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View Full Version : Better way to change Fets ?


ub0211042
2007.07.31, 12:21 AM
Hi Guys,

I was thinking, if is it better to change fets this way...

1. Remove the stock fets
2. Install single layer first
3. Install second layer on top of the first layer

From my xp, i found it easier to install fets on top of other fets when it is secured to the PCB, and it is easier to install single layer fets on the PCB (more working space) then only put one more layer on top.

What soldering iron u guys use? cheap or expensive ones?
how many watts and what is the temperature?

imxlr8ed
2007.07.31, 12:47 AM
I never stack turbo fets onto stock fets... seems to kind of defeat the purpose. The stock fets under the turbo ones will basically be redundant.

As far as stacking goes... I'll usually assemble the stack off the board. I use an alligator clip to hold the fets in position when doing so. After it's all together, then I put them on the board. Also... once installed, I now wad the solder onto the output side of the fets (mindful of keeping the heat down with cool down breaks in between). You can only do this on the output side (topside of the text on the fets... towards the motor pads. I find this just gives an added assurance that the connection will be made, and help to hold the fets onto the board alot more securely.

Always do the inside stack first, this should help with keeping away from that mysterious black box. Also... when the stock fets are off, I try to make sure that the "bubbles" of solder on the fet pads are all even and have a fresh run of solder on them. I usually tack a forward corner first, holding the stack with a pair of tweezers. Centering the front of the fets onto the pad pattern is critical here. Then tack secure the rest of the fronts... depending on how its going on.

I use a 15 watt junk soldering iron with a custom ground tip for the tight spots.

ub0211042
2007.07.31, 11:03 AM
I never stack turbo fets onto stock fets... seems to kind of defeat the purpose. The stock fets under the turbo ones will basically be redundant.

As far as stacking goes... I'll usually assemble the stack off the board. I use an alligator clip to hold the fets in position when doing so. After it's all together, then I put them on the board. Also... once installed, I now wad the solder onto the output side of the fets (mindful of keeping the heat down with cool down breaks in between). You can only do this on the output side (topside of the text on the fets... towards the motor pads. I find this just gives an added assurance that the connection will be made, and help to hold the fets onto the board alot more securely.

Always do the inside stack first, this should help with keeping away from that mysterious black box. Also... when the stock fets are off, I try to make sure that the "bubbles" of solder on the fet pads are all even and have a fresh run of solder on them. I usually tack a forward corner first, holding the stack with a pair of tweezers. Centering the front of the fets onto the pad pattern is critical here. Then tack secure the rest of the fronts... depending on how its going on.

I use a 15 watt junk soldering iron with a custom ground tip for the tight spots.

ermm...i don't solder turbo fets on top of stock fets.
What i was trying to say, by putting single stack of turbo fets on the PCB first and then only stacking em up might be an easier job. :) :D

imxlr8ed
2007.07.31, 11:39 AM
Guess I read that wrong... oops.

Guess I choose to assemble the stack first just to spend less time on the board itself.

ub0211042
2007.07.31, 11:49 AM
hehe...it's ok...ermmm reduce the time spent on PCB...that make sense.
Have u had any prob installing fets?

does the static hand strap a must in doing fet job?

imxlr8ed
2007.07.31, 01:27 PM
Yeah... early on I had some issues with poor soldering skills. Just have to learn how to keep steady when doing them. I try to prop my soldering arm more up towards my wrist onto the edge of the table now... seems to keep me alot steadier. Plus, early on there was the whole nervousness issue too.

I haven't really run into any issues in the past other than trying to repair over-fried boards from some of my members (lifted or scorched pads). The last issue was with the 3010 fets... I had a few just seem to not work at all. We have a thread on this out there... might be worth a read for you.

Never used a static strap in the past... and never had any issues about it either.

Here's the link to that thread:

http://www.minizracer.com/forums/showthread.php?t=24609&highlight=dead

ub0211042
2007.07.31, 10:48 PM
Yeah... early on I had some issues with poor soldering skills. Just have to learn how to keep steady when doing them. I try to prop my soldering arm more up towards my wrist onto the edge of the table now... seems to keep me alot steadier. Plus, early on there was the whole nervousness issue too.

I haven't really run into any issues in the past other than trying to repair over-fried boards from some of my members (lifted or scorched pads). The last issue was with the 3010 fets... I had a few just seem to not work at all. We have a thread on this out there... might be worth a read for you.

Never used a static strap in the past... and never had any issues about it either.

Here's the link to that thread:

http://www.minizracer.com/forums/showthread.php?t=24609&highlight=dead

haha...nervousness issue...i had that prob b4...i did burn 2 PCB when trying to change fets...

my prob is similar to old crowe...when we switch off the car...that is the time the car start to run by itself and then the fets burns...

imxlr8ed
2007.08.01, 11:10 AM
In my experience... that's usually caused by a crossed forward connection. Hasn't happened in a very long while to me, I'm extremely careful on the forward feet. Always run an exacto blade between the feet when done too, just to make sure there are no tiny "jumpers" of solder hiding between the feet.

Best thing to do is just make sure you're seeing everything when it comes to the connections, clean shiny solder lines and no errant runs is the best prevention for fried fets. Like I said earlier... I take extreme care with the input side of the fets (fwd direction of feet, bottom of text on fets), and kinda slop the connection onto the output side.