Phil,

I'm referring to a heat sink for several TO-220 packages that has one mounting tab at each end inserted into thru-holes with no crimp. Supposing the hole fill on the mounting tabs is well below IPC spec  I believe that is OK since the solder is a  mechanical mount only. I recall that soldering the source side only (with a complete fillet) creates a mechanical pull out strength relatively equal to when the barrel is full, since the hole wall contributes very little at that point.

Ed Popielarski
Engineering Manager


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-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]] 
Sent: Monday, January 20, 2014 4:08 PM
To: Ed Popielarski
Subject: RE: Mechanical fastening strength vs. hole fill

Are you referring to a mechanical post with crimp as opposed to soldered in post?  A post in a PTH without anything to bond it doesn't make sense.

I always have advised not to rely on solder for mechanical strength unless you have a lot of soldering locations and lots of surface area (RF/EMI shield with many soldered feet, for example).

On the other hand, if someone were to say that a post soldered in a PTH was not reliable, there are an awful lot of PGAs out there that say the opposite.

Phil

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ed Popielarski
Sent: Monday, January 20, 2014 3:06 PM
To: [log in to unmask]
Subject: [TN] Mechanical fastening strength vs. hole fill

Greetings, all.

I recall reading an article many years ago regarding "mechanical only" (such as a heatsink) through hole connections being more reliable and just as strong (pull out strength) if the barrel is not filled.

Might anyone have some insight?

Ed Popielarski
Engineering Manager

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                               970 NE 21st Ct.
                              Oak Harbor, Wa. 98277

                              Ph: 360-675-1322
                              Fx: 206-624-0695
                              Cl: 949-581-6601

https://maps.google.com/maps/myplaces?hl=en&ll=48.315753,-122.643578&spn=0.011188,0.033023&ctz=420&t=m&z=16&iwloc=A


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