soldering

bengali548 · #1 07-11-2006, 11:50 PM

okay as some of you might now i know NOTHING (well almost nothing) about soldering so i guess this can be a thread to noobs about soldering so ill start off

for the evolution cars if i cut off the FETS with a hobby knife than melted the solder and took out the remaining legs but left the solder there and i put the fet on top of that solder would an electrical connection be made because solder is metal or do i have to clean out all the excess solder thoroughly to get a proper connection

Namuna · #2 07-12-2006, 12:50 AM

Read this excellent tutorial by ph2t:
Xmods Evo FET Upgrade

It answers your question about leaving the amputated legs behind (basically you DON'T want to do that).

bengali548 · #3 07-12-2006, 07:24 AM

first yes i know u shouldnt leave the legs but my question is why not cant electrons still flow through them.

second i wasnt going to keep the legs in, it would have been awkward to solder.now my main question was if i could put the FET OVER the solder and how solder acts as a conductor or if i put the FET over the solder than melt the solder so it would engulf the legs.

third good explanation of why not to keep the legs all it said was to clean it up using a soldering iron and that was it

Rez · #4 07-12-2006, 08:16 AM

The solder will conduct. You don't want to leave the legs behind because they'll just be in the way and might result in a weak joint.

You need to be very carefull when soldering FETs or any other solid state device. If you get them too hot you will burn them out before you finish. Soldering wires is one thing, soldering solid state, especially surface mount, requires good equipment and skill. PRACTICE FIRST.

bengali548 · #5 07-12-2006, 08:24 AM

lol how do i practice

Namuna · #6 07-12-2006, 09:08 AM

Quote:

Originally posted by bengali548
first yes i know u shouldnt leave the legs but my question is why not cant electrons still flow through them.

Yes, if metal is touching metal (even if it's not the recommended way) then indeed electrons will flow. So if you wanted to do it extra-ghetto style, you could just cut the stock FET out and sit the upgraded FET on top and use glue on the legs or even just wrap electrical tape around the whole PCB

Quote:

second i wasnt going to keep the legs in, it would have been awkward to solder.now my main question was if i could put the FET OVER the solder and how solder acts as a conductor or if i put the FET over the solder than melt the solder so it would engulf the legs.

Same situation as from #1. Yes, you could do it and it would probably work. But the cleanest and most efficient way would be to just remove all remnants of stock pieces before upgrading.

Quote:

third good explanation of why not to keep the legs all it said was to clean it up using a soldering iron and that was it

He didn't bother to go into further detail because just saying to clean it up is enough info...Unless of course you're looking to do it "ghetto-style" like I was saying before, then he definitely should've gone more into glueing the legs or using duct/electrical tape and such.

Namuna · #7 07-12-2006, 09:11 AM

To practice, see if you can find any old junk electronics that you don't mind screwing up and go to town with soldering and un-soldering pieces to get comfortable with it.

Azimov · #8 07-12-2006, 12:39 PM

Quote:

my main question was if i could put the FET OVER the solder and how solder acts as a conductor or if i put the FET over the solder than melt the solder so it would engulf the legs.

The former will not work, You might get a feeble connection, but it won't last nor work for long. The latter is the way to go...always.

Quote:

good explanation of why not to keep the legs

You can leave the legs as long as you get a good, clean connection from the pads to the new legs. The removal of the old legs is to keep the job as neat as possible as these SM parts are very tiny and you could easily cause a short among the legs if you aren't careful. Neatness is very important in SM technology as just leaving huge globs of solder can imfluence the resistance of a circuit.
I would suggest you practice on junk before you attept this or you may be junking your car.

#9 07-12-2006, 08:51 PM

Those legs can get a bit tricky to solder without shorting two of them. If I'm in a really tight place, I will put my hobby knife blade between two of the legs to block the solder from adjoining another leg. I haven't looked to get a really sharply tipped soldering iron... I use a 40watt from RS, and while that is the iron with about the sharpest tip they have, it could still be better. I grinded down a tip to a really sharp point, but it didn't last as long as other tips.

The other guy was right too... Don't leave your iron on the legs for too long or the FET will get too hot and permanent damage could be done. If it takes a while for you to solder each leg, make sure to let it cool before you try the next one. They can still get pretty hot, I don't mean to scare you too much, but if it's going to burn your finger for touching it for less than a second, you're probably too hot.

bengali548 · #10 07-12-2006, 10:08 PM

hey thats actually quite smart using the hobby knife to seperate the legs but this raises another question what if the solder goes a bit out of the pad would anything happen and i doubt that im gunna burn out the legs i mean for solderig all u have to do is put some solder on the tip than transfer it to the leg make it so it sticks down and bam done

#11 07-12-2006, 10:35 PM

The solder sticking out won't matter provided it isn't touching anything it's not supposed to. Some of my solder jobs have little spikes here and there. And yes, put a tiny amount of solder on the end of the tipe and transfer it between the leg and the pad.

bengali548 · #12 07-12-2006, 10:41 PM

oh another problem i have with soldering is that if i get the solder on it just pulls off easily and the solder would just be stuck to the wire

and also i dont know if this is regular but i get a strong connection if i hold the wire down with my finger (this is out of the fet subject but i guess could still be related) and when i bring the solder closer the connection begins to fade and if the solder touches it the conection is lost

p.s. thx for all of ur help btw but man if i get this fet to work im putting on like 90 fets man 2x90 lol id have to redo my control also and add wings to my xmod so it can fly with that many fets lol

Rez · #13 07-13-2006, 08:01 AM

Just make sure you understand that FETs alone will not make your car any faster. FETs let you run a motor that draws more current. That's all. If you don't have a hot motor to run, don't bother stacking FETs.

bengali548 · #14 07-13-2006, 11:57 AM

no my throttle burned out so i have to to get back my throttle