Hello Myke,

It would be helpful if you could indicate what type of crack it is;

        At what magnification are you detecting these crack ?

        Where the cracks are located ?

        Is this a full or partial crack ?

        Are you baking the samples before sectioning ?

        Have you tried sectioning before thermal stress ?

        (You may find this interesting if you are noticing cracks before
any thermal stress. This would indicate         problems at the copper
plating area.)

        Did you check the temperature calibration of your solder pot ?

        What is the copper thickness at the edge of the hole compared to
the surface of the board and the middle         portion of the hole ?

        (An out of control leveler concentration may lead to thin copper
at the edge of the hole creating a weak         area which may cause a
typical corner crack.)
________________________________________________________________________
___
Here are some suggestions concerning this problem;

If you are able to quantify the brightner concentration into the
Electro-plating bath, you may want to try out different brightner
concentrations.

Higher Tg material will sure help and may compensate for some process
deviation most likely at an added cost.

Copper purity and plated copper elongation values should be within
acceptable limits.

Regards,
Charles Desroches
Technical Advisor
Viasystems Canada inc. (Granby)






> ----------
> From:         MICHAEL DODSON[SMTP:[log in to unmask]]
> Reply To:     TechNet Mail Forum.;MICHAEL DODSON
> Sent:         Wednesday, January 07, 1998 5:03 AM
> To:   [log in to unmask]
> Subject:      [TN] Cracked Vias
>
> Hello,
>
> My name is Myke Dodson and I would like
> to request feedback from individuals that have experience in dealing
> with "Cracked Vias" due to Z-axis expansion.
>
> My scenario deals with an .093" board with vias drilled at .0145".
> Standard FR4 material. There is sufficient copper in the hole (.001")
> and there are not multiple vias that are cracking. ( i.e. 2 brds
> out of 100 ).
>
> Will higher temp material help ?
> Will baking prior to assembly help ?
> What is your experience with boards that have cracked vias ?
> Possible solutions or suggestions.
>
> Please send all responses to: [log in to unmask]
> Phone: 408-978-8992 ext.266
>
> Thank you,
> Myke Dodson
>
> ##############################################################
> TechNet Mail List provided as a free service by IPC using LISTSERV
> 1.8c
> ##############################################################
> To subscribe/unsubscribe, send a message to [log in to unmask] with
> following text in the body:
> To subscribe:   SUBSCRIBE TECHNET <your full name>
> To unsubscribe:   SIGNOFF TECHNET
> ##############################################################
> Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
> additional information.
> For the technical support contact Dmitriy Sklyar at [log in to unmask] or
> 847-509-9700 ext.311
> ##############################################################
>

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311
##############################################################