After the completion of PCB manufacturing, there is a shelf life. Beyond this shelf life, the PCB needs to be baked. Otherwise, it is easy to cause the problem of PCB explosion when the PCB is produced online in SMT.
There are industry specifications for the preservation time of PCB, as well as the temperature and time of baking PCB in industrial oven. Details are as follows:
Industry specifications for PCB control:
1. PCB unpacking and storage
(1) The PCB board seal is not unpacked and can be directly put into use within 2 months from the manufacturing date
(2) The manufacturing date of PCB board is within 2 months, and the unpacking date must be marked after unpacking
(3) The manufacturing date of PCB board is within 2 months, and it must be put into use within 5 days after unpacking
2. PCB baking
(1) If the PCB is sealed and unpacked for more than 5 days within 2 months of the manufacturing date, please bake at 120 ± 5 ℃ for 1 hour
(2) If the manufacturing date of PCB exceeds 2 months, please bake it at 120 ± 5 ℃ for 1 hour before going online
(3) If the manufacturing date of PCB is 2 to 6 months later, please bake it at 120 ± 5 ℃ for 2 hours before going online
(4) If the manufacturing date of PCB exceeds 6 months to 1 year, please bake it at 120 ± 5 ℃ for 4 hours before going online
(5) The baked PCB must be used within 5 days (put into IR reflow). After the bit is used, it needs to be baked for another hour before it can be used online.
(6) If the manufacturing date of PCB is more than 1 year, please bake it at 120 ± 5 ℃ for 4 hours before going online, and then send it to the PCB Factory to spray tin again before going online
3. PCB baking method
(1) Large PCBs (above 16 ports, including 16 ports) are placed horizontally, with a maximum of 30 pieces in a stack. Open the oven within 10 minutes after baking, take out the PCB and place it horizontally for natural cooling (pressure prevention plate Bay fixture is required)
(2) Small and medium-sized PCBs (including 8ports below 8ports) are placed horizontally, with a maximum of 40 pieces in a stack, and the number of vertical types is unlimited. Open the oven and take out the PCB within 10 minutes after baking, and place it horizontally for natural cooling (pressure prevention plate Bay fixture is required)
Preservation and baking of PCB in different regions:
The specific storage time and baking temperature of PCB are not only related to the manufacturing capacity and technology of PCB manufacturers, but also related to the region.
The shelf life of PCBs made by OSP process and pure gold precipitation process is generally 6 months after packaging. Baking is generally not recommended for OSP process.
The preservation and baking time of PCB has a great relationship with the region. The humidity is generally heavy in the south, especially in Guangdong and Guangxi. There will be a “back to the South” weather in March and April every year. It is cloudy and rainy every day. At this time, it is very humid. PCB must be used up within 24 hours after exposure to air, otherwise it is easy to oxidize. It is best to use up in 8 hours after normal opening. For some PCBs that need to be baked, the baking time should be longer. In the north, the weather is generally dry, the preservation time of PCB is longer, and the baking time can be shorter. The baking temperature is generally 120 ± 5 ℃, and the baking time is determined according to the specific situation.
For the storage time, baking time and temperature of PCB, specific problems should be analyzed. On the basis of PCB management and control specifications, specific choices should be made according to the manufacturing capacity, process, region and season of different manufacturers.
Of course, if it is only an experiment, it can be adjusted between the room temperature 25 and the ultimate high temperature resistance temperature of general electronic products 120. It should be noted that in the electronic industry, the service life is generally doubled for every 10 degrees. If it is a batch product, it refers to dipping the insulating paint (drying insulating paint), putting it into the oven at 80 ℃ and baking for 2 hours.