Tin whiskers and other packaging problems

[Pat Pending]

Sorry Mark, afk for a bit. Everything Ok now just had a look at a KB set that Yorkie has restored, the fog is gone! Thanks v much. Andy.

[Crackle]

I just remembered, a program I was watching on deep sea underwater wrecks was saying that the excessive corrosion found on the Titanic iron work was/could be caused by anaerobic bacteria, or was it viruses.
I wonder if there is a possibility that the strange phenomenon of dendrites/whiskers growing from metals could be accounted for by a similar process.
http://news.discovery.com/history/titani...-wreck.htm

mike

[Pat Pending]

I think you may be correct Mike, I'm shure the ones made in the Netherlands had their problems but in my limited experience I've found no faulty AF11x's marked Holland either, perhaps they had tighter QC? I've found some made in England/Britain type's that I've "restuffed" that had no protective grease in the package at all. Your other point is also valid or else why would they be so hygine particlar in the production areas in semiconductor facilities?

[ppppenguin]

AFAIK, the main reason for extreme cleanliness in semiconductor production is the minute detail in modern devices. A tiny speck of dust in a photolith process can ruin an entire chip. By comparison AF11x, BCxxx are huge and you'd almost need the metaphoric half brick to do much damage. Chemical contamination is another matter, I've no idea if lack of purity in reagents would be a problem.

[Pat Pending]

Atmospheric bourn contamination of chemical or bacterial contamination of semiconductors has always presented a problem even back to the old cat's whisker, even if they didn't know it. There were even products on the market that claimed to protect the sweet spot by sealing the whisker to your lump of whatever, preventing mechanical or chemical disturbances. Mullard in the times of the AF transistors were still finding their way as it were, and death by contamination was still an early life failure mode for transistors in general, characterized by ever greater leakage current as the germanium died. I think however that Mike's point was that it's possible that some of the strange phenomena exhibited by mainly tin plated packages was caused by bacteria or similar present during production. Some transistors with metal enclosure's were made with gold plating to the can and lead outs, I'm sure this must have been done to improve the environmental resilience and therefore reliability. I don't recall reading the data sheets on these types to know what the exact reason was for it being done. Regards. Andy.

[Pat Pending]

Whilst casting about on the net yesterday, I came across a couple more sources of independent citation for my amateur "sleuthing", one being a lady who was taken on at the Philips/Mullard production facility in Southampton in 1971. She kindly answered a post I made on s.media asking for information on their products. I pasted my posts from GVR for her to read. The Lady replied: 

" I was taken on at the Philips factory in Southampton in 1971, as my Mum worked there already and I was only 17 at the time my Dad thought it was a good idea as I could be kept an eye on! When I arrived to start work, I had to report to personnel and told them that I was a new typist, (the job I thought I had applied for), however after an hours wait, someone came to fetch me and said that I was to start training with quality control and I would be working on a production line that had just been moved to Southampton from another factory. The line produced the transistors you mentioned, (sot25?) and there was talk at the time of a process that the engineering people were trying, to improve the quality of the parts that had been made at the other factory. It surprised me when I saw the comments as QC was always a major concern to the company and if there was even a hint of a problem in a production area, the TS (? Sic.) Boys would descend like vultures. There were an awful lot of employees there but it always seemed a quite friendly place to work. I continued working there till 1976 when I married. My husband was also an employee and continued with the company until he retired in 2009. All the best with your article. Sue L." 

I've also found reference to a radio that was produced in Poland in the 1990's using lockfit transistors on the radio museum site. Can't be NOS? I don't think any one produced them much into the 1980's. Willing to be flamed on that one if anyone knows differently.

Regards. Andy.

[Crackle]

I've also found reference to a radio that was produced in Poland in the 1990's using lockfit transistors on the radio museum site. Can't be NOS? I don't think any one produced them much into the 1980's. Willing to be flamed on that one if anyone knows differently.

Regards. Andy.

Quite often the dates of the radios in the Radio Museum are just guess work. It may be worth mentioning the model so it can be investigated.
Mike

[Pat Pending]

Actually it's called an ITT NOKIA . Very much doubt either firms work, it also clearly says stereo on the case but has only one speaker grill, bit of an oddball Mike. Thanks, Regards Andy.

[Pat Pending]

In addition to the previous post the Polish set looks as if it may be stereo capable, but only to earphones. Weird!.. Andy.

[Crackle]

In addition to the previous post the Polish set looks as if it may be stereo capable, but only to earphones. Weird!.. Andy.

Ah, I guess that could be the RP705 then, I think the clue about the stereo operation was in the name, "Stereophones"

It looks like Polish manufacturers were unique in using up stocks of BF194 etc transistors as late as 1990, there are 5 other models from 1990 listed with BF194 transistors.

Mike