Circuit Board Issue for Kid's Ride-on Electric Car

Thread Starter

painvestor78

Joined Nov 30, 2015
5
My daughter (4 yrs old w/special needs) absolutely loves driving her brother's electric car (Rastar Ferrari F12), but the car stopped working recently. After opening up the underbody, I located what I think is the primary circuit board. I was able to re-start the car by pushing on the silver metal piece in the center (see below picture) and the car then worked again for a couple of days. Our driveway is pretty bumpy, however, and when the car stopped working again recently I noticed that this silver metal piece (which is connected to the board by three small pins) is loose. I have been unable to pop it back into the board so that it is stable. I would greatly appreciate help from the community as to 1) what is this silver metal piece 2) any ideas as to how to fix this issue and get the car working again? FYI, this Rastar F12 is a ride-on that also has RC capability. I also know that the blue/yellow wires in the picture are coming directly from the car's battery. I have also included a diagram below from the car's user manual. Thanks!
Diagram.jpg

photo (23).JPG
 

Dodgydave

Joined Jun 22, 2012
8,594
Looks like an heatsink, with a device possibly a regulator or power transistor bolted on the side, it will need resoldering, take a photo of the device and also of the circuit board copper side.
 

Alec_t

Joined Sep 17, 2013
10,609
I agree, a heatsink. No apparent mechanical fixing for it. If the semiconductor bolted on the side is the heatsink's only attachment to the circuit board it's not surprising there's a dodgy connection. I'd try to add some extra physical support for the heatsink, or the problem could reoccur.
 

mcgyvr

Joined Oct 15, 2009
5,394
Yep.. ^^ redo the probably fractured solder joints
and slap some hot glue (caulk would work fine too) on the heatsink to secure to the circuit board and protect the IC from future vibration
 

ian field

Joined Oct 27, 2012
6,539
Hot glue + heatsink ? Hmmm, I'd go for epoxy instead.
Epoxy is hard to remove and start over if the first try doesn't get it, hot melt glue is useless if the heatsink gets hot.

Sometimes there's sufficient spaces between the copper track to make holes for zip-ties.
 

mcgyvr

Joined Oct 15, 2009
5,394
Hot glue doesn't start to "solidify" until around 100-120 deg C ..
If that heatsink at the end furthest from the IC is 100 deg C you've got other problems as the IC's junction temp would over its limit already
 

ian field

Joined Oct 27, 2012
6,539
Hot glue doesn't start to "solidify" until around 100-120 deg C ..
If that heatsink at the end furthest from the IC is 100 deg C you've got other problems as the IC's junction temp would over its limit already
If the heatsink gets that hot - there may also be a problem with epoxy, I think it starts to degrade at about 80C.

Speaking of which - hot melt glue is semi-plastic at a lower temperature. might not hold in a ride on toy on a bumpy drive.
 

mcgyvr

Joined Oct 15, 2009
5,394
If the heatsink gets that hot - there may also be a problem with epoxy, I think it starts to degrade at about 80C.

Speaking of which - hot melt glue is semi-plastic at a lower temperature. might not hold in a ride on toy on a bumpy drive.
yes.. its not optimal.. but its a kids toy with no vibration dampening on it at all
 

ISB123

Joined May 21, 2014
1,238
I'd carefully drill 2 holes while watching that I don't damage the traces,after drilling I would pull a plastic tightening strap through 2 holes that were just drilled and then tighten it across the heatsink.
 

Thread Starter

painvestor78

Joined Nov 30, 2015
5
Thanks everyone for this information. It definitely makes sense that this part is a heat sink, and you are correct that it is only attached on the one side, so it is not surprising that this piece has become dislodged given the bumps and the car’s lack of any shock absorption.

Attached are a few more pictures of the device itself as well as a picture of the other side of the circuit board (left middle side of this circuit board picture corresponds to the top in the original picture).

A couple of additional questions since I’m a newbie to all of this:

1) I guess I need to get a soldering iron. If anyone is willing to give me basic instructions as to how to re-connect this piece to the board so the circuit is fixed, that would be much appreciated. Am I correct that I don’t need any new parts but just need to re-solder the existing piece? Since I have not soldered anything since I was in high school (now 37), no explanation is too basic J

2) The part about using a zip-tie to secure the heat sink so this doesn’t happen again makes sense. I imagine I just drill two small holes in the circuit board where there are no existing circuits (by looking at the front and back of the board? What about super-gluing the other side of the heat sink to the board instead, or does that have similar issues to the other options (epoxy, hot glue)?

Once again, thanks for all of the help.

photo 1.JPG photo 3.JPG photo 4.JPG
 

ISB123

Joined May 21, 2014
1,238
Super glue is too weak and wont take the heat well.You wont be able to drill the holes since the pcb is too dense.You could buy a very long zip tie and then just tighten it across the pcb so it holds the heatsink.
 

markdem

Joined Jul 31, 2013
113
I would first fix that bad solder join. To fix it, just hold the soldering iron and a little new solder on each pin until it becomes one again. Then use some hot glue on the heatsink. I can confirm that this works "ok" as I have done it as "repairs" before too. Not ideal but as motioned above the device will probably shutdown or be destroyed before the glue melts.

Have fun
 

BReeves

Joined Nov 24, 2012
410
I'm in the resolder and hot glue camp. If it gets hot enough to melt the glue it will have worse issues than just melting the glue.
 

Thread Starter

painvestor78

Joined Nov 30, 2015
5
Great, thanks all. My soldering iron and hot glue gun are on order and will arrive on Friday. I also have some existing zip ties so will zip tie around the whole thing as well at the end. I'll post results once repairs have been made (hopefully successfully). To confirm, I am only soldering the three pins on the one side of the board, correct? (i.e. I don't have to solder anything on the copper side of the circuit board).
 
Top