How to Prevent the Warpage of Circuit Board_Shenzhen StarLight Industrial Development Co., Ltd.

How to Prevent the Warpage of Circuit Board

source:Other information release time:2022-11-18 Hits: Popular:PCB Assembly company: Share:

　　 1.5oz Multilayer Pcb Fabrication FR4 Printed Circuit Board Pcb 4 Layer

　　1、 Why is the PCB required to be very flat

　　In the automatic insertion line, if the printed circuit board is not flat, it will cause inaccuracy, and components cannot be inserted into the holes of the board and surface mount pads, or even damage the automatic insertion machine. The circuit board with components is bent after welding, and it is difficult to cut the component legs neatly. The circuit board can not be installed on the chassis or the socket inside the machine, so it is also very troublesome for the circuit board factory to encounter the board warping. At present, the printed circuit board has entered the era of surface mounting and chip mounting, and the requirements of circuit board manufacturers on board warping must be increasingly strict.

　　2、 Standard and test method for warpage

　　According to the U.S. IPC-6012 (1996 edition) (Qualification and Performance Specification for Rigid Printed Circuit Boards), the maximum allowable warpage and twist for surface mounted printed circuit boards is 0.75%, and 1.5% for other types of boards. Compared with IPC-RB-276 (1992), the requirements for surface mounted printed circuit boards are improved. At present, the allowable warpage of each electronic assembly plant, no matter the double-sided circuit board or multilayer circuit board, is usually 0.70-0.75% with a thickness of 1.6mm. For many SMT and BGA boards, it is required to be 0.5%. Some electronic factories are encouraging to raise the standard of warpage to 0.3%. The method of testing warpage shall comply with GB4677.5-84 or IPC-TM-6502.4.22B. Put the printed circuit board on the verified platform, insert the test pin at the place with the maximum warpage, and calculate the warpage of the printed circuit board by dividing the diameter of the test pin by the length of the curved edge of the printed circuit board.

　　3、 Anti warping plate during manufacturing

　　1. Engineering design: Precautions for PCB design:

　　A. Multilayer circuit board core board and prepreg shall be from the same supplier.

　　B. The arrangement of interlayer prepreg shall be symmetrical. For example, for six ply boards, the thickness between 1~2 and 5~6 layers shall be consistent with the number of prepreg sheets, otherwise it is easy to warp after lamination.

　　C. The area of the outer layer A and B lines should be as close as possible. If the A side is large copper and the B side only runs a few wires, this kind of printed board is easy to warp after etching. If the difference between the line areas on both sides is too large, some independent grids can be added on the thin side for balance.

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