help fixing my G3 stepper controller please

Hello All

I have fried one half of one of my stepper drivers (Makerbot G3) The motor wires came loose and now it only energises one of the 2 coils.

I am guessing it is the A3982 that has popped.

I see Farnell have the A3982SLB-T in stock for £4.78 and digikey at 4.03 so there is no problem sourcing the driver. A plus is that farnell does not charge for standard delivery so it seems the cost effective option to fix rather than replace with pololu.

Question is how the heck do I go about replacing the chip?

a) How do I remove the faulty chip without damaging anything else?
b) how do I put the new chip on without causing bridges etc?

I have a gass oven and stove so no go with an electrical hotplate...

I have never used nor seen SMT in action and have minimal soldering experiance otherwise.

Can anyone advise?

Thanks

... i'm desoldering SMD's by heating a pin and pushing a 0.05mm thick Nickel-sheet under the pin, so it cut clean through the solder. Such Nickel-sheets can be found in price-tags for inductive scanners, in Germany mostly used for DVD's, software and such ...

For resoldering i use a really thin solder-tip and 0.5mm-solder ... and i'm reworking/soldering SMD's with a microscope ...

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Viktor
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Hi Viktor

Sounds like you use a technique something like this guy for soldering SMT devices with an iron - a pretty good tutorial I think if you can stand the nasty and unavoidable advertising before the tutorial.

tangent tutorial 3 surface mount soldering techniques/

I think I will go ahead and try this approach...

I would appreciate any other advice anyone can offer.

Cheers

I desoldered a smoked IC on a extruder controller with soldering wick and tweezers. Soak up as much solder as possible with the wick, then heat all the legs on one side so they gets loose and bend the IC up with the tweezers. I find it simpler to do one side at a time, and it doesn't matter if you aren't going to reuse the IC anyway.

Edit: I didn't solder a new IC on, since I switched to a stepper controller instead.

Edited 1 time(s). Last edit at 11/10/2010 09:30AM by Nudel.

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-Nudel
Blog with RepRap Comic

So did you then replace the chip with an iron as per the attached video?

Since you don't want the old chip you can cut its pins close to the body with a pair a wire cutters with small sharp jaws. Then you can remove each pin with a soldering iron .

If it is lead free solder, then you need a temperature controlled iron, otherwise you risk lifting the pads.

There are many video tutorials of how to solder SMT chips with a soldering iron. The A3982 is quite a large pitch so not too difficult, but tricky if you haven't done it before.

Use a large flat bit to wipe solder off the pads to get them level. Tack two opposite corner pins to hold the chip in place. Put plenty of flux on the pins and then solder them with a small chisel shaped bit. If you don't put too much solder on surface tension should stop it bridging. If it does bridge adding some flux and wiping off the excess with the iron usually works.

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[www.hydraraptor.blogspot.com]

Hi Nop

One of the things I did do when starting this incredable journey was to purchase a temperature controlled iron. (I generally am of the mindset that if I need a tool once I will generally need it again and therefore go for slightly better quality).

I *think* the solder is lead free...

So what temperature should I be setting my iron to?

Cheers

... i'm soldering mostly with 350°C but try to avoid long heating times.

You can presolder all pads with 'leaded' solder, so they will went fluid faster.

And the tip in the tutorial-video isn't really fine enough for proper SMD-reworking.

In my first days with finepitch-SMD's i wound a piece of silver-wire on a bigger solder-bit and bent a short piece away, so i had a thin hot end ... but now you can buy fine sharp tips ...

Edited 1 time(s). Last edit at 11/10/2010 09:43AM by VDX.

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Thanks for that Viktor

My tip is about 2mm, perhaps slightly less... I will see if I can find a finer tip for my iron.

Sad news is Farnell require a minimum order of £20 before I can pay by CC. which is rather irritating.

Will need to try determine what else I need - maybe I will look at the parts for a homegrown Arduino/sanguino or maybe even a stepper driver

Cheers

Yes around 360C is OK.

I would tend to disagree with Viktor. Small sharp tips don't work because a) they don't conduct heat to the tip and b) the surface tension prevents solder getting to the tip. It is much easier to use a larger chisel tip that may even bridge the gap between pins and rely on the surface tension to prevent bridges. This works much better if you apply liquid flux as it removes the oxide from the surface of the molten solder and makes it flow a lot better. This is particularly true with lead free solder, which does not flow well compared to leaded.

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[www.hydraraptor.blogspot.com]

... the quality of the tip is depending on the manufacturer - i have a "Digital Solder Station ST-80D" from Conrad with a fine tip, what's doable, but you have to be carfull with the solder-type and the power is something poor ...

Then i have a "Digital 2000A" and an "i-Con2" from Ersa with even finer tips, that's a dream to work with!

At home i have two old Weller-stations with exchangeable tips, where the handling with the finest/shortest tip is something between the Ersa and Conrad ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Because the solder iron is moved by hand, the "hand" is what matter quite alot, and each person feels comfortable himself in different situations, thus opinions will always be different. And opinions better be different, coz the alternative says that we would be just a nation of brainless robots.

Generally soldering depends so much on own perspective that if you ask 10 ppls i think you probably would get 10 different opinions and also 10 different ways of doing things. For example on desoldering chips here is a more spectacular way to do it [www.youtube.com] - not really needed for 2 sided a3982 tho, and i dont suggest you to do this - link is just for watch for alternatives. If you have an old soldering pistol of those types that uses a bent wire as a heating element, you can also make a temporary wire for it in the shape of the ic u want to desolder and put it over all its pins at same time. All these are different ways of different ppls, and i think there are still many more out there. That to point out that choices like these are more about the person making them and slightly less about a certain tool. Because imo what is needed most, is courage, imagination, awarness and anticipation. Tools are just ... tools. Do w/e you feel comfortable with, but in general dont remain zoomed only on a certain tool.

man - that method I certainly won't use

Maybe I missed it but what about hot air? That's what I use.. a cheap model is about 80-100us.
Then I pick it up with a little pen size suction cup thingy I found in China.. easy as pie or cake or whatever.

One thing that seems rather important for SMT soldering using an iron according to the tutorials I have found is is flux.

I don't know which flux to get and need some advice. Water or alcohol based, no-clean, flux that specifically states lead-free, rosin etc.

Also, is it necessary to clean away the flux (some guides talk about even cleaning no-clean flux!) after having soldered your chip on.

I have found a rosin flux pen and wonder if this would be sufficient.

Thanks

Another suggestion is that if you're worried about bridging when soldering, buy some kapton tape. Put the kapton down either side of the pin you're working on. This will reduce the heat to those pins, allowing you to concentrate on the pin you're working on. Then just up and move to the next pin.

Since you're working over 300 Deg C, you will find the kapton does deteriorate. You may want to trim/replace the pieces you use regularly to avoid them completely burning up.

Yes Flux is the key to most SM soldering by hand.

If you flux the device pins and PCB pads of say a SM connector or row of fine pitch SM pins on a Micro etc. then you can run a soldering iron along the row of pins along with plenty of solder (not solder paste) the flux will help stop the pins (even very fine pitch) from bridging with solder. if you get a few shorts don't worry just keep on going down the line of pins. you should be moving a shiny looking blob of solder quickly down the row of pins it will solder them all along the way.

Then to remove any shorts (you will get the odd one or two) - ADD more flux and MORE solder with the iron and wipe down (away from the device) the bridged pins the short will just wipe right off along with 99% of the blob of solder on you'r soldering Iron.

Remember to clean off the tip and do the next line of pins. (adding the flux first)

I can do very fine pitch 200pin SM connectors or SM micros in just a few seconds using this method.

Good luck, don't mess about with 'dry' solder for too long, add more flux and solder and keep things moving quickly, the solder will do all the work for you.

Yes the Flux pen will be fine, it's the same as the one I use.

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[richrap.blogspot.com]

Thanks for that rich. Do you clean the flux away afterwards? If so, what do you use?

been practising on an old printer board I ripped apart. Been raising the traces so still need some practice

Off to bed now.

... i've tried with bigger tips and flux too, what was faster, but with shorts and i had to clean away the flux and carbonized residues after soldering, what was extra work.

But now my favorite method is working with the smallest and shortest tips i can get for the specific pens, microscope and only the solder embedded in the 0.3mm or 0.5mm solder-wires.

As i'm trained with some even finer micro-work, it's no problem for me de- and re-soldering fine-pitch SMD's, but this can be different for others, so you have to try your best/easiest methode ...

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Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

You can clean with solvent or water. Just make sure you dry the board if using water!

As Nophead stated if you want to remove a SM device cut it out, don't try to unsolder it.
Usually the only real reason for removing a SM device from a pcb is if it's faulty.

Good luck.

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[richrap.blogspot.com]

water

my goodness - I would have thought I would want to keep that well away from the electronics.

Does that mean that the electronics are resistant to the occasional dunking provided they dry completely before being powered?

Using water certainly would be better than spending loads on some commercial cleaner

Cheers

... pure alcohol (isopropanol) is perfect for cleaning ...

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Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

It's quite normal for electronics to be cleaned in water, many fluxes are designed to be water soluble.

But it's also normal for no-clean flux to be used so no further processes are required after flow-soldering.

You can just use a small stiff paintbrush and water or as Viktor stated IPA - IPA cleaner

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[richrap.blogspot.com]

The big problem with water is impurities. Distilled pure water is no where near as conductive as standard tap water.

The other thing is if it gets into the PCB material, it takes a while to dry out. You want to do this at a slightly elevated temp (40-50 Deg C), so the water evaporates before it reacts with anything and oxidises it. Not too hot though, as you don't want to damage anything.

I've had many electronic parts get wet, and after a good dry, they tend to work 95% of the time. If they still don't work, I use isopropyl alcohol, as there is undoubtedly still some residue somewhere holding in water (glue, muck, tomato sauce, wine, soft drink, etc). The Isopropyl clears away the water and the residue, and then the isopropyl evaporates.

I think "no clean" fluxed are named so because they require no clealing, thus i only work with those and i personally dont really care if they leave small traces: because my electronics look ugly enough even when they are perfectly clean

The ones that require washing are more agressive fluxes, i would say it shouldnt be needed normally. Afaik they clean with ipa or water, mostly depending if they are organic or not. At least i havent felt the need for such so i limit myself to no-clean fluxes. Only used some much powerful metal flux for direct metal soldering for some mechanical stuff, but not in electronics.

Further more, i would say that the ones that have very high viscosity (like the "gel" ones) seem to work out better than the "watery" type ones, but that may be just me.

Electronics are weird. Strangely sensitive to a bit of static, or powering up in the wrong sequence, but strangely durable in other ways!

I forget what specific device it was for, but running the circuit boards through the dishwasher turned out to be an excellent way to get them clean.

Make sure there's no leftover food bits before you start a load, and let them dry a day or two before plugging them back in. And like dishes, if your only doing one or two its probably easier to just do them in the sink.

We DID have to be more cautious with some of the capacitors, I can't remember which ones. Recent caps should have no problems though.

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I'm building it with Baling Wire

Arghhh

I have lifted a trace while removing the driver chip. Cutting the legs worked well except I obviously put too much pressure on one of the legs... Please see the attached image - the lifted trace is highlighted in yellow. fifth in from the right just under a little hole which it looks like it leads to...



Now I have read about a 'green wire' fix. ie. soldering a wire to the leg and the other end to where it is supposed to go... question is, where do I solder the other point to? Could I simply solder it into the hole or is there elsewhere it should go?

Also, if it is to the hole, would it be ok for the wire to run around the top of the board and enter the hole from the bottom as going directly will prevent the chip from laying flat and would raise a host of other problems...

Further inspection leads me to believe this is pin 20, the DIR pin. That is based on the pin out diagram in this document.

The schematic is rather confusing and I guess it does not map to the physical pin positions for neatness of the diagram? The schematic does seems to take it to pin 4 of the interface with the motherboard...

Please advise.

Thanks

Edited 2 time(s). Last edit at 11/15/2010 05:29PM by AgeingHippy.

i guess you couldnt open the board file
so i exported an image for you from the board file, maybe it helps you
top traces are red, bottom are blue

Edited 2 time(s). Last edit at 11/16/2010 05:04AM by NoobMan.

magic

Thanks Noobman. Did not even know about that file.

So it seems I can simply connect the leg directly to pin 4 of the interface as shown by the board.

I must say, I know nothing about electronics but examining the board last night and comparing it to the schematic I learned that the little holes are where the traces go from one side of the board to the other.

Well, let's hope that I can fix it succesfully...

Yes.

I think that is called via. From the latin "road" or smth like that. These connect top and bottom traces.

Just make sure you dont get any shorts with the wire. I do that myself alot, since im half blind and half brained

Also there is a toner transfer version, single sided (sort of), of that board here [www.thingiverse.com] However that requires specific tools and consumables.

Edited 3 time(s). Last edit at 11/16/2010 05:38AM by NoobMan.