How to Bake PCBs and Components - 2022 Most Comprehensive Guide

PCB baking is the pre-treatment to dry printed circuit boards and moisture-sensitive components before PCB assembly to bake them so that no moisture is left inside them or on their surface. With PCB baking, the PCB assembly is away from soldering defects such as IC popcorning.

How to Bake Bare Printed Circuit Boards

When PCBs are within 2 months of the manufacturing date and sealed well, there is no need to bake them before the PCB assembly. If the PCBs are manufactured within 5 days, there is also no need to bake them.

But if the circuit boards are unsealed and placed in a temperature and humidity-controlled environment ( ≦30℃/60% RH), according to IPC-1601, here are the set temperatures and time duration to bake them before they are going on the assembly line:

Baking temperature: 120±5℃

• 1. If the circuit boards are stored for 5 to 60 days, they need to be baked for 1 hour.
• 2. If the PCBs are stored for 2 to 6 months, they need to be baked for 2 hours.
• 3. If the PCBs are stored for 6 to 12 months, they need to be baked for 4 hours.
• 4. If the PCBs are stored for more than 12 months, they are out of date and not recommended to use. Moisture already causes corrosion to the PCB pads, and the solder mask may age or be harmed. The circuit conductivity is reduced, and the circuit loses the original resistance. So we don't bake them but discard them.

After the PCBs are baked, they should be assembled within 5 days. If they are not used within 5 days, one more time of baking is required.

How to Bake Electronic Components?

Some surface-mounted devices (SMD) such as ICs and BGAs are moisture-sensitive. Moisture-sensitive components are stored at 5-30℃ with relative humidity smaller than 50%. And usually, they need to be baked before going on the SMT line.

How to bake SMDs depend on the moisture-sensitive levels of the components and their storage time. The below chart shows the component baking standards made by the American Electronics Industry Association.

From the chart, you can find that at both 90°C and 40°C, component baking requires relative humidity equal to or smaller than 5%. This is to create a humidity difference between the internality and the externality of the component. In this way, moisture inside the component can leave the component.

How to decide whether the components need baking or not?

In the packaging bag of moisture-sensitive components, there is a humidity indicator card. And the control period is printed on the packaging bag. If the components are beyond the control period, or the humidity indicator card turns pink, the components need baking.

For the ICs that are beyond the control period or their indicator cards turn pink, here are some practices according to the component baking standards:

• 1. BGA ICs: IC trays are baked at 125±5℃ for 32 hours; reel ICs are baked at 60±5℃ for 64 hours.
• 2. QFP, TSOP, TQFP, PLCC ICs: IC trays are baked at 125±5℃ for 24 hours; reel ICs are baked at 60±5℃ for 96 hours.
• Other ICs: IC trays are baked at 125±5℃ for 24 hours; reel ICs are baked at 60±5℃ for 48 hours.

If the ICs need programming, they are baked before IC programming.

What to do after the PCBs and components are baked?

When baking is finished, the PCBs and components should be taken out to place flat and cool to room temperature. And then, for the best effect, they go on the PCB assembly lines in no time.

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Conclusion

This blog tells how to bake printed circuit boards and electronic components, including the baking temperatures and duration. If your PCBs or components need baking before the assembly, PCBONLINE is a reliable one-stop service option.