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Topic: Hand soldering a 0.5mm pitch connector (Read 1 time) previous topic - next topic

Grumpy_Mike

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the difficulty I've had clearing those bridges.
I can't understand why solder braid doesn't just lift it off. I wonder if you are not using fresh high quality braid?

jboyton

#31
Sep 18, 2015, 07:03 pm Last Edit: Sep 18, 2015, 07:03 pm by jboyton
I can't understand why solder braid doesn't just lift it off. I wonder if you are not using fresh high quality braid?
Fresh? I hadn't even considered that my braid might have gone off. There's no "use before" date on it. It's woven material, nice and shiny looking. It's made by "Archer" and it appears that Radio Shack sells it. I've had it a long time; I might have bought it at Radio Shack 15 years ago or something like that. I don't really remember. Up until about a year ago I desoldered something about once every two or three years.

The other thing is that I've been using the braid dry, only applying flux to the part. In this thread it has been suggested that I wet the braid itself with flux; or with solder. I'm not sure which of those two suggestions I should try first.

Grumpy_Mike

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I might have bought it at Radio Shack 15 years ago or something like that.
What happens is that the flux impregnated in the braid drys out making it not suck up the solder. It sounds like you should try some fresh stuff.
Some one told me that anything over 6 months was old but I have used braid that is three years old without problem.
You do have to wrap it round the iron tip like I said to get it hot enough.

jboyton

Flux impregnated in the braid? I had no idea. Thank you, that's really good information. Does rosin core solder dry out as well?

Desoldering braid is probably not available anywhere locally and I'll have to order it. In the meantime would saturating the wick with flux work okay?

Grumpy_Mike

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Does rosin core solder dry out as well?
No, that is totally encased in solder so that stays a lot fresher, although over long periods there is deterioration in the flux.

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In the meantime would saturating the wick with flux work okay?
Yes better than nothing but don't overdo it with the saturation or you will have trouble getting the braid up to temperature which is where a lot of people go wrong.

liudr

#35
Sep 18, 2015, 11:33 pm Last Edit: Sep 18, 2015, 11:33 pm by liudr
jboyton,

What wire solder size are you using? I could solder 0.05 inch pitch with 0.025" wire solder, or maybe even with 0.8mm pitch. But 0.5mm pitch needs thinner wire! I use 0.015". The FTDI chip has 0.65mm pitch.

Oh, by the way, to those cursing ROHS solder, you should read about the pros and cons of using ROHS first. One of the apparent pros is ... (so related to OP's peril, but what is it?)
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liudr

Got you! Lead solder is known to wet well, making jumpers easily. Lead free solder on the other hand is known to not wet easily, making it the only suitable thing for very fine pitch soldering.
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Grumpy_Mike

, making it the only suitable thing for very fine pitch soldering.
Simply no.

dmjlambert

It's amazing how much I can learn from just reading the stuff you guys post.  Thank you.

liudr

Simply no.
Mike,

I've read some articles that say the opposite. The industry thought it was a curse to be required to use leadfree solder since the earlier ROHS solders didn't wet well and didn't give shiny-looking junctions for inspection (they still don't). But as IC got more miniaturized, they found the curse to be a bless, i.e. really fine pitches don't bridge. The industry is still learning about leadfree solders and there is still R&D on different ingredients but it was clear that the finer pitches short more easily with lead solder, so I read.

My limited experience (I've only done about 50 boards) also indicate the leaded solder paste bridge more with the same board, same stencil. You need to corroborate you two-character opinion. I'm open to more readings but I sense that you may have an attitude against leadfree solder.

My opinion is not based on environment or bureaucratic policies, just what I think is better suited for what work. I have simple designs with SMD components on both sides of the board. I use leadfree paste for the side with less component but tighter pitch IC, then use lead paste for the more populated side with less tight pitch IC. That has worked for me. Tried both side leadbearing and both side leadfree, not too good. Melted/damaged plastic parts for two leadfree reflows, many bridges if I use all leadbearing pastes. For small components, stay away from the cheap leadfree paste with higher melting point, use SAC305, the less cheap paste.
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Boardburner2

The traces are not even close to being impossible to solder. That's not the problem. It's the ease with which the connector pins bridge and the difficulty I've had clearing those bridges.

I have another adapter board from the same Chinese source, same type of traces, 0.8mm pitch. Soldering a TQFP-32 part to the board was very, very easy.
I use a dab of flux drom a flux pen directly onto the braid.

It does age but i find that works on old braid provided i apply some pressure.


I find a pencil chisel bit to be best as it presses more of the braid into contact wuth the solder, the joint heats faster as well.

The fact it works for 0.8 but nosmaller makes me think it maybe that you are not getting intimate contact between braid and solder

Boardburner2

What happens is that the flux impregnated in the braid drys out making it not suck up the solder. It sounds like you should try some fresh stuff.
Some one told me that anything over 6 months was old but I have used braid that is three years old without problem.

Braid i store in a screwtop jar is ok for years.

Stuff left lying aroud my workshop definatley deteriorates.

6 months or so and it becomes discoloured and i have to use flux.

Boardburner2

If you are ordering braid i reccoment the techspray brand which can be had from intertronics at kidlington.

I think they do a party pack of different sizes, not sure?

Their no clean flux type are magic although they need to be stored in a sealed bag for longevity

liudr

My own experience is the chisel tip is well-suited for smd. Fine pencil tips might be better in removing a jumper or two. Weller has some gull-wing tips. It has a small cavity on the underside to hold the solder ball so only very little solder is left on the pins. I got one but have not used it yet since the chisel tip that came with the iron is working fine. Here is the flux paste. You will need a smaller size needle for slightly better control.

No Clean Rework Flux Paste - 10mLJameco2188300MG CHEMICALS LTD.8341-10ML$    12.95
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