Applications of Metallographic Microscopes in PCB Production
The role of incoming material inspection in the production of multi-layer PCB boards is that the quality of copper-clad laminates required for multi-layer PCB board production will directly affect the production of multi-layer PCB boards. The following important information can be obtained from the slices taken by a metallographic microscope:
1.1 Copper foil thickness, check whether the copper foil thickness meets the production requirements of multi-layer printed boards.
1.2 Thickness of insulation layer and arrangement of semi cured sheets.
1.3 The longitudinal and latitudinal arrangement of glass fibers and resin content in insulating media.
1.4 Metallographic microscope laminated plate defect information: The main defects of laminated plates are as follows:
(1) Pinhole refers to a small hole that completely penetrates a layer of metal. For the production of multi-layer printed boards with high wiring density, such defects are often not allowed.
(2) Pitts and dents refer to small holes that have not completely penetrated the metal foil: dents refer to small protrusions that may appear in some parts of the steel plate used for pressing during the pressing process, causing a gentle sinking phenomenon on the copper foil surface after pressing. The presence of the defect can be determined by measuring the size of the small hole and the depth of subsidence through metallographic slicing.
(3) Scratches refer to fine and shallow grooves drawn on the surface of copper foil by sharp objects. Measure the width and depth of scratches through metallographic microscope slicing to determine whether the existence of the defect is allowed.
(4) Wrinkles and folds refer to the creases or wrinkles on the copper foil surface of the pressure plate. The presence of this defect is not allowed as can be seen from the metallographic section.
(5) Laminated voids, white spots, and bubbles refer to areas where there should be resin and adhesive inside the laminated board, but the filling is incomplete and lacking; White spots are a phenomenon that occurs inside the substrate, where glass fibers separate from resin at the interweaving point of the fabric, manifested as scattered white spots or "cross patterns" below the surface of the substrate; Bubbling refers to the phenomenon of local expansion and separation between the layers of the substrate or between the substrate and the conductive copper foil. The existence of such defects depends on the specific situation to determine whether they are allowed.
