These are 2 distinct design conditions used for differing purposes -
tented vias and via in pad VIP.
Tenting vias was done using dryfilm soldermask (DFSM), as it is a rigid
polymer that capped the vias as it was laminated to the board surface,
imaged and cured. This is where the term "tenting" originated as
created a tent over the vias. With the obsolescence of dryfilm
soldermask for many reasons, the introduction of Liquid Photoimageable
Soldermask (LPI) presented issued in sealing vias as the material
applied as a liquid did not tent/cap. The solution was to plug the vias
in post-LPI process, which provided the same results but left a crown on
the surface that frequently presented issues in SMT placement. This
process is generally changed now to a pre-LPI plug, where the LPI
overcoat produces a smooth topography. As vias have become smaller, the
need to plug has been reduced as several of the coating technologies are
effective in plugging during the normal coating operation.
The VIP technology is specifically for improving densities and via/pad
access. In this process, the via is formed, filled (with an epoxy
filler) and plated over to "hide" the via under the pad, and also
providing a solderable interface in the case of a BGA or other terminal
site needing the via to be inside the pad.
VIP is also being used for thermal management where a conductive media
is used to fill the via and used to dissipate heat from smaller
high-power devices which do not have adequate surface area to
incorporate an efficient heat sink. The same benefits are evident in
this technology with an area that is conductive to ground, solderable or
attachable with conductive epoxies.
Jeffrey Bush
Director, Quality Assurance and Technical Support
VERMONT CIRCUITS INCORPORATED
76 Technology Drive - POB 1890
Brattleboro, Vermont 05302
Voice - 802.257.4571 ext 37
Fax - 802.257.0011
<http://www.vtcircuits.com/>
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wee Mei
Sent: Sunday, February 05, 2006 9:23 PM
To: [log in to unmask]
Subject: [TN] Definition of Tent Via
Hello,
Can someone give me a simple, clear and correct definition of tent via
(both
signal and via-on-pad)? What is the process that go into making this
tent
via?
Regards,
Wee Mei
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