Why did my CPC module fail? How do I fix it, and 3 common mistakes to avoid.


What is the most common fault with CPC4 modules? The short answer is Cracked Solder Joints on the BGA. But what does that mean?
Let's break down this jargon into something that makes sense.

What is a BGA

CPC4 modules use a processor chip which is connected to the circuit board via a Ball Grid Array otherwise known as BGA. Instead of using metal legs or pins, the processor sits ontop an array of solder balls such as shown in the picture. The solder balls unfortunately are suceptible to microfractures after being exposed to too many thermal cycles.

Thermal Cycles

A thermal cycle involves subjecting a material to alternating periods of heating and cooling. The CPC4 module, for example, undergoes thermal cycles when it is in use and not in use. When electricity flows through the device, it warms up and expands due to thermal expansion. When the truck stops and the device is no longer in use, it cools down and contracts due to thermal contraction.

Due to a difference in the processors and the circuit boards CTE (coefficient of thermal expansion) the circuit board expands at a faster rate than the processor which creates stress to the solder balls and thus microfractures over time.

How to fix a CPC4?

(If you need our team to service your CPC4, we have a promotion at the bottom of the page.)

To fix a CPC4, you must renew the broken bonds (solder balls) between the processor and circuit board. There are a few methods that can be used, which I will cover later down the page, but the method we use is called reballing. This requires removing the chip from the circuit board, replacing the old solder balls, and finally resoldering the chip back on. For a step by step process check out our video below to see exactly how we do it. I also recommend checking the 3 common mistakes to avoid below the video as they contain critical information to ensure a proper and long lasting repair.

Step by step reball repair video

3 Common Mistakes

Improper Board Prep

The CPC4 module is coated with conformal coating to protect the circuit board from moisture and damage from oxidization, corrosion, and rusting. This coating however must be removed before reballing the module to prevent both toxic fumes but also to allow the solder to expand. If you attempt to melt solder under conformal coating, it will burst as the solder will want to expand but the coating won't allow it. This has the potential to cause short circuits and will starve the joints which will then need to be resoldered to ensure a proper bond.

Reflowing instead of reballing

Reflowing is the process of melting and reforming existing solder bonds on a circuit board, while reballing involves replacing the old solder with new balls. Reflowing is faster and cheaper but less effective at repairing damaged joints, while reballing is more time-consuming and costly but provides better control over the repair.

Conformal coating on CPC4 modules will get underneath the processor chip, this will prevent the solder from expanding during reflowing, leading to the solder bursting, and starving the joints as well as causing potential short circuits. To repair CPC4 modules, reballing is necessary as the conformal coating cannot be removed without also removing the chip.

Using lead free instead of leaded solder

Leaded solder has a lower coefficient of thermal expansion compared to many lead-free solders. This means that it is less likely to experience significant expansion or contraction when subjected to changes in temperature. This can be beneficial when the joint is subjected to temperature fluctuations, as it can reduce the risk of stress or failure in the joint.
Leaded solder also has a higher electrical conductivity, which further reduces the risk of stress or failure in the soldered joints.
Nick's Electronic Repair always uses leaded solder for CPC4 repairs.

While I have just given you all the information you require to repair your own CPC4, what I have not given you is the high end equipment we use, nor the years of experience my team has acquired fixing thousands of BGA chips.
But I have something that may make up for that.

Deal of the month

The next 10 customers who fill out the form below (including a description of your symptoms), we are offering the following with our repair service at no extra cost:

1 Year Peace of Mind warranty
2 day expedited repair turnaround
Free Overnight return shipping
&
Repair or replace guarantee. If our team is unable to fix your module, we'll replace it with a refurbished one at no additional cost to you.

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