The role of metallographic microscope in the process control of PCB board slicing technology

The role in the inspection of raw materials as a copper-clad laminate required for the production of multilayer PCBs, its quality will directly affect the production of multilayer PCBs. The following important information can be obtained from the slices taken by the metallurgical microscope: 1.1 Copper foil thickness, whether the copper foil thickness meets the production requirements of the multilayer printed board. 1.2 The thickness of the insulating dielectric layer and the arrangement of the prepreg. 1.3 In the insulating medium, the arrangement of the warp and weft directions of the glass fibers and the resin content. 1.4 Defect information of metallographic microscope laminates The defects of laminates are mainly as follows: (1) Pinhole refers to a small hole that completely penetrates a layer of metal. For the manufacture of multilayer printed boards with higher wiring density, such defects are often not allowed. (2) Pockmarks and pits Pockets refer to small holes that have not completely penetrated the metal foil: pits refer to the fact that the pressing steel plate used may have some protrusions during the pressing process, resulting in the appearance of the pressed copper foil The subsidence phenomenon eased. The size of the small hole and the depth of depression can be measured by metallographic slice to determine whether the existence of the defect is allowed. (3) Scratches Scratches refer to thin and shallow grooves drawn by sharp objects on the surface of copper foil. The width and depth of the scratches are measured by metallographic microscopy to determine whether the existence of the defect is allowed. (4) Wrinkle Wrinkle refers to the crease or wrinkle of the copper foil on the surface of the pressing plate. It can be seen from the metallographic slice that the existence of this defect is not allowed. (5) Laminated voids, white spots and blisters Laminated voids mean that there should be resin and adhesive inside the laminate, but the filling is incomplete and there are missing areas; white spots occur inside the substrate at the intersection of the fabric The phenomenon of glass fiber and resin separation is manifested by scattered white spots or "cross patterns" under the surface of the substrate; blistering refers to the local expansion of the substrate layer or between the substrate and the conductive copper foil, causing local separation The phenomenon. The existence of such defects depends on the specific situation to decide whether to allow.