ABS Bosch 5.3 Module

Discussion in 'General Technical Questions and Answers' started by N3IDT, Aug 4, 2008.

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  1. N3IDT

    N3IDT Ham Member QRZ Page

    Unfortunately you can't solder aluminum like copper. I replaced the aluminum with a small copper wire. I'm afraid that you pretty much have totaled the board from the sound of things. I only compromised one via and used silver conductive epoxy to repair.
    http://www.ecstuning.com/
    This is a company that sells vw and passat modules only. You have to match the number stamped on the top of the valve body with their models. They sell the module only for about $500 depending on the model. If my unit fails again, I won't even bother to open it: I will go right to this place.
     
  2. AUDI20V

    AUDI20V QRZ Member

    The Russian website says to add a new wire overtop of the aluminum wires and they solder it directly to the aluminum wires. They have a picture of it so obviously there must be a way to do it. Is there a special solder they use?

    So what you did was remove those two aluminum wires and replace them with a single copper wire? How did you re-solder it to the board side? I couldn't get that pad to take solder even after scratching it up. Eventually I got it to take some solder, but then when I put the new wire down on it, the pad came up!

    Why would it not be possible to put a new pad down here with conductive epoxy like you did for the wirebond pads?
     
  3. N3IDT

    N3IDT Ham Member QRZ Page

    I initially tried soldering to the pad and it did not seem to want to take solder. I used the epoxy and the first thermal cycle on the unit caused the epoxy to lift. I got more agressive with cleaning the pad and achieved a small solder spot between the two aluminum wire stubs. I soldered a 30 ga copper wire and then worked some epoxy over and around the stubs. This seems to be holding. The factory joints are bonded ultrasonically so they can attach any kind of material to those pads. I used to bond aluminum wires to gold pads in watches back in the 70's. Technology hasn't changed much. I think this pad carries the power to the board to operate the logic and the valve coils. Unless a really secure connection can be made to the all the via's under that pad, the valve operation will be screwed up.
     
  4. AUDI20V

    AUDI20V QRZ Member

    There are commercial outfits that repair these units quite successfully, what are they doing? It does not look like removing the aluminum wires is a viable option as it will result in the lifting of the main pad when attempting to solder to it. The point of failure for these Al wires is on the gold contact side. There must be some way to beef up this connection right here and leave the pad/substrate side totally alone. So you're saying there is no way to solder to the aluminum? The Russians clearly have a picture of a copper wire soldered right to it. Any idea how they did it? Obviously the best thing to do would be to just leave the Al wires in place, solder a copper wire to the back of the gold contact, then attach that wire across the 2 Al wires. Can it be done as the Russians have?
     
  5. N3IDT

    N3IDT Ham Member QRZ Page

    I looked at the Russian picture again. I think they managed to get some solder to stick to the pad area between the 2 wires. This area may be different unit to unit depending on the spacing of the wires. I have read several reports that the "commercial" places have had failures after repair, also. Unless they can do ultrasonic bonding, they have the same problems. As I said in an earlier reply, my microscope was seeing double and that helped an otherwise steady hand to whack one of the gold wirebonds. I think these "commercial" places have gone thru a few failures and have come up with the right cleaning and soldering method. Those pads were only designed for ultrasonic welding, not soldering and obviously, as you and I found out, come off pretty easily. Fortunately, my pad was next door to the al pad and had only one via. I think another trick is to make a stress relief loop so that thermal and vibration do not stress the connection.
     
  6. N3IDT

    N3IDT Ham Member QRZ Page

    It's late and I just had a BF (brain f^^t). The two power wires break at the gold connector and not on the board. How to "solder" aluminum to copper??
    Lift the broken AL off the connector strip. Solder a copper 30 ga and extend it out. Carefully wrap the AL around the CU and bond with silver epoxy. Maybe too much mass in vibration. Bottom line. This module is poorly designed and too high priced. My repair is still holding even after Fay rolled thru Jacksonville and flooded the Passat inside. That's another issue by itself. I do have enough humility to come back and post if and when the repair fails. After all, Thomas Edison had many failures.
    P.S. Thomas was born exactly 100 years before me. Exactly!
     
  7. AUDI20V

    AUDI20V QRZ Member

    So you're not actually soldering them together at all, but just sticking them together with silver epoxy? What is the name of the epoxy you are using? Another thing I was trying was putting a big glob of solder on the gold pad and then sticking the Al wires into it. Even though the solder may not bond to the Al, it is completely encasing it. No idea how long that would hold though. Maybe a combination of both methods would work good.

    Here is the picture I was talking about: http://passat-b5.ru/remont/abs/11.jpg

    Clearly they have soldered directly to the Al!! Any idea how it was done? I am going to try and email them. Hope my Russian is up to snuff!
     
  8. AUDI20V

    AUDI20V QRZ Member

    Also,

    Do you think it would be possible to reattach the main Al wires pad on the substrate side using solder paste? Could I just put down some solder paste to cover all 6 of the vias and then put some copper on top and soler the new copper wires to it?
     
  9. N3IDT

    N3IDT Ham Member QRZ Page

    I did some searching and there are some types of solder fluxes that will allow regular solder to bond to aluminum. In my case, I think I got solder directly on the pad between the wires. The BF I described was in case someone else wanted to try without having to solder to the pad; they might be able to wrap the copper and aluminum together and then coat with the epoxy. The picture you posted is indeed from the same series of pictures I used before attacking this. It is the only published fix I found on the net. The epoxy is from Mouser Electronics and the P/N is 590-8331-14G for $23.95. It is a two part epoxy in tiny syringes and has a pot life of 5 min so you have to work fast. I made very small mixes half the size of a pea and let it dribble off a dental tool on to the joint. There was no way to dab it on without getting too much on the pad. It flows out after application so only a very small amount can be used.
     
  10. AUDI20V

    AUDI20V QRZ Member

    I would recommend not touching the pad if all possible given how it lifted up on me. Do you think that the wrap and epoxy method would be reliable? It would allow you to not have to solder to the pad. In fact, couldn't you just cover the Al wires on the gold contact with the stuff where they are broken and avoid soldering altogether? Do you think that the epoxy would hold up in this application?

    I certainly would feel more comfortable soldering. I was able to get the Al wires to take lead solder on another module, but only after trying for a long, long time. Where did you find the special aluminum-copper solder? I searched and have not found any. I will buy some of this and report back results if I can find some. I emailed the Russians and am still awaiting a reply. Although with my Russian I might have asked them if I could order a giraffe pizza with extra stoplights.
     
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