8 Steps to Re-Ball Cell Phone CPU Solder Paste

    Solder paste balls are the basis for the maintenance of mobile phone motherboards. As a beginner in mobile phone maintenance, you must practice frequently to lay a solid foundation. The China Phonefix Team will introduce the detailed steps for CPU solder paste re-balling here to improve your phone repair.

    1. Disassemble the solder paste balls of the CPU chip. The hardest part is the bottom layer of the phone's CPU. These points are the densest and most difficult. Once the lower layer of the CPU can be planted, other chips are basically easy to use.

   2. After unpacking, use a bit of paper towel to remove the tin from the chips. You need to pay attention to the following points:

- The temperature of the soldering iron should not be too high. We often use the QUICK 936A soldering station with a temperature of 330-350 degrees.

- Be sure to add solder oil when removing tin to avoid damage. If you notice oil loss during the process, keep adding oil, making sure it's wet.

- The removal time should be as short as possible and done gently. Soldering iron can easily damage the chip under high temperature and heavy pressure for a long time.

-The purpose of de-tinning is to make the solder joints roughly flat, without large bumps, and do not need to be particularly flat.

    3. After roughly leveling, you can wait about 20 seconds for the chip to cool, and then wipe the chip clean with special water and a dust-free cloth.

    Take a flat paper towel under the chip and press it by hand to 1-1.5 times the thickness of the chip. If it's too thick, there's no toughness, and if it's too thin, the CPU reballing stencil can bulge easily.

    4. After making sure that each ball template is clean, you can press the ball template lightly on the CPU chip with your fingers, if it does not rebound, it means that it fits tightly.

    Put the solder paste on top, not too hard, to make sure it's over each tin point. There are two kinds of solder paste: medium temperature or high temperature. Generally, high temperature tin is used, which has better quality and can be selected according to actual needs.

    In addition, it is best to use the same day's solder paste for CPU tin planting, because the solder paste overnight is relatively hard in some places, and unevenness is prone to occur during the tin planting process.

    5. Press the repairing knife at an angle of 45°, press once on top of each tin point, and pull from left to right. Do not wipe the tin repeatedly with a knife, which will easily lead to different sizes of tin spots.

    When you're done, you can use a lint-free cloth to clean any residual tin from the ball stencil. Many newly bought knives have uneven cut surfaces, which can be properly polished before this step to make them smooth and smooth.

    6. Now compress the CPU reballing template with angled tweezers and prepare to use the Quick 861DW heat gun station.

    Afterwards, do not remove the ball template immediately. Watch carefully and make sure all holes are evenly coated with solder paste.

    7. Add solder oil, blow the tin point, and let the tin ball return to its original position.

    8. Finally observe the solder beads on the chip. Make sure they are the same size and there are no missing cans. You can also use a microscope to observe whether the solder joints are uniform.

    For more technical support for phone motherboard repair, please comment us in the comment section.