I fully agress with Jack.This reminds me one statement which was made by Don Burr , X-Unisys(currently with cyberoptics) when he visited our facility in 1995, that the strength of a joint is contribted by: Heel joint; 70% Base and side Joints : 20% Toe joint : 10% That conforms Jacks' statement. Ashok Dhawan P.ENG. Manufacturing Engineering Unisys Canada Inc. 51 Burmac Road Winnipeg R2J4C9 CANADA Fone 204-257-9199 Fax 204-257-9104 > ---------- > From: Jack Crawford[SMTP:[log in to unmask]] > Sent: August 26, 1998 2:43 PM > To: [log in to unmask] > Subject: Re: [TN] reforming a SOIC > > 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. > 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 > ################################################################ > ################################################################ 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 ################################################################