David,
        Interesting, but look closer in the Claims portion of the patent
where the define their 'lead-free' solder: "wherein the lead-free solder
contains tin-zinc based solder, tin-silver based solder or tin-copper based
solder". I think by the omission at the end of the sentence of the
additional phrase "or any combination thereof" they may have left a big
loophole for SAC alloys. They are only making specific claim for the use
with two-alloy solders, not three-alloy solders.

Mike McMonagle
Quality Engineer
OYO Geospace
7007 Pinemont Drive
Houston, TX 77040
713-986-8650
 

-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of David Greig
Sent: Friday, August 19, 2005 7:38 AM
To: [log in to unmask]
Subject: Re: [LF] Design of THT PAD Size

US patent 6617529 might make life a little difficult. NIPPON ELECTRIC also
have a Japan patent, but I can't find a Europe
equivalent.
You may want to try
<http://v3.espacenet.com/textdoc?DB=EPODOC&IDX=US2002074164&F=0&QPN=US200207
4164> for a peak.

Looks like square or non circular pads are going to be the thing. Or a
circular pad extended to any distance from the hole and
with one or more blind or thru vias any place within the circumference.

Or perhaps solder with some lead content? What's the legal interpretation of
"lead free"?

Best Regards

David Greig
______________________________
GigaDyne Ltd
http://www.gigadyne.co.uk
______________________________

-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Colin Weber
Sent: 19 August 2005 03:12
To: [log in to unmask]
Subject: [LF] Design of THT PAD Size

Hi Folks,

Can someone please point me in the right direction with respect to design
guidelines for through hole device footprints to be
wave soldered in lead-free manufacturing?

I have heard that pads for THT device leads must be 30% larger.
However, I don't know what IPC standard this figure or advice originates
from and whether it refers to area, annulus, etc?



Regards,

Colin Weber

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