me of my mistake so I can send it to the right person.






ATOM RSS1 RSS2