I didn’t think I’d be following up so soon after my last post exploring how to disassemble an LB7 FICM and examining the reparability since it was a failed unit. That FICM ended up being damaged beyond repair due to multiple layers on the PCB getting burned by the leaking electrolyte. This observation lead me to recapping my working FICM shortly after realizing that failures should be avoided at all costs. There are numerous people on the internet offering reman FICM’s at a substantial cost, but my searches revealed no information about reconditioning FICM’s on your own. The purpose of this post is to document how I overhauled my FICM to help others that may want to take on this task on their own. Hopefully this helps.
Tools and parts needed to recap the LB7 FICM:
- T15 Torx driver
- Flat blade screw driver
- Small 90 degree pick
- >60w soldering iron
- Desoldering iron link to one I used here
- High quality solder
- Sharp Hobby Knife
- Gasket Scraper link to one I used here
- Isopropyl Alcohol
- Qty 4: 180uf 63V Panasonic Hybrid Aluminum Electrolytic Capacitors
- Thermally conductive glue
- Permatex Gray RTV
Disassembly

The FICM I removed from my truck was much cleaner than the damaged one I had disassembled for the previous post. As a result, the four T15 screws that need to be removed are much easier to see in this picture:

Once the screws are removed it’s time to remove the cover. The cover is sealed to the cooling plate that will require some effort to separate. In order to get the cover off you will need use a flat-blade screwdriver to lightly pry the cover off of the cooling plate. On the connector side of the FICM, at each corner there is a gap between the two halves that allow you to get leverage to pry the FICM open:

Once the sealant starts to let go the cover will pop right off. Once the cover is removed you can examine the board. Thankfully, mine was in good shape with no signs of leaking electrolyte. Since there’s no record of failures of the 100V film capacitors or the 40v polymer capacitor at the bottom right, the only capacitors I will be replacing are the two pairs of electrolytic capacitors nearest to the connector on the board.

Now the fun part </sarcasm> lifting the board off of the cooling plate. The board is adhered to the cooling plate with a thermal transfer silicone. Much like removing the upper rocker cover on the LB7, the key here is to get a small spot in the silicone to lift and the rest will come right up. In my last post I was able to use a small 90 degree pick to start lifting the board from the corner. That did not work well for lifting this board. I ended up going against my own advice in my last post and using the connector to lift my board off of the cooling plate. By grabbing the cooling plate and using my thumbs to lightly push up on the connector I was able to get my board to start lifting. Once I got the board to lift it peeled right off of the cooling plate. Once the board has been removed from the cooling plate you can bring it to your work bench to start the desoldering process.

Desoldering
By this point the solder on these board is over two decades old. It will have some layer of oxides on it and will require some amount of work to get the solder to flow properly to remove. One interesting issue I ran into on both this board and the board from the previous post is that there are multiple layers of large traces connected to these capacitors. As a result, my 40 watt Weller iron had difficulty melting the original solder without the heat getting wicked by the traces. This situation is less than ideal because now you’re heating components and not the solder. After running into this issue, I highly recommend using at least a 60 watt soldering iron to reflow the old solder and solder the new capacitors to the board. Thankfully the desoldering iron I used was able to fully melt the solder quickly and remove it. Before going any further, lets identify the points we’re going to rework and desolder. Also now is a good time to use a hobby knife to slice the silicone between each pair of electrolytic capacitors we will be replacing.


In order to get the solder to flow well enough to get a clean desolder I started by melting fresh solder into the existing solder joints. Once I got a little bit of solder to flow in I got onto the joint with the desoldering iron to suck out the solder. Since my soldering iron was inadequate for this task the desoldering iron only removed about half of the solder from the joint. I then had to flow more fresh solder into the joint to get to the solder that didn’t get reflowed from my first attempt. It took about three reflow / desolder attempts per joint which is less than ideal as it applies too much heat to the board, traces, and solder mask. Using the right tools here will prevent damage from overheating the board and / or surrounding components. Be absolute sure you have a clean desolder job before attempting to remove the capacitors. Any attempt to pull on the capacitors with even the slightest amount of solder still affixing the legs to the traces my result in pulling up a trace and turning your one hour job into a five hour job. Once the old capacitors are desoldered and removed, thoroughly clean the pad and surrounding area with isopropyl alcohol. If your board has some leaked electrolyte on it, you may also want to neutralize that with a basic substance before cleaning with alcohol.


Install New Capacitors!
The hard parts are over. With the board all cleaned up you can install the new capacitors. These capacitors won’t fail like the old ones and should outlast the vehicle. The new capacitors have a black dash on the top to indicate the negative leg. These all face away from the connector on the board. Even when soldering in the new capacitors I found my 40 watt Weller wasn’t up to the task. Again, using a good 60+ watt iron here will properly flow the solder in the joint the fist time. I ended up having to use my desoldering iron to flow the solder into the joint once I got it on the board. Once all four caps are soldered in, it would not be a bad idea to apply some non-conductive silicon to each pair, as they were before. You can use the thermal glue here we’ll be using to reapply the board to the cooling plate later on.

Reassembly
Prior to reassembling the FICM, we need to clean the remaining silicone off of the bottom of the board and the cooling plate. For cleaning the board and cooling plate I used a tungsten carbide gasket scraper. When cleaning the board itself, be sure not to put any cuts into the board itself. Unfortunately I forgot to take a picture of the cleaned up cooling plate, but make sure the surface that bonds to the board is clean and flat. Isopropyl alcohol was used after all of the silicone was removed to do a final clean on the bottom of the board and cooling plate were new thermal glue will be applied.

Reassembling the FICM will happen the reverse of disassembly. There’s no way to properly align the board directly to the cooling plate. Instead, the cover has the alignment bumps that align the board. Note alignment bumps in the cover circled in red below. Now would also be a good time to inspect the vent cover. This should flow a little bit of air, allowing the internal components to breathe.

I do not know what was originally used to seal the case to the cooling plate, but I also know it’s not going to come off and trying to get it off will likely cause more damage than what the effort is worth. When reassembling my FICM I used a very small amount of Permatex Gray RTV to go over the grooves where the old sealant was. I started by laying a small bead in the connector area of the cover. Once the connector area had a small bead of RTV I placed the FICM board into the top cover, being sure the connector sat down in the sealing groove and the board was aligned with the pins in the cover.


Once the board was placed into the cover it was time to apply the thermal transfer glue and a small bead of RTV around the rest of the sealing surface on the cover. After doing some testing on the bench, I found the GENNEL thermal glue to be quite effective at heat transfer and maintaining a good bond. This is essential as the board needs to be well bonded to the cooling plate with good thermal transfer characteristics to keep the driver FETs cool. The video below shows a test I did prior to using this glue to verify the heat transfer. A thermal camera was used to observe a heat sink glued with the GENNEL glue to the hot side of a Peltier device. When energized, the heat sink thermal image was observed to make sure it was rising proportionally across the surface of the heat sink without the surface of the Peltier getting considerably hotter than the heat sink:
Since the glue is non electrically conductive I was pretty liberal in applying a large bead to the thermal transfer surface of the board. I did not care to spread it across the surface. When cleaning the board with the carbide scraper I found the board is not perfectly flat. By applying the bead and allowing the glue to spread when the board is pressed to the cooling plate it will fill in the uneven voids between the board and the cooling plate.

Once the thermal glue and RTV is applied it’s time to put the cooling plate on. Leaving the cover and board assembly as it is pictured above and line up the cooling plate with the screw holes and carefully lower the cooling plate to the board and cover, ensuring proper alignment the whole time. Once the cooling plate is set on top of the cover and board the screws can be installed. Slowly work the screws in going cross-corner each time you move to a new screw. Using this method will allow the thermal glue to properly spread without applying too much stress to the board or components as the glue spreads. It should take about two minutes of this progressive tightening to get the screws to the point where they are fully tightened. Once the FICM cases are tightened together clean up any RTV that squished out of the case halves or connector area. You are now done with reassembly. You may immediately reinstall the FICM, but allow 24 hours for the thermal glue to cure before driving the vehicle. Trying to drive the vehicle before the glue is cured my result in improper thermal transfer and overheating of the driver FET’s.


Hope this helps anyone who may want to attempt to recap their LB7 FICM on their own.




















