Solder dots on perimeter of board

Quick question about the physical layout of the TX2 module. A large swath of copper is exposed around the edge of the module and that copper has a pattern of silver dots on it. I’m guessing they are solder. Does anyone know why such a large area of copper is exposed and what the purpose of the silver dots is?

Hi, can you show me a picture on your tx2 moudle ? I have not find what you said , attachment my TX2 module.

rita_wangning - You have a different version of the module, but you can see the same dots around the mounting holes in the second image you uploaded.

Here’s a photo of the board that has a lot of the silver dots:

That is for better contact to shell.