Optimize PCB board design from the perspective of PCB cost

2021-10-27

Author：Downs

The PCB splicing involved in this article refers to the splicing done during PCB design. An optimized panel size should enable the PCB to obtain the highest possible utilization rate of the board when making the production panel, and thus obtain a lower PCB price. Here we mainly discuss how to realize the optimized panel size by controlling the edge strips added on the panel, the number of PCB units, the arrangement of PCB units, the panel method, etc., so as to achieve the purpose of reducing PCB costs.

1. The significance of PCB board design

After the PCB is routed, due to the requirements of the PCBA assembly process, it is necessary to design the PCB with special shapes, so that the subsequent PCBA assembly process can proceed smoothly. It is usually necessary to add side strips during panel design, and connect one or several PCB units with the side strips in a certain way to form a PCB shape that meets the requirements of PCBA assembly. The size of the panel will have a direct impact on the material utilization rate and the size of the panel during PCB production, and even significantly affect the price of the PCB. The number, width, position, number of PCB units, the arrangement of PCB units, the connection method, and the slot width in the jigsaw will affect the size of the jigsaw.

This article mainly discusses how to optimize the size of the puzzle by controlling these influencing factors under the premise of meeting the requirements of the PCB and PCBA assembly process during the panel design process, so that it can produce high board utilization when forming the PCB production panel Rate and appropriate production board size, so as to obtain a lower PCB quotation.

2. Under what circumstances need to do jigsaw design

pcb board

In the following situations, the PCB needs to be spliced to form a spliced board to meet the PCBA assembly requirements:

(1) The mechanical structure requirements of the design itself

(2) The component pads are too close to the edge of the PCB, the top layer is less than 4.06 mm, and the bottom layer is less than 5.08 mm (the top layer is less than 0.16 inches, and the bottom layer is less than 0.2 inches)

(3) The test point that needs soldering tin is too close to the edge of the board, the top layer is less than 4.06 mm, the bottom layer is less than 5.08 mm (the top layer is less than 0.16 inches, and the bottom layer is less than 0.2 inches)

(4) Irregular shape or size is too small to pass the PCBA assembly line smoothly

(5) To improve the production efficiency of PCBA assembly

3. Terms and definitions about jigsaw

Introduce the terms and definitions of the puzzle, so as to explain how to optimize the puzzle from the perspective of cost.

1. What is jigsaw

Jigsaw puzzle refers to adding side strips to the PCB unit when necessary to meet the PCBA assembly requirements, and connecting one or several PCB graphics with the side strips in a certain way to form a larger and regular PCB shape. There are two common ways to join the board: connecting ribs and V-CUT.

2. What is production jigsaw

The production of jigsaw panels means that in order to improve production efficiency and meet the needs of the manufacturing process, adding process edges and connecting one or several panels to the process edges in the production of PCBs.

Production jigsaw refers to increase the process edge and connect one or several jigsaws to the process edge in order to improve the production efficiency and meet the needs of the process during the production of PCB

3. What is the utilization rate of plate?

Utilization rate of panels = (panel area * number of panels / area of production panels) * 100%, that is, panel utilization = (X * Y * n/AxB) * 100%

4. What is the standard production jigsaw

(1) Standard production board size.

The size of the copper clad laminate for PCB is fixed, and the PCB production jigsaw is cut from it, so the production jigsaw usually has the standard size A*B, as shown in Table 1. Because of the differences in the size of copper clad laminates and the production equipment capabilities of various PCB companies, Table 1 does not include all standard sizes.

The size of the copper clad laminate for PCB is fixed, and the PCB production jigsaw is cut from it, so the production jigsaw usually has a standard size of A*B, as shown in Table 1-Shenzhen Honglijie

(2) Conventional parameters in the production of jigsaw puzzles.

The conventional parameters on the production panels may vary among PCB companies. Table 2 shows some typical values (referring to the minimum values).

The conventional parameters on the production board may vary among PCB companies. Table 2 shows some typical values (referring to the minimum value)

Fourth, the cost control in the process of PCB design and assembly

In the PCB production jigsaw, the minimum spacing between the jigsaw (a1, a2) and the process edge dimensions (b1, b2) are relatively fixed. The change of the jigsaw size (X*Y) may cause the jigsaw in the production jigsaw The total quantity (n) increases, or the size of the production panel (A*B) is reduced, and the utilization rate of the board is improved. Therefore, the size of the panel will directly affect the utilization rate of the board and the size of the panel during the production of the PCB, thereby affecting the price of the PCB. The following describes how to optimize the size of the puzzle in the process of designing the puzzle.

1. Standardization of edge strips and slot widths

Under the premise of meeting the PCB manufacturing process and PCBA assembly process, the width of the edge strips and grooves of the panel should be minimized, so that the overall size of the panel can be reduced, and the flexibility of production panel selection and the utilization rate of the board can be improved.

In summary, the side strip width and groove width are formed as shown below.

When there are mounting holes in the PCB graphics that can be used for PCB production and PCBA assembly, there is no need to increase the mounting holes on the edge strips of the jigsaw board, and the size of the added edge strips can be further reduced. For example, the side strip width is further reduced to 2.007 mm (0.079 inch), while the slot width between the side strip and the PCB unit remains 2.007 mm (0.079 inch), so as to ensure that the minimum distance between the components and the board edge is 4.064 mm (0.16 inch). This narrow side strip should be used under the condition of fully evaluating the side strip rigidity and PCBA assembly requirements. When there is no reflective point designed for PCBA assembly and alignment in the PCB graphics, it is necessary to add reflective points on the side strips. At this time, a wider size side strip is required when the board is assembled. Therefore, from this point of view, it is not advisable not to design reflective points in the PCB graphics.

The following is an application example of optimizing edge and groove width in puzzle:

(1) PCB related parameters and puzzle.

The PCB is a 6-layer board with dimensions mm (in) 182.4*198.91 (7.181*7.831). There are impedance control requirements. The reason for the need to join the board is that the components are less than 4 mm from the board edge and the shape is irregular.

Jigsaw panels with different side strip widths and groove widths are used. Panel 1 uses standard side strip widths and groove widths, while panel 2 uses larger side strips and groove widths. The paneling methods are all connecting ribs.

Use different side strip widths and groove widths. Panel 1 uses standard side strip widths and groove widths, but uses larger side strips and groove widths. The splicing methods are all connecting ribs.

(2) Arrangement in the production puzzle.

(3) Analysis of the advantages and disadvantages of the puzzle and price comparison

The size of the production panels and the utilization rate of the panels required for these two panels.