Accurately locating a wide variety of components using automatic vision referencing involves a comprehensive system of optics, lighting, vision processing engine and higher level referencing alignment algorithms. Palomar Technologies’ design is based on decades of experience in die bonding applications. Red-blue lighting in combination with the multiple field of view optics for the lookdown camera and the industry-proven Cognex Vision System’s processing capabilities provide a robust and powerful referencing engine for the most demanding applications.
A Brief Description of Palomar’s Vision System
Lighting
Are three-colored LED lighting systems for pattern recognition necessary? Some organizations commonly misinterpret the need for a three-color lighting system to mix various colors, including white light. However, this assumption is dismissed through an LED vision referencing design based on decades of experience in die bonding applications with use of red-blue lighting. 
High-precision equipment, like the ultra-flexible 3800 Die Bonder, can be equipped with red-blue LED lighting for both OFF-Axis (Dark Field) and ON-Axis (Bright Field) lighting for the lookdown and look-up cameras.
Benefits of red-blue lighting:
- Monochromatic light is preferred to white or multi-color lighting in order to produce higher accuracy referencing
- Red monochromatic light has been documented to work very well in hundreds of unique applications for optoelectronic components
- Blue monochromatic lighting as second color allows distinguishing between different materials; for example, red will illuminate gold and silver approximately the same; however, blue will allow silver to shine and gold to remain dark
- Blue monochromatic light has a higher optical resolution than red or green
- Blue monochromatic light allows higher resolution than white light
- Mixing multiple colors together negates the positive effects of using monochromatic light
For further examples, red lighting will illuminates gold and silver approximately the same. However, blue lighting allows silver to shine and gold to remain dark. In fact, blue monochromatic light has a higher optical resolution than red, green or white light. In another words, green and white lighting have much lower optical resolutions than red or blue lighting. It is, therefore, not recommended to use green or white light for higher accuracy referencing. It is also worthwhile to note that mixing multiple colors together negates the positive effects of using monochromatic light and should be avoided.
Optics
Palomar has multiple magnifications on the lookdown camera. This aids in selecting the best field of view based on the geometry of the fiducial feature being referenced. Switching between optical magnifications is automatically completed during program execution.
Watch 0:00:30 - 1:50:00 of this video to see the red monochronic lighting in action on the 3800 Die Bonder:
Vision Processing Engine
Palomar uses the latest Cognex Vision System, which uses edge, blob, and pattern matching algorithms as foundation for referencing. Other equipment providers may use homegrown vision processing engines, raising the associated risk of less mature industry-hardened designs, which can be more sensitive to lighting and optics.
Higher-Level/Referencing Algorithms
Complex types of referencing algorithms can use 1-point, 2-point, 3-point, etc. Palomar adds multiple optical magnifications—and Red/Blue ON/OFF axis lighting—and combines this approach with the higher-level part referencing strategies to solve the most demanding referencing applications. Palomar bonders also use multiple levels of referencing if necessary, which uses low magnification followed by high magnification to find loosely constrained components at low magnification and then fine referencing at higher magnification.
As with many scenarios in the microelectronic packaging industry, LED vision referencing needs are application dependent and Palomar recognizes that a part may benefit from a color other than red or blue. In situations like this, Palomar capable of conducting a thorough study on the 3800 Die Bonder to determine the ability to see and resolve the specific part materials and requirement.
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PH Chan钟碧和
Asia Pacific Director
Palomar Technologies (S.E. Asia) Pte Ltd