Why is PCB baking necessary?

04/08/2021 Seektronics

PCB board industry partners know that the copper-lined board in the insulation material post a copper foil, and then baked dry. If you look carefully, you will see that there will be shrinkage in the drying process, the stress in all directions will be generated, which is the source of stress, followed by the purpose of PCB drilling before baking the board, in fact, the main moisture, PCB drilling before baking the board is to remove moisture from the board to reduce internal stress; pressed together behind the print resistance welding, including characters, etc. need to bake. Before shipping and packaging, there is also a process of baking the press board, also to remove moisture, after baking the board in terms of warpage has a relatively large improvement.
The baking mentioned above can eliminate the internal stress of the PCB board, which is to stabilize the size of the PCB. Its most significant advantage is that it can make the water in the pad dry after baking, strengthen the welding effect, reduce the weld defect, repair rate, etc. However, baking will make PCB board color change, and affect the appearance.

Usually baked at 100-120°C for about 2H. Do not bake for too long! If exposed to air within a day need to be used up, otherwise prone to oxidation, of course, this is not absolute, but also depends on the ability of the supplier to produce, some OSP relative preservation time a little longer. The following small PCB baking instructions for your reference.
1. For PCBs sealed and unsealed for more than 5 days within 2 months of the manufacturing date, please bake at 120 ±5°C for 1 hour.
2. For PCBs older than 2 months from date of manufacture, bake at 120 ±5°C for 1 hour before going online.
3. For PCBs older than 2 to 6 months after the manufacturing date, bake at 120 ±5°C for 2 hours before going online.
4. For PCBs older than 6 months to 1 year, bake at 120 ±5°C for 4 hours before going online.
5. Baked PCBs must be used within 5 days (put into IR REFLOW), or baked for another 1 hour before going online.
 6. If the PCB is more than 1 year old, please bake it at 120 ±5°C for 4 hours before putting it on line, and then send it to the PCB factory for re-tinning before putting it on line.