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Questions relating to designing PCBs
By george graves
#95498
So I was going through some of NASA's Workmanship reference documents (what can I say, it's friday night, and I decided to get a little crazy)

And I ran into this. Turret Terminals:

Image

I know I've seen them back in the day. But, when I need aboard to wire connection, and I don't want to spring for a "Terminal Block"

Image

I just design the PCB with a large enough hole for the wire and solder the wire as if it was a through hole and secure it to the board with a zip tie with an even larger hole.

Image

Anything wrong with doing that? And what the heck were these turret terminal for? Seems to me you are just making lever to rip things apart.

Thanks!
User avatar
By leon_heller
#95499
I remember them as turret tags. The wires were strain-relieved, of course, so there wouldn't have been any force on the tag. They are still available:

http://uk.rs-online.com/web/search/sear ... ag&x=0&y=0

Use of a tie-wrap like that is OK (I do it myself), but it can damage the wire. Plastic bushes are better. I prefer terminal blocks. I like the two-part ones - you just unplug them.
By rpcelectronics
#95532
george graves wrote:So I was going through some of NASA's Workmanship reference documents (what can I say, it's friday night, and I decided to get a little crazy)

And I ran into this. Turret Terminals:

Image
I am a NASA Soldering Instructor and I know exactly the document you found this in :D

Turrets used to be much more popular. Nowadays, you find more direct solder-on connections to a board. A variation on that is where the wire runs through a hole and the soldered in. This give a little strain relief. I think the major reason for turrets becoming rare is the overall cost of assembly.

Having said that, we still teach the turret, bifurcated, cup, tab and hook terminals in the week long class. Personally, other than cups on DB connectors and tabs on relays, the only turrets I have dealt with have been on small RF pre-amps.
By george graves
#95534
WOW! I'm impressed. It's very nice to know I'm getting answers from a NASA soldering instructor!

What's your take on flux and soldering to wire? I've been warned that flux will wick it's way up into the wire, under the insulation from capillary action. I've been warned that the flux will eat through the wire over time.

True? False? Only use no-clean flux? Clean with IPA and you'll be fine? What's your take on the matter?

Thanks!

George Graves
User avatar
By leon_heller
#95536
I think that the problem is more to do with solder wicking along the wire and making it brittle. When I was a student at English Electric, Kidsgrove, 50 years ago, I spent a few weeks in a couple of wiring sections. Although we were making commercial equipment, soldering had to be to military standards. I remember having to rewire an assembly three or four times before it was passed by an inspector.
By rpcelectronics
#95602
george graves wrote:WOW! I'm impressed. It's very nice to know I'm getting answers from a NASA soldering instructor!
Just remember, anyone that becomes an instructor at NASA is usually the last schmuck asked and stuck with it :D
What's your take on flux and soldering to wire? I've been warned that flux will wick it's way up into the wire, under the insulation from capillary action. I've been warned that the flux will eat through the wire over time.
Flux can wick up under the insulation. This is somthing that we teach to avoid. The belief is, the flux wicks under, thus causing the solder to wick under when you tin the wire (a requirement). I think the requirements are a bit strict and I don't tend to pay a A LOT of attention to it, unless its really badly tinned and the flux residue was not cleaned afterwards.
True? False? Only use no-clean flux? Clean with IPA and you'll be fine? What's your take on the matter?
The NASA spec requirement is for RMA (Rosin Mildly Activated). In general, this works well for just about all applications that we run into and would be my suggestion.
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