Come on, guys! All "I" said was the launch failure was due to a "Bad solderjoint". I never said anything about the actual mechanism, what type component, leadfinish or any other metric and/or mechanism---because I don't know. All I want is the "best joint possible" for any product type. That means getting good,wetted side/heel fillets for all leaded SMT devices. -----Original Message----- From: [log in to unmask] [mailto:[log in to unmask]] Sent: Tuesday, June 30, 1998 3:07 PM To: [log in to unmask]; [log in to unmask]; [log in to unmask] Cc: [log in to unmask]; [log in to unmask]; [log in to unmask]; [log in to unmask] Subject: Re: Pramod Patel/solder joint reliability Hi Mark & Vern, It definitely is news to me, "that the China Launch problems were due to a lack of side/toe filleting". Failure at launch can only mean one of two things: (1) the solder joint was never properly made (wetted), or (2) inappropriate flight-hardware testing prior to launch accummulated too much fatigue damage (micro/macro-cracks) to withstand the mechanical loads during launch (see Hubble, Magellan, Gallileo). In neither case, would the presence of side/toe filleting made a signficant difference. Side fillets will defintely increase the peeling stress required due to the forces necessary to rip through them; that does not however equate to a more reliable solder joint in the long-term. If you have inadequately wetted solder joints, however, solder and toe fillets will likely prolong the time at which an infant mortality failure will occur in the short-term. The decision makers for "Missile, Launch Vehicle, wartime avionics/sonar and/or Spacecraft" should properly educate themselves as to what and what not solder joints can do. #1 issue: get away from large ceramic components on FR-4, #2 issue: qual testing should not be done on flight-hardware. Werner Engelmaier Engelmaier Associates, L.C. Electronic Packaging, Interconnection and Reliability Consulting 7 Jasmine Run Ormond Beach, FL 32174 USA Phone: 904-437-8747, Fax: 904-437-8737 E-mail: [log in to unmask] In a message dated 6/30/98 10:38:55, [log in to unmask] wrote: >I suggest you fellas do some more homework before drawing to Mark's >conclusion, as one "can always make the statement that proper wetting >makes for better peel strengths", independent of which surfaces you are >discussing. Side fillets(PROPERLY wetted) make a VERY SIGNIFICANT >difference in peel strengths of properly formed gull-wing and/or J-Lead >products. The issue is not the raw peel strength itself, but the >long-term reliability of the joints continuously under thermo-mechanical >stress. That is where the side-fillets become essential to long-term >reliability of our systems. > >Bottomline, do YOU want to be responsible for Missile, Launch Vehicle, >wartime avionics/sonar and/or Spacecraft failures due to simple >solderjoint issues?? > >I firmly believe you all are playing with fire in downplaying the >importance of "side-fillets" to long-term solderjoint reliability. > >You likely missed or ignored the "multi-millions" lost on the China >launch due to a simple solderjoint failure(??) > >----Original Message----- >From: Kwoka, Mark [mailto:[log in to unmask]] >Sent: Tuesday, June 30, 1998 10:47 AM >To: [log in to unmask] >Cc: [log in to unmask]; [log in to unmask]; >[log in to unmask]; [log in to unmask]; [log in to unmask]; Kwoka, >Mark >Subject: RE: RE: Need Pramod Patel's email address and/or telephone # > > Werner, > Thanks for the clarification. Your second and fifth points are what I was >after. I infer that if inadequate wetting of the lead to the board > land is infact present, then the "lead peeling test" will indicate lower >"peeling forces" than would be obtained from identical leads > that were "adequately wetted". Also, side fillets are not important if >adequate lead wetting is exhibited. > Regards, > Mark > -----Original Message----- > From: [log in to unmask] [SMTP:[log in to unmask]] > Sent: Wednesday, June 17, 1998 4:33 PM > To: Kwoka, Mark > Cc: [log in to unmask]; [log in to unmask]; >[log in to unmask]; [log in to unmask]; [log in to unmask] > Subject: Re: RE: Need Pramod Patel's email address and/or >telephone # > > Hi Mark, > First, there is no such thing as a 'lead pull test;' while you are of course > pulling on the lead, what you are doing to the solder joint is peeling it- the > proper reference is a lead peeling test. Some of your notions about solder > joint strength result directly from the false mental picture resulting from > the words 'tensile pull'. > Second, the solder joint strength, as determined by a lead peeling test, has > no bearing on the reliabilty of the solder joint, provided the peeling test > does not reveal inadequate wetting. > Third, in a peeling test you always need to observe the whole peel-load > history for the whole peeling process; with a 1T or larger heel fillet, the > largest load will be at the initial portion of peeling through the heel > fillet, with lower loads subsequently depending on whether or not (at to what > extent) side fillets are present. > Fourth, the fracture surface of the peeled solder joints give typically more > infrmation than do the peel-load histories, because the ONLY realy important > finding is whether or not adequate wetting has taken place. > Fifth, the reliability in actual use does to a large extent depend on the heel > fillet and the 'bottom flat' wetting; if the foot length is <3W, than also on > the presence of a toe fillet, because short feet 'rock' during thermal > cycling. Side fillets are less important, unless you have wetting problems. > > Werner Engelmaier ################################################################ 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 web site (http://jefry.ipc.org/forum.htm) for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################