Research On Alignment Methods And Optical Systems For Automatic Flip Chip Bonders

An automatic flip chip bonder is a precision instrument used to align and bond one or more dies onto a substrate in semiconductor industry. It develops for the mass production of IC,MEMS and MOEMS with small feature sizes and high precise bonding demands.An alignment system is one of the key components in flip chip bonders. Today, the most advanced alignment methods have used the technology of machine vision and image proceeding, by which the feature marks on dies or substrate are recognized or measured, by which machine movement equipments are leaded to complete alignment. Die leveling and auto-focus usually be completed before vision-based alignment of die and substrate.In this thesis, the work on automatic alignment system is as follows:Firstly, after the methods and optical systems for alignment whose are used commonly now are discussed, a new die leveling method based on auto-focus is presented for the flip chip bonder. Auto-focus is completed by estimating from images; die leveling is completed by focusing for several feature locations. As a result, just a set of imaging optical components, which used to merely complete alignment, now can be used for the three procedures—die leveling, auto-focus, alignment.Secondly, two vision-based optical systems for alignment are put forward. Not only can high-resolution and high-quality images be gotten, but also straightforward hardware setup and good secular stability in the shop can be obtained.Last but not least, the specific microscope objective in an alignment optical system is emulated and optimized in ZEMAX software. During the procedures of design, objective is optimized at actual parameters of selective CCD camera and LED illumination light and a good aberration balance is also obtained. For another system, an experiment for alignment is carried out due to the off-the-shelf components, from which a group of images which can be used for alignment are obtained.