Precision PCB Fabrication, High Frequency PCB, High Speed PCB, Standard PCB, Multilayer PCB and PCB Assembly.
The most reliable PCB custom service factory.
PCBA Tech
SMT process and electrostatic protection in production
PCBA Tech
SMT process and electrostatic protection in production

SMT process and electrostatic protection in production

2021-11-07
View:30
Author:Downs

①SMT chip processing and placement process requirements. The characteristic marks such as the type, model, nominal value and polarity of the components of each installation position number on the circuit board should meet the requirements of the product installation drawing and schedule. Mounted PCBA components

SMT processing and placement process requirements. The characteristic marks such as the type, model, nominal value and polarity of the components of each installation position number on the circuit board should meet the requirements of the product installation drawing and schedule.

The mounted components must be intact.

The solder end or pin of the smt patch mount PCBA device is not less than 1/2 thickness and immersed in the solder paste. For general components, the amount of solder paste extrusion should be less than 0.2mm during placement, and for fine-pitch components, the amount of solder paste extrusion should be less than 0.1mm during placement.

pcb board

The solder ends or pins of the components should be aligned and centered with the land pattern. Because reflow soldering has a self-alignment effect, certain errors are allowed during component placement. The specific error range of various components can be found in the relevant IPC specifications.

②Three elements to ensure the quality of PCB circuit board mounting.

1. The components are correct. It is required that the type, model, nominal value, polarity and other characteristic marks of the components of each installation position number must conform to the requirements of the product installation drawing and schedule, and cannot be pasted in the wrong direction.

2. Accurate orientation. The solder ends or pins of PCB components are aligned and centered with the land pattern as much as possible, and it is also necessary to ensure that the solder ends of the components touch the solder paste pattern.

3. The pressure is right. The placement pressure is equivalent to the Z-axis height of the nozzle, the high Z-axis height is equivalent to the small placement pressure, and the low Z-axis height is equivalent to the high placement pressure. If the height of the second axis is too high, the solder end or pin of the component does not press the solder paste, and it floats on the surface of the solder paste. The solder paste cannot stick to the component, and it simply moves in orientation during transmission and reflow soldering.

In addition, the height of the Z axis is too high, causing the components to fall freely from a high place during the patch, which will cause the orientation of the patch to shift. On the contrary, if the height of the second axis is too low and the amount of solder paste squeezed out is too much, it will simply cause solder paste adhesion, and bridging will simply occur during reflow soldering. At the same time, the alloy particles in the solder paste will slide, causing the orientation of the patch to shift. It will also damage components. Therefore, the Z-axis height of the suction nozzle is required to be appropriate and appropriate during placement.

Electrostatic protection in SMT production!

1 Anti-static facilities in the SMT production line The requirements for the anti-static facilities in the SMT production line are as follows:

1. Anti-static facilities in the SMT production line

The requirements for anti-static facilities in the SMT production line are as follows: the anti-static facilities in the production line should have an independent ground wire and separate from the lightning protection wire; the ground wire is reliable and has a complete electrostatic leakage system; the workshop maintains a constant temperature and humidity environment , The general temperature is controlled at 23 °C ± 2 dragons, and the humidity is 65% ± 5% RH; the entrance is equipped with ion wind, and there is an obvious anti-static warning sign. What needs to be reminded is a device without a mark, which does not necessarily mean that it is not sensitive to static electricity. When there are doubts about the electrostatic discharge sensitivity of a component, it must be treated as an electrostatic discharge sensitive device until its properties can be determined.

In addition, an electrostatic safe working area must be established in the SMT production line, and various control methods must be adopted to keep the electrostatic voltage that may be generated in the area below the safe threshold of the most electrostatically sensitive components.

Generally speaking, to form a complete electrostatic safe working area, it should at least include effective conductive table mats, dedicated grounding wires, anti-static wrist straps, and floor mats to protect conductors (such as metal parts, conductive straps, conductive containers, and human bodies). Etc.) to discharge static electricity. At the same time, it is equipped with a static eliminator to neutralize the charge accumulated on the insulator. These charges cannot flow on the insulator and cannot be released by leaking grounding.

Dongguan smt chip processing products

2. Anti-static in the production process

(1) Regularly check the grounding system inside and outside the workshop. The grounding system outside the workshop should be tested once a year, and the resistance must be less than 2 Q, and the test must be retested when changing the line. Grounding systems such as carpets, floors, and table mats should be tested every 6 months, and the grounding resistance is required to be zero. When testing the resistance between the machine and the ground, the resistance is required to be 1 MO, and the test record should be made.

(2) Measure the temperature and humidity in the workshop twice a day, and make effective records to ensure constant temperature and humidity in the production area.

(3) Any personnel must take anti-static measures before entering the workshop. Operators who are in direct contact with the PCB should wear an anti-static wrist strap. Operators wearing the wrist strap are required to test once a day before going to work in the morning and in the afternoon to ensure that the wrist strap is in good contact with the human body. At the same time, arrange craftsmen to supervise and inspect every day. When necessary, train employees on anti-static knowledge and on-site management.

(4) When you need to hold the PCB in your hand during the production process, you can only hold it at the edge of the PCB where there are no electronic components; after production, the PCB needs to be installed in an anti-static package; during installation, it is required to take 1 piece at a time, and it is not allowed to take it at a time. Multiple PCBs.

(5) During the rework operation, the PCB to be repaired must be placed in an anti-static box, and then brought to the rework station.

(6) The tools used in the entire production process of PCB components should have anti-static capabilities.