Components placement systems

FIG. 36 Photograph of a fixed head with rotary motion capability and moving table component placement system. (Courtesy of Universal Instruments Corporation). 

High-performance placement systems ace available for the highest placement rates, especitilly for telecommunications products. These systems ttike advantage of several individual parallel pick-and-place systems. A placement rate of up to 140,000 components per hour can be attained. 

Several optical inspection systems are available that measure, for example, shape and height of the applied solder paste or placement positions of components. These systems, based on image... 

Conventional printing processes are less useful for applying conductive adhesives or solder paste. Dispensing of single dots in a complex geometric application is therefore necessary. Three-dimensional circuit carriers also decrease the freedom of component placement, which leads to restrictions for placement systems. 

Robot placement systems have till now been used primarily to place exotic THT components such as coils and plugs, whose assembly is not possible with pick-and-place machines. The application of... 

For both these concepts to be realized, it is necessary to extend and work on hardware and control software of the PCB basic assembly system. These systems are realized with a widespread standard system at the FAPS Institute. Figure 45 shows the developed MID placement system with the different modules for the handling of SMD components and MID. 

PI (proportional-integral) control models, 160 Placement systems electronic components, 425-429 3D PCBs, 435-438... 

The change to Pb-free solders does not have an explicit impact on component placement machine technology. Indirectly, however, the need for alternative surface finishes on both the components and circuit board fiducials, which have different reflectance characteristics, can affect the performance of the vision systems used to locate accurately both the circuit board and the tooling that delivers the component to the board. 

In addition, there has been a steady increase of odd-shaped devices that include inductors as well as LEDs, surface-mount connectors,etc. The result has been circuit boards with a greater mix of package types and sizes. Consequently, it is considerably less expensive and time-consuming to reprogram a computer-based, machine vision system to recognize these components than it is to retool a machine based on mechanical relays, detents, and such for component placement. 

Vision system limitations are determined by the speed with which the computer can process information (e.g., circuit board coordinates, component geometries, defects). The more information to be processed, the slower is the component placement step. For products requiring the placement of thousands of parts per circuit board, even an additional few tenths of a second per component can add up to a significant loss of production throughput. 

The automated assembly of odd-form components uses the same placement equipment as is used for other components, but with special tooling or a dedicated machine (cell), which is already set up with the required tooling and component feeder systems, that can be introduced... 

This chapter covers why manufacturers inspect printed circuit assemblies, how they have implemented and enhanced visual inspection, what automated inspection systems they are using, and how they have implemented these antomated systems. The scope of this chapter includes only inspection of printed circuit assemblies during the assembly process, as typically shown in Fig. 53.1. Thus, it includes inspection of solder paste after the paste printing process step, components after the component placement process step, and solder joints after the solder reflow process step. Not included, however, is incoming inspection of components and the bare printed circuit board (PCB). The focus of this chapter is on prodnction nse of inspection, not the collection of measurements dnring process development in a research and development (R D) environment. 

Inspection systems normally are dedicated to one type of measurement capabihty solder paste, pre-reflow, or post-reflow inspection. For example, systems for solder paste measurements do not normally also make component placement measurements. The cost of combining different measurement capabilities into one system would typically make that system prohibitively expensive. More importantly, to reduce manufacturing costs, manufacturers want to implement linear, sequential production lines where an assembly always flows in one direction and goes through each machine only once per assembly side. So automated inspection systems fall into three major categories ... 

For all three types, the automated inspection system compares the measurements taken against a specified conformance range to accept or reject autonaaticaUy a solder paste brick, component placement, or solder joint as being within specification. 

FIGURE 53.10 Schematic of automated inspection systems for component placement defect detection. The camera sensor obtains images of component positions relative to the printed circuit board. The image processing software extracts features from the image and compares them to present position limits to flag a placement as defective. 

Pre-reflow AOI systems also have the ability to inspect 2-D solder paste however, this ability is utihzed only to inspect a small percentage of the solder paste deposits combined with the component misalignment measurements. Component misalignment measurements cover the passive components, whereas the solder paste measurements cover deposits for BGA, CSP, or fine-pitch QFP devices. Therefore, these systems are placed within production lines after the pick-and-place systems for passive devices but before the pick-and-place systems for the larger area-array and leaded devices. These systems serve the same purpose as those only meant for component placement measurement, both detecting defects and monitoring measurements within control limits to discover process drift as early as possible. 

The placement system is based on multiple placement heads, each fed by a dedicated feeder. The heads operate in parallel, carrying out pick, component alignment and placement simultaneously. This technique reduces cycle time. 

The next section affords an overview of the possibilities and solutions for automated 3D component placement on MID. Interest focuses primarily on the different kinematic types of solution. This is not intended as a comparative assessment of available system technologies. 

The Space 400 3D precision assembly module from Xenon is a versatile in-line system with a four-axis gantry system and a component manipulator for 3D applications (Fig. 4.17). The conveyor brings carrier-mounted MID to the component manipulator. The manipulator grips the workpiece carrier and can then position the interconnect device s process surfaces about two rotary axes and along one linear axis. There are two parallel process axes for dispensing and component placement [5j. 

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