Soldering newbie

Please can anyone help? I am looking at supplies for the reflow soldering technique in the UK, but don't know what to buy.

I've looked for solder paste in the UK, and they all have different melting temperatures - does it make a difference? What should I look for? And What composition?

Can solder paste from a tub be used to refill a syringe? Or is the tub stuff thicker?

How much solder paste (it's sold in multiples of grammes or ml) is involved in making up all the boards?

Anyone have any suggested UK suppliers (Pb-free please). Thank you.
Hazel.

Looking at Farnell there are only really two temperatures, leaded around 183C and lead free around 220C.

I use leaded solder at home because it is easier and the fumes are LESS toxic than lead free solder. When we switched over to lead free at work we had to install fume extraction because the flux fumes are more toxic.

I haven't done much with paste myself yet, I have a collegue to do it for me at work. He recommends this one [uk.farnell.com].

You only use very small amounts so you will not use anything like a syringe full making all of the boards. It only has a storage life of a few weeks though and you should keep it cool. We have it in a tiny peltier beer fridge.

It does still seem to work fine long after the recommended shelf life though, which is just as well as it is expensive. A reel of normal solder lasts me many years so it much cheaper in comparison.

You could refill it from a tub, but the tub will probably have gone off long before you need to.

I will be making some surface mount boards with paste in the next few weeks so I will have more idea then.

Edited 2 time(s). Last edit at 05/20/2009 04:04AM by nophead.

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PS, you will probably want to get a flux pen as well. It is essential if you do any hand soldering or rework.

Edited 1 time(s). Last edit at 05/20/2009 04:04AM by nophead.

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Some useful tips from the makerbot blog:
[www.neufeld.newton.ks.us]

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I have been soldering for almost as long as I can remember, and I do electronics for both a hobby and a living, but I am surprised at the advice to have DIY reflow soldering. With the packages used here you would be much better off just placing with tweezers and soldering them down with a fine iron. The problem as I see it is the temperature profile, that is how quickly you can get the board up to temperature and down again. This is done professionally with a re flow oven where the boards are passed through various temperature zones on a conveyor belt. Too long at high temperatures could damage some components.

grumpy mike,
re the temperature profile, a small domestic is actually brilliant for the job, as they are designed for a much higher thermal inertia load, i.e. toast, potatoes, roast meat etc. All these contain water, which has a very high specific heat capacity, higher by volume than PCB components.

My advice is to buy a cheap meter with thermocouple, and insert this in the oven with the populated prepared PCB, and watch for the temperature to approach the stated solder melting temperature. Look for complete melting at the parts of the PCB with highest thermal mass, and then switch off the oven and open the door. Give it a couple of minutes, and you can carefully extract the PCB.

If you have a small convection oven, set up some baffles to restrict the air flow, small components can be blown out of place otherwise.

Graham

by 'baffles to restrict the air flow', do you mean put the PCB inside a high-walled cake tin/baking tray in the oven?

It sounds like it's heading towards a recipe (2 minutes in a pre-heated oven at 235C/gas mark 8)?

:-)

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hello
i've also been looking for paste in the UK or at least without the $35 delivery from zephpaste, i've found these two but i can't say if they are any good!?!

[chipquik.com]

[www.mrtechservices.co.uk]

I get your humour, but practically, some convection ovens have very fast air flow.

Some air flow is good, but not if it's blowing components around the PCB.

I bought solder paste on ebay from some one suppling old stock from RS I guess because of the address looking just like the RS address some of the packages are marked RS I got 150m syringes at 1.55 each.. you only need one syringe I over bought with 3 they were much bigger than they looked in the picture.. They need to be stored in a fridge thou.

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