[SI-LIST] Re: thermal relief

Jan,

it is not 100% clear whether you meant a COMPONENT pin or a VIA
(used to connect 2 tracks/pads on different layers). Thus there
are a few possibilities:

1. Normal VIAs: whether you use thermal reliefs or not for the
VIAS should be irrelevant with regards to manufacturing (unless=20
they are covered top and bottom with solder mask, which can result
in an air pocket - this may 'pop' during soldering). So for vias,
go ahead and make a solid connection to the plane.

2. COMPONENT PIN: you will still be able to use connections without
thermal reliefs, if the components will be soldered with a wave
soldering process - thermals or no thermals, makes little or no
difference these days. The only difficulty may then be replacing
the part at a later date, when the technician only has a low strength
soldering iron.

3. HAND-SOLDERED component pin (unlikely, unless you are working
on some kind of low quantity application/test board): you will find
that the components CAN be soldered, provided the components can take
higher than normal soldering heats (and you don't mind the =
hand-solderers
cursing you ;-) !!). Multiple plane layers would make the problem worse,
but with only 4 layers, you will be fine.

4. Even if you feel compelled to use thermal reliefs on component pins,
with a decent CAD system, you should have the opportunity to adjust the
width (and perhaps more importantly the NUMBER) of the connections to
the plane, plus the 'trench' around the pin (i.e. the gap between pin
pad and plane around it). This gives an infinite number of possibilities
to simulate, and provides a range of trade-offs between good =
solderability
and a 'solid' plane connection.

A final possibility for improving the connectivity of (and current =
spread
across) COMPONENT PIN joints with OR without thermal relief: you run =
lots of
short traces from the SMALL pad on the component side to a number of =
vias.
Even with a thermal on the inner plane, these vias will contact the =
plane
outside this thermal area, and approach the principle of a multi-core =
cable,
as opposed to the "single-core" pin joint, which in your high frequency =
area
must be preferable!!).
____________________________________
Sol Tatlow, M.Eng. (Oxon)
ProDesign Electronic & CAD Layout GmbH
Product Developer
Albert-Mayer-Str. 16
D-83052 Bruckmuehl
Phone: +49 (0) 8062-808-302
Fax:   +49 (0) 8062-808-333
Mailto:sol.tatlow@xxxxxxxxxxxxxxxxxxxx
www.prodesign-europe.com
____________________________________=20

-----Urspr=FCngliche Nachricht-----
Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] =
Im Auftrag von jan gillis
Gesendet: Mittwoch, 28. April 2004 13:09
An: si-list@xxxxxxxxxxxxx
Betreff: [SI-LIST] thermal relief


Hi all,

I am designing a four-layer microwave synthesizer. The second layer is=20
defined as a ground plane. For soldering purposes, it would be preferred =
to=20
make use of thermal reliefs for the ground vias. But I wonder what would =
be=20
the influence of the pin-to-ground plane impedance. Can anyone provide =
some=20
guideline for this purpose?

Thanks!

------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List FAQ wiki page is located at:
                http://si-list.org/wiki/wiki.pl?Si-List_FAQ

List technical documents are available at:
                http://www.si-list.org

List archives are viewable at:    =20
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
 =20

------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List FAQ wiki page is located at:
                http://si-list.org/wiki/wiki.pl?Si-List_FAQ

List technical documents are available at:
                http://www.si-list.org

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
  

Other related posts: