PCBA Reliability Manufacturing and Cleaning Process
“PCBA we manufacture are clean as we use NO CLEAN flux for soldering so we don’t need cleaning them”
I hear it all the time…. particularly at some EMS who are not working on critical electronic.
Although “NO CLEAN” fluxes are designed to be left on the board without cleaning, they still leave some residue. This residue, while not harmful to the PCB’s functionality under normal conditions, can still be visually unappealing or problematic in certain applications.
HIGH FREQUENCY & HIGH RELIABILITY
For high-frequency or high-reliability applications, such as in aerospace or medical devices, even small amounts of residue may interfere with the electrical performance or require removal to ensure stringent reliability standards are met.
TESTING & INSPECTION
The residues left by “No Clean” processes can sometimes complicate testing and inspection. Residues from “No Clean” flux can complicate testing procedures such as Automated Optical Inspection (AOI) and In-Circuit Testing (ICT). The presence of residues can cause issues with test probes making reliable contact with the board, leading to false readings or failed tests.
CONFORMAL COATING
Residues can interfere with the adhesion of conformal coatings, which are applied to protect electronic circuits from environmental exposure. Poor adhesion can lead to coating failures and reduced protection over time.
MOISTURE GENERATION
In harsh environments, even the benign residues left by “No Clean” flux can absorb moisture, which can lead to conductivity issues or corrosion over extended periods. This is a significant concern in high-reliability sectors like aerospace, automotive, or military applications, where even minor performance issues can have serious consequences.
CHEMICAL REACTION
While designed to be non-reactive under normal conditions, the chemical components of “No Clean” flux residues can still interact with other materials or chemicals used in further manufacturing processes. This can lead to unpredicted chemical reactions, especially if other process chemicals come into contact with the residue.
HIGH DENSITY CONSIDERATION
In some cases, even when using “No Clean” flux, selective cleaning might be necessary to remove residues from specific areas of the PCB, especially in high-density or precision applications where any contamination could impair functionality.
It’s important to note that while “No Clean” fluxes minimize the need for cleaning, they are not suitable for every application. In scenarios where high precision and ultra-clean environments are required, additional cleaning might still be necessary.
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