The Principle of Pick and Place Machine
Introduction of SMT
1. Why use surface mount technology (SMT)?
Electronic products pursue miniaturization.
2. Electronic products have more complete functions, especially large-scale and highly integrated ICs, and surface mount components have to be used product batching, production automation, the factory must produce high-quality products at low cost and high output to meet customer needs and strengthen market competitiveness
3. The development of electronic components, the development of integrated circuits (IC), and the multiple applications of semiconductor materials, Electronic technology revolution is imperative
The Characteristics of SMT
1.High assembly density, small size and light weight of electronic products. The volume and weight of SMD components are only about 1/10 of traditional plug-in components. Generally, after SMT is used, the volume of electronic products is reduced by 40%~60%, and the weight is reduced by 60% %~80%.
2. High reliability and strong anti-vibration ability. Solder joint defect rate is low.
3.Good high frequency characteristics. Reduced electromagnetic and radio frequency interference.
4.It is easy to realize automation and improve production efficiency.
5. Reduce the cost by 30%~50%. Save material, energy, equipment, manpower, time, etc.
Technical Components Related to SMT
1. Design and manufacture technology of electronic components and integrated circuits
2. Circuit design technology of electronic products
3.Manufacturing technology of circuit board
4, Design and manufacturing technology of automatic mounting equipment
5. Circuit assembly manufacturing technology
6.Development and production technology of auxiliary materials used in assembly manufacturing
The Key Factors of Pick and Place Machine
Ⅰ Arch Type (Gantry):
The component feeder and the substrate (PCB) are fixed, and the mounting head (installed with multiple vacuum suction nozzles) moves back and forth between the feeder and the substrate, and the components are taken out from the feeder. After adjusting the position and direction of the components , and then placed on the substrate. Because the patch head is installed on the X/Y coordinate moving beam of the arch type, it is named.
The method of adjusting the position and direction of the components: (1) The position is adjusted by mechanical centering, and the direction is adjusted by the rotation of the suction nozzle. The accuracy that this method can achieve is limited. (2) Laser recognition, X/Y coordinate system adjustment position, suction nozzle rotation adjustment direction, this method can realize the identification during the flight, but it cannot be used for the ball grid display component BGA. (3) Camera identification, X/Y coordinate system adjustment position, suction nozzle rotation adjustment direction, generally the camera is fixed, and the mounting head flies across the camera for imaging identification, which takes a little longer than laser identification, but can identify any component, There is also a camera recognition system that realizes recognition during flight, and there are other sacrifices in terms of mechanical structure.
In this form, due to the long distance of the patch head moving back and forth, the speed is limited. Nowadays, multiple vacuum suction nozzles are generally used to pick up materials at the same time (up to ten) and a double-beam system is used to increase the speed, that is, the mounting head on one beam is picking up materials, while the mounting head on the other beam is placing element, almost twice as fast as a single-beam system. However, in practical applications, it is difficult to achieve the condition of taking materials at the same time, and different types of components need to be replaced with different vacuum suction nozzles, and there is a time delay in changing the suction nozzles.
The advantages of this type of machine are: the system is simple in structure and can achieve high precision (the position and movement of the shaft beam can control the mounting accuracy of components to below 50µm (0.05mm)), suitable for components of various sizes and shapes, Even odd-shaped components, the feeder is available in strip, tube, and tray formats. It is suitable for small and medium batch production, and can also be combined with multiple machines for mass production.
Ⅱ Turret Type (Turret)
The component feeder is placed on a single-coordinate moving feeder, the substrate (PCB) is placed on a worktable that moves in an X/Y coordinate system, and the mounting head is installed on a turret. When working, the feeder feeds the components The feeder moves to the pick-up position, the vacuum suction nozzle on the patch head picks up the components at the pick-up position, and rotates through the turret to the pick-up position (180 degrees from the pick-up position). Adjust the direction and place the components on the substrate.
The method of adjusting the position and direction of the components: (1) Adjust the position by mechanical centering, and adjust the direction by rotating the suction nozzle. This method can achieve limited accuracy, and later models are no longer used. (2) Camera identification, X/Y coordinate system adjustment position, suction nozzle self-rotation adjustment direction, fixed camera, mounting head flying across the camera for imaging identification.
Generally, there are more than a dozen to twenty patch heads installed on the turret, and each patch head is equipped with 2~4 vacuum nozzles (earlier models) to 5~6 vacuum nozzles (current models) ). Due to the characteristics of the turret, the actions are miniaturized, such as selecting and changing the suction nozzle, moving the feeder in place, picking up components, component recognition, angle adjustment, worktable movement (including position adjustment), and placing components can all be performed in the same time period. It is completed within, so it achieves high speed in the true sense. At present, the fastest time period reaches 0.08~0.10 seconds for one component.
This model is superior in speed and is suitable for mass production, but it can only use strip-packed components. If it is a dense-foot, large-scale integrated circuit (IC), it cannot be completed only with tray packaging. Therefore, it also depends on other models to work together. This kind of equipment has complex structure and high cost. The latest model is about US$500,000, which is more than three times that of the arch type.
Ⅲ Massively Parallel System
Use a series of small individual mounting units. Each unit has its own screw position system, equipped with cameras and mounting heads. Each mounting head picks up a limited tape feeder and places a portion of the board, which is stepped through the machine at fixed intervals. Individually each unit machine runs slowly. However, their continuous or parallel operation results in high throughput.
The accuracy of automatic component mounting is accomplished by the vision system, which is generally divided into down-looking, up-looking, head-up or laser positioning, depending on the position or camera.
Look down at the camera to find the mark called the reference point on the PCB, which is mainly used to align the PCB to the correct position before component mounting. Up-view cameras are used to inspect components from a fixed position, so components must be moved over the camera for vision prior to mounting. Film shooters (i.e. turret types) do just that, with components moving around the turret.
Recognition time usually increases as components become larger or more complex. To compensate for this extra time, mounting equipment can use two up-looking cameras—one on each side of the machine—to reduce the distance traveled.
The overhead arch machine can support different feeder types, including bulk, tape-and-real, tube, odd-form and other customer designs. In contrast, high-speed turrets and massively parallel systems are fed entirely from bulk magazines or tape packs.
Overhead arch machines may be the only option when component packaging is not in bulk or in strip form: high-speed machines are excluded from consideration because they cannot feed these materials automatically.
Therefore, manufacturers should look for component mounting equipment that can expand their existing mounting options flexible Choice (Human Factors)
In addition to microscopic flexibility in positioning systems, imaging systems, and component feeding systems, macroscopic flexibility to adjust manufacturing throughput and accommodate product changeovers becomes critical to making decisions about new assembly equipment.
Classification of Surface Mount Methods
the First Category:
TYPE IA only has single-sided assembly for surface mount
Process: silk screen solder paste => mounting components => reflow soldering
TYPE IB only has double-sided assembly for surface mount
Process: silk screen solder paste => mounted components => reflow soldering => reverse side => silk screen solder paste => mounted components => reflow soldering
the Second Category:
TYPE II Single-sided or double-sided assembly with a mix of surface mount and through-hole components
Process: Silk screen printing solder paste (top) => mounting components => reflow soldering => reverse side => dripping (printing) glue (bottom surface) => mounting components => drying glue => reverse side => inserting components => wave soldering
the Third Category:
TYPE III uses through-hole components on the top surface and surface mount components on the bottom surface
Process: dripping (printing) glue=>mounting components=>drying glue=>reverse side=>inserting components=>wave soldering
Process Capability (Cpk, Process Capability): refers to the level of mounting accuracy related to X, Y and Θ. A machine's X, Y, and Θ errors are considered individually, not collectively.
Throughput: Involves the measurement of delivery, manufacturing and takt time.
Mounting Defects: the probability that mounting defects usually occur
Pickup Defects: Pickup defects can be categorized as feeder failures, vacuum failures, or visual failures. Picking defects reduces net output and wastes good parts
Reliability, availability and maintainability: Data on reliability, availability and maintainability are published by the supplier based on actual field experience.
Preventive Maintenance (Preventive Maintenance): Preventive and corrective maintenance keeps the SMT mounting system running at its specified speed and accuracy.
A Common Language: When suppliers and users use the same language to achieve consensus on standards and communications about equipment performance, the result will be increased efficiency in the industry and ultimately greater customer satisfaction and growth.
0201 mounting challenges
The mounting of 0201 components is more challenging than the component intervention before it. The main reason is that the 0201 package is approximately one-third the size of the corresponding 0402.
The previously acceptable machine mounting accuracy immediately became a limiting factor for the introduction of 0201. In addition, traditional industrial tape packaging (taping) specifications allow too much movement for reliable 0201 mounting, and the level of process control must also be improved to make 0201 mounting a production reality.
The Key to Reliable 0201 Mounting
1.Component Feeder Workbench: The ability to precisely position the carriage workbench.
2.Component Feeder: The feeder must be manufactured to extremely tight tolerances to ensure repeatability of the pick position is maintained. Additionally, the materials used to make the feeders must be strong and lightweight.
3.Feeder Drive Sprocket: The drive sprocket plays a key role in the machine's ability to position the component strip. The shape, taper and length of the drive sprocket teeth significantly affect the ability of the feeder to position the strip
4.Pickup Tips: Material selection, material hardness, machining tolerances and thermal characteristics must all be understood in order to construct a reliable pick up tip.
5.The nozzle must move freely within its holder.
6.Nozzle shaft assembly: In order to pick up components of 0.6x0.3 mm, the nozzle must have an outer diameter no larger than 0.40mm. This results in a long, thin nozzle shaft that is fragile to bend but must still maintain precision to maintain high reliability of suction.
7.Substrate Construction: All machinery vibrates during operation. Base frame design is a critical first step in reducing the effects of speed and motion that create vibration and harmonic resonance.
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