Hand soldering a 0.5mm pitch connector

That IC that Mike soldered looks like FTDI but not quite. You got too much solder on it! I have my tricks too:

  1. Use flux paste. Don't use liquid flux, as you know it evaporates too quickly. The paste doesn't dry up in hours to days so think about it as tooth paste.
  2. Use wire solder size proper to your pitch. When soldering 0.5mm pitch, use 0.01 to 0.015" diameter wire solder. Never use the typical 0.025" or 0.03" wire solder. You will constantly overload the pins with solder balls.
  3. Use solder braids, yes, wet them with plenty of solder before you can actually suck.
  4. Push the thin wire solder against the pins with your iron tip. Wipe the tip clean before soldering more pins. Once done with say half of the pins on one side, add flux paste to the entire side, start dragging with a very dry tip (clean tip first), back and forth along the entire side, until you spread out all solder jumpers, or suck them once you drag them to one side.

Inspection picture:

jboyton:
It looks like Grumpy_Mike has it figured out. My work looks like that when the pitch is 0.8mm. But at 0.5mm I

yes but his board looks like it has solder resist coating

with drag soldering small pitch components it makes a difference

I wonder if it's a combination of things. The FFC connector pins are short and skinny when compared to an IC. At least that's how it seems to me.

Here's an IC that is 0.65mm pitch. It was super easy to solder:

Here is the FFC connector and adapter board with 0.50mm pitch. This one took me two tries. I ruined the first board trying to remove bridges and spent about 45 minutes of sweating over the second one:

I think the extra difficulty has to be due to more than just that 25% reduction in pitch size.

In any case, I'm confused about what the best approach is. Solder paste? Flux paste? Liquid flux? Hold it upside down? Drag solder?

Both pix seem to have solder resist.

First pic has enig plating or gold , these whet well.

Second pic has lead or tin finish ,they age badly, a tin finish more than a few weeks old can be impossible to solder at all.

Edit

If this is the problem you cannot fix it, throw the board away.

Fwiw it can be fixed by the following method.

Dip in 30 % phosphoric acid for 30 sec.

Abrasive clean.

30 sec in hydrochloric acid.

Rinse .and clean.

Dip in electroless nickel at 100 deg c to flash coat with nickel.

Electroplate with copper until surface is copper coloured.

Electroless tin again for 20 min.

Solder.

Use distilled water throughout.

If you made a mistake in the above process anyway, throw it out

If it has through hole plating there is a good chance anyway that the acid processes will break the links

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.

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?

Grumpy_Mike:
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.

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.

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?

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.

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.

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?)

The solder is 60/40 0.38mm (0.015").

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.

liudr:
, making it the only suitable thing for very fine pitch soldering.

Simply no.

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

Grumpy_Mike:
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.

jboyton:
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

Grumpy_Mike:
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.

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

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 - 10mL
Jameco
2188300
MG CHEMICALS LTD.
8341-10ML
$ 12.95