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November 2009

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Subject:
From:
Bev Christian <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Bev Christian <[log in to unmask]>
Date:
Mon, 23 Nov 2009 09:21:18 -0500
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Makes sense. High voltage/high current + small solder cross-sectional area = electromigration

Bev
RIM

----- Original Message -----
From: TechNet <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Mon Nov 23 09:12:06 2009
Subject: Re: [TN] NTC Large Hadron Collider Restarts

Hi all, 
what a jump! From our daily and small PWB questions to worry about the LHC! My experience from extreme HiVoltage/HighAmpere equipment is that you should never use solder at all! Use material deformation systems. Such as crimp barrels. Or braze, but never soft solder! I don't know what connection you are pointing at, but if it's a 10,000 Ampere contact, I'd definitly used high pressure barreling. Hope I did not say something that works like a Molotov cocktail...
/Inge 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Creswick
Sent: måndag 23 november 2009 13:01
To: [log in to unmask]
Subject: Re: [TN] NTC Large Hadron Collider Restarts


Ioan,

Right you are, but arm-chair navigation techniques are common activities for all of us at one time or another.  I don't' think that any of us profess to have the answers, but it is interesting to listen to the dialog nonetheless.

My brief experiences with forced, intimate-contact conductive heating techniques showed that I could get very good joints at just above the theoretical liquidus IIIFFF, the joint were actually at that temperature.
The key is in thermocouple selection and placement ... and of course, temperature control.

Surely they have thousands of these joints around the collider and to have just one fail [this time] is pretty good.  Failure analysis of the joint itself was likely not possible - I'm sure there was one fantastic light show when the joint let go.

Since the components to be joined were supposed to have actually/really been pre-tinned.  I would have tried to eliminate the use of flux in the subsequent joining process by using a cover gas or possibly even vacuum ....
but these guys are in a pay-grade way above me .... well, so are many others! 

Whatever makes the nuclei go around!   :-)

Steve C

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ioan Tempea
Sent: Sunday, November 22, 2009 9:04 PM
To: [log in to unmask]
Subject: Re: [TN] NTC Large Hadron Collider Restarts

Esteemed colleagues,

I have always considered the knowledge of Technet as my supreme source and I have learned a lot!

But should we even think the people soldering the hadron had no idea what they were doing? Honestly, I am not worried a bit that just anybody got this task. I bet big scientists were involved, even if we don't know them. Let's not forget the soldering bible has been written by a Dutch...

Regards,

Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer T | 450.967.7100 ext.244 E | [log in to unmask] W | www.digico.cc

N'imprimer que si nécessaire - Print only if you must

-----Message d'origine-----
De : Steven Creswick [mailto:[log in to unmask]]
Envoyé : Sunday, November 22, 2009 7:46 PM À : [log in to unmask] Objet : Re: [TN] NTC Large Hadron Collider Restarts

Steve,

I admit that I should have taken more than a quick glance at the process document which you presented, however, if the both parts of the joint have been pre-tinned, AND the JOINT to be soldered is indeed brought up to 230C+, why shouldn't the joint be reasonable?

My recollection is that the Sn96.5/Ag3.5 is a eutectic solder, melting at 221C, so the 230C is certainly a whole lot closer than I would prefer to run with, but it should indeed have melted and bonded with the pre-tinned surfaces.

Subsequent posts have discussed tin pest, etc.

My greatest apprehension is in regard to the stresses imposed in the joint [any joint material] when transitioning from room temp to cryogenic and back again.  I hope there is some serious stress/strain relief built into the joint structure!

Werner, since you have had the opportunity to see the instrument to some degree, can you provide insight as to the physical size and potential delta length which may be involved in the soldered joint?

What are the physical sizes of the 'leads'.  Are they too large to join them with a high-power ultrasonic welder, and do away with solder altogether?? 

Steve C

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