AN1709 datasheet(34/38 Pages) STMICROELECTRONICS

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EMC DESIGN GUIDE FOR ST MICROCONTROLLERS

If the strongest source of perturbations is a dI/dt generator (i.e. a relay), it is a high source of

electromagnetic fields. Therefore, the permeability of the shielding material (i.e. alloy) is cru-

cial to increase the immunity of the board. In addition, the number and size of the holes on the

shield should be reduced as much as possible to increase its efficiency.

In critical cases, the implantation of a ground plane below the MCU and the removal of sockets

between the device and the PCB can reduce the MCU noise sensitivity. Indeed, both actions

lead to a reduction of the apparent surface of loops between the MCU, its supply, its I/O and

the PCB.

4.2 HANDLING PRECAUTIONS FOR ESD PROTECTION.

Electronic components have to be protected from the hazard of static electricity from the man-

ufacturing stage down to where they are utilized in order to avoid ESD related destruction. A

specific no-compromise strategy is implemented at ST for all ESD sensitive products.

From the wafer level to the shipping of finished goods, each workstation and processing step

is guaranteed. For final packing, ST uses anti-static tubes. This solution ensures full ESD pro-

tection of devices. However, the supplier's greatest efforts are in vain if the end user does not

provide the same level of protection and care in the application.

A relative humidity of 50% to 65% is the best to prevent electrostatic problems (the lower the

relative humidity, the higher the electrostatic voltage). Nevertheless, the person handling the

semiconductors as well as the equipment will be charged to a certain level. The work environ-

ment is very important to protect devices against static electricity

Anti-static electricity measures during work

(1) Conductive mat

(2) Wrist

(3) Conductive floor mat

(4) Work suit with anti-static measure

(5) Conductive shoes grounding the human body

AN1709 bảng dữ liệu(PDF) 34 Page - STMicroelectronics