This procedure covers baking and preheating of printed boards and printed board assemblies to prepare the product for the subsequent operations. Included are steps for:
- Baking
Baking is used to eliminate absorbed moisture. Whenever possible circuit boards and
circuit board assemblies should be baked prior to soldering, unsoldering and coating
operation to prevent blistering, measling or other laminate degradation.
- Preheating
Preheating is used to promote the adhesion of subsequent materials to the board
surfaces and to raise the temperature of the circuit board to allow soldering and
unsoldering operations to be completed more quickly.
- Auxiliary Heating
Auxiliary heating is the addition of a second source of heat. This can be from a hot air
tool, or from a second soldering station. A common application is to provide additional
heat when removing through hole components that may have connections to internal power or ground planes.
- Thermal Profiles
Ball Grid Array, Chip Scale Packages, and Flip Chip Packages may require the
development of "Time Temperature Profiles" to remove or install these devices.
Caution
Baking and preheating procedures must be carefully selected to ensure that temperature
and time cycles used do not degrade the product. Environmental conditions must also be
carefully considered to ensure that vapors, gases, etc., generated during the heating
process do not contaminate the product's surfaces.
Caution
Some manufacturers of ceramic chip capacitors recommend that the Preheat Ramp
Rate not exceed 2-4 °C/Sec.
Caution
To prevent fluxes or other contaminates from being baked onto the board surface,
thoroughly clean the board or assembly prior to baking or preheating.
