How to use MOS integrated circuits correctly

All MOS integrated circuits (including P-channel MOS, N-channel MOS, complementary MOS - CMOS integrated circuits) have an insulating gate to prevent voltage breakdown. The thickness of the insulating gate oxide layer of general devices is about 25nm, 50nm, and 80nm. There is also a resistor-diode network in front of the high-impedance gate of the integrated circuit for protection. However, the protection network in the device is not enough to avoid electrostatic damage (ESD) to the device. Experiments show that the device will fail during high-voltage discharge, and the device may also fail due to the accumulation of multiple lower voltage discharges. According to the severity of the damage, electrostatic damage has many forms. The most serious and most likely to occur is the complete destruction of the input or output end, so that it is short-circuited or open-circuited with the power supply end VDD GND, and the device completely loses its original function. A slightly less serious damage is intermittent failure or performance degradation, which is even more difficult to detect. Some electrostatic damage will increase the leakage current and cause the performance of the device to deteriorate.

Due to the inevitable high electrostatic voltage discharge phenomenon caused by short-term operation, for example, when people walk on waxed floors, they will cause high electrostatic voltages of up to 4KV - 15KV. This high voltage is related to the ambient humidity and surface conditions. Therefore, the following precautionary guidelines must be observed when using CMOS and NMOS devices:

1 Do not exceed the extreme working conditions listed in the manual.

2 All idle input terminals on the device must be connected to VDD or VSS and have good contact.

3 All low impedance devices (such as pulse signal generators, etc.) must be powered on before being connected to the input of a CMOS or NMOS integrated circuit. Similarly, the device can only be powered off after the device is disconnected from the device.

4. The printed circuit board containing CMOS and NMOS integrated circuits is only an extension of a device and also needs to comply with the operating guidelines. Directly connecting the connectors on the edge of the printed circuit board to the device can also cause device damage. General plastic packaging must be avoided. The address input or output of the CMOS or NMOS integrated circuit on the printed circuit board connector should be connected in series with a resistor, because the time constant of these series resistors and input capacitors increases the delay time. This resistor will limit the electrostatic high voltage damage caused by the movement of the printed circuit board or contact with materials that are prone to static electricity.

5 All CMOS and NMOS integrated circuits must be stored and transported in containers made of antistatic materials. The devices must not be inserted into plastic or placed in ordinary plastic trays as usual and can only be taken out of the antistatic material container when ready for use.

6 All CMOS and NMOS integrated circuits should be placed on a well-grounded workbench. Since workers can also produce electrostatic discharge to the workbench, they must be grounded before operating the device. For this reason, it is recommended that workers use a firm conductive tape to connect their wrists or elbows to the workbench surface.

7 Nylon or other materials that easily generate static electricity are not allowed to come into contact with CMOS and NMOS integrated circuits.

8 During the automated operation, the movement of devices, conveyor belts and printed circuit boards may generate very high static voltages. Therefore, ionized air blowers and humidifiers should be used in the workshop to keep the relative humidity above 35%. The top, bottom and side parts of all equipment that can come into contact with the integrated circuits should be made of grounded metal or other conductive materials.

9 The freezer must be refrigerated with carbon dioxide and have partitions, and the device must be placed in a container of conductive material.

10 When you need to straighten the external leads or use manual soldering, you must ground your wrist and the solder pot must also be grounded.

11 The following measures should be taken during wave soldering:

a. The solder tank and conveyor belt system of the wave soldering machine must be truly grounded.

b. The workbench should be covered with a conductive top cover and should be grounded.

c. Staff must follow prevention guidelines.

d. The finished workpiece should be placed in an anti-static container and sent to the next process first.

12 To clean printed circuit boards, take the following measures:

a. The steam degreaser and basket must be grounded, and the staff must also be grounded.

b. Do not use brushes or sprayers to clean printed circuit boards.

c. The workpieces taken out of the cleaning basket should be immediately placed in the steam degreaser.

d. High-speed air and solvents are permitted only when the workpiece is well grounded or an electrostatic eliminator is used on the workpiece. 13. The use of static monitors must be approved by the production line supervisor.

14 Do not insert or remove the integrated circuit when the power is on. The following procedures must be followed:

a. Turn on the power only after plugging in the integrated circuit or printed circuit board.

b. The integrated circuit or printed circuit board can only be unplugged after the power is turned off.

15. Warn personnel using MOS integrated circuits that operators must never be directly connected to the electrical ground. For safety reasons, the resistance between the operator and the ground should be at least 100K.

16 Operators should use cotton gloves instead of nylon gloves or rubber gloves.

17 Carpets are prohibited in work areas.

18 Unless absolutely necessary, workers are not allowed to touch the lead terminals of CMOS or NMOS devices.