Component repair, is it possible to do low level repair on modern motherboards?
Disclaimer - This is a tutorial and is not a substitute for a formal
Technical repair class that will teach you the art of troubleshooting, soldering, and
general safety. This web site and the owner are not responsible for any damage
you may do by following these techniques.
Note: You should do your testing and
to attempting the element repair of motherboard or you may have to do it again.
Component repair of motherboard, is it feasible on modern motherboards and
First a little description of a motherboard -
A motherboard has all the support chips for the operation
of the processor.
Simple to say, how hard to explain?
So let's simplify the motherboard down to some components.
- Support chips
- Clock chips
- I/O chips
- Serial port (includes the USB chips)
- Parallel ports
- Video (embedded)
- Sound (embedded)
- NIC Wired (embedded)
- NIC Wireless (embedded)
- Ports for the above chips
- Power supply circuits
- Resistors, caps, transistors
- The copper wires you see are called a traces (the thin
copper lines that are etched on to the PCB)
Now let's look at the make up of the physical properties of
Modern motherboards are made up of layers, some up to fifteen layers (high
end servers and workstations). Each layer of PCB (Printed Circuit
starting from the lowest or bottom layer has a series of traces, then the next
layer of PCB with a series of traces, then the next layer of PCB with traces,
and so on to the top layer that is why component repair will be difficult.
Once all the layers of the motherboard have the traces then each one is
precision drilled for the pass through that are pressed in the completed
motherboard. Then all the layers are stacked and a process (some are
proprietary) is used to compress and bind all the layers together.
Then all the pass through are pressed in the holes that were drilled earlier
in the process. Some motherboards have layers that the pass through is put in
before final assembly because they only go through two or more layers but not
all. Once this process is complete then the motherboard is sealed.
The next step is to bind or solder all the components on the mother board,
the smaller components such as support chips, resistors, caps, transistors (yes
they still use transistors), and diodes.
The process uses wave soldering where the motherboard is subjected to liquid
solder that adheres to the bare copper where the sealant is replaced with solder
flux. Then the next step is putting on all the micro components such as the list
above, this is done with robots that do what is called pick-and-place, then the
solder under the component is melted and the component is secured.
The next step is non micro components such as the processor socket, the
memory slots, add on card slots, the peripheral connectors (IDE, SATA, Floppy
Drive, external connectors for keyboard, network, usb, sound, and firewire) and
so on. Also any other items such as caps, switches, and other items.
The motherboard is complete, next the motherboard is tested, some
manufactures use a jig that the memory, processor, and the peripherals are all
simulated. Other manufactures use actual components to test the motherboard. The
motherboard is connected up to a test station then powered up.
How long and how rigorous the motherboard is depends on the manufacture. The
main thing is that the more rigorous the testing the less returns from dead
on arrival (DOA) when the motherboards are sold.
"Component repair of main board, also know as low level component repair,
removal and replacement of failed devices."
Troubleshooting done? Ready to do the component repair of motherboard?
Ok, to do component repair you have the following tools:
- Variable wattage soldering iron (minimum twenty-five watts)
- Small tips for the soldering iron (as small as 1/16th
of an inch)
- Heavy duty heat sink (Must absorb up to 300 degrees F)
- A good magnifying glass
- A strong light
- Various electronics tweezers (angled and straight,
spring loaded open or closed)
- Desoldering vacuum
- Desoldering copper weave
Now do you have the experience using the above list?
Any one can learn how to solder, takes a little practice to
keep from melting the component and burning your fingers. What I am talking about
is recognizing when the solder starts to melt, removing the heat and the
component at the same time. Then heating the solder to the point where you can
put the new component back with out destroying it?
Here is something a lot of people don't know "the
motherboard will start to degenerate when the
temperature reaches 425 degrees F".
That is the binding that the manufacture used when the motherboard layers were
pressed together will start to separate, if the separation happens to be where
there is a pass though then the motherboard is effectively destroyed. That is
the reason for the heat sink that will absorb the heat that will spread while
you are soldering.
If you are replacing a large component such as a cap or a
resistor or a socket then it is fairly easy. Just keep the heat from building up
and causing the layers or traces from separating. But the small components are
the hard part.
To remove a micro resistor or cap then you have to insure
that the heat stays local to the spot you are working on. You only apply the
heat to the failed component, and this is important, you only heat an area
twice. Once to remove the failed component and once to solder the new component.
Note: If you have to remove a part and replace it a second time after
removing the old part clean all the old solder and flux off the PCB area you are
working in, then apply a small amount of new flux to the contact pads or pass
through holes. New flux will allow the solder to flow easier with less heat. Old
flux will build up and create a heat barrier to the solder joint, making for a
bad or "cold" solder joint that will fail.
That takes care of the easy part. You know the component
failed by seeing it is brunt, or in the case of a bad cap it exploded. Or you
did a test and found the failed component by lack of voltage or resistance.
Now comes the hard parts-
How do you repair a trace that has lifted from the
Answer: You can't, once the trace lifts the only thing you can do
is to "by pass" the part that has lifted with a thin gage insulated wire.
You would do this by finding two points where the trace is
wide enough to accommodate the small gage wire.
I will warn you do not use a
pass through to put the wire in. Why? The heat that the solder will produce
cause the pass through to separate from the traces inside the
even cause the motherboard to "bubble" around the pass through.
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You would use an Exacto knife or thin razor blade knife to careful scrape off the sealant. Cut
the bad trace just past the places where you scraped of the sealant. Heat and
apply solder to both ends of the wire only. Apply flux to the trace where
the sealant was removed.
Once the wire is tined then put one
end of the wire on the scrapped trace and apply heat - just long enough to melt
the solder, be careful with the heat the trace is all ready exposed and will not
take much to separate it from the spot where the sealant has been removed. Solder both ends, then test the repair with an ohm meter. If it tests good then
use some fingernail polish to reseal the solder points, you could use the polish
to cover the wire and seal it to the PCB also.
You can do low level component repair but I will warn you
that a component failure due to the component material failure is low. Something
caused that component to fail, heat, voltage, or amperage above the component's
design specifications. You need to test further upstream before completing your
repair or you will either have a lot of smoke or a fire.