Originally Posted by Sir Alex of Yotto

There was a previous comment that even though cracked/failed solder joints in our ABS modules are a very common failure, no one seems to be trying to find the reason for this failure. Not so...

Several people have guessed that it was a new type of lead-free solder, that the solder joints were poorly done at the factory, that an insufficient amount of solder was used, etc. Generally, no, these reasons are not correct.

Have you noticed that it is always the same two solder joints that crack and fail? There hundreds, if not thousands, of solder joints (small-and-large inclusive) on the printed circuit board in the ABS module--but only the two large, power supply solder joints seem to fail. Why just those two? Why not the others?

It's pretty simple, really. The cracked solder joints are a mechanical failure, which then cause an electrical failure. The failure of the solder joints is caused by movement, mechanical movement, of the two power pins that are soldered to the board.

There are two separate electrical connectors to the ABS module: The large connector with 25 electrical pins (21 pins and 4 blade connectors), and the power connector with two pins.

The large connector, being larger, is held more firmly in place due to its sheer size, large electrical pin count, and a more substantial locking mechanism; while the power connector is much smaller, and only has two pins. As the car and engine bounce and vibrate, the larger connector is quite stable and secure, and those electrical pin-to-PCB solder joints are stressed little. But the smaller power connector is more affected by this constant vibration, and as the power connector vibrates, so vibrate and flex those two power pins, and that flexing movement is transferred to the solder joints.

Those two solder joints are flexed so much that eventually the solder joints begin fail with stress fractures; at first it will likely be intermittent ABS warnings as the solder electrical connection begins to make-or-break, sometimes it's connected, sometimes it's not. This is why some people sometimes experience ABS failure based on temperature, as the solder expands or shrinks due to temperature changes.

Eventually, the make-or-break nature of the cracked joint fails completely, and you have a constant ABS & Traction Control failure.

FYI: Attaching electrical pins for a connector directly to a printed circuit board (PCB) is usually a bad idea, especially in anything that moves and/or vibrates, and many electrical failures are caused by exactly that (movement of the connector causing failure of solder connections).

Reflowing (re-soldering) these joints will cure the problem (as long as you are careful and don't cause any others; see below), but not solve the problem. Wait long enough, and a reflow of those solder joints will fail again (but it may take a long time, but the cause of the problem is still present).

I added extra solder besides just reflowing what solder was already present, to make the joints a bit stronger. That will probably last as long as I own the car. Probably. It took about 13 years for the original solder joints to fail...

A (likely) permanent fix would be to reflow the solder, and, to add a short piece of stranded electrical wire from the printed circuit board solder pads to the end of the pin itself, so power can flow not only through the regular solder joints, but if they should crack and fail again, the added wire at each pin will still allow power to flow to/from the module (see illustration).

In other words, the short length of added wire duplicates the solder joints themselves, but will not be susceptible to the same mechanical failure, because unlike the solder joints themselves, the wire --can-- flex with the vibration, so the solder at the ends of the wires won't crack and fail; the wire is a backup to the fixed solder joint.

(Also, it is a good ideal to add a small amount of electrical flux to the solder joints before the reflow (remelting), or you risk producing a 'cold' solder joint which may be unreliable.)

It's important not to cause additional problems when making the repair. Personally, I chose not to crack open the entire case; all of that additional cutting and sawing increases the likelihood of causing additional damage to other components (at least for me, 'cause I'm such a klutz), so I drilled a hole roughly 15mm in diameter directly opposite the two power pins: the pins pass straight through to the PCB, where you'll find the two solder joints needing the reflow (only one of my solder joints was cracked, but that's all it takes to kill the module, as both connections must be good for power to flow).

Also, try to observe ESD (Electro Static Discharge) control procedure; ground yourself and your soldering iron before handling the module and soldering. Don't touch any electrical pin, component, or solder joint on the module unless you have discharged yourself of any static buildup. This is especially important if it is cold outside and the air is dry; also if you have been walking on carpet or doing any other activity that tends to build static charge.