Pressure Sensor Step Structure Blocks Flux Clogging

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Solution Overview

Problem

The existing pressure sensor devices malfunction due to liquefied flux clogging the pressure introducing ports during the soldering process, causing capillary action and wettability issues that prevent proper atmospheric pressure communication with the semiconductor pressure sensor element.

Innovation Solution

A pressure sensor device with a step-like structure on the mounting surface between the opening of the pressure introducing port and the soldered part, which prevents liquefied flux from reaching the ports by forming a recess or protrusion to stem the flow of flux during the reflow process, thereby preventing clogging.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the amount of flux in the solder is increased, then the soldering reliability is improved, but the liquefied flux flows into the gap between mounting surfaces and clogs the pressure introducing port

Engineering Contradiction:

Improvesoldering reliabilityVSAvoidflux clogging pressure introducing port

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The mounting surface is segmented into different levels by creating a step-like structure. The first mounting surface is positioned higher than the second mounting surface, forming a step that divides the soldering area. This segmentation prevents the liquefied flux from flowing from the first mounting surface to the pressure introducing port on the second mounting surface, while still allowing adequate flux for reliable soldering on the first mounting surface.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the mounting substrate are given different heights and functions. The region around the pressure introducing port (second mounting surface) is kept at a lower level to prevent flux accumulation, while the terminal mounting region (first mounting surface) is at a higher level to accommodate sufficient flux for reliable soldering. This local differentiation of surface quality solves the contradiction between needing flux for reliability and preventing flux from clogging ports.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If the gap between mounting surfaces is reduced, then the mounting precision is improved, but the capillary action causes liquefied flux to flow more easily into the gap

Engineering Contradiction:

Improvemounting precisionVSAvoidcapillary action flux flow

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The mounting surface is divided into two levels with a step structure. The first mounting surface for terminals is higher than the second mounting surface for the pressure introducing port. This segmentation creates a physical barrier that prevents capillary-driven flux flow from reaching the pressure introducing port, even when the gap between mounting surfaces is small for precise mounting.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The step-like structure acts as an intermediary barrier between the soldering area and the pressure introducing port. This intermediate structure intercepts the liquefied flux before it can reach the port, preventing clogging while allowing the gap between mounting surfaces to remain small for precise mounting alignment.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If the wettability of mounting surfaces is enhanced, then the soldering quality is improved, but the liquefied flux spreads more easily along the mounting surfaces

Engineering Contradiction:

Improvesoldering qualityVSAvoidflux spreading along mounting surfaces

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The mounting substrate has different surface heights in different regions. The first mounting surface has enhanced wettability for good soldering quality, while the step structure creates a physical boundary that prevents the flux from spreading from the first mounting surface to the second mounting surface where the pressure introducing port is located. This local quality differentiation allows high wettability where needed while preventing harmful flux spread.

Inventive Principle:

Principle #3Local quality

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

Effectively prevents the clogging of pressure introducing ports by managing the flow of liquefied flux, ensuring the semiconductor pressure sensor element can accurately measure pressure without malfunction.

Implementation Method 1

liquefied flux tends to flow into a gap formed between a mounting surface of the mounting substrate and the mounting surface of the circuit board due to the capillary action

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Implementation Method 2

The liquefied flux flown into the gap proceeds along the mounting surface and/or the mounting surface due to their wettability

Methodology Applied

Scientific EffectWettability: Wetting

Data Source

PatentUS8707794B2Pressure sensor device, electronic apparatus, and method of mounting pressure sensor device

Publication Date: 2014.04.29 MITSUMI ELECTRIC CO LTD

AI summary

A pressure sensor device includes a semiconductor pressure sensor element and a base part. The base part includes a mounting surface, a through hole having an opening on the mounting surface and configured to introduce a fluid to the semiconductor pressure sensor element, a soldered part that is to be soldered and is provided on the mounting surface, and a step-like structure formed on the mounting surface between the opening and the soldered part.