Read on Twitter
Back when I first started learning electronics, I could only get hold of a few old germanium transistors (they were long obsolete even back then). Everything I read about them said they were going to be damaged unless you took extreme soldering them - use a heat shunt, etc.
I assume this is because soldering irons in the 50s and 60s looked rather like this?
So what happens if you use modern temperature controlled soldering irons? Can you still damage a germanium transistor?
I took a vintage Green Spot PNP Germanium transistor (never used in circuit) and measured its parameters using a @peakatlas DCA75. So I had a baseline. Yep, Ge transistors really are that poorly performing.
I soldered the transistor to a bit of tag strip (also vintage and unused) with a modern temp controlled iron set at 300C. I used modern rosin cored eutectic lead / tin solder, with a heat shunt clamped to each leg of the transistor then measured the transistor again.
Leakage was perhaps fractionally higher, but no massive changes. Which is what I'd hope to see.
I unsoldered the transistor (with a heat shunt) then set the soldering iron to 400C and resoldered the part to fresh tagboard points using no heat shunt. Again I measured its performance after it had cooled down (metal case of transistor reached about 50c during soldering)
Measurements after soldering at 400C with no shunt.
Annoyingly, the DCA75 didn't use the same steps and currents for each set of measurements, but we can see that nothing drastic occurs to the transistor's performance.
This suggests to me that parts I had long though to be essentially thermal fuses, can stand up to a bit more abuse than was written about. Albeit with modern tools, not something you'd fix a stained glass window with. This makes me feel better about reflowing modern parts
So, should I torture the green spot further, should I see where it fails? Or should I give it a happy retirement in a circuit?
