The Suction Nozzle in SMT
What is SMT suction nozzle?
The suction nozzle in SMT is the part of direct material pick and place .which is composed of ① filter screen, ② sealing ring, ③ clamp rin,④ suction nozzle body , ⑤ suction nozzle head. Its structure is shown in the figure.
The suction nozzle is not only the key parts of the patch machine to attach and put the absorbed components. The background of the optical vision system camera when taking pictures.
It is mainly to absorb the components by vacuum adsorption.The use of blowing to adsorb the components in the suction nozzle on the coordinate position of the circuit board.
When the suction nozzle of the SMT machine absorbs the component, it must ensure that the center of the component. The center of the suction nozzle . the spatial center of the image obtained should be coincidental in order to achieve the ideal situation.
the adjustment of the optical vision system is actually to compensate,the deviation caused by this in coincidence in the actual work.
Basic principle of vacuum SMT nozzle suction
The principle of vacuum suction is to grasp and move objects by using the force formed. By the difference between vacuum system and atmospheric pressure.
This method of using pressure difference to fix or move objects has many applications in daily life. such as vacuum cleaner, vacuum adsorption hook and traditional Chinese medicine cupping, etc. Vacuum is widely used in industrial production.
- Atmospheric pressure and atmospheric pressureAccording to the principle of fluid mechanics.All objects in the earth’s atmosphere are subjected to the action of the gravity of the air.
- This force is the action of the atmospheric pressure. The atmospheric pressure per unit area is the atmospheric pressure.
- The standard atmospheric pressure at ground level (1 ATM) is equal to the pressure generated by a column of mercury 760 mm high (mmHg).
- Different units of pressure are used in different fields, different countries and regions. The common units of pressure used in this technology are.
- Vacuum and vacuum degreeA is usually a state in which the pressure of a gas is lower than that of the atmosphere.Rather than a “vacuum” in which there is no air at all.
- That is, the gas in a vacuum is thinner than the gas at atmospheric pressure.The measure of the degree of thin gas in the vacuum state is expressed by “vacuum degree”.
- Traditionally, the high vacuum degree means that the gas pressure is lower than the atmospheric pressure.Low vacuum means that the gas pressure is less than the atmospheric pressure.
Requirements for suction of vacuum suction nozzle in SMT
(1) No discarding (discarding rate is within the allowable range);
(2) No slippage (insufficient vacuum suction will lead to position slippage of components in motion after detection);
(3) Non-stick components(reliable separation from the suction nozzle after the components are attached in place).
Reasons for wrong suction nozzle of SMT machine.
(1) Suction nozzle wear, suction nozzle deformation, clogging, damage due to insufficient air pressure. As a result, the components cannot be absorbed. Therefore, it is necessary to regularly check the degree of the suction nozzle in order to replace the serious one.
(2) The influence of the feeder, the feeder the feeder bad (damage to the feeder gear). The hole without a card on the feeder gear, the feed under the wink of an eye. The spring wear), the pressure plate, the springs and other devices to deform the cylinder, rust, etc.
(3) This may result in elements not being able to afford to accommodate partially vertical discs or devices. Should be checked regularly to deal with it so that the device does not generate a large amount of waste.
(4) The negative pressure in the vacuum is insufficient when the nozzle picks up the components. The nozzle creates a certain negative pressure, the component is adsorbed on the nozzle. Pick up the suction nozzle to see if the picked components are abnormal.
(5) In general, the negative pressure detection method: When the vacuum sensor detection value is within a certain range. The machine regards the absorption as normal, otherwise it is bad.
During component suction
The vacuum negative pressure should be higher than 53.33kPa in order to have enough vacuum to absorb the components.
If the negative pressure in the vacuum is not sufficient, not enough suction and pressure parts can be provided. We need to check the use of vacuum negative pressure and clean the nozzle regularly. At the same time, pay attention to the contamination of each SMT tip with the vacuum filter element. The function is to realize the air filtration of the suction nozzle to maintain the air circulation.
Influence of the suction height The ideal suction height of the suction nozzle is to press 0.05 mm downwards. After the suction nozzle touches the surface of the part. If the pressure depth is too great, the part will be pushed into the water tank and the material cannot be removed.
If the absorption of the component is not good, the absorption height can be slightly adjusted upward. For example, 0.05 mm.
During the actual work process, I came across a situation where all components of a feeder are faulty. The solution is to set the system parameters of the feed table to an appropriate height.
The problem of nozzle feeding. Some chip component manufacturers have problems with the quality of the packaging, such as: B. large perforation defects. Adhesion between adhesive tape and plastic film as well as material grooves that are too small. Possible reasons why components cannot be included.
Select the suitable suction nozzle for the PCBA
This connection is used in one of our PCBA projects. It cannot be picked up by the SMT automatic machine. Our technicians manually solder them onto the first sample board.
After passing the sample test, we began to study the suction nozzle in order to improve the efficiency of mass production.
We set a nozzle first, but the effect wasn’t very good. The components in the conveyor belt are not fixed each time they are stepped on. However, the grip position of the suction nozzle is fixed and is not automatically adjusted. Therefore, the components placed by the nozzle are not suitable for the suction cup.
Then we talked to the engineers who made the connectors and they gave us some suggestions. We had a lot of conversations with the nozzle engineer and added 3 nozzles for testing. Finally set the thickness of the suction nozzle to 0.5 mm. The lower ends are thinner and at the same time ensure sufficient suction power.
When making batch orders, we used a nozzle with a final thickness of 0.5mm, which is very good and saves a lot of time.
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