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 Return-Path: <[log in to unmask]> Resent-Date: Tue, 19 Dec 1995 09:05:14 -0800 Old-Return-Path: <miso!psion.com!John-Burke> Date: Tue, 19 Dec 95 08:25:01 GMT From: "John Burke" <[log in to unmask]> Message-Id: <[log in to unmask]> To: [log in to unmask] Subject: Non solderable toes on QFP's Resent-Message-ID: <"L67HM.0.uB4.p7lrm"@ipc> Resent-From: [log in to unmask] X-Mailing-List: <[log in to unmask]> archive/latest/2096 X-Loop: [log in to unmask] Precedence: list Resent-Sender: [log in to unmask] ---------------------------------------------------------------------------- -- 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.