STRATUS VISION

STRATUS VISION
Vigitek in Ireland developed the technology that the model STRATUS is based on. A group of shareholders bought this line and founded a new company, the Stratus Vision GmbH, based in Munich. A team was formed around Mrs. Dr. Jola Mallon and two ex-Vigitek engineers, Damien Tobin and Vincent Fitzgerald. Stratus Vision GmbH will support the existing customer base as well as further enhance and improve the AOl for hybrids system technology.

The Stratus Vision GmbH will concentrate its efforts in AOl, vision and imaging of hybrids and LTCCs. Other handling companies are supplying the mechanical system the substrate handling. Screen printers from Baccini, EKRA and AMI have already been integrated with the STRATUS system. STRATUS VISION/EPP are supplying the entire system and are responsible for the integration and support. STRATUS VISION/EPP is located in the western outskirts of Munich, Germany.

STRATUS is a specialized AOl system for Hybrids and LTCC, used in following applications:

	In-Line (inspection of Wet Print), between screen printer and dryer
	Off-Line (inspection of wet print or dry substrates)
	Manual loading / unloading of substrates
	Automatic loading /unloading of substrates (single or cassettes)
	AOl of gold layer after burn-in furnace (manual or automatic loading)

In most cases the cycle time of in-line systems matches those of the screen printer. In some applications, especially in automatic clean room installations, every 2nd, 3rd and 4th substrate is inspected, which guarantees that any screen defect or screen ageing can be found.
The STRATUS system can be adapted to any system from any screen printer manufacturer. Depending on the cameras used, any defect of any size, that is relevant in today’s manufacturing technology of hybrids and LTCCs, can be found.

Stratus Vision Module (above).
Below, Stratus Vision with dual camera head "hanging" from the granite beam with closed-loop linear scale/linear motor drive system.

After the substrate is put underneath the imaging head, it is not moved anymore during inspection. Bottom lighting and top lighting make the structures visible for the digital pixel camera. The imaging head with camera(s) and lighting is moved across the substrate in a precise and well defined way by very fast linear motors with exactly defined positioning feedback. Pictures are taken with sufficient overlapping to ensure that no area remains un-inspected. When the CAD data is downloaded onto the STRATUS system, a bit map is created and automatically tolerances are applied to all structures (conductors, pads, resistors, etc) and to all areas between those structures. 
The system is then comparing all images against the CAD data and against the default tolerances or against the tolerances that the operator has modified, according to his requirements. The illumination with strobed LEDS is automatically applied under software control, with different lighting (for maximum contrast) for different materials. The defect sizes on installed systems, that must be detected, range from 5 µm up to 50 µm, depending on pixel size of the cameras used.

The STRATUS can make even glass visible with sufficient contrast to make fast and accurate decisions. All defects found are stored and, if required, downloaded to the factory network, for later evaluation and documentation. All defects are measured in X and Y direction and their area is calculated. Then, all these values are compared to the tolerance table. Whenever they exceed the values in this tolerance table, a defect is found. Then the type of defect is identified and the data is used for statistical calculations and histograms (see chart: defect ). The STRATUS comes with a very comfortable software package that includes various statistical features. All data can be monitored from remote stations and prepared or displayed in many different ways.

PICTURES 

1. Conveyer input - 2. The EKRA Stratus Vision System at Productronica 2003 
3. Four Camera Vision Head Unit -  4. Examples of defects found by Stratus Vision System