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Yet another resistance decade box
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johnmx:

--- Quote from: ez24 on July 29, 2016, 08:59:58 am ---Just curious - what soldering set up do you have?  Do you pre-tin the pads?

--- End quote ---
I have this soldering station:
http://www.jbctools.com/cd-2bc-soldering-station-for-general-purposes-product-710-category-1.html

It can heat up in less than 2 s. It's amazing.
More about this:
http://www.jbctools.com/heating-system.html

And I use this microscope:
http://www.optikamicroscopes.com/index.php?option=com_virtuemart&view=productdetails&virtuemart_product_id=254&virtuemart_category_id=5&lang=en

I do soldering since 12 years old. So I have a lot of experience in this matter.
I can get the same results with a normal soldering iron and no microscope with SMDs down to 0805.
With the microscope I can solder very well 0402 components.

About the soldering, there are several videos in the internet, but some are completely wrong. So be carefully.
What I do is the following:
- Put some solder in one pad of each footprint. Don’t put too much, it’s better to have little less than too much. Do this for all footprints.
- Now pick up the component with a good tweezer using your left hand (if you are right-handed). Place it over the footprint without releasing the component. This insures that the tip of the tweezer is higher than the bottom part of the component. If you release it, just make sure about this when you hold it again.
- Now with the component in place, heat the pre-soldered pad with the iron and press down the component while the solder is liquid.
- Remove the iron, wait some seconds. Could be 2, 3 or 5 s, it depends on how much heat you applied to the pad.
- Release the component by opening the tweezer.
- Put the tweezer on the table and hold the soldering wire (solder) with your left hand.
- Solder the other(s) pad(s) of the component.
 - If the first pad was not very well soldered, you can put a little more solder on it.
That’s it.
Some tips:
-   Don’t use “Free Lead Solder”. It’s much harder with this new type of solder.
-   Apply some flux to the pads if the solder is not fixing well to the pad or to the component. I prefer liquid flux and apply it with a small brush. I buy the flux in big bottles and put it in an old nail polish container (see the attached picture).
gblades:
Normally I would tin one pad and then pick up the resistor with tweezers and melt the solder on the pad again and move the resistor into position. Then solder the other end. Apply some flux to the 1st joint and touch it with the soldering iron to reflow it.

However when I assembled mine I dabbed a little solder paste on the pads and stuck down the resistors and then flowed the solder using a hot air gun. I did that mainly for practice and it generally worked well apart from putting too much paste on the first board and getting a short under one of the resistors. Easy to remove with a hot air gun though.

I use a jewellers headband with a built in light and different magnification lenses that you can clip in. It works and preserves your depth perception so way better than the 'helping hands' with a built in magnifier but still a poor comparison to a proper microscope but then again they are a lot cheaper!
ez24:

--- Quote from: johnmx on July 29, 2016, 10:00:51 am ---What I do is the following:
- Put some solder in one pad of each footprint. Don’t put too much, it’s better to have little less than too much. Do this for all footprints.
- Now pick up the component with a good tweezer using your left hand (if you are right-handed). Place it over the footprint without releasing the component. This insures that the tip of the tweezer is higher than the bottom part of the component. If you release it, just make sure about this when you hold it again.
- Now with the component in place, heat the pre-soldered pad with the iron and press down the component while the solder is liquid.
- Remove the iron, wait some seconds. Could be 2, 3 or 5 s, it depends on how much heat you applied to the pad.
- Release the component by opening the tweezer.
- Put the tweezer on the table and hold the soldering wire (solder) with your left hand.
- Solder the other(s) pad(s) of the component.
 - If the first pad was not very well soldered, you can put a little more solder on it.
That’s it.

--- End quote ---

This is what I did on the last one, and it works great  :-+
Nice to know I am doing it right

A fast heating iron is high on my list, my biggest fear is I will forgot that I plugged in my iron because it is so slow, I usually get distracted.  I try and set the timer on my phone (if I can remember)  :-DD

 

Thanks
ez24:

--- Quote from: gblades on July 29, 2016, 10:28:55 am ---.. and getting a short under one of the resistors. Easy to remove with a hot air gun though.

I use a jewellers headband

--- End quote ---

I am going to save my "bad" boards just in case someday I get a hot air gun.

I found my jewelers headband, this is how I determined that board #2 had solder in the via and #3 was ok (the switch was bad)
smgvbest:
In the FWIW area on soldering
I use one of these
https://www.circuitspecialists.com/Hot-Air-Soldering-Station-Power-Station-Plus.html

and one of these to apply solder paste
https://www.tindie.com/products/marjan_mike/electronic-solder-paste-dispenser-v5-air-freeair-/

the use the the hot air gun set to the reflow temp of the solder and move it back and forth over the boards.
done in no time.
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