Preventing Warpage in PCBs: Tips and Methods
- IPC-6012 specifies the maximum warpage for SMB-SMT circuit boards at 0.75%.
- Other circuit boards usually have a warpage limit of 1.5%.
- Electronic assembly factories typically allow 0.70-0.75% warpage for double-sided/multi-layer boards.
- Boards like SMB and BGA often require warpage below 0.5%, with some factories aiming for less than 0.3%.
Key Points for Preventing Warpage:
- Ensure prepreg alignment between layers, especially using the same supplier’s products for core boards and prepreg in multilayer boards.
- Bake boards at 150 degrees for 6-10 hours to remove water vapor, cure resin, and eliminate stress before cutting.
- Take note of different warp and weft shrinkage ratios when laminating prepreg and cutting core boards.
Warpage Calculation Method: Warpage height divided by curved edge length
Treating Warped Plates:
To address warpage, apply 150 degrees heat or hot pressing for 3-6 hours. Press the board with a flat steel plate and bake 2-3 times for optimal results.
Remember, proper prevention methods and treatment techniques can help maintain the integrity of PCBs and ensure high-quality electronic assemblies.
