# Soldering very small pads



## piesoup (Feb 9, 2009)

A few months ago I bought some bare XP-G emitters. By some, I mean 30!
Soldering these little buggers is a reet pain. The flux seems to cover the joint and prevents the solder sticking as the pads are so small. 1mm x 1mm! I originally got then to make a custom board but it is far too expensive to get one done.

Does anyone have any hints on how to solder these? If not, I haven't a clue what to do with them. 

Is it just a case of getting a really fine soldering iron tip or is there more to it?

Thanks


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## brad72 (Jun 12, 2009)

I usually clean my tip with a wet chux, touch it on the pad and touch some solder between the pad and iron tip. Usually takes about 3 seconds.

Another way is to get yourself a flux pen and put a dab of the liquid on each pad. Do the same as above and it takes even less time and heat.

The main trick however is to have a clean tip on your soldering iron


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## gozal (Jun 16, 2010)

*we got your back!*

yeh brad72 is right..
once again - make sure the tip is clean!

1.take a little solder on the tip and apply it on the wire to get it ready
2. put some solder on the tip and apply to the led's pad.
3. put the wire on the pad and the tip on the wire so it melts both solder of wire+pad and there u go!

dont use too much flux, sometimes it tends to get in u'r way instead of helping.

good luck chuck


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## jmitchell13 (Nov 20, 2005)

I've found the best way to solder small surface mount components is to use solder paste instead of conventional solder wire. Solder paste is liquid flux with small particles of solder suspended in it. You place a small drop of it on each pad and touch it with the solder iron. Use a small tip and as others mentioned keep it clean. Wiping on a damp sponge works fine to keep it clean.

It also helps to do it under a microscope, but not everyone has a microscope at their disposal.


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## troutie-mtb (Sep 20, 2007)

piesoup said:


> A few months ago I bought some bare XP-G emitters. By some, I mean 30!
> Soldering these little buggers is a reet pain. The flux seems to cover the joint and prevents the solder sticking as the pads are so small. 1mm x 1mm! I originally got then to make a custom board but it is far too expensive to get one done.
> 
> Does anyone have any hints on how to solder these? If not, I haven't a clue what to do with them.
> ...


Get some bare stars and reflow them on to those .


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## acezone (Jul 6, 2010)

troutie-mtb said:


> Get some bare stars and reflow them on to those .


This is what i did, Got some blank stars and attached them by putting them over the gas hob in a dry frying pan, worked great


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## piesoup (Feb 9, 2009)

Chris, I remember your super video on it now!! 

Thanks for the other tips chaps, I will have a go with the solder paste and reflowing.
Got a microscope somewhere, I'll dig it out and have a go...


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## highdelll (Oct 3, 2008)

what kind of flux are you using?
I mean, 1mm is small, but not _that_ small..

I use a liquid flux (not sure of the composition as the label is worn) and a small syringe/needle to apply.
'Flux not allowing soldier to enter' seems like either too much flux or not enough heat on the contacts.
As others have said, a clean tip is a must - especially when using as fine of one for heat transfer.

(I know I don't really post here - just lurk - so, I was an avionics tech in Nav, and soldiered a few tiny things - just so you know I'm not the jokester I am most of the time)

using something as simple as a mechanical pencil (lead out) can help with pad contact - of course that's a 'third hand' somewhere...


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## scar (Jun 2, 2005)

There is a slight layer of conformal coating sprayed on top of the pads on the bare emitters. Carefully scrape the very thin layer of conformal coating and you should be able to tin and solder the wire to the pads.

The next problem you will have is that since the pad is so small the mechanical connection between the wire and the emitter is so tiny that any slight movement of the wire will break the solder connection. You would also need to secure the wires so that they don't get bumped around during assembly and come loose.

Good luck




**


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## jmitchell13 (Nov 20, 2005)

highdelll said:


> (I know I don't really post here - just lurk - so, I was an avionics tech in Nav, and soldiered a few tiny things - just so you know I'm not the jokester I am most of the time)


Wow! Who knew you were a DIY'r... :thumbsup: 
I'm an avid lurker in most of the other sections you regularly post in...

Off topic but, can you post some new pics of Emily in the hot mtb chick thread? please...


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## highdelll (Oct 3, 2008)

jmitchell13 said:


> Wow! Who knew you were a DIY'r... :thumbsup:
> I'm an avid lurker in most of the other sections you regularly post in...
> 
> Off topic but, can you post some new pics of Emily in the hot mtb chick thread? please...


heh,
I'll see what I can dig up


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## OldMTBfreak (Apr 8, 2006)

The very most critical important thang: DON'T USE ROHS solder. Use 60/40 rosin core. I also like to use a flux pen for those special jobs. Practice, practice, but don't practice on your projects. Solder things together, make art. Then go work on your projects. A soldering station is a good addition to your tools. I have a Weller WTCP that is 35 years old. Watch some of those utoob vids to pick up a few pointers. Other thing; all parts must be clean. Scrape all the corrosion and coatings off first. Here is a pic of my WTCP


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## highdelll (Oct 3, 2008)

^^^ fcuk off spammer

*Edit* - Not you OldMTBfreak  - Spammers post deleted...


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## georges80 (Jan 5, 2010)

^ x 2

Did a similar stunt on CPF - resurrected a 7yr old thread about soldering as an excuse to link to his/her website.

cheers,
george.


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## piesoup (Feb 9, 2009)

Haha! I thought his post looked fishy!

I am going to try and reflow the emitters. I have a load of 20mm stars and triple boards from cutter. Going to use my gas cooker out in the shed as the words, "no chance" got said when I mentioned using the ceramic hob!!

My soldering is usually spot on, but these are SMALL! I seem to have the last bit of non ROHS solder in the UK. Can't get the stuff for love or money. Luckily I have quite a lot left. 

But there was a result this weekend, found 4 bFlex drivers lurking in my parts cabinet. Winner!!!


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## emu26 (Jun 23, 2008)

ooh piesoup let me know how you get on.

Troutie had success a while ago placing them on an al block and heating that, I think. I've often thought about using our ceramic cooktop, I have a quad board I want to salvage the LED from, but have been too scared to give it a try.


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## piesoup (Feb 9, 2009)

Will do! I have machined a plate that fits on my camping gas cooker. Got a temp sensor rigged up so I got go too hot. 

Will let you know how it goes!!


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## HuffyPuffy (Jun 9, 2008)

Hey Piesoup, since you are going the reflow route, I'd suggest checking the datasheet for the reflow "profile". It will give you an idea of where it should be temp-wise and how long it is safe to keep it there. Good luck.


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## HEY HEY ITS HENDO (Feb 23, 2008)

> Off topic but, can you post some new pics of Emily in the hot mtb chick thread? please...


hey i`m sure piesoup wont mind a few hot pics of Emily on here!!
..btw good luck soldering !!


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