Semiconductor Chip Pad Structure for Reliable Solder Thickness Control
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Solution Overview
Problem
As semiconductor devices downsize, it becomes challenging to ensure a sufficient thickness of solder between the semiconductor chip and the metal plate without using protrusions on the metal plate, which can lead to unreliable connections and increased on-resistance.
Innovation Solution
A manufacturing method where a first space is maintained between a metal plate and a semiconductor chip, and a second lead frame is mounted over a first lead frame with conductive adhesive material, allowing for a heating process that fixes the thickness of the conductive material between the chip and the plate, ensuring reliable connections without protrusions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protrusions are provided on the metal plate to ensure solder thickness, then connection reliability is improved, but device complexity increases and manufacturing difficulty increases for small devices
Solution Approach 1:
The invention extracts the protrusion structure from the metal plate and relocates it to the semiconductor chip side as a pad structure. This resolves the contradiction by maintaining the thickness assurance function while simplifying the metal plate structure, especially for small-scale devices where forming protrusions on the metal plate becomes difficult.
Solution Approach 2:
Instead of providing protrusions on the metal plate to press into the chip, the invention inverts the approach by providing corresponding pad structures on the chip that receive and accommodate the metal plate. This inversion maintains the thickness control function while eliminating the complexity of forming protrusions on small metal plates.
2Reliability
If protrusions are provided on the metal plate to ensure solder thickness, then connection reliability is improved, but ease of manufacture deteriorates for downsized devices
Solution Approach 1:
The protrusion function is extracted from the metal plate manufacturing process and transferred to the semiconductor chip manufacturing process. This resolves the manufacturing ease contradiction because pad structures can be formed using standard semiconductor fabrication techniques, whereas forming protrusions on small metal plates becomes increasingly difficult as device size decreases.
Solution Approach 2:
The pad structures are preliminarily formed on the semiconductor chip during the chip fabrication process before the metal plate is attached. This preliminary action ensures that when the metal plate is subsequently mounted, the solder thickness is automatically assured without requiring complex post-processing or specialized protrusion formation techniques on the metal plate.
3Productivity
If device size is reduced for downsizing, then productivity is improved, but manufacturing precision deteriorates for ensuring solder thickness
Solution Approach 1:
The thickness assurance mechanism is extracted from the metal plate and transferred to the chip pad structure. This resolves the precision contradiction because the pad structure dimensions can be precisely controlled during semiconductor fabrication using photolithography and etching techniques, maintaining manufacturing precision even as device size decreases.
Solution Approach 2:
The invention changes the critical parameter from protrusion dimensions on the metal plate to pad structure dimensions on the chip. Since semiconductor fabrication processes excel at controlling microscopic dimensions, this parameter change enables precise control of solder thickness even in downsized devices, maintaining manufacturing precision while improving productivity through standard fabrication techniques.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively maintains the thickness of the conductive material between the semiconductor chip and the metal plate, enhancing the reliability of the connection and reducing on-resistance, even as devices shrink in size.
Implementation Method 1
a heating process for heating the conductive adhesive material at a first temperature is performed
Implementation Method 2
heating the conductive adhesive material... to thereby be melted
Implementation Method 3
the conductive adhesive material... in contact with the first portion of the metal plate and the electrode pad of the semiconductor chip
Data Source
AI summary
To enhance the reliability of connection between a semiconductor chip and a metal plate by ensuring sufficiently the thickness of a conductive material interposed between the semiconductor chip and the metal plate. A lead frame is arranged over a jig and a clip frame is arranged over protruding portions provided on the jig. In this state, a heating process (reflow) is performed. In this case, high melting point solders filling first spaces are melted in a state in which the first space is formed between a High-MOS chip and a High-MOS clip and the first space is formed between a Low-MOS chip and a Low-MOS clip. At this time, even when the high melting point solder is melted in the first space, the size (in particular, the height) of the first space does not change and the first space is maintained.