Remedy for BGA Pad Shedding
BGA's full name is Ball Grid Array, which is an array of solder balls on the bottom of the package substrate as the I/O end of the circuit and the printed circuit board (PCB). The device packaged with this technology is a surface mount device.
BGA packaging emerged in the early 1990s and has evolved into a mature high-density packaging technology. Among all the package types of semiconductor ICs, the BGA package grew fastest during the five years from 1996 to 2001. In 1999, the output of BGA was about 1 billion. However, to date, this technology has been limited to packages of high-density, high-performance devices, and the technology is still moving toward fine pitch and high I/O ends. BGA packaging technology is mainly suitable for PC chipset, microprocessor/controller, ASIC, gate array, memory, DSP, PDA, PLD and other devices.
BGA main process
- 1. Shovel flat front plug hole: It is suitable for the BGA plug hole where the single surface of the solder mask is exposed or partially exposed. If the hole diameters of the two plug holes are different by 1.5mm, the process is adopted regardless of whether the solder mask is covered on both sides;
- 2. soldering plug hole: applied to the BGA plug hole soldering on both sides of the board;
- 3. Plug holes before and after leveling: for thick copper foil or other special needs. The size of the plug hole is 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55 mm.
Remedy for BGA pad shedding
- 1. Clean the area to be repaired.
- 2. Remove the failed pad and a short connection.
- 3. Use a knife to scrape off residual glue, stains or burns.
- 4. Scrape off the solder mask or coating on the wire.
- 5. Clean the area.
- 6. A small amount of liquid flux in the connection area of the board, and tinned and cleaned. The overlap length of the solder joint should be less than twice the width of the wire. The new BGA pad trace can then be inserted into the via hole of the original BGA pad. The solder mask of the via hole is removed and properly processed, and the new pad area of the board surface must be smooth. If the inner layer of fiber is exposed, or if there is a deep scratch on the surface, it should be repaired first. The height of the replaced BGA pad is critical, especially for eutectic solder balls. Remove the solder mask between the BGA pad and the board surface or via hole to maintain a low profile. If necessary, gently grind into the board to ensure that the height of the line does not affect the replacement components.
- 7. Select a replacement pad for the BGA that is closest to the pad to be replaced. If you need a special size or shape, you can order it. These new BGA pads are made of copper foil with a tin-plated top surface and a glue-bonded sheet on the underside.
- 8. Carefully scrape off the glue bond between the solder joints on the back side of the new pad before trimming the new pad. The resin substrate is scraped off only from the solder joint area. This will allow welding of the exposed areas. When handling replacement pads, avoid touching fingers or other materials to the resin substrate, which may contaminate the surface and reduce bond strength.
- 9. Cut and trim the new pad. It can be cut from the tinned edge and the length of the cut should be such that the maximum allowable welding line overlap.
- 10. Place a high-temperature tape on the top surface of the new pad, place the new pad on the surface of the PCB, and use tape to help locate it. The tape remains in place during bonding.
- 11. Select the bond tip that is appropriate for the new pad shape. The tip should be as small as possible, but should completely cover the surface of the new pad.
- 12. Position the PCB to make it stable. Gently place the hot tip on the tape that covers the new pad. Apply pressure as recommended by the repair system manual. Note: Excessive bonding pressure can cause spots on the PCB surface or cause new pads to slide out.
- 13. After the timed bonding time has elapsed, lift the soldering iron and remove the tape for positioning. The pads are completely refurbished. Carefully clean the area and check that the new pad is properly positioned.
- 14. Apply a small amount of liquid flux to the solder wire bonding area and solder the new pad wire to the circuit on the PCB surface. Try to use a minimum of flux and solder to ensure a reliable connection. To prevent excessive solder reflow, tape can be placed on the top surface of the new pad.
- 15. Mix the resin and apply it to the welded joint. Curing the resin with the maximum recommended heating time to ensure the highest strength bond. BGA pads can typically withstand one or two reflow cycles. In addition, a resin can be applied around the new pad to provide additional bond strength.
- 16. Apply a surface coating as required.
Next Post: Use a Few Resistors to Improve the Accuracy of the Multimeter