1、Setting of through-holes(applicable to two-layer,four-layer,and multi-layer boards)
The setting of holes through wire holes:The minimum aperture definition of the finished plate depends on the thickness of the plate,and the ratio of plate thickness to aperture should be less than 5-8.
The preferred pore size series are as follows:
Aperture:24mil 20mil 16mil 12mil 8mil
Pad diameter:40mil 35mil 28mil 25mil 20mil
Inner thermal pad size 50mil 45mil 40mil 35mil 30mil
The relationship between plate thickness and minimum pore size:
Plate thickness:3.0mm 2.5mm 2.0mm 1.6mm 1.0mm
Minimum aperture:24mil 20mil 16mil 12mil 8mil
Blind hole and buried hole:Blind hole is a through hole that connects the surface and inner layers without penetrating the entire board.Buried hole is a through hole that connects the inner layers but is not visible on the surface of the finished board.The size settings of these two types of through holes can refer to through hole.When applying blind hole and buried hole designs,it is necessary to have a thorough understanding of the PCB processing process to avoid unnecessary problems in PCB processing.If necessary,it is necessary to negotiate with the PCB supplier.Test hole:Test hole refers to a through hole used for ICT testing purposes,which can also be used as a through hole.In principle,the aperture is not limited,the diameter of the solder pad should not be less than 25mil,and the center distance between test holes should not be less than 50mil.It is not recommended to use component welding holes as test holes.
2、Setting Grid Points in PCB Design
Reasonable use of the grid system can help us achieve twice the result with half the effort in PCB design.But what is rationality?Many people believe that setting a smaller grid point is better,but in fact,it is not.Here,we mainly discuss two aspects:the first is the selection of grid points at different stages of design,and the second is the selection of different grid points for wiring.Different stages of design require different grid settings.In the layout stage,large grid points can be selected for device layout;For large devices such as ICs and non positioning connectors,a grid accuracy of 50-100mil can be selected for layout,while for passive small devices such as resistors,capacitors,and inductors,a grid accuracy of 25mil can be selected for layout.The accuracy of large grid points is beneficial for device alignment and layout aesthetics.In the design with BGA,if a 1.27mm BGA is used,we can set the grid point accuracy to 25mil during fan out,which is beneficial for the through-hole of fan out to be precisely punched in the center position of the four pins;For BGA of 1.0mm and 0.8mm,it is best to use mm units for layout,so that the fan out via can be set well.For fanout of other ICs,it is also recommended to design with a large grid point design accuracy.We suggest that the grid point for fan out should preferably be 50mil or even larger.It is best to ensure that wires can be routed between every two vias.
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Design standards and process requirements for PCB pads and vias
View：3248 Release Date：2023/6/8 19:16:51