In addition to Mr. Hersey's comments, the rationale used by the Military when 
imposing a simliar requirement in the MIL-STD-2000A (ie. you can't clinch dip 
leads) was that this had caused component damage (loss of hermiticity to 
actually "popping off" the top of the DIP).

In discussions on a proposed Revision "B" to MIL-STD-2000A (now long dead), it 
was generally agreed that this this was an isolated incident and there were 
indications that the parts were "hammered" prior to part placement (something to
do with tinning and then "quenching" the hot parts in solvent causing cracking 
in the ceramic.)   It should be noted that the DoD members attending agreed to 
change this from a "shall not" to a "should not" (ie. not a requirement) and it 
is not a requirement in the ANSI/J-STD-001 either.  

Jim Maguire
Boeing
(206)657-9063

______________________________ Reply Separator _________________________________
Subject: DES:ASSY: component mounting
Author:  [log in to unmask] at esdigate
Date:    5/29/96 4:10 PM


     
     
     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 ?  
     
     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 ? 
     
     What are the disadvantages ?
     
     This board is subject to both high temperature and high vibration.
     
     Any advise would be helpful.
     
     Thanks
     
     D.Drake