I have suggested to member of the IPC610 committee and comments via IPC that
there should not be a necessity to change the basic criteria in terms of
height up the fillet etc but reference joints should be included of
different alloys for accept reject.
With regard to design rules the IPC documents have always been wide, the
refinement based on process experience is important and the key factor is
reducing shorts during wave. The design guide is weak on wave soldering for
tin/lead and all the design tricks should be considered, like wave supports.
Proper definition of drainage pads for SMT and through hole. Reducing
through hole pad size on plated through boards. Include guidelines for QFPs,
they may not be recommended but they are used. Look at reducing pad widths
on SOICs, many shorts are caused by pads on the top end.
Bob Willis
2 Fourth Ave, Chelmsford, Essex, CM1 4HA
Tel: 01245 351502
Fax: 01245 496123
Mobile: 07860 775858
Email: [log in to unmask]
Web: www.leadfreesoldering.com
Web: www.bobwillis.co.uk
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]]On Behalf Of Thomi
Sent: 25 October 2003 23:03
To: [log in to unmask]
Subject: Re: [LF] New to the group : Lead free landpatterns question
Hi Rene,
with regard to land patterns for leadfree electronics production, from all
we have tried and heard in various leadfree circles, we have not found a
necessity to change land patterns for better soldering results. One note,
though, on IPC-SM782 (and I am eager to responses to this from other
LEADFREE members, though this discussion might fit better in TECHNET) - I am
not convinced that this is the most appropriate commonly available
landpattern standard. It is desperately lacking to distinguish between
reflow and wave pads, if I don't lack information regarding it's
interpretation.
For our layout, we prefer the Philips guidelines, as shown e. g. in the
reference
Klein Wassink, R. J., Verguld, M.M.F.: Manufacturing Techniques for Surface
Mounted Assemblies. Electrochemical Publications Ltd., Asahi House, Port
Erin, Isle of Man (1995).
(There are other comprehensive collections from Siemens, and further
component specific advisories).
But as mentioned, I'd like to find comments on this from others. I would
also like to get information on the next issue of IPC-A-610, which will be
revision D, if there will be special input on leadfree solder joints -
although I'd anticipate equal requirements for acceptability in terms of
wetting, smooth surface, concave shape, no opens, no bridges, no corrosive
residues and whats more...
Best regards
Thomas Ahrens, D-Boostedt
----- Original Message -----
From: "Rene Maas" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, October 23, 2003 3:03 PM
Subject: [LF] New to the group : Lead free landpatterns question
> Hello to you all, I am investigating the impact on our product portfolio
if we have to adapt
> it for leadfree production. We currently use the IPC-SM-782+A1+A2 standard
for the definition
> of land patterns of components that we use. However, we would like to
prepare new designs for
> lead free production.
>
> Can anyone please advise for a standard/recommendation or website where I
can
> find details on the definition of lead free land patterns ?
>
> Thanks in advance,
>
> Rene Maas.
>
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