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May 2004

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Subject:
From:
Dave Chapman <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Sat, 15 May 2004 06:46:06 -0500
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Most often with 16 mil pitch our board suppliers prefer to clear out the
mask between pads, hard to get good adhesion at that pitch.
Dave C.
CSI

-----Original Message-----
From: Jeffrey Bush [mailto:[log in to unmask]]
Sent: Saturday, May 15, 2004 6:33 AM
To: [log in to unmask]
Subject: Re: [TN] Solder Masking SMT


No standard exists for minimum spacing requirements and the use of mask.
Our basic rule is any features with a less than a 1.25mm pitch will have
mask webs added, with confirmation from the design activity.  LPI
capabilities are fairly good - a .003" web is very common with spacing
as small as .001" to the pad (.005" space pad/pad).  Several designs we
are seeing now have .002" webs and 1:1 feature sizes - mask to pad. The
tools that PCB fabricators use to analyze your data should report this
as a potential issue if the pin to pin spacing is close.

Jeffrey Bush
Director, Quality Assurance and Technical Support

                          76 Technology Drive - POB 1890
                             Brattleboro, Vermont 05302-1890
                                Tel. 802.257.4571.21 Fax. 802.257.0011
                                    [log in to unmask]
                              http://www.vtcircuits.com



-----Original Message-----
From: Lance Mayes [mailto:[log in to unmask]]
Sent: Friday, May 14, 2004 4:40 PM
To: [log in to unmask]
Subject: [TN] Solder Masking SMT
Importance: High


Something for the weekend.

We have a SMT prototype board in the works and around the leads for the
IC's there is no mask.  Is there a standard that states whether mask is
required or not?  These are fine pitch leads also.  Another thing is how
much of pad clearance should there be on either side of the lead?  As I
see now there appears to be less than .001 on either side of the leads.
This doesn't allow for any variance of component placement with our pick
and place machine.  Recommendations, suggestions and or directions
please.  Anything to help prevent changing a process further down the
road, rev changes are really cost eaters.

Thanks Net Buddies and Buddettes

                        P.  Lance Mayes

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                        Mfg. Trainer

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