The trend in semiconductor packages is to become smaller, hence tighter clearances in the design

With tight clearances in Fig. 1 denoted by A-D parameters, wirebonding from die to bond finger becomes more critical and challenging, and risk of wire-related rejects increase

Frederick Ray I. Gomez

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International Research Journal of Advanced Engineering and Science  ISSN (Online): 2455-9024   267  Frederick Ray I. Gomez, “Specialized interposer for critical wirebonding on substrate LGA semiconductor package,” International Research Journal of Advanced Engineering and Science, Volume 4, Issue 2, pp. 267, 2019. Specialized Interposer for Critical Wirebonding on Substrate LGA Semiconductor Package  Frederick Ray I. Gomez  Central Engineering & Development NPI, Back-End Manufacturing & Technology, STMicroelectronics, Inc.  Calamba City, Laguna, Philippines 4027    Keywords— LGA; wirebonding; interposer; substrate; wire sweep. I. BACKGROUND OF THE STUDY  The trend in semiconductor packages is to become smaller, hence tighter clearances in the design  With tight clearances in Fig. 1 denoted by A-D parameters, wirebonding from die to bond finger becomes more critical and challenging, and risk of wire-related rejects increases  Fig. 1. Cross-sectional illustration of substrate land grid array (LGA) semiconductor package. II. PROBLEM IDENTIFICATION  High wirebond looping has low resistance against the drag force/stress that molding compound applies during molding process, causing wire sagging and sweeping  With tight clearance between edge of die and bond finger (parameter B), wire-to-die short and wire-to-wire short could happen  Fig. 2.  Wire sagging and sweeping.  Possibility of high parts per million (ppm) level in terms of wire breakage, due to large height difference and formation of wire looping  III. PACKAGE DESIGN SOLUTION  A specialized interposer is designed in Fig. 3 to reduce the wire loop span, thus increasing the wire strength and providing strong loop to prevent wire sagging and wire sweeping during molding process  The interposer acts as an electrical interface between the top die through the wire and the substrate bond fingers  Fig. 3. Substrate LGA semiconductor package with specialized interposer.  The design helps prevent wire-to-die and wire-to-wire shorting due to tight clearances during wirebonding process  With the specialized interposer, ball neck strength of the wires is increased, thus preventing neck damage during formation of a low loop and in turn increasing the package reliability    Interposer could also provide a widespread connection or a wider pitch that could allow rerouting of the wires if needed 

Specialized Interposer for Critical Wirebonding on Substrate LGA Semiconductor Package

https://zenodo.org/record/3153597/files/IRJAES-V4N2P493Y19.pdf

Specialized Interposer for Critical Wirebonding on Substrate LGA Semiconductor Package

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