Spacer Structure for Double-Sided-Cooled Power Module
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Solution Overview
Problem
The existing spacer structures for double-sided-cooled power modules, made of composite materials like CuMo or AlSiC, face challenges in ensuring electrical and physical connections due to poor wettability with joining materials, leading to deterioration of semiconductor chip characteristics and potential burnout from intermetallic compound formation at high temperatures.
Innovation Solution
A spacer structure comprising a conductive composite material layer with an undercoat and a copper plating layer, where the copper plating layer is in contact with the joining material, and optionally a metal layer like gold, silver, or palladium, to enhance wettability and prevent exhaustion of the thin metal layer on the semiconductor chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a spacer made of composite material (CuMo or AlSiC) is used to electrically and physically connect the semiconductor chip and insulating substrate, then the joining force between components is maintained, but the wettability with joining material is poor and interface reaction does not occur
Solution Approach 1:
An undercoat layer is introduced as an intermediary between the composite material spacer and the joining material. This undercoat layer serves as a mediator that enables proper wetting and bonding, allowing the joining material to adhere effectively to the spacer surface while maintaining the structural integrity provided by the composite material.
Solution Approach 2:
The spacer is constructed as a multi-layer composite structure combining the composite material (CuMo or AlSiC) with an undercoat layer and optionally a copper plating layer. This composite structure integrates the mechanical strength of the composite material with the surface properties needed for joining material attachment.
2Ease of manufacture
If nickel is applied onto the surface of the spacer made of composite material to enable joining, then the joining capability is improved, but the thin metal layer on the semiconductor chip reacts with joining material at high temperature forming intermetallic compounds that exhaust the metal layer
Solution Approach 1:
The undercoat layer acts as a protective intermediary that prevents direct contact between the joining material and the thin metal layer on the semiconductor chip. This intermediary barrier stops the harmful intermetallic compound formation while still allowing effective joining through the undercoat layer's controlled reactivity with the joining material.
Solution Approach 2:
The undercoat layer, which might seem like an additional complexity, actually converts the harmful high-temperature reaction between joining material and chip metal into a beneficial controlled reaction at the undercoat layer interface. This protects the chip's electrical characteristics while maintaining joining effectiveness.
3Reliability
If the double-sided-cooled power module is operated in high-temperature environment, then the cooling performance is tested, but the intermetallic compound grows and exhausts the thin metal layer causing semiconductor chip burnout
Solution Approach 1:
The undercoat layer transforms the harmful high-temperature environment from a destructive force that causes metal layer exhaustion into a controlled testing condition. The undercoat layer withstands the thermal stress and prevents the harmful intermetallic compound growth that would otherwise occur between the joining material and chip metal layer.
Solution Approach 2:
The undercoat layer provides beforehand cushioning protection against the harmful effects of high-temperature operation. It anticipates and prevents the intermetallic compound growth issue before it can affect the semiconductor chip, allowing reliable thermal testing in high-temperature environments.
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
The proposed spacer structure improves the electrical characteristics and durable life of semiconductor chips by inhibiting the loss of the metal layer, reducing the reaction rate with the joining material and preventing burnout, thus maintaining performance in high-temperature environments.
Implementation Method 1
the copper plating layer is in contact with a joining material that joins the spacer to the semiconductor chip and the insulating substrate
Implementation Method 2
a thin metal layer applied onto the surface of the semiconductor chip reacts with the joining material due to the heat produced from the semiconductor chip, and as a result, an intermetallic compound is formed and grown
Data Source
AI summary
A spacer structure, which connects an insulating substrate and a semiconductor chip of a double-sided-cooled power module, includes: a conductive material layer which is composed of a composite material; an underlying plating layer disposed on the conductive material layer; and a copper plating layer disposed on the underlying plating layer, in which the copper plating layer is in contact with a joining material that joins the spacer to the semiconductor chip and the insulating substrate.