Thermosetting Sheet Sealing for Void-Free Substrate Underfill
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Solution Overview
Problem
Simultaneous underfilling and overmolding with a mold underfill material often results in sealing material-unentered portions (voids) between electronic components and the substrate, making stable underfilling difficult.
Innovation Solution
A method involving a thermosetting sheet placed on the substrate to contact electronic components, heat-molded to fill spaces between components and the substrate, with specific dimensions and properties to ensure complete coverage and curing, minimizing voids and achieving sufficient underfilling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If simultaneous underfilling and overmolding is performed with mold underfill material, then the number of process steps is reduced, but sealing material-unentered portions (voids) are formed in the spaces between electronic components and the substrate
Solution Approach 1:
The sealing process is divided into two distinct stages: first underfilling with a liquid sealing material to fill the spaces between electronic components and substrate, then overmolding with a different material to seal the entire assembly. This segmentation allows each material to perform its specific function optimally without interfering with the other, preventing void formation while maintaining process efficiency.
Solution Approach 2:
The underfilling step is performed as a preliminary action before overmolding. The liquid sealing material is first introduced to fill the gaps between components and substrate, ensuring complete penetration and void-free filling. Only after this preliminary underfilling is complete does the overmolding process begin, sealing the already-filled spaces.
2Device complexity
If mold underfill material is used for simultaneous underfilling and overmolding, then process complexity is reduced, but stable underfilling becomes difficult due to void formation
Solution Approach 1:
The process is segmented into distinct underfilling and overmolding steps using different materials with appropriate viscosities and curing characteristics. The underfilling material is specifically selected for its ability to flow into and fill narrow spaces between components, while the overmolding material provides structural sealing. This segmentation ensures stable and reliable underfilling without voids.
3Manufacturing precision
If a thermosetting sheet is heat-molded to fill spaces between electronic components and substrate, then complete coverage is achieved, but the sheet must have specific dimensional relationships to prevent voids
Solution Approach 1:
The patent establishes specific parameter relationships for the thermosetting sheet dimensions relative to the substrate and electronic component layout. By defining precise dimensional parameters and their interrelationships, the method ensures that when the sheet is heat-molded, it will completely cover the spaces between components and substrate without forming voids, while maintaining manageable manufacturing complexity.
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 prevents the formation of voids, allowing for stable and complete underfilling and overmolding, ensuring a sealed substrate with a continuous cured product.
Implementation Method 1
heat-molding the placed thermosetting sheet, to allow a melt of the thermosetting sheet to fill the space between the electronic component and the substrate
Implementation Method 2
a melt of the thermosetting sheet to fill the space between the electronic component and the substrate and be cured
Data Source
AI summary
A method for sealing an electronic component mounting substrate including: preparing an electronic component mounting substrate including a substrate and electronic components mounted thereon and having a space between an electronic component and the substrate; placing a thermosetting sheet on the electronic component mounting substrate; and heat-molding the placed thermosetting sheet, to allow a melt of the thermosetting sheet to fill the space between the electronic component and the substrate and be cured. When a distance between the center of the substrate and an optional point P on a frame line that surrounds all the electronic components and minimizes the surrounded area is denoted by Lp, a distance Lq between the center of the substrate and a point Q at which a straight line passing through the point P and the center of the substrate intersects with an outer periphery of the thermosetting sheet is 0.9Lp or more.