what is baking before reflowing?

Community PCB Design
1

Some datasheets advise on baking before actually reflowing. What does it mean? How do you bake?

Thanks

smdfan

2

Chips absorb moisture from the air, which is why they are usually supplied in packaging with silica gel. If they have been removed from the packaging for any time they have to be baked at about 130C for 24 hours, IIRC, before they are reflow soldered.

Leon

3

leon_heller:
Chips absorb moisture from the air, which is why they are usually supplied in packaging with silica gel. If they have been removed from the packaging for any time they have to be baked at about 130C for 24 hours, IIRC, before they are reflow soldered.

Leon

I have reflow oven but I do not know if there is any setting for just heating/baking. There are just some setting for reflow. So it is basically heating the IC before putting them on pcb. Right? Thanks

smdfan

4

PCB assemblers use special ovens. It’s only needed for reflow soldering (the humidity can crack the package), manual soldering is OK.

Leon

5

As Leon mentioned, you must drive out the moisture from the chip before trying to reflow. If you do not, the chips can split and even explode.

All chips that are sensitive to moisture, will have a section in the datasheet or in the section on standard packaging on how to drive out the moisture. This might be a few hours to a full day at medium heat. Check the datasheets for specifics.

The fact your oven does not have baking settings does not mean you do not need to bake your chips. If you pull them stright out of the hermiticaly sealed anitistatic moisture bags, you do not need to bake. Otherwise you do. A standard kitchen oven can perform this function.