The role of metallographic microscopes in the process control of PCB board technology
1. The role of metallographic microscope in process control of PCB slicing technology
The production of PCB boards is a process of multiple processes collaborating with each other. The quality of the product in the previous process directly affects the production of the product in the next process, and even directly affects the quality of the final product. Therefore, quality control of key processes plays a crucial role in determining the quality of the final product. As one of the detection methods, metallographic sectioning technology is playing an increasingly important role in this field.
The role of metallographic microscope in the process control of PCB slicing technology includes the following aspects
2.1 Function in raw material incoming inspection
The quality of copper-clad laminates required for multi-layer PCB 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:
2.1.1 Copper foil thickness, check whether the copper foil thickness meets the production requirements of multi-layer printed boards.
2.1.2 Thickness of insulation layer and arrangement of semi cured sheets.
2.1.3 The longitudinal and latitudinal arrangement of glass fibers and resin content in insulating media.
2.1.4 Defect Information of Laminated Plates There are mainly the following types of defects in laminated plates:
(1) Pinhole
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
Pitting refers to small holes that have not fully penetrated the metal foil: Concave pits refer to the slight protrusions that may appear on the surface of the copper foil after being pressed, which may be caused by the use of local grinding steel plates during the pressing process. 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
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
Wrinkles 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
Laminated voids refer to areas where there should be resin and adhesive inside the laminated board, but the filling is incomplete and there are missing areas; 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.
