PCBA: Comprehensive explanation of basic knowledge of SMT nozzle
SMT nozzle refers to the SMT nozzle installed on the chip head, which is used to absorb components and parts and mount them on the circuit board. With the miniaturization and high density of components on the circuit board, higher requirements are put forward for the precision of the SMT mounter and the precision and quality of the SMT nozzle.
1、 Cleaning of SMT nozzle
In the actual installation process, the nozzle is blocked due to being contaminated with solder, flux or other dirt, which is easy to cause throwing. Previously, we could not solve the problem by steel needle poking or ultrasonic vibration. The nozzle cleaner developed for this situation adopts a new cleaning method, which can remove the dirt on the nozzle that cannot be removed before in a short time. The nozzle will not be damaged during cleaning. Since non-toxic and harmless cleaning fluid is used, the whole process is more environmentally friendly.
2、 Reasons for poor suction element of SMT nozzle
(1) The vacuum negative pressure is insufficient. When the suction nozzle picks up the element, a certain negative pressure is generated at the suction nozzle, and the element is adsorbed on the suction nozzle. The negative pressure detection method is generally used to determine whether the suction nozzle picks up the element abnormally. When the detection value of the negative pressure sensor is within a certain range, the machine considers that the suction is normal, and vice versa.
(2) The suction nozzle is worn, and the deformation, blockage and damage of the suction nozzle cause insufficient air pressure, resulting in the inability to suck up the components. Therefore, the wear degree of the suction nozzle should be checked regularly, and the serious ones should be replaced.
(3) The influence of the feeder, the feeder's feeding is poor (the feeder's gear is damaged), the material belt hole is not stuck on the feeder's gear, there are foreign matters and the circlip is worn under the feeder), the pressure belt cover plate, spring and other operating mechanisms are deformed, rusted, etc., resulting in the component's absorption deviation, vertical slice or inability to absorb the component. Therefore, it should be checked regularly, and the problems found should be handled in a timely manner to avoid a large waste of components.
(4) The ideal suction height is 0.05mm when the tip mounter nozzle contacts the surface of the element. If the pressing depth is too large, the element will be pressed into the chute and cannot be picked up. If the suction of a component is not good, the suction height can be adjusted slightly upward, for example, 0.05mm.
(5) Incoming material problems. Some manufacturers have quality problems with the packaging of chip components, such as large error of the hole spacing, excessive adhesion between the paper tape and the plastic film, and too small size of the trough.
3、 Selection of SMT nozzle
1. Nozzle material:
(1) Tungsten steel suction nozzle: Tungsten steel suction nozzle is solid and durable, but it is easy to whiten and is not afraid of trouble, or SMT newcomers can choose tungsten steel suction nozzle. When it turns white, it can be coated with an oily pen and can still be used.
(2) Ceramic nozzle: The ceramic nozzle will never turn white, but it is fragile and easy to break. Careful use can avoid or reduce fracture.
(3) Diamond steel suction nozzle: solid, easy to use, never whitening, but extremely expensive, cost-effective.
(4) Glue tip suction nozzle: when the surface of the material is uneven or the material is sticky, it is suitable to use the glue tip suction nozzle, but the service life of the glue tip suction nozzle is not long. It is recommended to buy more glue tip for standby when the glue tip suction nozzle is used. When the tip is worn, you can directly replace the glue tip by yourself.
2. Suction nozzle size:
For materials with standard specifications, the specifications of suction nozzles are basically fixed. Take Samsung SM for example, 0805 material corresponds to CN065 suction nozzle, 0603 material corresponds to CN040 suction nozzle, etc. When some materials are not large or small, and the shape is strange, the suction nozzle needs to be customized.
3. Nozzle shape:
The shape of the suction nozzle is square hole, round, V-groove, etc. Customized suction nozzles are generally selected as flat suction points according to the shape of the material. Some are made into elongated suction nozzles, which extend into the groove plane of the material for suction. Some are made into a zigzag shape according to the edge of the material. Some are made of flat surfaces at both ends. If the middle is uneven, a bridge should be built. Some materials are sticky, and it is not easy to place materials, so it is necessary to make some grooves on the wall of the suction nozzle, or make a rubber head.
During the use of SMT nozzle, pay attention to cleaning and maintenance, so that the nozzle can be recycled and the production cost can be reduced.
PCB manufacturers, PCB designers and PCBA manufacturers will explain the basic knowledge of SMT nozzles.