Multi-layer printed circuit board machining process

Abstract

The invention discloses a multi-layer printed circuit board machining process, which sequentially comprises the following steps: 1) manufacturing a circuit diagram and frame diagrams on a copper clad board, wherein the frame diagrams comprise a frame diagram I and a frame diagram II, the circuit diagram, the frame diagram I and the frame diagram II are sequentially arranged from the central zone of the copper clad board to the outside, and the copper residual rate of the frame diagram I is smaller than the copper residual rate of the frame diagram II; 2) laminating the copper clad board into a multi-layer circuit board, and milling off the outer edge of the multi-layer circuit board comprising the frame diagram II; 3) manufacturing a through hole, an outer diagram and a solder mask of the multi-layer circuit board; and 4) milling the multi-layer circuit board into the designed finished size. By adopting the machining process of the invention, the machining precision of the PCB is high, and the size of the PCB is accurate.

Description

technical field [0001] The invention relates to a processing technology of a printed circuit board, in particular to a processing technology of a multilayer printed circuit board. Background technique [0002] The current multilayer printed circuit board processing technology is to make graphics on the copper clad laminate, press it, and then mill out the frame. There are two main techniques: [0003] One is "glue dot jigsaw frame", and the other is "big copper skin jigsaw frame". [0004] Such as figure 1 The frame of glue-flow point assembly shown is outside the design pattern 1 of the copper-clad laminate, and the copper-clad surface other than the circuit pattern is made into circular copper-clad points 21, also called "glue-flow points". The circular copper-clad The copper skin other than point 21 is etched away to expose the substrate. Using the frame of the flow point is beneficial to avoid the shrinkage effect of the frame on the graphics in the board, and the ro...

AI Technical Summary

Problems solved by technology

However, due to the inconsistent stress parameters such as the material shrinkage rate of the substrate and the copper skin during the processing of the copper clad laminate, stress is generated between the copper skin and the substrate of the copper clad laminate.

Generally, the shrinkage or expansion coefficient of the substrate is relatively large, and the copper skin is relatively stable. The frame of the single flow glue point will have a low residual copper rate, and the shrinkage and expansion of the flow glue point frame with independent design will be relatively large, which will lead to internal wiring. Figure 1 is subject to the shrinkage pressure or expansion tension of the frame of the flow glue point, resulting in a large dislocation, that is, the expansion or contraction ratio of each layer of copper clad laminate may be different, which affects the alignment between the layers during the lamination process, so The alignment accuracy between the layers of the flow glue point frame is low

[0005] The frame of the large copper skin panel is to keep the copper skin 4 on the copper clad board outside the circuit pattern 1, or simply divide the copper skin 4 into several large copper skins. The copper coating rate is very high, so the "big copper skin" is used The outer frame of the copper clad laminate with "leather puzzle frame" is relatively stable. During lamination, the alignment accuracy between layers is high. However, after lamination, after milling part of the frame, the remaining part of the frame is still required for the follow-up Processes, such as making via holes, outer layer graphics, making solder mask, etc., if a large copper frame is used, at this time, the internal effective graphic part of the circuit board is still restrained by the external stable large copper frame, so its size is not large. change, but the stress between the frame and the internal circuit pattern 1 is very large, which induces the reverse direction stress of the circuit pattern 1 in the board

When all the processes are completed and we mill off the remaining frame, once the restraint or restriction of the original frame on the internal graphics is removed, the circuit board containing the internal graphics will immediately shrink or expand due to the internal stress that existed before, resulting in the size of the final product and The original design did not meet

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