John Curl's Blowtorch preamplifier part II

[jneutron]

I know, but it is still doable without the gold get consumed.

for 200 micron wire, you seem happy with whatever process you devised. It wasn't possible to get a good attach at the 25 micron level.

I took the best from the military specced PCBs and parts and avoided the safety issues that would compromise... Inside equipment I use air as dielectricum as as I use gold conductors.

The mil flight and weapons hardware I made parts for did not allow the use of thick pure gold. They went to great lengths to remove it all. Nobody likes it when the detonation control component of a torpedo fails.

But using the gold as the etch resist made for some beautiful looking boards, that I will admit. But gold rich tin/lead solder joints is not a good way to go.

jn

 

[RayCtech]

The mil flight and weapons hardware I made parts for did not allow the use of thick pure gold. They went to great lengths to remove it all. Nobody likes it when the detonation control component of a torpedo fails.

The pure gold traced PCBs was used in Sonar pre-amplifiers to reduce the noise spectrum..
Also in radio equipment gold was used. In the radars it was mostly silver and teflon, and my first very good audio interconnect cables was made with two runs of a silver / teflon coax from a radar. Each center conductor as + and - (return), and the screens as screens and connected in one end.
Actually I still have those cables and during the 40 years the silver screens have miss colored to some degree.
I never really checked what material qualities the torpedo equipment was using, but there was used gold in the computer PCBs..

 

[jneutron]

I have always wondered if Gold should be used in the solder when the pads are immersion Gold. I see 35 year old Threshold boards with Gold plate and Ersin multi core still doing fine.

I recommend leaving the gold out of the solder.

The ersin leaches the gold, and the flux activates the underlying metals, so it woiks...

If it ain't broken, don't fix it.

If you were really nitpicking, flood the joint with solder, wick it off, put new in. No gold, hunky dory.

jn

 

[gpapag]

Thank you demian, gootee, marce, jneutron.

I wasn’t aware of diffusion taking place according to vacancy diffusion mechanism (Kirkendall ideas).
I held diffusion takes place only between metals which are in a liquid phase.
I had half a day reading on this topic and there is material for some more days. (I just start to understand jneutron's condensed give-aways on soldering)

George

 

[jneutron]

Thank you demian, gootee, marce, jneutron.

I wasn’t aware of diffusion taking place according to vacancy diffusion mechanism (Kirkendall ideas).
I held diffusion takes place only between metals which are in a liquid phase.
I had half a day reading on this topic and there is material for some more days. (I just start to understand jneutron's condensed give-aways on soldering)

George

Aha!! Your mention of kirkendall reminded me...

I mis-spoke of purple plague and gold/tin.. purple plague is between aluminum and gold. The intermetallic is much lower density, so as the intermetallic forms, it pushes the gold conductor away from the aluminum. Failures typically have a purplish growth, which is the intermetallic color.

Sorry about that "condensed" thingy. I really hate long drawn out posts, I worry about putting people to sleep. specially me..

jn

 

[TerryO]

No, I'm afraid your wrong the top of that language tree was simply renamed proto-indo-european for mostly political reasons.

Yes, that's exactly right. It is sometimes referred to as Indo-Germanic as well.

Best Regard,
TerryO

 

[gpapag]

Yes. And it is by far the worst for large surface mount devices. The removal of lead made this problem even bigger, as the extra 38 degrees C causes even more differential expansion between solidus and operational temperature.

Also, lead/tin shrinks 15% during solidification(edit: I read the article in 1984, so will have to find it again, it may be 15% bismuth and 25% shrink, but the idea's the same..), so puts the solder in tension. That, low cycle fatigue, and lead tin creep tendencies cause lots of "top of the pole" (telephone pole) failures.

Some mechanical/thermal properties of various solder alloys:
http://www.indium.com/products/alloy_sorted_by_temperature.pdf
(standard 60/40 is No 109)

I was sure others here would be more up on soldering technology than me.

That’s modesty !

Not at all, illuminating and fascinating Sounds like we should have a soldering thread.

A lot of gems to be found here:
Soldering Defects Database

George

 

[gpapag]

Aha!! Your mention of kirkendall reminded me...

I mis-spoke of purple plague and gold/tin.. purple plague is between aluminum and gold. The intermetallic is much lower density, so as the intermetallic forms, it pushes the gold conductor away from the aluminum. Failures typically have a purplish growth, which is the intermetallic color.

jn

Kirkendall effect - Wikipedia, the free encyclopedia :

Both Kirkendall voids and Horsting voids are known causes of wire bond fractures, though historically this cause is often confused with the purple colored appearance of one of the five different gold-aluminium intermetallics, commonly referred to as "purple plague" and less often "white plague".[2]

[2] https://nepp.nasa.gov/index.cfm/20987

George

 

[john curl]

There are books on soldering that answer most of these questions, especially for hand soldering, such as: 'Solders and Soldering' by Howard Manko
Today a Wiki search can give you most of what you need.
Extreme examples, such as small gold wires, are inappropriate for manual soldering of hi fi equipment, either as an amateur or for small runs.

 

[jneutron]

Kirkendall effect - Wikipedia, the free encyclopedia :


[2] https://nepp.nasa.gov/index.cfm/20987

George

Interesting. Horsting was investigating plated gold with aluminum wires. My speak was about aluminum bonding pads on transistors and IC's, with pure gold wires. His analysis was about the gold plating and it's impurities. I didn't see any reference to bright gold plating, which contains organic levelers, so am guessing that's what he was speaking about.

This link has a drawing of what we speak of..

Quality and Reliability Handbook ver.3



This link is inconsistent with what I recall. I was told it was less dense, so pushed the bond apart. Interesting. I believe the information given me was wrong.. Same end result, but different physics. I stand corrected...egg on face..

Gold-aluminium intermetallic - Wikipedia, the free encyclopedia

jn

 

[jneutron]

There are books on soldering that answer most of these questions, especially for hand soldering, such as: 'Solders and Soldering' by Howard Manko
Today a Wiki search can give you most of what you need.
Extreme examples, such as small gold wires, are inappropriate for manual soldering of hi fi equipment, either as an amateur or for small runs.

Books are boring...who reads anyway??

Wiki, what can you believe??

RayC disagrees with your term inappropriate for manual soldering of hi fi equipment..

jn

Threads like this...now, that's where I learn a lot..

 

[gpapag]

Interesting.
My speak was about aluminum bonding pads on transistors and IC's, with pure gold wires.
I was told it was less dense, so pushed the bond apart. Interesting. I believe the information given me was wrong

I guess you may find some info here:
Wire Bonding Metallurgical Systems - Page 1 of 2 : Au-Al, Au-Ag, Al-Al, Au-Au and Au-Cu
Ball and Wedge Bond Lifting


A byproduct from my googling This technology maybe of interest to some of you:
Clad Metal from Engineered Materials Solutions - Anatomy of a metallurgical bond

George

 

[jneutron]

I guess you may find some info here:
Wire Bonding Metallurgical Systems - Page 1 of 2 : Au-Al, Au-Ag, Al-Al, Au-Au and Au-Cu
Ball and Wedge Bond Lifting


A byproduct from my googling This technology maybe of interest to some of you:
Clad Metal from Engineered Materials Solutions - Anatomy of a metallurgical bond

George

I did a lot of production work using copper clad moly.

Thanks for the info links..

ps. What I'm looking for now is my 4 sheets of berquist board..a pc board made of aluminum/epoxy/copper foil. A friend is looking to make a ring light for his camera using LED's off a few bulbs out of home depot...

I know I put them somewhere...

jn

 

[wayne]

I recommend leaving the gold out of the solder.

The ersin leaches the gold, and the flux activates the underlying metals, so it woiks...

If it ain't broken, don't fix it.

If you were really nitpicking, flood the joint with solder, wick it off, put new in. No gold, hunky dory.

jn

It ain't broke but I trust your answer too.

 

[Kindhornman]

JNeutron,
Seeing your expertise here with metals and soldering and failure modes a question about copper clad aluminum. I am working on a dome tweeter and was considering using cca flat wound wire for a lite weight voice-coil. Do you see this as a long term failure mode or is this an acceptable application? I know this has been used in compression drivers for many years but at the same time I understand that soldering has always been an issue and on some very expensive TAD drivers the failure mode was the connection from the lead-out wire to the CCA voicecoil. Looking forward to your opinion on this.

Steven

 

[fas42]

Yes, thanks to jn and everyone for this excellent discussion on soldering. To add to the mix, what is the optimum method of forming a metallic bond to aluminium - as a trivial example, adding an earthing wire to an aluminium heatsink beyond a crude lug and screw approach?

 

[Bonsai]

Yes, thanks to jn and everyone for this excellent discussion on soldering. To add to the mix, what is the optimum method of forming a metallic bond to aluminium - as a trivial example, adding an earthing wire to an aluminium heatsink beyond a crude lug and screw approach?

I'd love to know how to do that! The other one is aluminum epoxy bonding.

 

[Kindhornman]

fas42,
I don't see any way you can permanently attach any copper lead to an aluminum heat sink. If you were to use aluminum wire you could Tig weld it but what of the other end? Of course you wouldn't use aluminum wire so I don't see any practical method besides your original method of a screw and terminal.

I understand that with aluminum wire voice-coils on some compression drivers, not copper clad, attempts have been made to use a gas tight crimped connection and this has been a common failure mode with a connection to the lead-out wires also.

Bonsai,
Epoxy aluminum bonds are always suspect. You can get a semblance of a good bond if you mechanically rough up the surface but it is never a great bond. Impact and peel strength are not very great in this type of bond. The best bonds will be with the slowest curing epoxies, never with very fast cure systems.

 

[john curl]

I got my background by reading Manko. He gives fair warning about gold, and advocates adding silver in many situations. This is one good reason for using SN62, if you can find it. I always recommend it.
Perhaps I should say 'Google' rather than 'Wiki'. I have a fairly extensive technical library, but I always find something new when I 'Google' a subject. I presume that is the direction everyone is going.
What I find most useful on this website is the LINKS to other articles, that I most probably would not ever see, so I find the computer most useful.

 

[bcarso]

I got my background by reading Manko. He gives fair warning about gold, and advocates adding silver in many situations. This is one good reason for using SN62, if you can find it. I always recommend it.
Perhaps I should say 'Google' rather than 'Wiki'. I have a fairly extensive technical library, but I always find something new when I 'Google' a subject. I presume that is the direction everyone is going.
What I find most useful on this website is the LINKS to other articles, that I most probably would not ever see, so I find the computer most useful.

Since the evil bastard from the city forced me to move so many books into storage, without Google/Wiki I would be fairly crippled.