9 Steps for Cellphone CPU Solder Paste Reballing

Solder Paste Reball is the foundation of cellphone motherboard repair, so VIP FIX Shop Team will introduce the detailed steps here for CPU solder paste reballing to improve your phone repairs.



1. Disassemble a CPU chip for solder paste reballing. The most difficult part is the lower level of the cellphone CPU. The points are the most dense and the most difficult. Once the lower layer of the CPU can be planted, other chips are basically easy to start.

2. After disassembly, put a little paper towel to remove the tin from chip. There are something you need to pay attention to:



- The temperature of the soldering iron should not be too high. We often used i2C 2SCNi Nano Soldering Station, the temperature is 330-350 degrees.

-When removing the tin, you must add soldering oil to avoid damage. If the welding oil is found to be lost during the process, continue to add welding oil to ensure that it is wet.

-The removing time should be as short as possible, and do it gently. The chip is easy to be damaged by the high temperature and heavy pressure of the soldering iron for a long time.

-The purpose of removing tin is to roughly level the solder joints without large bumps, they do not need to be particularly flat.

3.After roughly leveling, you can wait about 20 seconds for the chip to cool down, and wipe the chip clean with specific water and dust-free cloth. Get a flat paper towel under the chip, the thickness after hand pressing is 1-1.5 times of the chip. If it is too thick, there is no toughness, and if it is too thin, the CPU reballing stencil is easy to bulge.



5. After making sure that each reballing stencil is clean, you can lightly press the reballing stencil with your fingers on CPU chip, if it does not rebound, it means that the fit is tight. Put soldering paste on the top without pressing too hard to make sure that it’s above each tin point.

The solder paste is available for medium temperature or high temperature, and high temperature tin is commonly used, which has better quality, you can choose according to actual needs. Also, It is best to use the same-day solder paste for CPU tin planting, because the overnight solder paste is hard in some places and tends to be uneven during tin planting.

6. Get the soldering repair knife tilted 45° and pressed firmly, pressing the top of each tin point once and pulled from left to right. Do not wipe the tin with knife repeatedly, which will easily lead to different sizes of tin dots.

After completion, you can use a dust-free cloth to clean the tin remaining on the reballing stencil. Many newly-purchased knives have uneven cut surfaces, which can be properly polished to make them flat and smooth before this step.



7. Now get elbow tweezers compress the CPU reballing stencil. After that, do not remove the reballing stencil immediately. Observe carefully and make sure all the holes are evenly applied with soldering paste.

8. Add soldering oil, blow the tin point and let the tin ball return to its place.

9. Finally, observe the tin beads on the chip. Make sure they are uniform in size and there is no missing tin. You can also use a microscope to observe whether the solder joints are uniform.

For more technical support for cellphone motherboard repairs, contact VIP FIX Shop Team on www.vipfixphone.com