Corrected During PCB Fabrication
As with any manufacturing process, things can go wrong. When things do, it’s critical that the board’s manufacturer knows about it and can quickly correct it. Defects in PCB fabrication are typically corrected through automated optical inspection, X-ray inspection, ionic cleanliness testing and flying probe testing. Some defects are corrected through manual touch-up, re-etching, or re-soldering. Inspecting after each major fabrication step catches defects early on when they are easiest to fix.
Before the actual board is made, it must be fabricated from its raw materials. During this stage, the PCB design is printed onto films by laser direct imaging (LDI), which create photo negatives of the board layout. This digital image is then used as a guide for the rest of the fabrication process.
The film is then applied to the pcb board fabrication material layers and exposed to ultraviolet light. The areas not covered by the film are then chemically etched, exposing copper in precise locations. The conductive patterns and drilled holes are then filled with copper. Once the copper is plated, it is inspected and reworked as needed.
How Defects Are Corrected During PCB Fabrication
This process is prone to a number of defects that can impact the quality and reliability of the finished product. Some of the most common issues include: Plating voids: When copper does not coat evenly during the deposition process, it can cause short circuits and other problems. This may be caused by contamination, air bubbles caught in the coating, rough hole drilling or uneven catalyzation of the copper.
Surface oxidation and contamination: When copper, solder mask, or silk-screening flakes off the finished board, it can result in poor conductivity, welding performance, and visual defects. This may be caused by improper cleaning or etching, over-etching, solvent dripping, airborne contaminants, etc.
Internal layer misalignment: When drilled holes are positioned incorrectly on the inner layers, it can interfere with assembly and connection reliability. Hole position is also a problem when buried or blind vias are not positioned properly.
Out-of-tolerance features: When traces, spaces, or holes are not sized correctly per specifications, it can cause shorts and other problems. Board warpage: When the board is not flat enough to meet tolerances, it can cause flexing and other problems during use.
Mechanical damage: Because they are so thin, PCBs are susceptible to mechanical damage during fabrication. Impacts, scratches, bends, and dents can destroy the traces and solder joints. Vibration, stretching and dropping can also damage the boards.
The best way to avoid these common defects is to work with a PCB manufacturer that incorporates their engineers into the design stage so they can identify and remove manufacturability risks early. Design for Manufacturability (DFM) analysis and simulation tools help verify that the finished board will withstand real-world stresses and perform reliably. In addition, a thorough QA program can catch and prevent many of these defects before they are ever produced. This helps ensure that the finished product will meet your exact requirements. Contact Levison Enterprises today to request a quote on your next project.
