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:
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.
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