LTCC Shrinkage Control via Self-Constraining Tape
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Solution Overview
Problem
Current low-temperature co-fired ceramic (LTCC) technologies face challenges in achieving precise shrinkage control, leading to distortion and high tolerance issues, which limit the size and complexity of electronic circuits, especially with the use of multiple dielectric chemistries and surface-mount components.
Innovation Solution
A process combining high dielectric constant and self-constraining tapes with primary tapes, where the self-constraining tape controls x- and y-shrinkage, and the high dielectric constant tape provides capacitive functions, allowing for predictable shrinkage and reduced distortion, enabling larger and more complex circuit designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If free-sintering process is used for LTCC, then manufacturing simplicity is improved, but shrinkage tolerance increases to ±0.15-0.30% causing distortion
Solution Approach 1:
A self-constraining tape layer is introduced as an intermediary element within the LTCC laminate structure. This tape layer has different shrinkage characteristics than the surrounding dielectric layers, acting as a internal constraint that compensates for shrinkage variations during firing. The self-constraining tape serves as a built-in reference that maintains dimensional stability without requiring external fixtures or complex processing, thus resolving the contradiction between manufacturing simplicity and shrinkage control precision.
2Manufacturing precision
If constrained sintering with release tape is used, then shrinkage tolerance is reduced to <0.04%, but device complexity increases due to additional processing steps
Solution Approach 1:
The self-constraining tape layer is integrated directly into the LTCC laminate stack during the lamination process, merging the constraint function with the structural layers. Unlike external release tape methods that require separate application and removal steps, the self-constraining tape is co-fired with the laminate, eliminating post-processing steps and reducing overall device complexity while maintaining precise shrinkage control.
Solution Approach 2:
The self-constraining tape layer performs the shrinkage compensation function autonomously during the firing process. The tape's inherent differential shrinkage characteristics automatically counteract distortion in the surrounding layers without requiring external intervention, fixtures, or additional processing steps. This self-service mechanism eliminates the complexity associated with external constrained sintering methods.
3Reliability
If multiple dielectric chemistries are used in LTCC laminate, then capacitive performance is improved, but shrinkage control becomes unpredictable causing distortion
Solution Approach 1:
The self-constraining tape layer is strategically positioned within the laminate stack at specific locations where shrinkage compensation is most needed. By placing this specialized layer locally rather than uniformly throughout the entire laminate, the invention provides targeted shrinkage control in regions with multiple dielectric chemistries, maintaining capacitive performance in functional areas while correcting distortion in structural areas.
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 approach results in a flat, distortion-free, and mechanically strong LTCC structure with predictable shrinkage, enabling the production of larger and more complex electronic circuits with improved capacitive performance.
Implementation Method 1
the self-constraining tape controls x- and y-shrinkage
Implementation Method 2
thick film paste via fill composition for use in the formation of multilayer low temperature cofired ceramic circuits
Data Source
AI summary
The present invention is directed to the use of a thick film paste composition comprising, in weight percent total paste composition, materials selected from mixtures of lead iron tungstate niobate solid solutions 30 to 80%, calcined mixtures of barium titanate, lead oxide and fused silica 20 to 70%, barium titanate 30 to 50%, calcined mixtures of barium titanate 30 to 50%, barium titanate and calcined mixtures of barium titanate 30 to 50%, lead oxide and fused silica 50-80%, and a lead germanate glass 3-20%, as a thick film paste via fill composition for use in the formation of multilayer low temperature cofired ceramic circuits.