AMB Circuit Carrier Recessed Contact Points for MLCC Fracture Prevention
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Solution Overview
Problem
MLCC ceramic multilayer chip capacitors are prone to fractures when used with AMB circuit carriers due to thermal expansion coefficient differences between ceramic and copper, leading to mechanical and thermomechanical stresses, which can cause functional failures in electronic units.
Innovation Solution
The electronic unit design features a conductor structure with recessed contacting points that reduce mechanical and thermomechanical stresses by following mechanical statics principles, where deepened structural areas are formed to lower stress states and provide local material resilience, allowing for reduced thermal expansion mismatches between Si3N4 ceramic and copper metallization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If AMB circuit carriers with Si3N4 ceramic and thick copper metallization are used, then thermal and electrical performance are improved, but mechanical and thermomechanical stresses cause MLCC fractures
Solution Approach 1:
The patent applies local quality by creating recessed areas with reduced copper metallization thickness specifically at MLCC contact locations. This localized modification reduces thermal expansion stresses only where MLCCs are mounted, while preserving thick copper metallization in other areas for optimal thermal and electrical performance. The recessed areas have copper thickness of 5-50 μm compared to 100-500 μm in non-recessed areas.
Solution Approach 2:
The patent changes the copper metallization thickness parameter locally by forming recessed areas with reduced copper thickness. This parameter change reduces the coefficient of thermal expansion mismatch effects at MLCC contact points, thereby reducing thermomechanical stresses and preventing MLCC fractures while maintaining overall high power capability.
2Reliability
If copper metallization thickness is reduced to prevent MLCC breakage, then thermomechanical stresses are reduced, but electrical current carrying capacity decreases
Solution Approach 1:
The patent implements local quality by applying different copper metallization thicknesses to different functional areas. MLCC contact areas have reduced copper thickness (5-50 μm) to prevent fractures, while other areas maintain thick copper metallization (100-500 μm) for high electrical current carrying capacity. This spatial differentiation resolves the contradiction between reliability and power performance.
Solution Approach 2:
The patent segments the copper metallization into functionally distinct zones: recessed areas with thin copper for MLCC mounting and non-recessed areas with thick copper for power conduction. This segmentation allows each zone to be optimized for its specific function, preventing MLCC breakage while maintaining high electrical performance.
3Temperature
If Si3N4 ceramic substrate is used, then thermal performance is improved, but large coefficient of thermal expansion difference with copper causes internal stresses
Solution Approach 1:
The patent applies local quality by creating recessed areas with reduced copper thickness specifically at MLCC contact locations. This localized modification reduces thermal expansion stresses only where MLCCs are mounted, while preserving thick copper metallization in other areas for optimal thermal and electrical performance.
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 design effectively prevents fractures in MLCC ceramic multilayer chip capacitors, ensuring operational reliability and robustness even with previously unfavorable ceramic circuit carriers, thereby enhancing the functional reliability of electronic units.
Implementation Method 1
The recessed arrangement of contact points for the MLCC multilayer ceramic chip capacitor advantageously utilizes the principle in mechanical statics that, in a mechanical system under bending, inner layers exhibit a lower stress state than outer layers
Implementation Method 2
The causes of breakage are attributed, among other things, to the thermal expansion of the copper material. It is suspected that this leads to the buildup of internal stresses within the chip capacitor
Implementation Method 3
which are then electrically contacted with corresponding contact terminals of the at least one MLCC multilayer ceramic chip capacitor, for example by means of a solder, sinter or conductive adhesive connection
Implementation Method 4
which are then electrically contacted with corresponding contact terminals of the at least one MLCC multilayer ceramic chip capacitor, for example by means of a solder, sinter or conductive adhesive connection
Data Source
Figure 1
Figure 2a~2c
Figure 2d~2e
AI summary
The electronic unit comprises at least one circuit carrier with a ceramic substrate made of Si3N4, in particular an AMB (Active Metal Brazing) circuit carrier, wherein the substrate has a top and a bottom surface, and at least one conductor structure comprising at least one layer of copper or a copper alloy is arranged on the top and/or bottom surface. Furthermore, the conductor structure has an outermost termination surface on which contact points are formed that are electrically contacted with contact terminals of at least one electrical and/or electronic component, forming an electronic circuit of the electronic unit. The electronic circuit includes at least one MLCC (Multi-Layer Ceramic Capacitor).In addition, the conductor structure has at least one recessed structural area compared to the outermost termination surface, wherein recessed contact points are formed in the at least one recessed structural area, which are then electrically contacted with corresponding contact terminals of the at least one MLCC multilayer ceramic chip capacitor, for example by means of a solder, sinter or conductive adhesive connection.