Semiconductor Package Lead Structure for Through-Hole-Free Mounting
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Solution Overview
Problem
The existing methods for mounting semiconductor devices on mounting boards are limited by the need for through-holes, which restrict the wiring layout and lead to inaccuracies in the height of the semiconductor device's upper surface.
Innovation Solution
The semiconductor device design includes a semiconductor chip sealed by a sealing body with leads connected to the chip, and a metal plate with an exposed surface that allows for surface-mounting without through-holes, ensuring accurate height alignment and improved heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a through-hole is formed in the mounting board for lead insertion, then the lead can be electrically connected with the board, but the wiring layout of the mounting board is limited and the height accuracy of the semiconductor device is reduced
Solution Approach 1:
The invention extracts the lead insertion function from the mounting board structure by using a dedicated lead frame with exposed leads that make direct contact with terminals on the mounting board surface, eliminating the need for through-holes in the mounting board. This allows the leads to be positioned precisely relative to the semiconductor chip while enabling flexible wiring layouts on the mounting board without through-hole constraints.
2Ease of manufacture
If the end of the lead is bent to face the terminal for surface-mounting, then the device can be mounted without through-holes, but the height of the upper surface of the semiconductor device varies due to lead shaping accuracy errors
Solution Approach 1:
The lead frame is pre-formed with leads that extend from the sealing body toward the mounting board surface in a controlled manner before mounting. The leads are positioned at predetermined locations and orientations, allowing precise height control when the semiconductor device is mounted on the mounting board. This preliminary positioning eliminates the need for post-mounting lead bending and associated height variations.
3Reliability
If a through-hole is formed in the mounting board, then the lead can be inserted and fixed, but the layout flexibility of multiple wiring layers is restricted
Solution Approach 1:
The invention transitions from a three-dimensional through-hole penetration approach to a two-dimensional surface-mount approach. The leads extend from the sealing body and make contact with terminals on the mounting board surface, allowing wiring layouts to be designed in multiple layers without the constraint of through-hole positions. This dimensional change enables greater flexibility in routing wires across different layers while maintaining reliable electrical connections.
Data Source
AI summary
Performance of a semiconductor device is improved. A semiconductor device includes a semiconductor chip, a sealing body having an upper surface and a lower surface, a plurality of leads, and a metal plate exposed from the sealing body at the upper surface of the sealing body. An outer lead portion of each of the plurality of leads includes a portion extending from the upper surface toward the lower surface in a thickness direction of the sealing body. The portion includes an end of the outer lead portion. When it is assumed that the lower surface is a reference surface in side view, in the thickness direction of the sealing body, a distance from the end of the outer lead portion to the reference surface is less than a distance from the upper surface to the reference surface.