In a perfect world, I absolutely agree of course. Given a choice between no heel fillet (with proper toe and sides evident) and the reforming of leads? I would take the lack of a heel fillet any day. Some of the other solutions are interesting as well, and the preferred one would be to acquire properly designed boards, but when stuck between a rock and a hard place - analyze the intended purpose of the board and make the best quality, reliability decision. Jan Pelchat ______________________________ Reply Separator _________________________________ Subject: Re: [TN] reforming a SOIC Author: Jack Crawford <[log in to unmask]> at 0UTG0ING Date: 8/26/98 2:43 PM Please refer to current documents J-STD-001B and/or IPC-A-610. The heel fillet is the most critical part of the solder joint on a gull lead device. Insufficient heel fillets even with max to the top side/toe fillets are NOT acceptable for any class product. There is high probability of cracking of the side/toe fillets with minimal normal thermal excursions if there is not heel fillet. Conversely, a proper heel fillet will survive a lot of environmental stress screening even if there are no side/toe fillets. This topic has been discussed as great depth in IPC technical meetings in the past. There are no plans to change these requirements in the C revisions now out for proposal on both the documents. Jack IPC HAS A NEW PHONE SYSTEM!! EXTENSIONS HAVE CHANGED!! Be sure to listen to the prompt for new directions. 8/20/98 IPC/SMTA Electronics Assembly Expo Technical Committee Meetings, Conference, Exhibits Providence RI October 24-29 More info at http://www.ipc.org Jack Crawford, IPC Project Manager - Assembly 2215 Sanders Road, Northbrook IL 60062-6135 [log in to unmask] NEW DIRECT NUMBER 847-790-5393 fax 847-509-9798 >>> PELCHAT_JM <[log in to unmask]> 08/26/98 07:18AM >>> If I were the Customer, I would rather leave the leads alone and rely on the toe and side fillets than even attempt to reform the leads. Particularly on Class 3 product. The reforming would require buyoff from the Customer and if they're going to buy off on anything, they should buy off on the lack of a heel fillet. If you get good wetting on the toe and sides, that is by far the preferred scenario. Depending on how many boards you have with this situation (hopefully, not too many otherwise it should have shown up in prototyping) it may be better to have the components hand placed and soldered for optimum pad to lead interface and to give every advantage to good solder filleting. Jan Pelchat ______________________________ Reply Separator _________________________________ Subject: [TN] reforming a SOIC Author: "Collins; Graham" <[log in to unmask]> at 0UTG0ING Date: 8/26/98 8:54 AM Technetter's Let's say a customer designed a board with the wrong pad size, too far apart, such that a gull wing lead placed on the pad doesn't have a heel fillet. Obviously a bad thing. A redesign is in progress, but in the interim it has been proposed that the part be reformed to spread the feet a bit further apart (by about 20 thou). Component is a 20 lead SOIC. My questions and concerns are: - the bend will have to occur at the point where the lead enters the component body, otherwise there will be no clearance between the part and the board. How dangerous is this from a reliability perspective (class 3 product, conformally coated)? Should I take the next few weeks off? Flee the country? Anyone have job openings? - do any technetters have suggestions of a half decent way to reform these? I'm currently faced with doing it to about 100 to 150 parts, and doing it by hand does not appeal to me due to the variability. Any other suggestions? I did consider borrowing some of the Freeze-it that Steve's using on his diodes, and shrinking the boards, but the reflow process might disagree with that... thanks! Graham Collins ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. 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For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################ ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################