# electrically conductive glue?



## mailint

I'm making my first experiments with LEDs and I need a cheap solution for soldering little electrical contacts.

Does exist an electrically conductive glue?

What's the most active forum about electronics on the web?


----------



## georges80

mailint said:


> I'm making my first experiments with LEDs and I need a cheap solution for soldering little electrical contacts.
> 
> Does exist an electrically conductive glue?
> 
> What's the most active forum about electronics on the web?



Yeah - it's called solder... 

http://www.mgchemicals.com/products/8331.html is a 2 part epoxy that is very conductive (silver bearing) - but at >$20 you really should learn to use a soldering iron...

cheers,
george.


----------



## m13a8

georges80 said:


> Yeah - it's called solder...
> 
> http://www.mgchemicals.com/products/8331.html is a 2 part epoxy that is very conductive (silver bearing) - but at >$20 you really should learn to use a soldering iron...
> 
> cheers,
> george.



I agree, soldering is the best way to go. Soldering would be much cheaper in the long run than that epoxy.


----------



## mailint

Great! I'll buy it! 

I have the soldering iron (that with the tin spin) but I find very difficult to use it for little contacts (think of Rebel LED) and difficult to make a steady connection with some flat materials, for example with the poles of a battery..


----------



## Lyndon

That might just be the iron or your technique.

A small conical or screwdriver tip may be what you need for the tiny contacts. Soldering to battery contacts if they are not tabbed can be difficult. Make sure the terminal is very clean -- an alcohol swab (don't touch it after cleaning) and a quick wipe with a flux pen then heating it with a well-tinned tip before applying solder should help. Be careful not to overheat the battery.

You can get various iron tips & flux pens from the usual suspects, but I find that Circuit Specialists has good prices and selection.


----------



## mailint

Lyndon said:


> That might just be the iron or your technique.
> 
> A small conical or screwdriver tip may be what you need for the tiny contacts. Soldering to battery contacts if they are not tabbed can be difficult. Make sure the terminal is very clean -- an alcohol swab (don't touch it after cleaning) and a quick wipe with a flux pen then heating it with a well-tinned tip before applying solder should help. Be careful not to overheat the battery.
> 
> You can get various iron tips & flux pens from the usual suspects, but I find that Circuit Specialists has good prices and selection.


 
Another problem I have with the soldering iron is that it requires me to have an hand busy with the solder, the other hand busy with the iron, and a third hand for the battery and a fourth hand for the spin to be soldered to the battery pole.
Does Circuit Specialists sell a third and a fourth hand too?


----------



## legtu

mailint said:


> Another problem I have with the soldering iron is that it requires me to have an hand busy with the solder, the other hand busy with the iron, and a third hand for the battery and a fourth hand for the spin to be soldered to the battery pole.
> Does Circuit Specialists sell a third and a fourth hand too?



i'm not sure where you can get them but there are 'helping hand' thingies for these purposes.  some of them also includes a magnifying lense or loupe.

to give you an idea on what it looks like, click this.

there's also some threads here about soldering which you can use as a guide, if you need one.


----------



## yellow

sounds like You just learn the basics of soldering 
(You could also use Your mouth to hold the solder package, when both hands are occupied)

PS: immediately FORGET the idea of glueing contacts


----------



## 65535

I'm with everyone else sure the glue conducts, but compared to solder it's a better resistor. 

If you have to find someone to do the soldering for you and ship it, or buy pre mounted on PCB rebels.


----------



## Lyndon

Actually, I think I got mine at Radio Shack a few years ago. You can also pick up one of these http://www.circuitspecialists.com/prod.itml/icOid/7205 and it can be pretty useful.




legtu said:


> i'm not sure where you can get them but there are 'helping hand' thingies for these purposes.  some of them also includes a magnifying lense or loupe.
> 
> to give you an idea on what it looks like, click this.
> 
> there's also some threads here about soldering which you can use as a guide, if you need one.


----------



## mailint

legtu said:


> i'm not sure where you can get them but there are 'helping hand' thingies for these purposes.  some of them also includes a magnifying lense or loupe.
> 
> to give you an idea on what it looks like, click this.
> 
> there's also some threads here about soldering which you can use as a guide, if you need one.


 
Ahah beautiful! I think I'll buy it too. Thanksss!


----------



## mailint

Lyndon said:


> Actually, I think I got mine at Radio Shack a few years ago. You can also pick up one of these http://www.circuitspecialists.com/prod.itml/icOid/7205 and it can be pretty useful.


 
Thanks to you too but I prefer that of *legtu* for my applications (little objects)...


----------



## mailint

65535 said:


> I'm with everyone else sure the glue conducts, but compared to solder it's a better resistor.


 
Do you also know how better? is it trascurable for LED application? for example if the result changes from 170 lumen to 169.9 lumen it's trascurable for me...



65535 said:


> If you have to find someone to do the soldering for you and ship it, or buy pre mounted on PCB rebels.


 
What's the best channel to search for someone to do the soldering for me (for money of course)?


----------



## mailint

yellow said:


> sounds like You just learn the basics of soldering
> (You could also use Your mouth to hold the solder package, when both hands are occupied)


 
That of using mouth is an interesting suggestion too. I think I'll try it. Thanks 



yellow said:


> PS: immediately FORGET the idea of glueing contacts


 
Can I ask you why are you so against the electrical conductive glue?


----------



## yellow

it will have too much resistance (1) and might be unstable (2)

1: even if the led wont be dimmer than when soldered, the resistance at the glue point will heat it up and the glue will get loose

2: if any wire gets loose, it might make a short and damage else the led, the circuit, the ...

soldering solves these problems

PS: isnt soldering much easier than glue?
You have to mix the parts, glue the contacts, fix them for the time the glue cures, ...


----------



## mailint

yellow said:


> it will have too much resistance (1) and might be unstable (2)
> 
> 1: even if the led wont be dimmer than when soldered, the resistance at the glue point will heat it up and the glue will get loose
> 
> 2: if any wire gets loose, it might make a short and damage else the led, the circuit, the ...


 
Do you think it or saw it?

soldering solves these problems



yellow said:


> PS: isnt soldering much easier than glue?
> You have to mix the parts, glue the contacts, fix them for the time the glue cures, ...


 
As I wrote I'm not currently happy with soldering. Most of the times the soldered thing detaches....


----------



## MikeLip

The best conductive epoxy is loaded with silver. I did some experiments on it some time ago for Westinghouse. It is actually quite a good conductor up to a point. At high currents the epoxy does something weird - it goes open circuit. I never figured out why, I just know it happens. We went to welding for our high temperature and ruggedized connections. It has to get hot to do that though. But using it on an emitter that is going to run warm and then putting a good bit of current through a smallish conductor is a recipe for heating.

Solder is brittle and is not intended to carry a load. If your joints are breaking it is because of one of several reasons;

1) You are not getting wetting. Wetting is when the solder bonds to the substrate (with or copper) you are soldering to.

2) The joints are subject to vibration tending to pull them apart. No solder joint will last long under those conditions.

3) The solder joint has not been cleaned of flux. Flux will tend to damage the connection after awhile. 

Of the three, 1 and 2 are most likely and are typical amateur solderer problems. 3 takes a while and is most notable on conductors like stranded wire. The wire will break right where it enters the stripped back insulation.

Clean surfaces, a good iron, good solder (lead/tin is still the easiest to work with) either fluxed or using a good flux are essential. Flux remover chemicals are available, but good old denatured alcohol from Home Depot will work along with cotton swabs.

Practice until your joints are nice and shiny, smoothly filling the joint between conductors with solder, and make a good bond with no gaps, pits, or inclusions. there are lots of web sites showing you how to solder and what a good joint looks like.

Don't buy a junker $5 iron either.

This site has some reasonable information. Even their "good" joints are pretty amateurish, but they will do the job;

http://www.bestinc.org/docs/Survival_Guide/education_resources/sasoldering.html

NASA used to have good videos, but I'm not finding them. No doubt a more thorough search would find them.

I was taught to solder many years ago to military weapons specifications and still keep those standards at my current job as an engineer - I find there is no such thing as too good a joint! .


----------



## Ganp

I just found these NASA soldering videos here.


Colin.


----------



## mailint

Thank you very much MikeLip and Ganp! very useful informations/videos!

You made me remember the main cause of the weakness of my soldering. Often the dye or the material of the things next to the part that I'm soldering mixes up with the iron that becomes dirty.
The "Clip 4" of the NASA videos shows the main material that makes my iron dirty and weak to attach to materials. Do you see that part of the PCB around the soldered contacts that becomes brown because it's fused by the heat? it is that thing! :huh:


----------



## georges80

mailint said:


> Thank you very much MikeLip and Ganp! very useful informations/videos!
> 
> You made me remember the main cause of the weakness of my soldering. Often the dye or the material of the things next to the part that I'm soldering mixes up with the iron that becomes dirty.
> The "Clip 4" of the NASA videos shows the main material that makes my iron dirty and weak to attach to materials. Do you see that part of the PCB around the soldered contacts that becomes brown because it's fused by the heat? it is that thing! :huh:



The 'brown' stuff is the left over flux. It is not brown because it is fused by heat... God knows what solder/flux that 'expert' was using to solder - looks like rosin core or something disgusting like that. I would have hoped for a NASA video it would have been a LOT more informative.

Anyhow, the choice of solder/flux is CRITICAL to good solder jobs (as of course is good technique AND non-contaminated items to be soldered). Where no clean up is possible, I use a Kester No-Clean flux cored solder. I use a 0.031" diameter #245 flux based Kester solder ->

http://www.kester.com/en-us/products/prodcat_detail.aspx?pid=45

Works very well for a no-clean solder.

cheers,
george.


----------



## mailint

georges80 said:


> The 'brown' stuff is the left over flux. It is not brown because it is fused by heat... God knows what solder/flux that 'expert' was using to solder - looks like rosin core or something disgusting like that. I would have hoped for a NASA video it would have been a LOT more informative.
> 
> Anyhow, the choice of solder/flux is CRITICAL to good solder jobs (as of course is good technique AND non-contaminated items to be soldered). Where no clean up is possible, I use a Kester No-Clean flux cored solder. I use a 0.031" diameter #245 flux based Kester solder ->
> 
> http://www.kester.com/en-us/products/prodcat_detail.aspx?pid=45
> 
> Works very well for a no-clean solder.
> 
> cheers,
> george.


 
Sorry but my english knowledge is too bad to follow you in your last message... (my first/everyday language is italian...)

Can you please define the following words/expressions?
- flux
- no-clean flux cored solder

Thank you again for your kind help!


----------



## georges80

mailint said:


> Sorry but my english knowledge is too bad to follow you in your last message... (my first/everyday language is italian...)
> 
> Can you please define the following words/expressions?
> - flux
> - no-clean flux cored solder
> 
> Thank you again for your kind help!



Flux -> pasta per saldare

no-clean flux - pasta per saldare che non serve a pulire dopo di saldare

ciao,
george.


----------



## yellow

pragmatic approach:
noone uses this method!
If it would work as good as soldering, someone would do it this way.

but just try it for Yourself: make it that way, and when the led is running bright (what I would wonder), take a wire and connect "over" the glue point --> brightness will increase considerably

PS: maybe its just Your equipment. Since I switched away from my expensive temp. capable soldering station to a small 15 W iron, all my soldering points got better.


----------



## mailint

georges80 said:


> Flux -> pasta per saldare
> 
> no-clean flux - pasta per saldare che non serve a pulire dopo di saldare
> 
> ciao,
> george.


 
Grazie George 

I didn't know that there is a pasta for solding. I always used tin in form of wire, not something in form of pasta.
This is a picture of what I used:







how does this flux and no-clean flux look like?
and what does "cored" solder mean?


----------



## mailint

yellow said:


> PS: maybe its just Your equipment. Since I switched away from my expensive temp. capable soldering station to a small 15 W iron, all my soldering points got better.


 
My two soldering tools are like these:


















Do you say that there are significantly better soldering kits?

if so, can you please suggest a soldering station <$100?


----------



## georges80

Flux core solder - solder that has flux inside (in long 'cores'). When you solder the flux 'melts' inside the solder and helps to cover what you are soldering. The flux helps the solder to flow and cleans the contacts that you are soldering.

You can buy "flux pens" that contain liquid flux (make sure it is flux for electronics components). The liquid flux helps with some soldering when the flux inside the solder is not enough.

Your soldering irons (in the pictures) are really not good enough for soldering delicate electronics. Google for HAKKO or WELLER for some reasonable brand names.

Go to www.kester.com to find good solder - I provided a URL in this thread for one solder I recommend.

cheers,
george.


----------



## yellow

imho that pic shows a much too powerful iron (50 W?) with a too large tip for small soldering.

wherever You got that one, get a 15 W there with a needle point tip and try again


PS: hold down wire with the hot tip, apply solder, quickly change solder with screwdriver, hold down wire, move tip away --> done


----------



## mailint

yellow said:


> imho that pic shows a much too powerful iron (50 W?) with a too large tip for small soldering.
> 
> wherever You got that one, get a 15 W there with a needle point tip and try again


 
Question: why 15W can be better than 50W? doesn't it take loger to warmup?
isn't a 50W with needle point tip better?


----------



## yellow

no, 
gets to hot 
+ tip must be too thick


----------



## Lyndon

A 50W iron is just fine as long as it's temperature controlled. I have 35W and 40W Weller irons that I used for years. I stopped using them on active devices only because I was concerned about ESD (they are the magnetically controlled ones). But I still use them for assembling cables because of the higher thermal capacity.


----------



## laserblue

i dont think electrically conductive glue would work satisfactorilly.


----------

