Semiconductor Package Adhesive Layering for Reflow Cavity Filling
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Solution Overview
Problem
In semiconductor device packaging, it is challenging to completely fill the gap between the wiring substrate and the die attach film, leading to cavities that can expand under high temperature, causing pressure buildup and potential package damage during reflow tests.
Innovation Solution
A semiconductor device design featuring a first adhesive layer with resins of varying molecular weights and a filler, and a second adhesive layer with smaller molecular weight resins and lower filler concentration, which separates to fill the gap between the substrate and the first adhesive layer, reducing cavity size and preventing package damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a die attach film is used to fill the gap between the wiring substrate and the adhesive layer, then the gap filling is improved, but cavities still occur and expand under high temperature causing pressure buildup
Solution Approach 1:
The adhesive layer is segmented into multiple layers with different molecular weights. The first adhesive layer has higher molecular weight and provides structural support, while the second adhesive layer has lower molecular weight and flows to fill cavities during heat treatment, preventing pressure buildup from moisture expansion
Solution Approach 2:
The patent changes the molecular weight parameter of the adhesive layer by using a multi-layer structure. The lower molecular weight second adhesive layer becomes more fluid under heat treatment conditions, enabling it to flow into and fill cavities that form during the process, thereby maintaining package integrity
2Ease of manufacture
If the adhesive layer is made with uniform molecular weight resins, then the manufacturing process is simplified, but cavities cannot be effectively filled during heat treatment
Solution Approach 1:
The adhesive layer is divided into two distinct layers with different molecular weight characteristics. This segmentation allows each layer to perform its specific function: the first layer provides initial adhesion and structure, while the second layer responds to heat treatment by flowing to fill cavities, achieving both manufacturing simplicity and effective cavity filling
Solution Approach 2:
The patent uses a composite adhesive layer structure combining resins of different molecular weights in distinct layers. This composite approach leverages the complementary properties of each layer type to achieve cavity filling during heat treatment while maintaining ease of manufacture through a systematic multi-layer design
3Shape
If moisture is present in the cavity, then the package structure is formed, but moisture expansion under high temperature causes pressure that may damage the package
Solution Approach 1:
The patent converts the harmful effect of moisture expansion into a beneficial process. The moisture expansion pressure that would normally damage the package is instead utilized to drive the lower molecular weight resins to flow and fill cavities. The pressure generated by moisture expansion becomes the driving force for cavity filling, transforming a harmful factor into a useful mechanism for improving package integrity
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 solution effectively reduces cavity size and prevents package damage during heat treatments by filling the gap with resins of smaller molecular weights, enhancing reliability and maintaining the integrity of the semiconductor device.
Implementation Method 1
resins of smaller molecular weights among the plurality of types of resins separates to form the second adhesive layer which fills the gap between the substrate and the first adhesive layer
Implementation Method 2
Moisture (water vapor) in the cavity expands due to a high temperature in mounting reflow and moisture absorption reflow reliability tests
Data Source
AI summary
A semiconductor device includes a substrate, a first adhesive layer, a first semiconductor chip, and a second adhesive layer. The first adhesive layer is provided above a first surface of the substrate and includes a plurality of types of resins having different molecular weights and a filler. The first semiconductor chip is provided above the first adhesive layer. The second adhesive layer is provided in at least a part of a first region between the substrate and the first adhesive layer, and the second adhesive layer includes at least one type of resins among the plurality of types of resins having a molecular weight smaller than a molecular weight of other types of resins among the plurality of types of resins, and a filler having a lower concentration than that of the first adhesive layer.