Tin whiskers and other packaging problems

[boater sam]

Way back in the late 60s when I was an apprentice at Ferranti they were producing ZTxx series transistors with gold leads and gold plated cans and headers but a lot of their product was for military use so not so much mundane production. I threw away a bag with about 2kg of these when we moved, fool.

They also produced E line ZTX epoxy transistors in vast numbers. The lead spacing was very close in line and our applications used these with sockets similar to loc fits. They were a pest even then. We were told off if we respaced the leads and soldered them in for use in our lab work. They were/are very reliable and considering that they were made in an old cotton mill which was not the cleanest of places there must have been severe precautions taken about contamination. They don't suffer the intrusion of damp through the lead interface like loc fits either, oh, and the leads don't rust!

It was all small slice silicon then of course so a contaminated slice was not so serious as it would be today. I forget how many dice were on each slice, maybe about 200. 

[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.

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

Thanks Mike. Didn't see name on the front of the set at first my, browser keeps opening image files in thumbnail for some reason, do you know any history on this manufacturer? Regards Andy.

[Pat Pending]

Way back in the late 60s when I was an apprentice at Ferranti they were producing ZTxx series transistors with gold leads and gold plated cans and headers but a lot of their product was for military use so not so much mundane production. I threw away a bag with about 2kg of these when we moved, fool.

They also produced E line ZTX epoxy transistors in vast numbers. The lead spacing was very close in line and our applications used these with sockets similar to loc fits. They were a pest even then. We were told off if we respaced the leads and soldered them in for use in our lab work. They were/are very reliable and considering that they were made in an old cotton mill which was not the cleanest of places there must have been severe precautions taken about contamination. They don't suffer the intrusion of damp through the lead interface like loc fits either, oh, and the leads don't rust!

It was all small slice silicon then of course so a contaminated slice was not so serious as it would be today. I forget how many dice were on each slice, maybe about 200. 

I cried a little at the thought of the bag of mil-specs going to the dump! I'd be interested to know what the encapsulation processes were on the E-line transistors, they were a package that you wouldn't think would be any good, but were, any insights appreciated. Thanks. Andy.

[ppppenguin]

............... with gold leads and gold plated cans and headers but a lot of their product was for military use so not so much mundane production. I threw away a bag with about 2kg of these when we moved, fool.

I hate to think what the gold alone was worth.

AFAIK most silicon transistors are made using a planar process which give a final product that're relatively immune to contamination problems. Obviously all has be nice and clean during manufacture otherwise the photolith and etching won't work too well.

[jimmc101]

... I'd be interested to know what the encapsulation processes were on the E-line transistors, they were a package that you wouldn't think would be any good, but were, any insights appreciated. Thanks. Andy.

I haven't got much information about this, but the E-Line  and Later Super E-Line data books give some information, see attachments.
As far as I can remember the original package used tinned Kovar??? leads which were thin and stiff, at some time there was a change to thicker more flexible tinned copper leads for all devices.

I've been a fan of E-Line devices ever since I first encountered them in the 60s.

Jim

[ppppenguin]

When I was at Michael Cox Electronics in the early 1980s we used the ZTX314 and ZTX510 as our universal video and switching transistors. Excellent devices that never gave us any grief. Along with BC548 and BC558 they satisfied the vast majority of our transistor requirements.

[Gingpeakin]

It does make you wonder why there are quite so many general purpose small signal transistors manufactured. Most designers stick to a few types they know.

Ging

[ppppenguin]

I've wondered that too. Unless you have some very specific requirements to do with high speed or high power a lot of devices will work perfectly well. My rule of thumb when replacing a transistor is to use a BC548 or BC558 unless I can see a reason why they might not be suitable.

[Pat Pending]

As far as I can remember the original package used tinned Kovar??? leads which were thin and stiff

Thanks for your post Jim. The worst thing about kovar is that it work hardens, bend the 
lead more than once and it will likely facture. As for standardising transistors I said before in this topic the (ELEKTOR magazine) "tup & tun" system should have been adopted by manufacturers. Regards. Andy.

[boater sam]

So that's why we were discouraged from bending them! We operated on the mushroom system, keep them in the dark and feed them s---, as apprentices.
As I recall the leads where a dull silver colour, rectangular in section, presumably to aid insertion into sockets.
We trusted those devices, you could cook them till too hot to touch and they always worked.
They were batch loaded into a carousel tester and sorter, little bins collected the different types, the markings being printed on later.
Happy days, on £6 1/9p a week!