Re: Soldering Diodes

[K3yPr0gg3r]

Hi,

Is soldering diodes suppose to be such a pain? Barry over at GuitarPCB.com has a video regarding soldering to a circuit board which was very helpful. He suggested a 10 count when contacting the iron to the board/lead before applying solder. I have followed that process and found most of my joints are very good! However, when it comes to soldering diodes, especially 4001s, 5817s, etc., my joints look like hammered crap! They still work, but they're bumpy, mis-shapen globs... I'm using a heat-sink on ALL diodes. Do I need one on silicons or just glass / germanium?

Thank you

[madbean]

10 seconds is way overkill. Two to three seconds should be more than enough. Touch the pad and joint simultaneously, count to two or three and flow solder. If you are not getting good flow at that point your iron temperature might be too low.

[midwayfair]

10 seconds is not only more than you need, but it's likely to damage many parts, especially semi-conductors.

Maybe Barry counts REALLY fast.

[K3yPr0gg3r]

Thanks...BUT, why do my resistors, caps, sockets all come out looking good, and my diodes not so much? I've noticed that the leads are thicker on the diodes vs other leads. Do you guys solder diodes differently in some way? Also, do I need the heat sink on silicon?

Thanks again

[madbean]

You don't need a heat sink. I could see using one on maybe a germanium diode but personally I never use one for anything. Again, the key here is a properly hot soldering iron to minimize the heat exposure of the parts and pads. Of course you get good looking joints from 10 seconds of heat, but as Jon said you are really rolling the dice with on your components. If you cannot get a good joint within 2-3 seconds your iron is not hot enough. Or, maybe you are using an inappropriate solder type or core diameter. What iron and solder are you using?

Personally I do "ghetto" soldering on everything. This means touching the iron to the joint and solder to the iron instantly for a very small melted bulb over the pad and lead (technically the wrong way to do it). But then I lift the iron off for a couple of seconds and repeat the same process on the joint. This gives a nice bulb of melted solder with a small break from the heat in between. This method never fails to get good solder joints for me without damaging components.

[wgc]

Flux helps a lot too.  If you have a digital temp display on your iron, shoot for around 700f. Try not go to over 750.

Also, make sure you're tinning your tip. And hold the iron so that you have as much tip surface in contact with the work and the lead at the same time- not just the very point of the tip.

That helps the heat transfer to the lead and the pcb.  the solder from tinning helps fill in the gaps to maximize surface contact and heat transfer. (Kind of why beans ghetto method works.). The goal is that the work pieces are hot enough to melt solder, not just the iron. Tin tip, touch work 1 Mississippi 2 Mississippi add solder 3... Off work Should do it.

Agree about the heat sink too

[galaxiex]

The key to good soldering is CLEAN.

Try cleaning the leads of the diodes with some fine sandpaper, scotchbrite scrub pad, or even some alcohol or lighter fluid.

Really, anything you solder should be cleaned in some way,
but it's just possible that the diode leads you have been soldering have some corrosion or oxidization on them.

Clean them well and I bet your solder issues disappear. 

[K3yPr0gg3r]

Cool! I'd of NEVER thought of that. Thank you!!

[galaxiex]

You're welcome!

Actually, I can't stress enough about clean parts when soldering.
I suspect most of us (me included) don't clean parts leads (R's, C's and the like) when soldering..... but....

It is very good practice/habit to do so.

A good parallel is welding.
You will never see a professional welder "just start welding" on a piece of metal that has not been well cleaned.

To be sure, most of the time we get away with not cleaning parts leads and even board traces and it works out fine.

The flux usually takes care of any little impurities in the solder joint and... no problem.
But if/when you have a corroded or tarnished part it will quickly bring home the fact that you really do need to clean the part. 

If you've never tried it,
I very much recommend cleaning some parts leads that "look" clean and notice how easily they solder compared to the ones that you don't clean.

My favorite way to clean part leads is to pull them a couple of times through a folded piece of scotchbrite pad.

[komigenie]

For good soldering joint, try to DONT use led free solder ...

For GREAT soldering joint use Cardas Quad Eutectic solder ...

http://www.cardas.com/solder.php