Case Study Series

Utilizing Tools for Process Characterization.
–Phil Tomasello

Q: Why should I clean “No-clean” solder paste/flux residues?

A: Despite their name, “no-clean” fluxes will leave left over residues on boards after reflow. Removing residue prior to conformal coating, is essential to ensure that soils are not remaining on the board, underneath the coating. This will lead to dendritic growth, leading to mechanical failure, which is unacceptable for Critical Cleaning.

Q: What are the key concerns in determining best cleaning processes?

A: Successful cleaning of PCB’s starts with understanding the cleanliness expectations (e.g. IPC Class 1, Class 2, Class 3). This depends upon the complexity of the board, cleanliness specifications and other details and variables involved. The amount of residue left on a PCB relates directly to a broad range of cleanliness expectations and the willingness of the user to pay for that level of cleanliness.

Q: How long does it take to dial-in new process parameters?

A: The time needed to confirm a balanced cleaning process, will depend upon details regarding conformal coating, board components and then factoring in details of time, energy, solvency, and temperature.