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Board level Shielding Can Design Guidelines | Ningbo Hexin Electronics

Board level Shielding Can

In the RF hardware design, electromagnetic interference needs to be considered, and the design of the board level shielding cover is essential. Today this article introduces the design specifications of shields and the types of shields.

Some considerations about shield design:

Board level Shielding Can
The shielding cover can be made of Tin plated, or Nickel silver (good soldering and not rust), or stainless steel (only used as shielding cover). The shield frame material is Tin plated and Nickel silver alloy ensure good soldering performance. Material thickness is generally between 0.1-0.3mm, 0.2mm is more commonly used.

The shield cover pad width is between 0.7-1mm.

Board level Shielding Can
Design of heat dissipation holes: In consideration of heat dissipation, heat dissipation holes need
to be added. The hole diameter is generally between 1-1.5mm, and the hole spacing is about
5mm.(Nickel silver is good for heat) When considering batch soldering, a vacuum washing area needs to be reserved in the middle of the shield (it is guaranteed to be a flat surface without openings). Generally, the diameter of this area is not less than 5mm.

The distance between the device pad and the edge of the shield cover must be at least 0.3mm. When soldering, consider a solder height of 0.1mm, during which the distance from the top of the shield to at least 0.2mm is guaranteed. Great Wall Foot Design: Shield welding should not be soldered on the whole surface as much as
possible, which will cause tin stacking. Generally, the wall of the Great Wall is welded by 2-1-2-1mm method, 2mm contact, 1mm floating to facilitate tin climbing, which can ensure the adhesion strength of the shield. If the shield is symmetrical, you need to add labels, such as adding positioning holes or regular triangle scribe lines. Regarding welding methods, there are three main types as follows:

One piece Board Level shielding Cans

Board level Shielding Can
The one piece shield can is directly soldered on the circuit board, and the single piece is easy to process and the cost is low. The biggest disadvantage is that once the welding is not easy to remove it makes maintenance and debugging more difficult.

Two pieces Board Level shielding Cans

The two-piece shield cans are composed of a frame and a cover. The shield frame made of Nickel
silver for easy soldering and the cover is generally made of tin plated, 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 two sets for the mold, and the cost is higher then one piece shield cans.

SMT Shield clips + Shield cover

Shield clips are now used instead of brackets, which can save the cost of mold and shield. The shield cover clip fastens the shield cover by a buckle, and about one can be placed about 25mm, and a minimum of four is required, which can be implemented flexibly. The disadvantage of this solution is that the clamping force of the buckle needs to be researched, and it is not suitable to be used in the scene with large vibration intensity.

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