Grinding and Polishing Techniques for PCB Manufacturing

Grinding is a crucial step in PCB manufacturing, where the sample is ground to the center of the hole using sandpaper to observe the cross-section of the hole wall. A rapid grinding method with a fast turntable is often employed for efficient mass production.

• Rough Grinding: Start with No. 220 sandpaper until two parallel lines of the hole wall fault appear. Use water or other liquids to reduce heat buildup.
• Further Grinding: Switch to No. 400 sandpaper and regrind until the indication line of the center of the hole is visible.
• Final Touch: Use fine sandpaper above 600 grit to correct any non-parallel oblique grinding.

After grinding, careful polishing is essential to remove sandpaper scratches and reveal the true slice. Micro-contact polishing with a rotary felt and alumina suspension is recommended for a uniform effect. Changing the cutting sample direction frequently during polishing helps eliminate sand marks.

Microetching is then performed after polishing to analyze the metal layers and crystallization condition. A micro-etching solution of ammonia, pure water, and hydrogen peroxide is applied to the surface for a few seconds before rinsing and drying.

Photography is a valuable tool for record-keeping and communication in PCB manufacturing. Proper alignment of the focal length is crucial for capturing detailed images. Calculating the required light intensity and exposure time is essential for achieving optimal photos. Various filters can be used to enhance different effects, but ensuring a flat image surface is critical to avoid distortion.