Pressure Sensor Cap Inner Receiving Section Adhesive Control
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Solution Overview
Problem
The challenge in developing high-accuracy pressure sensors is the excessive spreading of conductive adhesive when attaching a cap, which can lead to contact with pad electrodes, making it difficult to reduce the overall size of the sensor due to the need for a large spacing between the cap and pad electrode to prevent adhesive contact.
Innovation Solution
A pressure sensor design featuring a tubular cap with an inner receiving section between its inner peripheral surface and ground-electrode-side end surface, which prevents excessive adhesive spreading by receiving the adhesive and keeping it from reaching the pad electrodes, allowing for controlled application and attachment without short-circuiting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the cap is attached with a conductive adhesive using the transfer method, then the adhesive can be uniformly applied to the end surface of the cap, but the adhesive may spread excessively and come into contact with the pad electrode when the cap is pressed to attach
Solution Approach 1:
A non-conductive adhesive layer is introduced as an intermediary between the conductive adhesive and the pad electrode. This non-conductive layer acts as a barrier that prevents the conductive adhesive from spreading onto the pad electrode, while still allowing the conductive adhesive to provide electrical connection to the ground electrode.
Solution Approach 2:
The adhesive application is segmented into two distinct layers: a conductive adhesive layer for electrical connection to the ground electrode, and a non-conductive adhesive layer as a protective barrier. This segmentation allows each layer to perform its specific function without interfering with the other.
2Reliability
If a relatively large distance is maintained between the pad electrode and the cap to prevent adhesive contact, then the risk of adhesive short-circuiting is reduced, but the overall size of the sensor increases
Solution Approach 1:
The non-conductive adhesive layer serves as a protective intermediary that allows the cap to be positioned closer to the pad electrode without risk of conductive adhesive contact. This eliminates the need for large safety margins in the design.
Solution Approach 2:
The electrical properties of the adhesive layer are changed by introducing a non-conductive material, which fundamentally alters the risk profile. Instead of relying on distance to prevent electrical contact, the non-conductive material provides inherent electrical isolation, allowing reduced spacing.
3Reliability
If the amount of conductive adhesive applied is increased to ensure reliable attachment, then the attachment reliability is improved, but the excessive spreading of adhesive increases and may contact the pad electrode
Solution Approach 1:
The non-conductive adhesive layer acts as a containment barrier that allows more conductive adhesive to be applied without increasing the risk of pad electrode contact. The non-conductive layer absorbs or blocks the excess adhesive, preventing it from reaching the sensitive pad electrode area.
Solution Approach 2:
The non-conductive adhesive layer is applied in advance as a protective cushion between the conductive adhesive and the pad electrode. This pre-positioned barrier compensates for potential excessive spreading of the conductive adhesive during the attachment process.
Data Source
AI summary
A pressure sensor includes a pressure detecting element; a base material on which the pressure detecting element is mounted; a pad electrode provided on the base material and electrically connected to the pressure detecting element; a ground electrode provided on the base material and spaced from the pad electrode; and a cap having a tubular shape, the cap surrounding a periphery of the pressure detecting element on the base material and being attached to the ground electrode with a conductive adhesive. An inner receiving section is provided between an inner peripheral surface of the cap and a ground-electrode-side end surface of the cap, the inner receiving section thereby preventing excessive spreading of the conductive adhesive. The cap can be attached to the base material with the conductive adhesive without causing excessive spreading of the conductive adhesive.