Standard IPC Coupon Layouts for Panelized PCB Verification
Standard IPC coupons placed along panel waste borders verify plating, registration, and impedance without consuming functional board surface area.
Cross-Section Polish
Metallographic Preparation
High-precision surface finishing of encapsulated electronics samples allows the inspection of internal solder joint structures without introducing mechanical damage or smear. Destructive physical analysis relies on cross-section polish to reveal microstructures, intermetallic compound layers, and internal voids within a sample. The smooth finish is essential for accurate scanning electron microscopy or optical inspection.
Analysis Action
Rotary grinding plates with increasingly fine grit sizes are used to remove material from the cut sample before final finishing. This sequential grinding phase of cross-section polish requires a lubricant to prevent thermal damage to the epoxy-mounted circuit board. A final step uses sub-micron diamond or colloidal silica suspensions to polish the surface to a mirror finish.
This process allows microscopic features down to fifty nanometers to be measured accurately. Ensuring a clean finish is critical because mechanical smears would otherwise obscure tiny cracks in the intermetallic layer.
Acceptance Boundary
Solder joint integrity is confirmed by measuring the continuous intermetallic compound layer that forms between the lead and the pad. When evaluated after a cross-section polish, the copper-tin intermetallic layer should measure between one and three microns to indicate a reliable metallurgical bond. Any presence of microcracks or separation at this boundary marks the assembly as a failure.