To bake or not to bake: that is the question!
The authors of a technical article by ECD, a specialist in building MSD wardrobes, asked themselves, why don't you bake everything before assembly, just to be on the safe side?
First of all, baking MSD components can permanently damage the plastic tape or spools, or other component carriers. Damage to packaging/carrier materials can occur as low as 45 ° C (113 ° F), which then prevents their trouble-free use in the assembly process.
What's more, bake also intensifies the oxidation process at MSD soldering tips, which is one of the most important factors causing soldering defects.
Bake also takes a long time: the extreme case the authors cite is… 79 days for some relatively thick components (from 2 mm to 4.5 mm) at 40 ° C (104 ° F) safe for their packaging. Of course, this is usually a shorter period, for example, three hours for MSL 2 components. Of course, the higher the temperature, the shorter the bake time, but always be aware of the packaging limitations. The authors of the article recommend that if the components cannot be unpacked, heat them to a very high temperature and then, after repackaging, at 40 ° C (104 ° F). If it is necessary to bake at this safe temperature, the baking time starts from five days and can reach the astronomical 79 days mentioned at the beginning.
Bake wastes a lot of energy, up to 20 times more than simply keeping the components dry. In summary, the authors argue that instead of baking, it is more economical and safer to store components in an MSD cabinet.
Traditionally, baking has been considered a cure for many soldering problems. However, there are a few situations where this just isn't the case. There are many mandatory thermal processes (curing, solvent evaporation, etc.) in the manufacturing process of components, as a result of which most components should not require additional annealing between their removal from the moisture barrier packaging (MBB) and the assembly process. In fact, there are only two cases where MSDs require baking: if the component is MSL 6 or its service life has been exceeded (Figure).