How to Avoid Oxidation Problems on PCB Pads?
PCB assembly is the process of soldering electronic components to printed circuit boards (PCBs), where PCB pads are copper foil areas used to fix and connect component pins. The solderability and reliability of PCB pads directly affect the quality and performance of PCBA, therefore, avoiding and removing PCB pad oxidation is an important issue in PCB assembly. This article will introduce the causes of PCB pad oxidation, and the techniques of using different surface treatment processes and cleaning methods to prevent and eliminate PCB pad oxidation.
The causes of PCB pad oxidation mainly include two aspects: one is the influence of external environment, and the other is the problems in the soldering process. The influence of external environment includes humidity, temperature, pollutants, etc. in the air, which will accelerate the reaction of copper foil with oxygen or other substances, forming oxides or sulfides, etc. The problems in the soldering process include high soldering temperature, long soldering time, flux residue, etc., which will damage the protective layer on the PCB surface, making the pads exposed to the air and prone to oxidation.
PCB pad oxidation will cause pad refusal or false soldering, affecting the circuit connection and signal transmission, and even causing short circuit or open circuit faults. Therefore, in order to ensure the quality and reliability of PCB assembly, effective measures must be taken to prevent and remove PCB pad oxidation.
The measures to prevent PCB pad oxidation mainly include two aspects: one is to choose a suitable surface treatment process, and the other is to use a correct cleaning method. Surface treatment process refers to coating a protective film on the PCB pad to isolate air and moisture, delay or prevent oxidation. Common surface treatment processes include organic solderability preservative (OSP), hot air leveling (HASL), gold plating, tin plating, silver plating, etc.
Different surface treatment processes have their own advantages and disadvantages, which need to be selected according to the use, performance requirements, cost budget and other factors of PCB. Generally speaking, OSP process has the advantages of environmental protection, low cost, good flatness, etc., but also has the disadvantages of poor heat resistance, easy pollution, short storage period, etc. HASL process has the advantages of good heat resistance, long storage period, etc., but also has the disadvantages of not environmental friendly, poor flatness, easy peeling of pads, etc. Gold plating process has the advantages of good corrosion resistance, good solderability, long storage period, etc., but also has the disadvantages of high cost, easy production of gold-tin compounds, etc. Tin plating process has the advantages of good solderability, low cost, etc., but also has the disadvantages of easy oxidation, easy production of tin whiskers, etc. Silver plating process has the advantages of good conductivity, good solderability