Following from the EMPF HelpLine in Indianapolis, prepared by Jeff Kukelhan:

I would like to point out that both the EIA and IPC consider the "toe" area 
of gull wing leads as non-critical (per ANSI/J-STD-001 and ANSI/J-STD-002). 
 In otherwords, the "toes" do not have to accept solder in either 
solderability tests or production assembly operations to meet these 
specifications.  I think we may eventually determine that the "toe" joint is 
critical to long term performance, particularly for fine pitch devices.  But 
for the time being commercial specifications do not require a toe joint.  If 
you want to maximize "toe" joint formation without pretinning, look for 
vendors that apply 500 to 1000 microinches of fusible plating, and then trim 
the lead from the bottom up.  This bottom-up trimming motion will smear some 
of the thick plating over the lower half of the toe, and will generally 
facilitate the formation of a solder joint half way up the thickness of the 
toe.

 ----------
From: TechNet-request
To: TechNet
Subject: Non solderable toes on QFP's
Date:  19 Dec 95 8:25AM

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Subject: Non solderable toes on QFP's
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     Hi all,

     Wonder if you can help. We occasionally experience problems with
     solderability of joint toes on QFP's where the lead frame has been
     cropped after packaging, which leaves non solderable nickel iron lead
     frame at the toe of the joint.

     My questions are :-

     1  Is there any post cropping process which will avoid this
     condition??

     2  What practical problems has this caused in production??

     3  Which manufacturers if any are worse than others in this respect??


     Hope you can help.

     If I don't come on the net again before have a good Christmas and new
     year.

     Kind regards.

     John Burke.