PCB Pick and place technology and feature

The complex issues surrounding component placement include equipment usage, throughput, product conversion time, footprint constraints, total operating costs, and emerging cutting-edge technologies. This article focuses on some of the features that affect the placement of components.

In the past 10 years, SMT placement machines have been divided into the following four types:
* The traditional rotary mounter is large in size and high in reliability, but its adaptability is very poor.
* Multi-axis straw type placement machine with high output and poor adaptability.
* Precision low speed door hanger type flexible placement machine (SMC and profiled).
* Rugged mass placement system.

High yield does not necessarily mean poor adaptability, and a small, flexible placement system does not necessarily mean low yields. The “best type” of assembly lines offered by hybrid manufacturers does not mean that the actual assembly process and results are optimal. Today, advanced technologies such as flip-chips and CSPs are becoming mainstream technologies for board-level circuit assembly, which has prompted some specialized-oriented vendors of specialized equipment to reach out to previously unrelated business areas. End users of equipment also There is no need to always use the configuration of a dedicated assembly line, just because it was so well configured at the time of initial purchase, and it is difficult to change, or the cost is expensive to change. High precision does not mean low tact time. How high precision is needed. To achieve the assembly characteristics of such components to achieve an acceptable yield?

In fact, users are always subject to advanced packaging techniques, manufacturing operations strategies that affect logistics support and infrastructure settings, and opportunity costs such as total operating costs, repair costs due to one-pass rate differences, and time-market factors associated with new products. Driven by other factors. When the capacity plan is simply not available, and the application level is always below 40%, adjustments must be made.

Yield and mass effect
The inherent problems of rotary discomes are related to the speed and accuracy based on the basic principles of machine design. As the size of the device changes, the turntable speed and the placement rate must be changed to match the different components and feeders. The structure fits. Although Figure 1 seems confusing, the actual situation may be worse. One of the confusing facts shown in the figure is that if a large component appears on the turntable, all other components are posted. The mounting speed must also slow down. Otherwise, the reliability of the mounting will be affected. In essence, the other components on the turntable are controlled by the processing speed of the slowest component. This situation is due to the mechanical transmission in the large gap. The multi-search operation required on the reel feeder is further aggravated. As shown in Figure 1, the valley of the recessed part is selected after any fine pitch device. The balance of the matching production line becomes an important issue. Which components are determined On which placement machine is placed, the key effort is to get an optimized and balanced production line. If more varieties are combined, the problem will be more serious. In short, Speed is determined by the size of installed components, and between components size and placement speed relationship is not linear. This will balance and optimize the assembly lines become more complex and difficult.

After a long time of use of the rotary disc film machine, due to the wear and tear of the parts, the picking and mounting accuracy of the components may also occur. Since the lead screw and the cam surface begin to wear-in (or wear), the X-Y table and the turntable The placement head, the θ rotation, the tolerance relationship between the reel and the lead screw, the reference recognition ability, etc., which are superimposed on the accuracy factors, cause deviations in the target placement or pick-up points. The result is that the pickup and placement accuracy deteriorates. Large components may not be a problem, but when placing 0402, 0201, or 01005 passive components, they can cause trouble.

Door-mounted placement machines have their own unique problems. Although not exactly the same as rotary-type placement machines, they have their own proprietary problems. In order to get the best possible tact time, it must be set to motivate "queue The occurrence of "pickup". In other words, the feeder and components must be accurately positioned so that the movement interval of the pickup nozzle is strictly consistent with the spacing of the feeder. One must also speculate that this affects the optimization process and the machine only depends on Simple setup handles the intrinsic capabilities of multiple products. As the number of placement heads and nozzles increases, this feature creates more difficulties in process optimization and line balance. Finally, the performance of the feeder and its use The number of camera fields in the optical alignment of components will have an impact on the placement process. Therefore, multiple feeders are often required for the same component to achieve optimal performance, which will reduce the feeding of single components. The number of materials greatly increases the cost of users.

The pick-up accuracy of the door-mounted placement machine is affected by its mechanical structure. Although the placement machine can obtain fine results in the slow single-pickup mode, when the product is transferred to the placement platform, the traditional door-hanging pipe-type placement machine is inherent. The defect becomes apparent. The picking accuracy becomes a function of the cumulative tolerance from the positioning of the feeder. In conventional rotary mounters, it is affected by the movement and tolerance of the feeder frame. In the placement machine, due to the picking method of production speed linkage, accurate picking is affected by six key factors. The two preferred factors are the repeatability of the coil position and the repeatability of the feeder positioning.

The third key factor affecting picking accuracy is the position of the components in the reel housing. For larger components, such as the 0603 type, the problem is not significant, and for components such as 0402, 0201 or 01005, the tolerance is close to the component. 50% of the width of the body requires different techniques to ensure proper picking. The fourth factor affecting the pick-up reliability of a conventional door-hanger is the deflection of the shaft itself. The more the shaft in the placement head, the problem The processing is more difficult.

The fifth factor affecting pick-up reliability is the parallelism of the pick-up head to the picker centerline. The last key factor affecting pick-up reliability is related to the limitations of specific component types that can be placed on the mounter. This factor can reduce the number of specific components on the placement machine by 60%, thus greatly limiting the adaptability of the placement machine.

Despite the above drawbacks, the door-mounting machine can provide excellent performance in terms of versatility and placement accuracy. The board does not move in the X and Y directions when mounting, which makes large fine pitch devices or bare. Chip, micro BGA or CSP devices minimize variations in placement cycle displacement. On door-mounted placement machines, these features may be selected by "queue picking", multiple camera selections, multiple placement heads, and requirements. Multiple feeder types and other options suggest the optimization of the type of placement machine and the balance of the production line. All these issues must be carefully considered in order to obtain the best throughput. This situation is due to the host computer and The inconsistency between the software of the lower computer becomes more complicated.
The combined placement machine combines the advantages of a rotary table and a door-mounted placement machine. If the combination is reasonable, this type of placement system will not exhibit the negative performance characteristics shown in Figure 3, providing the highest picking accuracy and specificity. Feeding of components, optimum placement accuracy and control, adaptability of assembly of shaped components and high quality of components. In addition, the combined placement system has the advantages of modular structure and added functional components, so that all types can be assembled. Components without degradation of performance. Today's high-precision combined placement system has a single module with a tact time of 10 to 60KCph. The scalability of each module of this placement machine, with its light weight, in the user's factory The convenience of mobility and the combination of features that do not require recalibration make the reassembly of factory assembly capabilities very easy. The use of multi-function feeders further enhances the adaptability of the assembly line and enables the feeders required for multi-machine assembly. The total number is minimized and ultimately reduces user costs.
The placement head on the combined placement machine is often referred to as the rotary placement head. The key factor affecting the placement rate here is the diameter of the placement head runner, which applies centrifugal force to the attached components. The larger the diameter of the runner, the slower the rotation of the placement head is to prevent the negative effects of centrifugal force. Therefore, on the conventional larger rotary disc camera, the weight of the larger component produces the same centrifugal force for placement. Negative effects. Dimensional factors reduce the mechanical amplification of the associated tolerances, so the pick and place accuracy must be improved. This placement machine can pick up multiple components in the “mount head load” range from a single feeder and not Deceleration, can load many types of components on the placement machine, because it has many feeder positions.

Spare heads can also be used for fine pitch placement and advanced technology applications, with the appropriate combination of heads, such as grippers, custom nozzles, for final placement control without compromising the combined placement The advantages of the system. The key is the ability of the placement machine to mount the components, as well as the highest level of module overlap and the wider range of components.

Conclusion: Component processing affects equipment utilization, throughput, conversion time footprint limitations, total operating costs, and the impact of emerging cutting-edge technologies. Current advanced combined placement systems are worthwhile for placement equipment solution.