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Vision systems now offer even higher resolution, greater speed and better colour properties

Sensors & Measurement Optimising electronics production

Oct 1, 2015

Today, semiconductors cannot be manufactured without using machine vision. In fact, machine vision is an enabling technology that has made it possible to achieve the density featured in today’s integrated circuits and it permits cost-effective manufacturing of such circuits. The article focuses on how the new machine vision technology optimises electronic component manufacturing.

Suppliers of electronic materials, active components, IC packages, passive components and finished electronic equipment all use machine vision to drive high quality production at lower costs. The technology that serves as the basis of both 2D and 3D machine vision is becoming more powerful and even more useful in electronic assembly applications. Vision systems now offer even higher resolution, greater speed and better colour properties. Lighting is more capable thanks to LED development which is making multi-directional and sequential lighting more cost-effective on production lines.

Vision system products featuring powerful vision tools and deployed by professionals with extensive application expertise enable electronics manufacturing engineers to meet tough production and packaging requirements for product quality and safety.

Inspection challenges

Surface mount devices (SMD) such as transistors, capacitors, resistors and other components shrunk in size to just a few millimetres or less allow for greater density and functionality on printed circuit boards (PCBs). The combination of size reduction and increased functionality has greatly improved the performance capabilities of electronic devices but made it practically impossible for either manual assembly or inspection at cost-effective production speeds.

For many years, machine vision has been a critical tool in PCB warpage inspection prior to device population; SMD picking, placement, and mounting verification; and solder validation. Using 2D and 3D solutions, machine vision locates the PCB on the tray, guides high-speed pick-and-place robots to individual SMD components for picking, guides the arm back to the PCB to place the SMD and, finally, validates the solder connections for each SMD lead through the PCB via or mounting hole.

Without the speed and precision of machine vision as a robotic guidance mechanism, assembling modern PCBs would not be possible. In addition, solder validation would be completely impossible using manual methods due to the density of the components on the board. Machine vision not only validates the connection, but also provides feedback on defects in the event of solder cracking, inadequate reflow or other process characteristics that manufacturing engineers need to troubleshoot on problematic assembly lines.

As both passive SMD and active microprocessor components continue to shrink in size, the chance of the wrong component being placed, or reversed on a fast production line can only be determined through an automated inspection routine provided by machine vision technology. As with the SMD device example, machine vision allows electronics manufacturers to correctly place and verify components before additional value-add steps are taken, reducing rework and improving production yields.
Historically, laser scanning devices were used to verify the miniscule solder connections on each SMD and microprocessor lead where it connects to the PCB. While this approach allowed the manufacturer to automatically inspect the increasingly small pitch between devices, laser scanning was slow & expensive. New 3D machine vision techniques allow for volume analysis of solder paste, balls, etc to validate electrical connections before additional value add steps are taken.

This has become even more critical in light of new government regulations such as Restriction of Hazardous Substances (RoHS) that prevent the use of toxic metals, such as lead, in electronics components manufacturing. While safer for the environment, replacement solder materials using tin and other metals bring a new set of challenges to the electronics manufacturer, such as whiskers, along with more common problems like gaps and cracks. Each of these conditions requires careful control of the reflow solder process to prevent shorts and bad connections. Only through careful monitoring and use of real time machine vision inspection data can manufacturing engineers hope to maintain control of their solder processes.

Machine vision products

Vision sensors: These are all-in-one solutions featuring a built-in camera, processor, lighting, optics and input/output capable of detecting and inspecting up to 6,000 parts per minute. For electronics manufacturers, vision sensors can check component orientation on the production line. These sensors deliver reliable readings even with variable positions and sizes. They help reduce production downtime and maintain high speeds by eliminating position adjustments and minimising resets.

Vision systems: These are unmatched in their ability to inspect, identify and guide parts. These self-contained, industrial grade vision systems combine a library of advanced vision tools with high-speed image acquisition and processing. A wide range of models, including line scan and color systems, meet all price and performance requirements.

Vision software: This software combines the power and adaptability of advanced programming with the simplicity of a graphical programming environment. A library of powerful, proven vision tools allows for total hardware independence, no matter what camera, frame grabbers and other peripherals you use. VisionPro® is ideal for systems integrators, OEMs and advanced vision users that require large numbers of cameras or applications that integrate with existing PC and human machine interface (HMI) hardware.

The various machine vision tools that help in improving quality for the electronics industry are as below:

  • Inspect: Machine vision inspects for assembly errors, surface defects, damaged parts and missing features. Vision tools identify the orientation, shape and position of objects and features.

  • Guide: Vision software guides automation equipment and robotic devices. Proven vision tools align parts for high accuracy assembly operations and other manufacturing processes.

  • Gauge/measure: Vision tools gauge parts to check critical dimensions and measure product components for sorting and classification processes.

  • OCR/OCV: Powerful algorithms read and verify alphanumeric characters marked directly on parts and printed on labels.

  • Presence/absence: Cognex vision devices detect the presence or absence of simple features and objects on high-speed production lines to give basic pass/fail results.

  • Code reading: Specialised tools read 1-D barcodes or 2-D matrix codes from slow moving to high speed and hard to read direct part marked codes.

Machine vision in action

Reduced application development time: ASYS Automatisierungssysteme GmbH based in Dornstadt, Germany, faced the challenge of complete component traceability in its prize-winning INSIGNUM 2000 laser marking system. VisionPro software with its solution provided a digital data printed directly on products allows for complete component traceability even in high volume production environments, and the use of laser marking technology guarantees extremely low error rates in this process. The performance and flexibility of the hardware installed to facilitate this process is entirely dependent on the quality and functionality of the image processing software being used. The INSIGNUM 2000 laser now reads up to 20 codes in less than 15 seconds, including handling.

Provides faster inspection: Bangze Equipment based in China, faced the challenge of performing inspections of heat protection short circuits in temperatures of around 300°C (572°F), and at short circuit distances of only around 1mm (0.04 in). In-Sight® vision systems with its solution was installed in a very narrow insulated space and using the edge tool found in the software, the bi-metal sheet edges are found. Finally, a measurement tool is used to measure the direct distance between the two lines. After the system receives the inspection signal, it makes ten heat protection measurements at a precision of ±0.04 mm and sends a signal within 10 milliseconds, providing Bangze Equipment with ideal production manufacturing conditions.

Provides optical control of lasered codes on PCBs: Rommel GmbH based in Ehingen, Germany, faced the challenge of using lasered data matrix codes to ensure that the PCB boards are produced without errors. In-Sight vision system provides a solution, where there is usage of innovative laser scan head that features a moving deflection mirror, CO2 lasers and the In-Sight vision system to reach its precision goals. It helped the company to execute the required laser marking tasks perfectly. Captured images and data are easily handled using the software and extensive library of proven vision tools. In addition, the system’s robust die cast aluminium and stainless steel housing are highly effective in making the system resistant to high vibration stress, and protecting the inner workings of the system against dust & debris.

Reduces inspection time: DWFritz Automation based in USA, faced the challenge in their Microelectro-mechanicalsystems (MEMS) need to be positioned in a plastic housing to submicron tolerances to align mechanical components on the die with interfacing components on the housing. VisionPro software with its solution along with MEMS part inspection tool uses two Cognex cameras and a Cognex frame grabber to perform over 500 measurements across nine manufacturing steps with a cycle time of no more than 30 seconds per step. The benefits achieved includes the precision inspection machine inspects over 500 measurements across nine different process steps at a rate of 120 parts per hour, enabling 100% inspection with only one operator. The kinematic fixture provides better than 0.2-micron repeatability when removing and replacing parts. The inspection system measures large and small features on the same part and co-relates measurements between high and low magnification cameras. The Cognex cameras and frame grabber provide the high levels of resolution needed to ensure that submicron tolerances are met on every unit.

Product traceability made easy

To ensure product safety and efficient recalls, producers must be able to quickly identify and locate potentially faulty parts in the supply chain that could pose a hazard to consumers.

While electronic product prices have remained relatively stable in the face of increasing functionality thanks to cost savings from miniaturisation and automated assembly, manufacturers must have visibility across their production floor to maintain profit margins. This means product inspections at each manufacturing node and closed loop control of automated assembly processes must be performed successfully before additional labour and energy are expended on defective products.
At the same time, manufacturers face a greater regulatory burden to track their products and validate environmental compliance as well as the need to limit liability from product recalls caused by defective components from secondary suppliers. In each of these cases, machine vision product tracking is at the cutting edge of the enterprise network, tracking all products throughout the manufacturing process and providing management with the data they need to optimize production while protecting their company from financial risks.

The better and more precise the traceability system in an electronics manufacturing process, the faster problems can be identified and resolved. Machine vision helps manage the supply chain in four ways such as improves management of work in process, reduces inventory, optimises availability and use of production tools and minimises distribution of non-conforming products.

Summary

With capacitors and other passive components measured in the microns and critical dimensions of semiconductors measured in nanometers, automated machine vision offers the only cost-effective way to check the quality of semiconductor components and electronic assemblies. When combined with direct automated signal testing, machine vision puts manufacturers in control of each step in the electronic manufacturing process—from incoming component inspection, to assembly, packaging and shipping.

Furthermore, machine vision’s ability to read 2D data codes on components and JEDEC tray symbols give OEMs the capability to view and manage their entire supply chain, resulting in lean, profit-driven electronic enterprises for today’s fast-moving markets.

Image Gallery

  • Vision software combines the power and adaptability of advanced programming with the simplicity of a graphical programming environment

  • Reduced application development time and faster inspection with machine vision

  • Machine Vision provides optical control of lasered codes on PCBs and reduces time to inspect

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