In the design of RF hardware, electromagnetic interference needs to be considered, and the design of the shield is essential. Today's article introduces the design specifications of shielding covers and the types of shielding covers.
Some notes about shield design are as follows:
The shield material can be made of tinplate, or white copper (good performance and easy to process), or stainless steel (can only be used as a shield cover). The material of the shielding frame is tinplate alloy or white copper to ensure good welding performance. The thickness of the material is generally between 0.1-0.6mm, 0.2mm and 0.3mm are more commonly used.
Shield pad width is between 0.7-1mm.
Design of heat dissipation holes: Considering heat dissipation, it is necessary to increase heat dissipation holes. The hole diameter is generally between 1-1.5mm, and the hole spacing is about 5mm.
When considering batch welding, it is necessary to reserve a vacuum cleaning area in the middle of the shield (guaranteed to be a flat surface without openings), and generally the diameter of this area is not less than 5mm.
The device pad should be at least 0.3mm away from the edge of the shield pad.
When soldering, consider the solder height of 0.1mm, and ensure at least 0.2mm above the top of the shield.
Great Wall Foot Design: Try not to solder the entire surface of the shield cover, which will cause tin stacking. Generally, 2-1-2-1mm method of Great Wall foot welding is used, 2mm contact, 1mm hanging in the air to facilitate tin climbing, which can ensure the adhesion strength of the shield.
If the shield is symmetrical in shape, additional markings are required, such as positioning holes or equilateral triangle scribe lines.
Regarding the welding form, there are currently three mainstream types as follows:
Two Piece shield can
The two-piece is composed of a frame and a cover. The shield frame generally made of Nickel silver for easy soldering, and the cover is generally made of stainless steel, which is cheaper. The advantage of the two-piece type is that it is convenient for maintenance and inspection. The disadvantage is that the two pieces need to be opened twice, and the cost is high for the mould and the goods
One Piece Shield can+SMT Shield Clips
The shield clip is now used instead of the shield frame , which can save the cost of opening the shield frame . The shield clip is used to fasten the shield through the buckle, and it is enough to place one about 25mm, and at least 4 are required, which can be flexibly implemented. The disadvantage of this solution is that the clamping force of the buckle needs to be studied, and it is not suitable for use in scenarios with high vibration intensity
