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Nic-Z
2008.04.08, 07:35 PM
I read up on a few tutorials for stacking fets, I seem to get the idea I have done numberous re-soldering wires on boards and servos etc. but I have five questions. I currently have a 15w iron with the smallest tip they make.
Is 15 watts I have enough?
Would grinding the tip down to a fairly small point be better?
Has anyone used an exacto iron and the tip on that to solder fets?
Do I need to remove the fets if I am stacking the same fet on top of it?
and last question. On some boards I see all but one leg soldered on one side and others I see ALL legs on one side soldered does it matter? (thats five) Thanks in advance and forgive me if this in the wrong section feel free to move it.

byebye
2008.04.08, 08:03 PM
Have you seen any videos?

When I do it I use lots of solder and a hot iron. I usually use a 25-30 watt.

I've filed some tips down. The smaller the better but when you file it down the tips doesn't last as long.

I've never used an exacto.

If you are stacking a 3010 on top of a 3010 then don't remove them if they are attached to the board already.

On the side of the fet closest to the motor leads you can solder all of them together. They are already shorted together you just can't see it on the surface.

No this isn't in the wrong section.

Kris

pinoyboy
2008.04.08, 08:18 PM
I also use a 30w soldering iron. I use a cheap one from radioshack that you can replace tips with and I grind down the tip to be very thin.

If you have 3004 fets, remove them. If your stacking on top of 3010s, I don't see any harm in that. My awd has 3010s, and I just stacked 2x2 of 4562 fets on top.

Nic-Z
2008.04.08, 09:25 PM
Thank you guys for the quick response, I have an overland that I am going to use as a rock crawler (nothing serious) but don't want to blow the fets, and I just bought a lambo mini-z boat (119 at my LHS) that I am throwin in a lipo and an atomic stock motor so I want to stack the fets on that one as well. Question


How do I know if need a new tip? (since I will grind down my 15w tips they are far to fat for fet stacks)

If I have 3004 fets its not wise to put 3010s or somethign like that?

Aurora
2008.04.10, 03:35 AM
Nic-z,

I think a thin tip will obviously help, but I would also strongly recommend getting the thinnest solder wire you could get--often time when I do a fet-stack job, it is not how fat your solder tip, but how much solder you get onto that tip that might ruin the stack. I had quite a few times messed up a stack by having just a bit too much solder on a big tip, and the excess solder somehow connecting the neighboring legs together...so thin tip and thin solder wires help.

Another important pointer is I usually have compressed air handy to cool things down. I use an emptied airbrush to blow cool air onto the parts that I use solder or desolder, each time after I use the soldering iron. One biggest point of the game, I figure, is to keep the heat down. Too much heat will kill the fets, or even components on the board.


Finally, I do suggest to mentally think thru what to solder first before doing the job--sometimes the fet stack happen right next to other big components on board, and choosing the right priority will make the job that much easier.

Good luck! :)

Nic-Z
2008.04.11, 12:06 PM
thanks much I'll need it.

Ninja
2008.04.11, 01:08 PM
another way I have done large stacks of 3+ FETS is to go ahead and solder the group of legs together as a whole. (yes both sides) as this will take less heat and concentration in the long run. Clean the tip of the iron with a wet, natural sponge, so there is no excess solder on the tip. The when the iron is good and hot again, make swift steady passes between the legs of the FET stack, from bottom to top, to seperate the individual legs. Clean the tip again after each pass to remove the excess solder. and allow the FETs to cool after each pass. The clean tip will allow it to "pull" off any excess solder from the tip and leave a clean stack. once this has been done, I use a small alligator clip to hold the FET stack onto the board, and just touch the tip of the iron to each of the bottom legs. Pressing gently on each of the FETs legs, you will feel when the solder on the board melts, and you will feel the leg of the FET sink into it.

The heat of the iron is not as important as a good pointed tip, and steady hand. I completed my first FET stack successfully many years ago with a Wood Burning Iron. :eek:

briankstan
2008.04.11, 02:10 PM
I completed my first FET stack successfully many years ago with a Wood Burning Iron. :eek:

that's what I'm using still. :o

Nic-Z
2008.04.11, 02:58 PM
sweet tip thanks mucho. I need to find some spare tips, I current use a 15w iron and its plent hot.

ProfoxCG
2009.03.16, 02:39 AM
A 15W iron is about what temp? 350-400C ?

can a board be shorted by using too much heat (700C) while removing fets