An Automated CAD System for Progressive Working of Irregular Shaped Metal Products and Lead Frame for Semiconductors

This paper describes the development of computer-aided design of irregular-shaped sheet metal products and 32LD PLCC lead frames and semiconductors, requiring very precise piercing operations for progressive working. The approach to the CAD system is based on knowledge-based rules. Knowledge for the CAD system is formulated from plasticity theories, experimental results, and the empirical knowledge of field experts. This system has been written in AutoLISP using AutoCAD on a personal computer and the I-DEAS drafting programming language on the I-DEAS master series drafting with an HP 9000/715(64) workstation. Transference of data between Auto-CAD and I-DEAS master series drafting is accomplished using DXF and IGES methods. This system is composed of five main modules, which are input and shape treatment, production feasibility check, strip-layout, data-conversion, and die-layout modules. Based on knowledge-based rules, the system is designed by considering several factors, such as V-notches, dimple, pad chamfer, spank, cavity punch, camber, coined area, cross bow, material and thickness of product, complexities of blank geometry and punch profile, and availability of presses. As forming processes and the die design system using 2D geometry recognition are integrated with the technology of process planning, die design, and CAE analysis, the standardisation of die parts for lead frames requiring a high precision piercing process is possible. The die-layout drawing generated by the die-layout module is displayed in graphic form. Results obtained for each module provide help to the designer and the manufacturer of lead frames for semiconductors.