word of caution here... I have accumulated some scar tissue on this topic.
While we typically allow this with our qualified suppliers, this shouldn't
granted just so fabricators can get sloppy in plating setup (i.e. crankup
ASF, pay too little attention to mitigating effects of of high/low current
density areas, etc.).
If by "plated shut" you mean "substantially filled" then yes --
fine. However BEWARE of entrapment.
We have had vias plate shut at the knee that had sufficient air/moisture
entrapped to blow off pad/delaminate surface copper during reflow. Gnd
areas of tightly packed thermal via farms are especially susceptible to
this lifting (get that many vias blowing out together and it generates
significant stresses).
dw
At 09:44 AM 4/26/2007, Ryan Grant wrote:
>I agree with John, that I don't mind the via being plated shut. (Don't
>place more restrictions on the fabricator than necessary). HOWEVER,
>that should not be confused with a via being closed off by debris or
>nodules and then plated over, making it appear plated shut! If anything
>blocks that via during plating, the inside of the via will not be
>sufficiently plated and will cause latent open failures.
>
>-Ryan
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of John Foster
>Sent: Thursday, April 26, 2007 9:37 AM
>To: [log in to unmask]
>Subject: Re: [TN] "plated shut vias"
>
>I am a printed circuit board designer and I will tell you that
>quite often when I am speaking to a fabricator and I need to take
>the vias way down say 8 mils or below the first thing I hear from the
>fabricator is "Is it okay if the vias are plated shut"
>
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]]On Behalf Of David Greig
>Sent: Thursday, April 26, 2007 8:39 AM
>To: [log in to unmask]
>Subject: [TN] "plated shut vias"
>
>
>Hi List,
>
>Yet again I've come across fabrication notes on other pcb designers
>notes that specify that thru board via's may be plated shut.
>
>Is there any historical reason for this, or is it just hysterical?
>
>I would be rather concerned to see a closed via that is neither blind or
>filled, mental images of trapped process chemistry etc.
>
>Best Regards
>
>David Greig
>______________________________
>
>GigaDyne Ltd
>5 Albany Business Centre
>Gardeners Street
>Dunfermline KY12 0RN
>United Kingdom
>t: +44 (0)1383 624 975
>www.gigadyne.co.uk
>______________________________
>
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