Semiconductor Lead Frame Asymmetric Dicing for Short Circuit Prevention
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Solution Overview
Problem
Resin-sealed semiconductor devices using lead frames face challenges in improving reliability and reducing the spacing between leads, which can lead to short circuits due to metal burrs formed during the dicing process, affecting manufacturing yield and cost.
Innovation Solution
The method involves a lead frame design with leads having different thickness portions, where the thinner portions are cut at different heights to prevent metal burrs from causing short circuits, and the use of a dicing blade to cut the resin sealing portion and leads, ensuring that the cut surfaces of the leads are exposed at varying heights to prevent contact between adjacent leads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the spacing between leads is reduced to improve device integration, then productivity and device density improve, but the risk of short circuits due to metal burrs increases, worsening reliability
Solution Approach 1:
The patent applies asymmetry by making the lead thickness non-uniform along its length, with a first thickness in the first region and a second thickness (greater than the first) in the second region. This asymmetric thickness distribution ensures that during dicing, the thicker portion generates burrs that extend further than those from thinner portions, creating staggered burr heights that prevent short circuits between adjacent leads while maintaining reduced spacing.
Solution Approach 2:
The patent transitions from a two-dimensional planar arrangement to a three-dimensional staggered configuration by varying lead thickness along the cutting direction. This dimensional change creates height differences in the cut surfaces and burrs, allowing leads to be positioned closer in the planar view while maintaining electrical isolation through vertical separation of their respective burrs.
2Ease of manufacture
If uniform lead thickness is used to simplify manufacturing, then ease of manufacture improves, but all leads are cut to the same height creating short circuit risks, worsening reliability
Solution Approach 1:
The patent applies local quality by varying the thickness of different portions of the leads based on their specific locations and functions. The first portion has a first thickness while the second portion has a second thickness greater than the first. This localized thickness variation ensures that critical leads generating burrs have appropriate dimensions for short circuit prevention, while other portions maintain optimized dimensions for their specific functions, allowing differentiated treatment of different lead regions.
Data Source
AI summary
An improvement is achieved in the reliability of a semiconductor device. After a resin sealing portion is formed to seal a die pad, a semiconductor chip mounted over the die pad, a plurality of leads, and a plurality of wires electrically connecting a plurality of pad electrodes of the semiconductor chip with the leads, the resin sealing portion and the leads are cut with a rotary blade to manufacture the semiconductor device. In the semiconductor device, at least a portion of each of first and second leads is exposed from a lower surface of the sealing portion. End surfaces of the first and second leads as the respective cut surfaces thereof are exposed from each of side surfaces of the sealing portion as the cut surfaces of the resin sealing portion. The distance between a lower side of the end surface of the first lead and an upper surface of the sealing portion is smaller than the distance between an upper side of the end surface of the second lead adjacent thereto and the upper surface of the sealing portion.