Do the heatsinks on a A4988 make you nervous?

I look at the heatsinks on a cheap A4988 board and they make me nervous. The sit very close to some of the passive components on the board. Does this bother anyone else? Any risk of them shorting something out?

I have has some short due to the heatsinks. If you choose to use them you must make sure they are secure. I am running 1.5 amp motors and they don't even warm up the drivers so I didn't bother putting on a new heatsink. Good airflow can make all the difference.

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animoose
I look at the heatsinks on a cheap A4988 board and they make me nervous. The sit very close to some of the passive components on the board. Does this bother anyone else? Any risk of them shorting something out?

Consider that the sink has thermal tape on the bottom, so while it is close, it isn't necessarily conductive. And yes, I spent quite a bit of time on this, and still made sure to align them so as not to be over the higher parts on the module.

- Tim

Heatsinks placed on top os a A4988 chip are not very effective. These chips are designed to be cooled via the thermal tab underneath and thence by the PCB. The plastic case of the chip is not a good thermal conductor.

Unfortunately, stepstick PCBs are too small to do a good job of conducting the heat away. However, you can get improved boards with 4 layer PCBs that do it better, such as the Ice Blue stepsticks from T3P3. All-in-one controller boards do a better job of cooling the chips because they have more board area.

There are a few stepstick designs that put the chip on the underside and the heatsink on top, with thermal vias to conduct the heat from one side of the board to the other. Those should work quite well, especially if you use a fan to blow air on the heatsinks.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

As mentioned by gmckee and dc42 above, you can do without the heatsinks as in the A4988 and DRV8825 they are practically useless. On the other hand, active cooling (i.e. a small fan blowing cool air over the MOSFETs and drivers) should really be compulsory on every RAMPS setup.

Just buy $1000 drivers that are sized to handle 100A without cooling!

Or buy a system with cryo-coolers on it.

People want cheap components with ridiculous specs

100s of A4988 driver out there running without heat sinks without any problems

If it does get too hot --- get another one for $5

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cozmicray
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100s of A4988 driver out there running without heat sinks without any problems

If it does get too hot --- get another one for $5

@cozmicray

You are not getting the real issue here: overheating during printing does not damage these driver chips, because they shutdown before they reach a critical temperature.

The point is that when they shutdown during a print and ruin it, you have essentially wasted a lot of time, electricity and filament for nothing.

Replacing them does not solve anything at all. You just have to cool them properly. A small 12V DC fan costs $1, much less than the value I put on most of the parts I print on my 3D printers.

Edited 1 time(s). Last edit at 08/02/2015 04:57PM by AndrewBCN.

The chip is designed to thermal sink thru the bottom of the chip.
I hope the designers of the A4988 considered that.
Users try to pull too much current thru these drivers.
or diddle with them when they are ON.

Fan a good idea.

Use the proper motors, don't draw more than spec
and there will be nirvana --- well at least driver won't be a problem.

There are thousands of things that ruin prints.
If you haven't had to re-print and article 5 times (with an 8 hour print time)
-- you are not 3D printing, or truly blessed