Study And Analyze On Resistance Relationships And Control Strategy Of Laser Trimming

For small volume, high precision and well reliability, the chip resistors have been used in many fields. And there is a trend that the chip resistor will fill in the traditional resistor. Resistor material is printed on chip resistors using silkscreen. So they have the manufacture error that is less than 40%. Generally, using laser trimming to adjusts the resistance of chip resistors accurately. Trimming precision is an important technique item for laser trimming. The study of trimming precision isn't well done in our country. Compare to other country, the trimming precision of Laser Trimming System made in our country need to be improved. Firstly, the thesis analyzes the items that affect the trimming precision. And determines to improve the trimming precision by optimizing control strategy of laser trimming. The precondition of optimizing control strategy is mastering the relationships of resistance and laser cut paths. So the relationships of resistance and laser cut paths studied firstly in the thesis. Then according to the relationships of resistance and laser cut paths, the control strategy of laser trimming is optimized. Before study the relationships of resistance and laser cut paths, the investigation methods must be elected. Five methods are discussed here. They are Physics Model method, Conforming Mapping Method, Resistor Subsection Method, Numeric Method and Experimentation Method. Though analyzing their advantages, disadvantages and feasibility, decides using Resistor Subsection Method to study the relationship of resistance and single ordinate cutting, using Numeric Method to study the relationships of resistance and I(L)-cutting , using Experimentation Method to study the relationships of resistance and all cutting paths. And a series of conclusions about resistance and cutting paths are gained. The experimental data validated that these conclusions are right and acceptable, and can provide theory bases for optimizing control strategy. According to the relationships of resistance and all cutting paths, two control strategies that base on increment of single facula are introduced. They are fixing ordinate cutting length and control ordinate cutting length dynamically. Though analyzing, the two control strategies can improve trimming precision without changing the hardware of trimming system.