Soldering Hell

I always use flux pens on braid, top tip that! Certainly helps clean up pads and such :slight_smile:

Since we're on the subject of the best soldering techniques, I am getting my hand into fine pitched ICs. I have a few 2560s that I am trying to solder. I have a syringe with solder paste and I used my hot air station. The problem I am having is that no matter what I do, I keep getting solder bridges across the pins. I use very little paste and still get bridges. I use so little solder that it barely solders the pin, but I still get bridges. I have tried not using extra flux and using a ton of it. Using more paste, still get the same result. It seems like the solder just isn't reflowing very well. I have also tried different temps.

Solder paste is from Kester and is 63/37

Maybe try an oven? I sometimes find that hot air moves the solder around too much and end up with bridges like you say

You can use both. I do.

The problem I am having is that no matter what I do, I keep getting solder bridges across the pins. I use very little paste and still get bridges.

This is usual with manual soldering. People just take some solder wick, and wick away
the bridges.

codlink:
Since we're on the subject of the best soldering techniques, I am getting my hand into fine pitched ICs. I have a few 2560s that I am trying to solder. I have a syringe with solder paste and I used my hot air station. The problem I am having is that no matter what I do, I keep getting solder bridges across the pins. I use very little paste and still get bridges. I use so little solder that it barely solders the pin, but I still get bridges. I have tried not using extra flux and using a ton of it. Using more paste, still get the same result. It seems like the solder just isn't reflowing very well. I have also tried different temps.

Solder paste is from Kester and is 63/37

Are you laying the solder paste across the pins? or individually on each pin?
I just lay a very very thin bead across all the pins, and on the outer edge.
(I'm using lead free solder paste.)

Don't have your hot air blowing too hard... because that can push molten solder to places you don't want to (forming a bridge).

Still with this technique, 2 pins out of 16 may form a bridge (SSOP-16)... then just use some flux and wick to fix it.

vasquo:
Are you laying the solder paste across the pins? or individually on each pin?
I just lay a very very thin bead across all the pins, and on the outer edge.
(I'm using lead free solder paste.)

Don't have your hot air blowing too hard... because that can push molten solder to places you don't want to (forming a bridge).

Still with this technique, 2 pins out of 16 may form a bridge (SSOP-16)... then just use some flux and wick to fix it.

I am laying across all the pins. The tutorials I've watched use that method. The velocity of the air was low.

oric_dan(333):
This is usual with manual soldering. People just take some solder wick, and wick away
the bridges.

It's funny you say that. I have tried to use wick to remove the extra solder, but I can't get it suck up into the wick. The bridges are on the board crossing the pads.

I will just have to keep practicing.

It's funny you say that. I have tried to use wick to remove the extra solder, but I can't get it suck up into the wick. The bridges are on the board crossing the pads.

I don't do a lot of really fine-pitch smt myself. But someone else mentioned that you
might try taking some flux or solder and flow it onto the wick first. It does tend to be
difficult to get the heat transferred enough to get the surface-tension working through
a dry wick, even on non-smt parts.

I have used flux on the wick, but never thought about tinning it. I will try that.

The bridges are on the board crossing the pads.

Do your boards have soldermask?

This stuff isn't just for looks, it's actually more "solder-phobic" than bare substrate. When I made my own boards I found they'd bridge quite badly as compared to boards with soldermask.

-j

kg4wsv:
Do your boards have soldermask?

Yea

I tried tinning the wick and it works. But I still want to get the solder to flow correctly without having to "clean up." I have few ideas that I am going to try, one of them is to tin the pads before placing the IC.

Good point, which should have been mentioned previously. I always dab a bit of solder
on the chip pins before placing on the board, and I also usually take the exacto knife
and scrape the oxidation off the pins before that. I'll bet if you try this last bit it will
make a big difference. The solder will flow right to where it belongs without blobbing
up. Flip the chip over, and pre-tin the legs after scraping.

I'm sure the "official" smt fab schemes are designed to get around these silly extra
steps, but I don't do much smt fab.

If you're using paste, you should try using a stencil instead of a syringe. You can also get cheap boards with solder mask in low runs from a company called OSH Park. Solder mask can make a world of difference in how the solder flows and lays out.

This is an old thread.

I have had similar threads pop up recently for no apparent reason

I agree that flux is a great thing to have, but I solder all the time and don't usually need it. I know I need it if the solder doesn't flow onto the part and then I go hunt some down . I think the problem is none of the above but the OP's technique.

@OP,
Are you aware that the iron tip needs to "tinned" before you can start ?
Do you know what that means ?
Do you know that if the solder doesn't melt when you touch it to the iron tip at the point of contact, 2 to 3 seconds after touching the iron to the part that something is wrong ?
STEP-1: Warm up iron
2: Tin iron tip
3: pick up solder with left hand
4: pick up iron with right hand
5: touch tip to part, wait about 1 to 2 seconds
6: touch solder to part at point of contact closest to the iron tip
7: wait a second or two for the solder to flow
8: when the solder flows, remove tip. (tip should not be in contact with part > 5 seconds

If the solder isn't flowing either the part is contaminated (and needs cleaning with Muriatic acid (10%)
or you need flux to get it to flow. Flux is essential for surface mount work and soldering heavy guage
wire but isn't 100% necessary all the time. As I said, I know right away if I need it and that's when
I get it. If I'm working on surface mount I won't start without it.

This is an old thread.

Oh damn ! I didn't catch that . oh well...

Necro'ing an old thread such as this one is not bad, as there seemed to be lots of good info in it. It's when somebody answers an old thread as if it's an actual response and doesn't add anything pertinent, that's a problem.

Sorry I cant follow that link.

I had one from maplin where the tips were very difficult to wet for some reason

raschemmel:
Oh damn ! I didn't catch that . oh well...

ARRGH
Done it again

Boardburner2:
ARRGH
Done it again

Seriously? LOL.

You necro'd your own necro.... that's a new one.... I'll have to add that to my scoring system...