LTCC Ceramic Substrate Thickness Control via Protective Cavity Layers
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Solution Overview
Problem
Low-Temperature Co-fired Ceramic (LTCC) substrates face challenges in achieving precise thickness measurement and control, especially when used for sealing or mounting devices, as surface polishing can alter thickness, affecting circuit properties, and cavity deformation occurs during stacking, making accurate thickness measurement difficult.
Innovation Solution
A ceramic substrate with a cavity penetrating through each member, where the gap is formed and covered with protection layers to allow for high-accuracy thickness measurement using optical microscopes, and the substrate is manufactured by stacking and firing green sheets with through vias and internal wires, allowing for precise control of thickness and circuit properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the LTCC substrate surface is polished to reduce surface roughness, then sealing quality and airtightness are improved, but the thickness of the substrate changes, affecting circuit properties
Solution Approach 1:
The patent applies preliminary action by forming the cavity before the polishing process. This allows the cavity structure to be established in advance, so that subsequent polishing operations can be performed with reference to the cavity's position and dimensions, thereby maintaining thickness control while achieving the required surface quality for sealing.
Solution Approach 2:
The cavity serves as an intermediary reference feature during the polishing process. By using the cavity's known dimensions and position as a reference, the polishing operation can be controlled to achieve the desired surface roughness reduction without causing unpredictable changes in substrate thickness that would affect circuit properties.
2Adaptability or versatility
If green sheets are stacked to form LTCC substrate with cavity, then device mounting capability is improved, but cavity shape deforms, making thickness measurement difficult
Solution Approach 1:
The patent applies preliminary action by forming the cavity at a stage before final stacking and firing, when the green sheets are still in a relatively stable state. This preliminary cavity formation allows for accurate dimensional reference to be established before the deformation that occurs during subsequent stacking and firing processes, enabling thickness measurement capability to be preserved despite the eventual cavity shape changes.
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 accurate measurement and control of substrate thickness, reducing errors in capacitance values and improving the reliability and accuracy of the internal circuit, while minimizing the influence of gaps on the module's dimensions and airtightness.
Implementation Method 1
co-firing a ceramic material constituting the green sheets and a conductor material constituting the vias
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A ceramic substrate (10) having a cavity which can be used for measuring the thickness of the substrate includes a plurality of stacked ceramic substrate members (1). Each of the plurality of ceramic substrate members (1) includes a via (2) reaching the other main surface from one main surface. A gap (6) is formed in each of first and second ceramic substrate members (1a, 1f) of the plurality of stacked ceramic substrate members (1) to penetrate each of the first and second ceramic substrate members (1a, 1f), the first ceramic substrate member (1a) being arranged at an outermost surface on one side in a stacking direction of the ceramic substrate members (1), the second ceramic substrate member (If) being arranged at an outermost surface on the other side opposite to the one side in the stacking direction. At least a portion of a side surface and a bottom surface within the gap (6) are covered with a protection layer (7, 8). The protection layer (7, 8) is made of a material having an etching rate lower than that of the ceramic substrate members (1).