€1m boost to optical inspection and placement machines at TDK-Lambda

Business news | August 2, 2019

By Nick Flaherty

As part of the overall €1m investment at the TDK-Lambda plant in Ilfracombe, Devon, UK, the company is adding a new YSi-V AOI machine from Yamaha (above).

The inspection process on AOI requires multiple images of the board to be taken and processed. The movement time for the camera far outweighs the processing time required for the image, so reducing the number of images required during inspection has a direct impact on the throughput of the machine.

The existing NV-175 equipment takes 65 images of the board, the much larger field of view on the Yamaha system requires only 9. Board handling then adds a similar amount to the processing time for each system and, as such, the increase in throughput offered through the new equipment varies depending upon board complexity but is generally in the region of increasing the current throughput by 150% to 175%.

Three placement lines are also being added, using Yamaha YSM-20 placement machines with a new optical detection system. The new machines provide placement accuracy of +/- 25µm @ 3 Sigma, compared to 50µm for the existing machines. However, the accuracy of component placement is not solely dependent upon how well the machine can repeatedly find the placement location. To place the component correctly, once the device has been picked, the machine must examine it to determine where its centre is. If the machine cannot accurately determine the centre of the component, it will not be able to place it in the desired location, irrespective of how accurately it can locate the position the device is to be placed at.

The current equipment uses a laser alignment system, shining a thin beam of light across the device and determining its centre by looking at the shadow it creates.

This technique works well with devices that have several axes of symmetry, such as chip resistors, as the shadow created is consistent irrespective of the height that the laser is set to when interrogating the component. However problems can occur when using plastic moulded devices with leads or devices without solid sides, such as wound inductors with ferrite cores. In these situations, the shadow that is generated by shining the thin beam of light against the device will vary depending how high up the on the side of the device you choose the set the laser.

This variability in the shadow can lead to variability in where the machine believes the centre of the component to be, and so a variability in the position it is placed on the board. Ultimately variations from component to component can lead to inaccuracy in placement, this situation is exacerbated when using multiple sources for the same component – changing a reel halfway through a run, for instance, can present the machine with a device that is packaged slightly differently as to how it was previously. This can lead to a difference in the perceived centre of the component and so a difference in the how the part is placed on the board. What used to run perfectly prior to changing the reel no longer applies.

The new machines use ‘vision centring’, imaging the base of the picked device prior to placement to determine the location of the important features, such as the component’s terminations, and uses this information to determine the component’s centre. This technique ensures that the device leads are always placed accurately onto the pads on the PCB, irrespective of the shape of the device’s body.

Of course, placing the part accurately is of no use if the wrong part is picked. TDK-Lambda has developed software systems to guarantee that the right reel is loaded onto the machine on the existing lines, but it does rely on operator discipline to ensure that they stay in the correct place during reel changeover. The new machines have intelligent feeders that will recognise if a feeder has been removed during a run and not returned to the correct location, preventing any further production until the feeder set-up is corrected.

The intelligence in the feeders is also used to identify which feeders require maintenance and prevents them being used on subsequent machine set-ups until they have been through the specified maintenance procedure. This feature reduces the likelihood of incorrect component feeding, which can itself contribute to poor machine placement.

The machine needs to ensure a good vacuum can be applied to the component to enable it to be handled securely throughout the ‘pick – centre – place’ process. Key to applying this vacuum is the condition of the placement nozzles. Whilst the current machines will warn if the vacuum levels associated with particular machine spindles are not sufficient, the new machine automatically performs its own maintenance on the nozzles to optimise the vacuum levels.

The first installation of the new lines is planned for May 2020 and the other two lines will be added over the next three years.

“The equipment replacements, including the new Surface Mount Technology (SMT) placement line and Automatic Optical Inspection (AOI) equipment, will enable us to increase capacity and maximise uptime,” said Phil Scotcher, Joint Managing Director at TDK‑Lambda UK. “However, we are also investing in new leading-edge technologies, such as additive manufacturing equipment [also known as 3D printers], laser marking and an experimental robotic arm, which will help reduce cost and time to market for new product introductions.”

www.tdk.com