PCB inspection and testing is conducted as a part of PCB manufacturing. Today, PCBs are becoming a must-have for industrial electronic circuits. Today’s PCB designs are more complex, which make PCB testing and inspection two essential processes. Various types of testing and inspection is conducted by PCB assembly manufacturers to detect defects, issues, and faults in the PCB. These methods also help ensure that PCBs are working as per the requirement. This post discusses various PCB challenges, types of testing, and inspection services performed by PCB assembly manufacturers.
Understanding PCB Challenges
The manufacturing of a PCB is complex, and it consists of various components and processes. Although PCBs are manufactured through a series of automated processes, but sometimes defects are introduced unintentionally. The following are various challenges incurred by PCB failure analysts, when they are testing and inspecting PCBs for defects.
- Growing Demand for Lead-Free Assemblies: The demand for lead-free assemblies is on the rise. The assembly of lead-free PCBs is conducted at high temperatures with traditional tin-lead soldering processes. The high temperature may affect the electronic components and solder joints. To examine this, a special type of testing known as tin whisker testing is conducted by failure experts on lead-free assemblies. This is done to ensure both soldering and components are in good working condition.
- Thermal Stress: Stress from humidity or heat is the common cause of failure in PCBs. As the expansion rates of components vary, there are chances that the soldering joint may break down. The stress builds up even if there is a change in copper weight, or plating alignment. The performance of a PCB may get affected by the temperature of the room as well.
- Surface Finish Irregularities: The surface finish is the most important decision for any PCB assembly manufacturer. Any irregularities in surface finish affects the productivity, increases rework, field failure rates, scrap rates, and overall production costs.
- High-speed Printed Circuit Boards (HSCBs): The demand for high speed printed circuit boards is growing. These circuit boards are made from a variety of components, which are fixed on multilayer boards to avoid failure in high speed applications. Failures may be introduced by wrong placement of chips and pins on the circuit board.
- Flux Contamination: This is a most common soldering problem found in PCBs. Flux residues absorb moisture and become conductive. This conductivity causes short circuits, and contaminates the solder.
- Metallic Electro Migration: This is an electro-chemical process, which involves transportation of a metal across the non-metal medium under the influence of a current. This condition may cause current leakage, or a breakdown between conductors, and electrical shorts.
- Chemical Fluid Leakage: Any fluid leaked from a component may damage the PCB. Although most chemicals are removed during the manufacturing process, however, trace elements may be left behind, which causes leakage. The leakage may take place within the component, which may affect the performance of the PCB. The chemical leakage may cause corrosion as well as create shorts between conductors.
- Barrel Fatigue: This refers to the cracking of the copper plating that forms the Plated Through Hole PCB Assembly (PTH Wall). This occurs due to the out-of-plane coefficient of thermal expansion (CTE), and the plating of copper.
The above-mentioned challenges will help you understand why testing and inspection is becoming a necessity of a PCB design process. In the next post, we will discuss various types of tests and inspection services provided by PCB manufacturers.