Using Essemtec’s SMD Tower for IGBT storage in a clean room

18th century writer and adventurer Giacomo Casanova said that we owe the best things to chance. This holds true for ABB — a coincidence brought the end to a long search for a suitable storage system for the production of HiPak IGBT modules in Lenzburg.



Background



The HiPak from ABB Semiconductors is a high-performance semiconductor switching module for high current and voltage, and is known worldwide for its extremely short switching time and reliability. Therefore, the product is used where high power must be switched fast, for example, on a train or in a wind power plant.



A HiPak module consists of several IGBT modules that must switch simultaneously and in absolute synchronization. Therefore, it is important that all IGBTs within a HiPak have the same properties. ABB measures and marks each IGBT individually and stores its characteristic in a database. This ensures that only suitable IGBTs are combined in a HiPak module.



Buffer Store Automation



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During production, the IGBT modules are placed in a buffer store for one to two days. The IGBTs are held in so-called washing baskets, which are identified with a barcode. For production, the specific baskets holding the required IGBTs are required from the buffer store.



Previously, the buffer was a simple shelf where the baskets were moved in and out by hand. However, using this method, it was not possible to store the IGBTs in an inert gas atmosphere as recommended. Furthermore, the constant searching for the right baskets was time-consuming, cumbersome and prone to errors.



Prabath Lewdeni, process engineer for ABB Semiconductors, was looking for alternatives. For a long time Paternoster systems was the only choice. However, these were unable to fulfill ABB’s requirements regarding inert gas atmosphere, access protection, scaleability and redundancy. So Lewdeni continued searched for something better. He found the solution — by coincidence — in another industry.



Coincidence Leads to a Solution



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During a visit to Essemtec AG, the leading Swiss manufacturer of production systems for electronics, Lewdeni learned about the SMD Tower, which is an automatic and scaleable storage system for electronic components in the form of reels and trays.



Storage and retrieval is possible only through a lock. This lock secures access to the stored material while separating the storage area from the environment, allowing an inert gas atmosphere with controlled temperature and humidity to be formed within.



The Tower features a small footprint of only one square meter and several Towers can be grouped for larger scale storage. For Lewdeni, this was the ideal solution for HiPak production at ABB Semiconductors. However, it still needed a few modifications.



Flexible Adaptation to ABB’s Requirements



SMD reels are round, thin and have very exact measurements. ABB’s washing baskets are the complete opposite. They are square, thick and their sizes differ by several millimeters. Also, a clean room atmosphere is not likely for an SMD production. Therefore, the SMD Tower could not be used “out of the box.”



Essemtec has many years of experience in customer-specific adaptation of standard machines. The engineers constructed and build a new gripper arm for the washing baskets. The height of the lock and the position of the barcode reader were adapted. Additionally, the Tower was made clean room compatible.



Connection to the Production Control System



ABB Semiconductors uses a special control system, Manufacturing Execution System, with which all machines must be able to communicate. The Tower offers an open Web-Service-Client interface that a user can implement for such purposes. Therefore, ABB was able to integrate the Tower to the MES easily and by themselves.



The adaptation by Essemtec and ABB took only a few weeks. In February 2012, Essemtec delivered two Towers in advance for installation and testing. The installation went smoothly. “Normally, we have to fight a few days with new machines, but not with the Tower,” recalls Lewdeni. In April 2012, the remaining Towers were delivered and installed.



24/7 Continuous Operation



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A total of eight Towers are currently in operation for the HiPak production. Seven of them are productive, and the eighth can be placed into operation to replace another during maintenance. In this configuration, the buffer storage is ready for the 24 hour/7 day production.



Awareness and a coincidence helped ABB find the right system for its HiPak buffer storage. But only the flexibility, the adaptability and the scaleability of the Tower storage system has ensured that all ABB Semiconductors’ requirements were met with one simple, robust system.