Yes, I filed and sanded the copper down to the shiny, used acid flux with 95/5 Sn/Sb and heated with a mini butane torch. But cannot get the braid to solder to the pipe! Any hints? I am worried about too much heat on the circuit board inside...


Yes, I tried it with rosin flux first...

 

Hi Sam,
You need too ''tin' an area of copper pipe before attempting to solder the braid onto it
E

 

I tried that first with my regular Kester 186 and Kester eutectic rosin core solder. Solder just will not stick to it! Maybe turn the temp on my iron up from 670F?

 

Yes, you need to get the copper hot enough for the solder to flow.
A larger propane torch might be better since it will heat up the local spot faster and thus the heat won't have time to spread and damage your circuit.

 

I ran my Hakko up to max and thought I had it until I put some pressure on the solder blob after it cooled and it slid off... Should have a propane torch around the garage somewhere...

 

I tried that first with my regular Kester 186 and Kester eutectic rosin core solder. Solder just will not stick to it! Maybe turn the temp on my iron up from 670F?

Use 60Sn/40Pb for tinning. The wetting action of eutectic Sn/Pb alloy is noticeably inferior. This is why solder pot alloy is generally 60Sn/40Pb. Also, use a good flux and don’t overheat it. You only need to get the local area hot enough for the solder to melt.

 

Also, a mechanical connection to the pipe, using a screw and ring terminal may be a good option.

 

I would have used a clamp.

 

I would have used a clamp.

A hose/gear clamp is very common for that sort of application.

 

It's not very pretty but it took a propane torch to get it hot enough to wet the solder onto the tube cap. I'll cover it up with some heat shrink later after I tack the end caps on for good ground continuity. Grommet took a beating but everything tests OK from the outside so the copper ground braid didn't come unsoldered from the board. Thanks folks!

 

A proper grounding clamp is the way to go.

 

I would have used a clamp.

I thought about drilling and threading a machine screw through the cap into the pipe and using a solder lug but don't have the tap or screw to do it so...

 

A proper grounding clamp is the way to go.

That would be a handfull for an RF/AF probe... But what I would normally use for a water pipe and have on my antenna ground rods.

 

You only need to get the local area hot enough for the solder to melt.

Which is why I was surprised my small butane torch didn't work. I fully expected it to be able to heat a pea sized area hot enough but it couldn't do it. It was close but not quite hot enough. Maybe if I had used 60/40. I'll try that on the next one. I've got 4 designs that I'm going to try out and this was the 1st so low on the learning curve. Only thing holding me up is the BNC connetors since the ones I have use a bushing for RG-59 instead of RG-8X and had to order some more.

Oh yeah, and next time I'll tin it before I put the grommet and wire in so all I have to do is tack the braid to the tinned area.

 

Definitely go for the crimp or clamp connection. That tinned braid will be so brittle that it will break before long.
(If it were a connection to a pcb, safety standards would dictate that it be secured by another method, in case of breakage of the solder joint)

 

Any hints? I am worried about too much heat on the circuit board inside...
Yes, I tried it with rosin flux first...

Can you not solder the braid to the cap first before it is placed on the pipe?
As per other quotes, sufficient heat is the key!

 

Can you not solder the braid to the cap first before it is placed on the pipe?
As per other quotes, sufficient heat is the key!

I wanted to say no, but when I thought it out... The better solution is to solder it inside at the rear of the tube. If I make the solder puddle before putting the board into the tube, I should be able to do it. The board isn't as long as the tube but barely fits inside the ID. I made one tube 4" and one is 5" just to see how easy they are to hold and the board is ~3" long. I'll try it on the next one. Thanks for the heads up, always good to get input.

 

It's not very pretty but it took a propane torch to get it hot enough to wet the solder onto the tube cap. I'll cover it up with some heat shrink later after I tack the end caps on for good ground continuity. Grommet took a beating but everything tests OK from the outside so the copper ground braid didn't come unsoldered from the board. Thanks folks!
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This is odd because a plumber would routinely solder copper pipes with a basic torch, I've done it many times, it's not obvious why you had such difficulties.