Steve, Where can I find the information that supports the barrel fill strength as compared to the lead ? Was there a paper written ? Thanks for the response. Darrell Drake SSDS Houston, Tx. ______________________________ Reply Separator _________________________________ Subject: Re: DES:ASSY: component mounting Author: [log in to unmask] at Internet-Mail Date: 5/30/96 11:03 PM >Message was resent -- Original recipients were: To: [log in to unmask] -------------- [log in to unmask] asked ............ > > To all, > > In reference to IPC-D-275 Section 4.2.1.2 Clinched Leads (Type 1) the third > paragraph states "Type 1 is not applicable to leads of dual-inline packages > (DIPs)...." Q > > Question: What are the technical reasons why Type 1 clinching is not > considered applicable for DIP packages ? > ....................Another reason, from personal experience, is that the stiff steel leads of DIPS, require large amounts of force to bend to a full clinch. The pressure exerted against the knee of the PTH can cause lifted pads or damaged barrels, including tearing of the copper. Inward is worse than outward because of the extra force required to overcome the natural outward bend of the lead. > We have a customer who has designed a Class 3 board where all DIP packages > (as well as all pins for each DIP) are PTH with full clinch pads, the > clinch is towards the body. > > Are there mechanical advantages to this method ? No....If your leads meet solderability requirements, the solder in the PTH is far stronger than the lead. > > What are the disadvantages ? Full clinch partially blocks the PTH, possibly causing soldering defects. Also major rework hassle... > > This board is subject to both high temperature and high vibration. If the only way the designer could think of to make his design resistant to temp and vibe was full clinch, somebody ought to forceanly drag him from the sixties into the nineties. Full clinch is a holdover from single and double sided boards without PTHs. If I recall the number, a stud joint with a full barrel fill and top and bottom solder fillet is about seven times stronger than the lead. This sounds like another of those legacy requirements started by an incident at your customer's facility many years ago. I would suggest wooden stakes and silver bullets. Good Luck Steve Mikell SCI Systems Huntsville, AL [log in to unmask] Steve Mikell, Process Engineer, Soldering & cleaning processes SCI Systems Plant 13 [log in to unmask]