Practical and reliable BGA solder ball technology

BGA solder Ball Technology Introduction

BGA as a large-capacity packaged SMD has promoted the development of SMT. Manufacturers and manufacturers have realized that the introduction of large-capacity.
BGA on the pin package has strong vitality and competitiveness. However, the price of a single BGA device is very high. For pre-developed products,
There are many tests. It is often necessary to remove the BGA from the substrate and hope to reuse the device. Because the BGA is removed
After that, its solder balls are destroyed and cannot be directly soldered on the substrate. The balls must be repositioned. How to regenerate the solder balls.
The technical problem lies in front of our process technicians. Indi um company can buy special solder balls for BGA.
The process of repairing each solder ball one by one in BGA is obviously undesirable. This article introduces a Solder quick pre-formed bad pair.
BGA process technology for solder ball regeneration.

Equipment, tools, and materials

• Bad preform
• Fixture
• Flux
• Deionized water
• Cleaning plate
• Cleaning brush
• 6 inch flat tweezers
• Acid-resistant brush
• Reflow oven and hot air system
• Microscope
• Finger cot

Process flow and matters needing attention

3.1 Preparation

• Confirm that the BGA fixture is clean
• Heat the reflow soldering furnace to the temperature required by the temperature curve

3 2 Process steps and matters needing attention

3. 2. 1 Put the broken preform into the fixture

• Put the broken preform into the fixture, and the side marked Sol der Quik faces the fixture to ensure that the broken preform is loosely matched with the fixture.
• If the preform is broken and needs to be bent before it can be loaded into the fixture, it cannot enter the operation of the subsequent process. The preform cannot be put in
• The fixture is mainly caused by dirt on the fixture or improper adjustment of the flexible fixture

3. 2. 2 Apply a proper amount of flux on the reworked BGA

• Use an injection syringe filled with flux to apply a little flux on the BGA soldering surface that needs to be reworked
• Note Make sure that the BGA soldering surface is clean before applying flux

3. 2. 3 Apply the flux evenly

• Use an acid-resistant brush to evenly brush the flux on the entire soldering surface of the BGA package. Ensure that each pad is covered with a thin layer of flux.
• Flux
• Make sure that each pad has flux. Thin flux is better than thick ones.

3. 2. 4 Put the BGA to be repaired into the fixture

• Put the BGA to be repaired into the fixture. The flux-coated side faces the broken preform

3. 2. 5 Flatten the BAG

• Gently press the BGA to make the performance broken and the BGA enters the fixture for positioning. Make sure that the BGA is flat on the preform broken.

3. 2. 6 Reflow soldering

• Put the mixture into the hot air convection oven or hot air reflow station and start the reflow heating process

• All the used reflow station curves must be set to the developed curves dedicated to the BGA solder ball regeneration process

4. 2. 7 Cooling

• Use tweezers to remove the fixture from the furnace or reflow station and place it on the heat transfer plate to cool for 2 minutes

4. 2. 8 Take out

• When the BGA cools, take it out of the fixture and place its solder ball face up in the cleaning pan

4. 2. 9 Soak

• Soak the BGA in deionized water for 30 seconds until the paper carrier is saturated before proceeding to the next step.

4. 2. 10 Peel off the solder ball carrier

• Use special tweezers to remove the solder balls from the BGA. The best way to peel off is to start peeling from one corner.

• The peeled paper should be intact. If the paper tears during the peeling process, stop immediately and add some deionized water, etc.

• 15 to 30 seconds before continuing

4. 2. 11 Remove paper dust on BGA

• After peeling off the carrier, a small number of paper scraps will occasionally be left. Use tweezers to hold the scraps away. When using tweezers to hold the scraps, the tweezers are welding.

• Move gently between the balls

• Be careful：the tips of the tweezers are very sharp. If you are not careful, you will scratch the fragile solder mask.

4. 2. 12 Cleaning

• After removing the paper carrier, immediately wash the BGA in deionized water. Rinse with a large amount of deionized water and brush the BGA with a brush.

• Be careful: Support the BGA when scrubbing with a brush to avoid mechanical stress

4. 2. 13 Rinsing

• Rinse the BGA in deionized water. This will remove the small amount of flux and the paper scraps from the previous cleaning step.

• After air-drying, you can't wipe it dry with a dry tissue

3. 2. 14 Check the package

• Use a microscope to check whether the package is contaminated, the solder balls are not placed, and the flux remains. Repeat “3. 2. 11- 3. 2. 13” if cleaning is necessary

• note：Since the flux used in this process is not a no-clean flux, it is carefully cleaned to prevent corrosion and prevent long-term reliability failure

• is compulsory， The best way to determine whether the package is clean is to use ionization diagrams or efficiency equipment to test for ion contamination. All processes The test results must meet the pollution standard of less than 0.75mg NaaCI / cm². In addition, the cleaning steps of 3. 2. 9- 3. 2. 13 can be replaced by tank cleaning or spray cleaning process.

Conclusion

As the devices on the BGA are very expensive, it is necessary to repair the BGA. The key solder ball regeneration is a technology.
Difficulties The process is practical and reliable. Only need to purchase broken preforms and fixtures to perform BGA welding regeneration. This process solves the problem.
Key technical problems in BGA rework