PlayStation 4 has a major component called APU, it hosts CPU and GPU inside of itself. This component is the powerhouse of your game console which processes all the information. You will find it soldered onto the board using multiple connections. This type of SMT mounting is called BGA.

What is PS4 reballing?

PlayStation 4 has a major component called APU (Accelerated Processing Unit). AMD in cooperation with Sony developedĀ it to host both CPU and GPU inside of itself. It is actually manufactured by TSMC using 28nm manufacturing process. This component is the powerhouse of your game console. ItĀ processes all the information as well as acts as a graphics card for your PS4 to output all the video on your screen.

You will find it soldered onto the board using multiple connections, which sit in between the APU integrated circuit and the board. These connections are made out of solder and serve two purposes: provides physical mounting to the component as well as electrical connectivity to the board. BGA is a type of SMT mounting; it stands for Ball Grid Array. This ball grid array consists completely out of hundreds of tiny solder alloy connections which tend to fail from time to time. Specifically, due to such a high population of them and due heat cycles, your PS4 is exposed to during gaming.

This APU is extremely powerful, and we all know powerful components on circuit boards do tend to run quite hot. APU is cooled down by a heatsink and fan; however, within itself, it still operates at temperatures up to 90C. The problem lies when the substrate temperature raisesĀ and the material expands. However, when aĀ console powers down the heat reduces and all the components retract back to their original positions. Of course, we are talking micro levels here, and you wonā€™t see this actual expansion happening. This expansion and retraction arenā€™t healthy for solder joints. Coupled with factors, such as moisture accumulation in the air and dust contamination, these little solder spheres tend to fail by developing microcracks within the ball grid array.

Even if any one of these connections fail, and there are hundreds of them, APU loses its connectivity with the circuit board. Consequently, your PS4 usually does not turn on at all or malfunctions. Moreover, this can cause artefacts on the screen or video freezing during the gaming session. This is where PS4 reballing procedure comes in.

PS4 reballing procedure means we replace all these solder joints between SoC (System on Chip) and a printed circuit board. As a result, new fresh solder spheres re-establish that lost connection, and the game console comes back to life. During the reballing procedure, we remove the component; in this case, PS4 APU. Then, we clean all the old solder from the circuit board and the component. Next, we place the new spheres on the removed part and solder it back on the board. These are the essential steps of any BGA reballing procedure.

However, to do it professionally and to make the process is scale-able there are a few factors to consider. In this case, it’s moisture sensitivity, environmental temperature and ESD precautions. Therefore, we have to think about all of these when developing complicated soldering procedures. Also, we have to ensure we carry out the process in a clean environment. Remember, any kind of dust particles can interfere with the soldering process. Lastly, we recommend introducing numerous quality control steps during the BGA reballing procedure. As a result, it will provide additional verification in case of errors, such as solder mask damage, solderability or contamination issues.

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Step 1 – Prebaking

Playstation 4 Reballing Procedure - Prebaking
Playstation 4 Reballing Procedure - Prebaking

Before we do any kind of soldering work on flip-chip design components or any BGA, QFN, CSP devices that require complete reflow, we must carry out a procedure known as pre-baking. The mentioned devices are sensitive to moisture, and we donā€™t mean they will fail if submerged in waterā€¦ Therefore, it is crucial to understand the built up of moisture adsorbed from the environment. It is a well-known fact from physics that water turns into a gas when heated and changes in volume. As a result, this exact effect, at micro levels, happens inside the substrate layers of printed circuit boards. And of course, PlayStation 4 ASICs (Application Specific Integrated Circuits).

As we need to melt the solder alloy, to remove PS4 APU, we will have to increase the temperatures to nearly 250C. It is way above the water boiling temperature. Therefore, we somehow have to eliminate this moisture. If trapped inside and heated, it will expand in volume and look for an escape. As a result, it will crack the substrate and damage the component or even a circuit board. This water boiling, changing its volume when turning into steam and cracking the structure is known as delamination. Otherwise,Ā called ā€œpopcorningā€ as you can actually hear it making an audible sound, similar to the popcorn popping.

To get rid of theĀ risk, we have to eliminate the moisture from the board. Thatā€™s when pre-baking comes in. It is a process when we increasingly raise the temperature of the board and components. Precisely, just above water boiling temperature and keep it there for anĀ extended period of time. ItĀ eliminates the moistureĀ at a controlled /slower pace. The process is happening in environmental ovens for a period between 24 and 48 hours.

Once we have the board prebaked, we have 8 hours to carry out all the necessary work before we would have to pre-bake the board again. However, it is not suggested to pre-bake the boards multiple times as this reduces ENIG surface solderability.

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Step 2 – De-soldering and cleaning board and IC

To refurbish BGA connections we have to remove the component completely from the board. We do this by targeting BGA and raising temperature of that solder alloy to its melting point so we could remove it while itā€™s liquid. As all of these connections are hidden away underneath the component, it means the whole component will have to be heated to around 225C in order to melt these joints. Now we canā€™t just apply heat directly to this area as it will damage the APU component. This is where reflow soldering profiles come into play. We have to use a rework station, which can run a soldering profile meaning it can heat up the targeted component at a pre-programmed pace. This will ensure the least amount of stress is caused to the substrates.

The soldering profile usually consists of 4 stages with different rates of heat radiation. It has to be fast enough to minimise the time a component spends at extreme temperatures. However, long enough to safely raise the temperature for solder alloy to become liquid. The critical point here is safely. This soldering profile is custom which we have to develop before we can integrate it into production level repairs.

Consequently, it means we most likely won’t be able to re-use these soldering profiles for different rework stations or different boards. There are, however, some guidelines of what theĀ usual reflow profile can look like. Lead-free solder alloy profile would have four stages: preheat, soak, reflow, cooling. These stages all have different rates of raising the temperature of the targeted area so we could reflow BGA solder spheres.

In order to remove the component, we have to mount the board on the rework station. We have to ensure we mount and support it to avoid sagging or bowing during the heating stage. If we leave the board unsupported, heated circuit board fibreglass will flex. As a result, it could develop cracks on other component solder joints, which would be hard to identify and rectify.

Next, we will heat the board from the top and bottom. From underneath to around 160C as this will help to control inner copper planes expansion levels. Keeping substrate expansion levels at the same rate across the whole board will help to avoid delamination.

Once we have preheated the board,Ā we will increase the intensity of the top heater to target the area where BGA is and completely melt the solder alloy. Then, we have a 10-15s window to pick up the component. We do it using aĀ vacuum suction system. Monitoring the whole process and using a camera helps to ensure that solder spheres have melted all around the actual BGA site. WeĀ have to lift the component with extreme care. In an attempt to pick up the IC while all solder spheres are not liquid will cause serious damage to BGA pads. Most of the time they are not economical to repair.

Cleaning all that residual old solder requires specialised soldering equipment. To clean the board, we would use the soldering iron tip with wide tunnel type tip. To ensure we do not cause stress, we recommend to preheat the board temperature to around 140C and keep it within this range, while cleaning. The skill during cleaning is to minimise the temperatureĀ and the number of strokes it takes to completely clean BGA padsĀ as well as re-tinĀ them to revive that solderability back into these oxidised pads. We usually use a de-soldering wickĀ to absorb all the solder from the pads. Once we remove the solder, we clean the excess flux using variations of de-fluxers and IPA.

Playstation 4 Reballing Procedure - Cleaning BGA Site

We have to perform the same procedure with a PS4 APU, which in this case we have to mount in a special jig. To help remove residual solder we can use another alloy with a possibly lower melting point. ItĀ will allow an easier flow of that lead-free solder. Once we remove the residual solder, it is safe to clean PS4 ASIC using an ultrasonic cleanerĀ as it is a flip-chip design IC, unlike wire-bond technology ICs.

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Step 3 – PS4 reballing and IC reflow

Now that we have removed PS4 APU and cleaned the board, the IC is ready for the actual reballing procedure. DuringĀ this process, we will place new solder spheres and reflow them on the component side. It is done using reballing fixtures, stencils and dedicated reballing oven. We are using 0.5mm solder preforms to reball this ASIC and place them using a stencil. This stencil is specifically designed to fit reballing fixtures and has apertures wide enough to accommodate solder spheres. The stencil also has to be thick enough to ensure pre-forms roll into place and stay there, however, thin enough it does not act as a heatsink during reflow.

Playstation 4 Reballing Procedure - Reballing
Playstation 4 Reballing Procedure - Reballing

After we placed and inspected all spheres, we have to solder them onto the component. The process melts all these little solder spheres on the BGA pads. Again, same rules apply, we have to create a profile. Especially, considering the new solder alloy properties as well as component heat absorption rates. These reballing ovens act as mini rework stations and create a safe and repeatable environment around the component. It is crucial when working on such complicated soldering procedures. Using this method allows us to automate the reballing process and ensure we achieve successful result each and every time.

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Step 4 – Placement and soldering

At the next stage, we introduce the first quality control step, which helps to evaluate the condition of the PCB and reballed PS4 APU.Ā  It is crucial to ensure no damage or contamination occurred up until now. Things we look for are:

  • Discoloured pads, which can cause solderability issues;

  • Foreign particles such as dust or lint;

  • Solder mask damage, which causes solder joint starvation;

  • Cratering on the solder spheres, caused by overheated alloy;

  • Alignment of the ball grid array, as even slight misalignment can cause solder bridges later.

Next, we will be carrying out a visual inspection under the microscopes.

Once we are happy with all inspection results and the condition of the solder mask of both BGA sites, we are ready to place and solder the component on the board. We mount the board on the soldering rework station in the same way as during the removal of APU. Now, for us to precisely mount the PS4 ASIC on BGA site, we need to use a mechanism called split vision positioning system.

Playstation 4 Reballing Procedure - IC Inspection
Playstation 4 Reballing Procedure - Soldering
Playstation 4 Reballing Procedure - Soldering

This system consists of two different cameras and a monitor. We have two feeds; one from the bottom of the component, one from the top of the PCB. As a result, it allows us to align theĀ component precisely on the BGA pads using micro adjustment levers. We can also zoom in and adjust the contrast of each image to really get in there and align it perfectly.

Once we align the component, a vacuum suction system automatically lowers it into the place. The sensors within the rework station allow easy placement, as it automatically stops if sensors detect a force-back.

When it comes to reflowing/soldering component back into place, we most certainly cannot use the same reflow profile we used during the removal. And so we have to develop a new soldering profile, which runs according to the characteristics of the new solder spheres placed on the APU BGA. Once theĀ profile is running, we can monitor the process on the screen with cameras at a macro level. They allowĀ us to see how the solder behaves. We can actually see when component finishes reflow as it levels itself into the place once all solder is liquefied. Again, during theĀ development of this soldering profile, we have to be aware of a few factors. Such as environmental exposure and already existing heat cycles. It is importantĀ we consider these to ensure the profile is safe enough to carry out the soldering procedure successfully.

Next, it is vital we do not overlook the cooling of the soldered board. We must complete it at recommended 5C per second down the curve to minimise thermal shock. Specifically, because it can cause solder joints to become brittle and develop cracks.

As we have used the flux to help with oxidation when soldering, we now have to clean it off carefully.Ā And we always like to make any of our soldering procedures presentable and tidy.

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Step 5 – Prism inspection

Playstation 4 Reballing Procedure - IC Inspection

Post-reball quality inspection is one of the most important steps during quality control. We inspect the BGA solder spheres using prism microscope. It allows seeing underneath component and into the array. We evaluate such factors as:

  • coplanarity,

  • solder ball shape,

  • bridges,

  • missing spheres,

  • bleeding,

  • solder mask damage

to confirm PS4 BGA reballing went successfully.

Step 5 – Assembly and soak test

After we finish that last step of quality control, it is time for a full service. We clean every single part and finally assemble back to go through a soak test. This soak test puts it under stress, while we monitor the temperature and ensure we have successfully fixed the fault.

Once it passes stress testing, we then release it for the customer to collect with our standard three months warranty.

PlayStation 4 Games Freezing And Crashing Repair
PlayStation 4 Games Freezing And Crashing Repair

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