the weight must be rather high.  we did samething for lab exp in 2nd  
yr university (early 80s), three different weight, same length of the  
wire to start with.  the last one refuse to break at 5:45pm (lab  
start 1pm).  we tried to kick the table to get it break, so we can go  
home for dinner...
On Nov 14, 2017, at 5:31 PM, George Wenger wrote:

> Richard,
>
> Although I have a good analytical mind and remember this  
> demonstration very well I may have not gotten the dimension exact.   
> The more I think about it I think the blackboard was 4 ft tall and  
> the solder wire may have only been 2.5 to 3 ft long and the class  
> was all morning (9:00am-11:30) so the solder wire broke before the  
> class was over so it might have broken closer to two hours then one  
> hour.  Nevertheless, the demo made its point.
>
> George
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D
> Sent: Tuesday, November 14, 2017 5:21 PM
> To: [log in to unmask]
> Subject: Re: [TN] Question on Loading Solder Joints
>
> I can just hear Bev cutting the 4 ft section of wire solder as I  
> write this.......LOL!
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of BEV CHRISTIAN
> Sent: Tuesday, November 14, 2017 3:37 PM
> To: [log in to unmask]
> Subject: Re: [TN] Question on Loading Solder Joints
>
> George, Ioan and Dave.
> Thx!
>
> Regards,
> Bev
>
> Sent from Mail for Windows 10
>
> From: George Wenger
> Sent: Tuesday, November 14, 2017 4:00 PM
> To: 'Bev Christian'
> Cc: 'TechNet E-Mail Forum'; 'David Hillman'
> Subject: RE: [TN] Question on Loading Solder Joints
>
> Bev,
>
> I'm really an old timer with lots of practical experience and I can  
> remember back in the early 70's taking a class at The Western  
> Electric Corporate Education Center in Hopewell NJ and the teach  
> said that you should never have a solder joint under a tensile  
> load.  He continued to say that rather than give you a 1000 words  
> to tell you why not that he would show us a very simple and very  
> graphic demonstration.  He pulled a roll of solid solder wire out  
> of his desk and said it was Sn60 but it really didn't matter what  
> the solder alloy was.  He cut off a 4 foot length of the solder  
> wire and tied one end to a hook at the top of the blackboard and  
> then tied a weight to the other end of solder wire.  He took a  
> chalk and marked a line on the blackboard just where the bottom of  
> the weight was.  He then continued teaching the days lesson but  
> every 15 minutes of class, without saying anything, he would take  
> the chalk and mark where the bottom of the weight was.  After about  
> a little over an hour, while he was busy instructing us on the days  
> lesson, we heard a loud "bang".  The solder wire had continued to  
> elongate while it was under the tensile load of the weight and  
> finally the solder wire broke approximately in the middle and the  
> weight dropped onto the floor.  Right after every one heard the  
> loud "bang' of the weight hitting the floor he stopped what he was  
> talking about and simply said "that is why you never what a solder  
> joint to be subjected to a continuous tensile load".  Although it's  
> been almost 45 years since I attended that class I'll never forget  
> what he said.
>
> George
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of David Hillman
> Sent: Tuesday, November 14, 2017 3:33 PM
> To: [log in to unmask]
> Subject: Re: [TN] Question on Loading Solder Joints
>
> Hi Bev - I would point them to RJ Klein Wassink's book "Soldering  
> In Electronics", ISBN 0-901150-24. In the Mechanical Properties  
> Section 8.4 it states "From the data in section 4.7.2 it is obvious  
> that a normal soldered connection on a printed board is not well  
> suited to withstanding a permanent mechanical load."
>
> And in Section 4.7.2 Creep, there is some good data on the creep  
> properties of solder backing up that statement.
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
> On Tue, Nov 14, 2017 at 2:12 PM, BEV CHRISTIAN  
> <[log in to unmask]>
> wrote:
>
>> TechNetters,
>> A fellow ex-BlackBerry employee sent me the following query. I
>> obviously no longer have access ot the search capabilities I had at
>> BB.  Can anyone offer any suggestions for papers that will meet his
>> needs?  I mean I know the reason why, but he wants a paper that  
>> proves it.
>>
>> I need help with locating a couple of good papers and research  
>> studies
>> that explain why designs that place a constant tensile or shear load
>> on board connectors(USB, HDMI, RCA, AC inlet etc.) are a bad idea.  
>> Can
>> you point me to a couple of papers on this ? Thanks.
>>
>> Regards,
>> Bev
>>
>> Sent from Mail for Windows 10
>>