How long is the shelf life of the PCB? And how is the baking time temperature determined?

How long is the shelf life of the PCB? And how is the baking time temperature determined? I customized a number of boards on ALLPCB last year, and Now I am worried about its performance due to the event for too long.

After the PCB is manufactured, it has a shelf life. If the shelf life is exceeded, the PCB needs to be baked. Otherwise, it is easy to cause the PCB to explode when the PCB is produced on the SMT. Usually within one year. You can contact your supplier ALLPCB to pay for some baking costs.

This is the first I'd heard about a PCB shelf life so I did a bit of research.This discussion has some good information
http://www.circuitnet.com/experts/84214.htmlThe bottom line is that baking may not be the best way to restore the PCB since it can affect solderability. The best way is to store the PCB in a very low humidity enclosure. If the boards are in the original sealed package they may have a longer shelf life.
You should check with your supplier for their recommendation.

Your best bet it to ask your fab house about shelf life and storage. It can vary a bit based on the processes used by them. The moisture can be baked out, but there are limits and OSP finish (rarely used except in high volume boards) doesn't like to be baked.
Beyond that, it somewhat depends on the finish of the PC board and storage. Immersion silver boards will tarnish and can easily corrode during that time frame. Light tarnish can often be removed from a silver board with a pencil eraser. I wouldn't do that for a production run though. If they've been kept sealed in a dark, cool environment, they may still be okay.ENIG needs to have been kept clean. Any fingerprints or other contaminates will likely have eaten through the gold surface over the year.HASL / HAL, which has a solder surface will probably last the best of common finishes, but still could be susceptible to moisture absorption.They may be usable, but in general, I would recommend new boards rather than something a year old.

I often get small runs of PCBs done since I am doing a lot of custom work for small companies. At times I have to do another board or two, so I always get a few extras on the first run (they are usually supplied "free", built into the cost) I have found that if the boards are gold plated, rather than the more usual solder or silver, and are stored in a completely sealed packet with a desiccant, that they are good for some years.The gold adds a few dollars to the cost of the board, but the return is well worth it.Cheers,Richard

I'm sure there will be different types of answers for this question.Is the full shelf life of bare PCB's restored, or reset after it has gone thru a baking cycle?How many times can bare PCB's be baked to restore shelf life?I'm curious as to what is meant by shelf life of the bare boards. IPC-J-STD-003 and IPC-A-600, describe the Coating Durability for three categories, 1, 2, and 3. Category 1 is for boards which will be soldered within 30 days, category 2 is for boards which will be soldered within 6 months and category 3 is for boards which will be stored over 6 months.Therefore the questions I would ask are what shelf lives do you want to restore?The ability of the board to be soldered without delaminating orThe solderability of the board.Board baking will remove moisture and it does help to prevent delamination if done correctly, so in a sense baking does reduce the potential of delamination but it does not restore anything.Board baking will destroy solderability. By baking the boards, the growth of the intermetallic compound is accelerated and depending upon the final thickness of the plating on the boards, one could end up with exposed intermetallic layer which is no longer solderable. This is where the coating durability categories are defined and utilized.How often can the boards be baked? I would hesitate to answer this as the boards should be kept in a dry environment or dry box if they are to be stored for any length of time. If baking is deemed necessary after the assembly process then the baking process can be implemented at that point in time. I would not recommend continuously baking the boards.The ability of the laminate material to absorb moisture is very high; hence the boards should be soldered immediately after the baking cycle. The laminate will absorb all the moisture removed in a baking cycle within the following 8 to 12 hours. This is from work we did at PCBGOGO.

The shelf life is connected with the surface treatment,for HASL and Immersion gold, it's 6 month, immersion silver and OSP is 3 month, baking time is connect to the TG value, for Tg 130, we bake at 150 degree centigrade about 2 hours,   and  bake at 170 degree centigrade about 4 hours for Tg 150 material, you can see the difference HASL, immersion gold, immersion silver, OSP surface treatment at this link,http://www.headpcb.com/html/2018/news-blog_0813/76.html