PCBA cleanliness standards are very helpful to increase the reliability of finished products. You may not know, but PCBA can pick up several contaminations during the manufacturing procedure. If not properly cleaned this could impact the functioning of the whole product. With components manufacturers developing smaller and smaller packages, ensuring cleanliness has become ever so difficult.
Although there are various PCBA cleanliness standards to protect PCBA from such failures, it pretty much depends on your contract manufacturer or supplier to bind a robust mechanism for inspection and cleaning of manufactured boards.
What happens when Cleanliness specifications are not met?
From etching the metals to the application of solder, a PCBA is subjected to various processes in manufacturing. These processes can leave residues and contaminants that can cause several short-term and long-term problems in finished products. Short term concerns might not appear as issues in some cases but they can cause functional problems that are difficult to investigate or reproduce. A common example of this is the No-clean flux residue. Although there doesn’t seem to be an evident concern associated with it it may leave the board looking messy and the residue left can create issues while testing.
Long term issues such as ionic contamination pose a much bigger threat to the integrity of the entire manufacturing process. When exposed to humidity, these ionic contaminations can become conductive resulting in accelerated corrosion of conductive materials in PCBA, consequently shorting the nets. Other long term issues include poor adhesion of the conformal coating, functional issues with mounted components, poor soldering of contacts, and interconnects.
Effective Cleaning and Testing methods for robust electronics
Using an in-line wash mechanism with heated De-ionized water is one of the most effective methods of ensuring PCB cleanliness. The water pressure is selected and set in accordance to certain guidelines issued from the solder and component manufacturer or supplier. In addition to this, your contact manufacturer may also employ other cleaning methods such as removal of no-clean flux residues, Iso-propanol wipe downs, and ultrasonic cleaning. Usually, you will have to submit a written request demanding these specialized cleanings.
Cleaning of PCBA’s should be followed by an effective testing strategy to ensure the measures taken are providing results. Manufacturers usually include the Resistivity of Solvent Extract (ROSE) to ensure this. Your Contact Manufacturer is likely to provide you approval from a third-party service provider as proof of standard cleanliness among their manufacturer products.