Semiconductor Module Case with Opening for Visual Inspection
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Solution Overview
Problem
Existing semiconductor module production methods face challenges in visual inspection after reflow soldering, require high mounting accuracy, and struggle with thermal stress-induced expansion and shrinkage of sealing materials, leading to potential insulation degradation and contact failures.
Innovation Solution
A semiconductor module design featuring a rectangular case with divided rooms, including a central room for the semiconductor chip, a stress absorption room, and a driving terminal room, with external terminal holding portions and a lid body that allows for easy visual inspection, accurate terminal mounting, and absorption of thermal expansion, using silicone gel and epoxy resin for sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the case main body and lid are put together in position on the substrate for reflow soldering, then the module structure is compact and integrated, but visual inspection of soldering becomes impossible
Solution Approach 1:
The case main body is divided into a case body portion and a lid portion that can be separated. The lid portion is removed before reflow soldering to enable visual inspection of the substrate and soldering process, then reattached after soldering completes. This segmentation allows both integrated structure and inspection accessibility.
Solution Approach 2:
The lid portion is preliminarily removed before the reflow soldering process to enable visual inspection. This preliminary action allows inspectors to observe the substrate and soldering in real-time during the heating process, then the lid is reattached after soldering completes.
2Difficulty of detecting and measuring
If the upper part of the case main body is kept open for visual inspection, then soldering can be inspected, but workability deteriorates due to the need for external terminal fixation using a jig
Solution Approach 1:
The case is segmented into a case body and a removable lid. The lid can be temporarily removed for inspection purposes and then reattached, providing inspection access without requiring complex external fixation jigs for the terminals. This simplifies the manufacturing process while maintaining inspection capability.
3Manufacturing precision
If the external terminal is fixed on the substrate before lid attachment, then terminal positioning is precise, but mounting accuracy requirements increase and insertion difficulty arises
Solution Approach 1:
The external terminal is preliminarily fixed to the substrate before the lid is attached to the case body. This preliminary fixation allows the terminal to be positioned and secured in place, and subsequent soldering operations can proceed without requiring the lid to be present, thereby reducing mounting accuracy requirements and facilitating easier insertion.
4Reliability
If the case is sealed with gel material and epoxy resin, then insulation and protection are improved, but thermal expansion and shrinkage cause insulation degradation
Solution Approach 1:
A stress absorption room is provided within the case structure that accommodates the thermal expansion and shrinkage of the gel material and epoxy resin. This dedicated space allows the sealing materials to expand and contract without generating excessive stress that would degrade the insulation properties or damage the substrate, thereby maintaining insulation stability under thermal stress.
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
Enables easy visual inspection of soldering, ensures high accuracy in terminal mounting, absorbs thermal expansion, and prevents insulation degradation by allowing gas discharge and preventing cleaning agent residue, thus maintaining the integrity of the semiconductor module.
Implementation Method 1
sealing inside of the case with a gel material and/or epoxy resin
Implementation Method 2
a volume change caused by a thermal stress of the sealing material is absorbed in the stress absorption room
Implementation Method 3
a small hole that is provided at an upper part and communicably connected to outside, through which a gas generated when the sealing material is thermally cured is discharged outside
Data Source
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AI summary
Sought is to provide a semiconductor module that makes it possible to easily perform visual observation of soldering, and to perform a reflow soldering process in a state where external terminals are attached to a case. A semiconductor module includes a rectangular base plate; a substrate which is placed on the base plate and on which a circuit including a semiconductor chip and so forth is formed; a rectangular parallelepiped case made of resin that is attached to the base plate and houses the substrate within; and a plurality of external terminals lower ends of which are fixed to the substrate with upper ends thereof being exposed on a top face of the case. The case is provided with a first case opening portion and a second case opening portion that are respectively formed by cutting off a front face and a rear face of the case from an upper edge thereof along a longitudinal direction thereof; and the top face of the case between the first case opening portion and the second case opening portion includes an external terminal holding portion to hold the plurality of external terminals along the longitudinal direction with the upper ends thereof being exposed. A sealing material is injected from the first case opening portion and the second case opening portion onto a top face of the substrate, and thereby the semiconductor module is sealed.