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PCBA Tech
​Mounter development and PCB electrostatic protection
PCBA Tech
​Mounter development and PCB electrostatic protection

​Mounter development and PCB electrostatic protection

2021-11-10
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Author:Downs

The development direction of SMT placement machine

With the rapid development of SMT, not only the size of electronic components is getting smaller and smaller, the assembly density of SMT patches is getting higher and higher, and new packaging forms are constantly being introduced to better apply high-density and difficult SMT patches. In the need of processing and assembly technology, SMT placement machines are slowly developing towards height, multi-function, modularity, and intelligence.

1. High speed

1. "Flight alignment" technology. In-flight alignment technology installs the CCD image sensor directly on the placement head while moving and holding it and picking up the device, then optically centering the component during the movement to the placement position of the printed circuit board for SMT patch processing.

2. The high-speed SMT placement machine is modularized.

3. Two-way conveying structure. While retaining the performance of the traditional single-channel placement machine, the conveying, positioning, and inspection of the printed circuit board for SMT patch processing is designed into a dual-channel structure. This dual-channel structure SMT patch processing and placement machine can be divided into working methods It is synchronous and asynchronous. When operating in a synchronous mode, another printed board completes the steps of transmission, fiducial alignment, and bad board inspection, thereby improving the production efficiency of the SMT chip processing plant.

pcb board

4. Automatic nozzle conversion function. Some companies in Japan and Europe have made improvements to the placement head of the new SMT placement machine, such as the use of a turntable and a double nozzle structure. The turntable structure automatically replaces the required suction nozzles during the movement of the placement head, and can simultaneously pick up multiple electronic components in a pick and place process, reducing the number of times the placement arm moves back and forth, thereby improving the work efficiency of the SMT placement machine.

2. High precision

At present, many SMT placement machine manufacturers adopt various technologies to meet the requirements of narrow pitch and new devices for SMT placement accuracy, so that the highest placement accuracy can reach ±0.01~±0.00127MM. The main measures are as follows.

1. Adopt high-resolution linear encoder closed-loop system.

2. The intelligent service system is adopted to improve service performance and quick-break adjustment time, reduce the load of the host, and improve the reliability of SMT placement.

3. Improve the SMT placement machine vision system, adopt a high-resolution linear scan camera, and perform gray-scale processing on the image to improve the accuracy of image processing and further improve the accuracy level of the SMT placement machine.

4. The temperature compensation function is adopted to reduce the environmental impact on SMT processing and placement of ultra-fine-pitch ICs.

PCBA processing electrostatic protection requirements

Since PCBA processing often involves a variety of electrostatic sensitive electronic components and some processing techniques that have certain requirements for electrostatic protection, certain anti-static requirements are required in PCBA processing. Electrostatic warning signs are mainly used to post, hang, and place on factories, equipment, components and packaging to remind people of the possibility of electrostatic discharge or electrical overload damage during operation.

Workshop anti-static requirements

According to the requirements of product production level, the production workshop should be equipped with corresponding anti-static facilities, and the ground wire should be independent and reliable. Keep constant temperature and humidity in the workshop. Separate static safe working areas, and affix obvious anti-static warning signs.

The grounding system outside the workshop is inspected once a year, and the grounding systems such as the floor/mat, workbench, etc. in the workshop shall be inspected once every six months, and corresponding records shall be made.

The temperature and humidity in the workshop are respectively controlled at (25±2)℃ and 65%±5%RH; measure twice a day and make corresponding records.

Statutory protection requirements for employees

When entering the anti-static area, you must wear anti-static overalls and anti-static shoes as required;

Before touching electrostatic sensitive components, you must wear a grounding wrist strap or grounding foot strap as required, and pass the corresponding electrostatic test;

Articles prone to static electricity are not allowed to be brought into the anti-static area;

The handling, storage and distribution of electrostatic sensitive components must be stored in anti-static packaging;

The anti-static package can only be opened after the corresponding anti-static measures have been taken;

Trolleys and shelves used in anti-static areas must have proper grounding devices;

Anti-static work clothes and work shoes are prohibited from being worn out of the work area, and cleaned regularly according to regulations;

The cleaning of the anti-static work surface must use a cleaning agent approved by the electrostatic protection personnel;

Avoid placing static sensitive components and circuit boards with plastic products or tools (such as computers and computer terminals);

Connect all tools and machines to the ground;

Use static protection table mats;

Employees who do not wear a wristband are prohibited from approaching the static protection workstation;

Immediately report all possible causes of electrostatic damage.

Matters needing attention during operation

Touch the work surface with both hands before holding the component, so that the static electricity on your hands is transmitted to the ground through the anti-static work surface;

Place the device pins down on a table that dissipates static electricity;

When holding an integrated circuit, you should grasp the body of the integrated block, not the pins;

When operating electronic components, they should be held at the edge of the PCB, and do not directly touch the components or the circuit on the board;

Do not drag or slide electronic components on any surface;

The non-conductor should keep a distance of more than 1m from the static safe working area;

Take out the components and circuit boards from the anti-static packaging box only in the static safe working area;

Place the static sensitive components that are not in use temporarily in an antistatic container or packaging box;

Reduce the number of handling to a minimum.

Anti-static requirements of other relevant departments

Design department

The design department should be familiar with the types, models, technical performance and protection requirements of SSDs, and choose ICs with electrostatic protection as much as possible. In circuit design, the application of electrostatic suppression technology, such as electrostatic shielding and grounding technology, should be considered. Warning symbols must be included in the preparation of design files containing SSD. The main design documents involved are: instruction manual (user manual), technical manual, detailed list, PCB diagram (lead end processing), assembly drawing and debugging, inspection instructions (including SSD inspection in the factory).

 craft department

When reviewing the design process, review the relevant content of the design documents; prepare special process documents, guidance documents and related systems for anti-static projects; propose and check whether the required anti-static equipment is complete; be responsible for guiding the assembly workshop to the department Application and precautions of anti-static equipment.

Material department

When there is an SSD in the purchase summary table, the PCBA manufacturer should be selected together with the design and process departments. The packaging of the SSD and the anti-static requirements during transportation should be clarified when supplying.

Inspection department

Check if the package of SSD device is complete. SSD testing and aging screening should be carried out in an electrostatic safe area, and operators should wear anti-static overalls/shoes.