PCB Technical - Problems to be considered in PCB design

For ease of expression, analysis from seven aspects: cutting, drilling, wiring, solder mask, characters, surface treatment and forming:

one. Cutting material mainly considers the board thickness and copper thickness:

The standard series is 1.0 1.2 1.6 2.0 3.2 MM for the thickness of the sheet material greater than 0.8MM. The thickness of the sheet material is less than 0.8MM and does not count as the standard series. The thickness can be determined according to the needs, but the commonly used thicknesses are: 0.1 0.15 0.2 0.3 0.4 0.6MM, this material is mainly used for the inner layer of multilayer boards.

When designing the outer layer, pay attention to the thickness of the board. PCB production and processing need to increase the thickness of copper plating, solder mask thickness, surface treatment (tin spraying, gold plating, etc.) thickness, characters, carbon oil and other thickness. The actual production of sheet metal will be thicker than 0.05-0.1 MM, the tin plate will be slightly thicker than 0.075-0.15MM. For example,

when the finished product requires a thickness of 2.0 mm during the design, when the 2.0mm sheet is normally used for cutting, the thickness of the finished sheet will reach 2.1-2.3mm, taking into account the sheet tolerance and processing tolerances. In the meantime, if the design requires that the thickness of the finished plate should not be greater than 2.0mm, the plate should be made of 1.9mm unconventional plate material. The PCB processing plant needs to temporarily order from the plate manufacturer, and the delivery cycle will become very long.

When the inner layer is made, the thickness after lamination can be adjusted through the thickness and structure configuration of the prepreg (PP). The selection range of the core board can be flexible. For example, the thickness of the finished board is required to be 1.6mm, and the choice of the board (core board) can be 1.2 MM can also be 1.0MM, as long as the thickness of the laminated plate is controlled within a certain range, the thickness of the finished plate can be met.

The other is the board thickness tolerance issue. PCB designers should consider the board thickness tolerance after PCB processing while considering the product assembly tolerance. There are three main aspects that affect the tolerance of the finished product, including the incoming sheet tolerance, the lamination tolerance and the outer layer thickening tolerance. Several conventional sheet tolerances are now provided for reference: (0.8-1.0)±0.1 (1.2-1.6)±0.13 2.0±0.18 3.0±0.23 The lamination tolerance is controlled within ±(0.05-0.1) according to different layers and thicknesses MM. Especially for boards with board edge connectors (such as printed plugs), the thickness and tolerance of the board need to be determined according to the requirements of matching with the connector.

The board thickness and copper thickness are the most important issues to consider in PCB design. Pay attention and be careful in PCB production.