Tenting is a term used when PCB fabricators used dryfilm
soldermasks. That is not the general practice anymore. LPI
soldermasks have replaced dryfilm soldermasks. LPI is more
robust and passes lower ionic contamination specs. With
LPI's, a true tent cannot be accomplished. Our approach
when we see a tent requirement is explain to our customer,
the via plugging process (this is explained in detail on
our website sbcinc.com , "Guidelines for
Manufacturability") If your need is to close the vias to
help draw a good vacuum during ICT, then plugging works
very well. If you are trying to avoid solder bridging it
also works well. A true tent with dryfilm soldermask will
cost more. Hope this helps.

On Wed, 3 Jul 2002 10:12:21 -0400
 Ray McKinnon <[log in to unmask]> wrote:
> Thanks Gary.
>
> Although "tenting" refers to covering the pad (in our
> case via pad) we are
> only allowing encroachment of solder mask to .002' of the
> finished drill
> hole. Does IPC have guidelines for this methodology?
>  And, is this a cost
> addeder as well? (we are questioning our board suppliers
> right now)
>
>
>
> Thanks,
> Ray
>
>
>
>
>
>
>
> Gary Ferrari <[log in to unmask]>
> Sent by: TechNet <[log in to unmask]>
> 07/03/2002 09:54 AM
> Please respond to "TechNet E-Mail Forum."; Please respond
> to Ipcgary
>
>
>         To:     [log in to unmask]
>         cc:
>         Subject:        Re: [TN] Guidelines for tenting
> via's
>
>
> Ray,
>
> You can find information about tenting vias in IPC-2221
> Generic Standard
> on Printed Board Design, section 4.5.1 Solder Resist
> Coatings. It does
> indicate that the maximum size for tenting is 1.0 mm for
> Class 1 and 2 and
> 0.65 mm for Class 3 equipment. The tenting acceptability
> for larger sizes
> should be discussed between user and supplier.
>
> Regards,
>
> Gary
>

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