[sdiy] Two really dumb questions re Schaeffer and soldering

[Batz Goodfortune]

Y-ellow DIY collective souls.
         I didn't read this of course because Jim and I are on each other's 
kill file. So Jim, just for the record, you're not reading this either OK.


At 12:05 PM 8/9/02 -0700, Jim Johnson wrote:
>.. so as I sit here waiting for CVS to download a huge project over my
>IDSL line, I decide to use the time "productively" to get the answers to a
>few things that have been bugging me..

I don't know about the first one. I went to the "Master Butcher's" school 
of panel making. However...

>2) Here's a soldering question. I haven't done any serious DIY since my
>Paia days many decades ago, but one bit of advice I remember from the Paia
>manuals was to always heat-sink semiconductors when soldering them. This is
>a royal pain in the ass, and tremendously impractical. Is it really
>necessary?

If you read the fine print at the back of the data sheets, at the bottom of 
a stair well in a disused lavatory with a sign on the door saying "Beware 
of the leopard." You'll note that they usually give you soldering time and 
temperature. I seem to recall the rule of thumb being 350c by 10 
seconds/Per pin.

In practice I'm much the same as Harry. A slightly hotter iron and as quick 
as possible. Having said that, I might go to the trouble if the device is 
expensive and/or delicate. I keep a range of chrome plated bulldog clips 
around. You can clip these onto a DIP package, solder it in place and it 
even makes pick 'n' place a bit easier. This is actually really good for 
CMOS ICs because it shorts all the pins together at the same potential 
right out of the foam etc. Having said that, my prototyping methods are 
somewhat unorthodox and often put undue stress on individual pins. I 
haven't lost one yet. (Knock on wood)

I wasn't ready to tell this story but since it's relevant I'll post a 
couple of pictures here. 
<http://all-electric.com/keybastard/4066-keyboard-small.jpg>

What you're looking at is the left hand upper edge of a PC keyboard PCB 
with the keys removed. They are of the metalized rubber variety so you just 
have contact pads. That's a 4066 there. (I have to do something about 
fudging a macro focus for that stupid camera) It's glued upside down to the 
PCB with some hotmelt, then everything is soldered directly to the pins. In 
some cases as many as 4 connections. All wired together with kynar wire 
with a very much "Don't give a shit" attitude.

It's a long story but essentially the 4066 closes 3 switches at once so a 
single key pulls together, CTRL/ALT/DEL at the same time. Actually there's 
an electrolytic on the pin that controls the DEL switch so that the CTRL & 
Alt sink slightly ahead. And it all works. No heatsink. No static 
precautions. Nothing.

Now I know someone's going to ask why I would do such a thing so I'll 
briefly tell you. Apart from the fact that these are the three most 
frequenly used keys under windows, On a linux box, there's really only a 
couple of keys necessary most of the time. One to bring it up, one to bring 
it down and F1 to get you out of trouble. And the LEDs can be set/reset for 
status. No keyboard. No mouse. No monitor. Everything else is done on a 
virtual or remote console so it only takes a couple of LEDs to tell you 
what the machine's thinking.

So there you have it. Use a heatsink when you think it's probably a wise 
idea against the hassle, otherwise you're probably wasting your time.

Be absolutely Icebox.

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