Die Bonder for the Stacking of Membrane Chips with One Micron Post-bond Accuracy

The Institute for Microelectronics Stuttgart (IMS Chips) is engaged in business-oriented research in the fields of silicon technology, application-specific circuits (ASIC), nanostructuring and image sensor technology and provides professional training. The institute partners with small and medium-sized enterprises, especially in the German federal state of Baden-Württemberg, and cooperates with leading international semiconductor companies and suppliers.

For a new application, key requirement was the stacking of a number of membrane chips, each several cm in size, on top of each other with very high precision. After completion of all placement and stacking steps, the post-bond accuracy of the overall process had to be less than 1 µm.

The previous system, an in-house design based on an old 3-inch mask aligner, reached its limits here due to a lack of spare parts and flexibility. For example, the lens distance could not be reduced, which limited the number of membranes which could be stacked on top of each other. The bonding force could not be controlled, which endangered the fragile membrane chips. Also, the adhesive for bonding the chips could not be applied in a defined manner and the overall process stability was not consistently given.

Therefore, IMS Chips were in the market for a new assembly system that would continue to ensure the highest assembly precision, but offer more flexibility in terms of supported substrate and component dimensions. The bonding force should be process-controlled and adjustable over a wide force range, and the system should also have the option of precisely applying adhesive with a dispenser.

Membrane chip stacking with 1 µm post-bond accuracy

IMS Chips’ first contact with Finetech was at a trade show, where the advertised flexibility combined with high accuracy piqued the company’s interest.

After a second meeting in Stuttgart, IMS CHIPS accepted the invitation to Finetech’s Micro Assembly Day in Berlin. There, IMS Chips‘ Mr. Jurisch had the opportunity to experience the FINEPLACER^® placement and assembly systems in more detail. First demonstrations with original membrane chip samples from IMS Chips ensued.

In order to meet the required accuracy, Finetech developed a demo tool. Together with Finetech’s application team, the whole assembly process was also re-engineered and further developed until the 1 µm post-bond accuracy could be reproducibly achieved.

Now the one thing left to do was to choose the most suitable FINEPLACER^® system. In the sub-micron class, there are several systems to choose from that could map the membrane stacking process. However, since IMS Chips was explicitly looking for a system with automatic operation for series production, which at the same time also offered unrestricted manual intervention options due to the high percentage of process development, they finally decided in favor of the fully automatic die bonder FINEPLACER^® femto 2.

Pleased with the FINEPLACER^® femto 2 for membrane stacking and more

IMS Chips is using this die bonder as their main placement and assembly system for the packaging of special MEMS components as well as a test platform for other R&D projects and applications. Since it has its own clean room housing, the controlled environment allows implementing even the most demanding processes.

Extensive in-process measurement options have significantly increased reproducibility compared to the previous system, where work had to be done “by eye”. In addition, UV adhesive can be applied in a defined manner for the first time and cured very quickly with UV light. This reduces the overall process time by several hours, during which the old system was practically blocked.

By choosing the FINEPLACER^® femto 2 die bonder, IMS Chips can reproducibly implement and continuously develop the demanding membrane stacking application and has also found the ideal production and development platform for a wide range of future applications.

“We are very pleased with our decision for the FINEPLACER^® femto 2. All our expectations have been met, the die bonder is robust and reliable. Finetech’s support team has always been there for us and is quick to solve any obstacle.”

Michael Jurisch
Project Manager, IMS CHIPS