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April 2007

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Subject:
From:
"Smith, Richard" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Smith, Richard
Date:
Thu, 26 Apr 2007 14:54:42 -0400
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text/plain (134 lines)
Hi David, 

You may want to specify the hole tolerance on the drawing as +.000 -hole
diameter. For example : .010 +.000 -.010. This does not specifically
state that the hole is plated shut.

Rick

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David Greig
Sent: Thursday, April 26, 2007 1:33 PM
To: [log in to unmask]
Subject: Re: [TN] "plated shut vias"

Hi John,

What concerns me is the prospect of:

1. Plated over, but with pinholes
2. Plated over on one side only, with trapped chemistry that will never
wash out fully 3. Plated over, but extremely thinly

The problems that may occur are venting during assembly (under BGA's
etc) and subsequent leaching out afterwards (even if not corrosive,
surface resistivity and CTI will reduce over time).

I would be happier to specify "plated over, both sides, with a minimum
thickness copper each side of xxx".

So far have not run into the prospect of plating over occurring
naturally because I go directly to microvia for anything requiring less
than 0.25mm/10mill drills @ 1:6 aspect.


Best Regards
 
David Greig


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Foster
Sent: 26 April 2007 16:37
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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