Copper Heat Spreader Package for Low-Warpage Semiconductor Assembly

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Semiconductor devices with components of different linear coefficients of expansion experience stress due to heating and cooling cycles, leading to warpage and reliability issues, particularly when using high-modulus materials like copper, which increases manufacturing costs.

Innovation Solution

A semiconductor device design incorporating a copper or copper alloy heat spreader, solder layers, and a sealant with a linear coefficient of expansion between 11 ppm/K and 21 ppm/K, along with copper alloy lead frames and blocks, to minimize stress and enhance reliability while reducing material costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high-modulus materials like copper are used to reduce stress, then stress buffering capability is improved, but manufacturing cost increases

Engineering Contradiction:

Improvestress buffering capabilityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the material parameters by selecting copper or copper alloys with specific properties (high modulus of elasticity and high linear coefficient of expansion) for the heat spreader and lead frames. This parameter selection allows the material to effectively buffer stress from thermal expansion while remaining relatively inexpensive compared to specialized low-expansion materials like invar or kovar.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent utilizes the thermal expansion property of copper and copper alloys to match and buffer the stress generated by thermal cycling. The high linear coefficient of expansion of copper (11-21 ppm/K) allows it to absorb expansion stress from the semiconductor element during heating cycles, preventing warpage and bonding failures without requiring expensive specialized materials.

Inventive Principle:

Principle #37Thermal expansion

2Reliability

If solder is used as bonding material, then stress buffering is improved, but surface electrode damage risk increases

Engineering Contradiction:

Improvestress buffering functionVSAvoidsurface electrode damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces the heat spreader made of copper or copper alloy as an intermediary component between the semiconductor element and the external environment. This heat spreader acts as a stress buffer that protects the aluminum surface electrode from direct stress exposure, while the solder serves primarily as a bonding material rather than the main stress buffer. This intermediary structure distributes and absorbs thermal stress before it reaches the vulnerable surface electrode.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the stress buffering function from being primarily performed by solder to being performed by the copper heat spreader and lead frames. By selecting materials with high modulus of elasticity and high linear coefficient of expansion for the heat spreader and lead frames, the stress buffering capability is shifted to these components, allowing solder to focus on bonding while the copper components absorb thermal expansion stress.

Inventive Principle:

Principle #35Parameter changes

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 design effectively reduces stress-induced warpage and enhances the reliability of semiconductor devices while lowering manufacturing costs by using copper and copper alloy components with a suitable sealant expansion coefficient.

Implementation Method 1

a sealant having insulating properties and having a linear coefficient of expansion more than or equal to 11 ppm/K and less than or equal to 21 ppm/K

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

Solder also functions as a stress buffer that deforms to absorb the stress from subject components

Methodology Applied

Scientific EffectStress buffer deformation: Elasticity

Implementation Method 3

a heat spreader made of copper or a copper alloy

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 4

a first lead frame welded to the heat spreader and made of copper or a copper alloy; a second lead frame welded to the block

Methodology Applied

Scientific EffectWelding: Welding

Data Source

PatentUS20240178100A1Semiconductor device and method of manufacturing semiconductor device

Publication Date: 2024.05.30 MITSUBISHI ELECTRIC CORP

AI summary

The semiconductor device includes: a heat spreader; a first solder layer; a second solder layer; a semiconductor element including a first surface bonded to the heat spreader through the first solder layer, a second surface facing the first surface, a first electrode disposed on the first surface, and a second electrode disposed on the second surface; a block bonded to the second electrode through the second solder layer; a sheet including a first portion, and a second portion having insulating properties and being in contact with the heat spreader; a first lead frame welded to the heat spreader; a second lead frame welded to the block; and a sealant having insulating properties and sealing the first and second lead frames, the heat spreader, the first and second solder layers, the semiconductor element, and the block.