Issue link: https://iconnect007.uberflip.com/i/551288
50 The PCB Magazine • August 2015 Iv. Risk Mitigations at PCB Manufacturer A. Sample Inspection on Base Laminate IPC-4101 [8] specifies sample frequency and criteria for acceptability of sub-surface imperfec- tions. Some PCB manufacturers use this as a test method for incoming inspection of batches of base laminates. The method may be inefficient, since copper cladding needs to be etched from the laminate before inspection is possible, after which the laminate cannot be used any more for PCB manufacture. Furthermore, the sample LATENT SHoRT CIRCUIT FAILURE IN HIGH-REL PCBS continues Figure 8: Top view of a laminate after etching of copper cladding, showing a plant seed embedded in the dielectric material, probably carried into the clean room on clothes of personnel. The scale is in mm. Figure 9: Top view of a prepreg showing an embedded insect. Figure 10: examples of etched innerlayers scrapped due to the presence of contamination. FeAture