Leadless MLCC Termination via Transient Liquid Phase Sintering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current lead-free attachment technologies for electronic components, particularly stacked multi-layered ceramic capacitors, face challenges in achieving reliable high-temperature bonds without using banned materials like lead or cadmium and at lower processing temperatures, while also addressing stress cracking issues due to circuit board flexure.
Innovation Solution
The use of transient liquid phase sintering (TLPS) or polymer solder to form terminations on electronic components, allowing for low-temperature initial bonding with high subsequent melting points, suitable for leadless attachment and accommodating components of varying lengths without the need for intimate surface contact or solder balls, thereby enhancing reliability and reducing manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If lead-free solders with low liquidus temperatures are used for attachment, then the processing temperature can be reduced, but the reliability of external lead attachment deteriorates because the melting point is not sufficiently above subsequent processing temperatures
Solution Approach 1:
The attachment system is segmented into two distinct materials: a low-temperature melting material (e.g., Sn-Bi alloy) applied to one surface and a high-temperature melting material (e.g., Ag, Cu, or Au) applied to the mating surface. This segmentation allows the bonding process to occur at low temperatures while the final joint maintains high temperature resistance, resolving the contradiction between low processing temperature and high reliability.
Solution Approach 2:
The invention uses composite material pairing where a low-melting-point material is combined with a high-melting-point material in the same joint system. The low-melting material enables low-temperature bonding while the high-melting material provides thermal stability for subsequent processing, achieving both low processing temperature and high attachment reliability simultaneously.
2Reliability
If high-melting-point materials such as gold/germanium or gold/silicon alloys are used for attachment, then the temperature capability and bond strength are improved, but the processing temperature increases which prevents wider use in electronics
Solution Approach 1:
The attachment system is segmented into two distinct materials: a low-temperature melting material (e.g., Sn-Bi alloy) applied to one surface and a high-temperature melting material (e.g., Ag, Cu, or Au) applied to the mating surface. This segmentation allows the bonding process to occur at low temperatures while the final joint maintains high temperature resistance, resolving the contradiction between low processing temperature and high reliability.
Solution Approach 2:
The invention changes the melting point parameter of the bonding material dynamically through the two-stage process: initially using a low-melting-point material for bonding, then introducing a high-melting-point material that transforms the joint's thermal properties after bonding, achieving low processing temperature followed by high temperature capability.
3Temperature
If zinc and aluminum powder are used in solders to form higher temperature lead-free solders, then the temperature capability is improved, but oxide films form on the surface which are associated with poor wettability making them impractical to use
Solution Approach 1:
The invention uses a two-material system where the low-melting-point material serves as an intermediary bonding layer that provides excellent wettability and ease of manufacture, while the high-melting-point material provides temperature capability. This intermediary approach allows the system to achieve high temperature resistance without suffering from the oxidation and wettability problems of Zn-Al-based solders.
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
TLPS or polymer solder bonds provide robust, high-temperature-resistant connections that withstand secondary reflow processes, minimize stress cracking, and enable efficient stacking of components without gaps, offering improved mechanical and electrical performance while avoiding the use of hazardous materials.
Implementation Method 1
heating to a temperature sufficient to melt the low temperature melting material... The resulting bond will have a secondary reflow temperature greater than the temperature of the low temperature material
Data Source
Figure 1~2
Figure 3~5
Figure 6
AI summary
A stacked MLCC capacitor is provided wherein the capacitor stack comprises multilayered ceramic capacitors wherein each multilayered ceramic capacitor comprises first electrodes and second electrodes in an alternating stack with a dielectric between each first electrode and each adjacent second electrode. The first electrodes terminate at a first side and the second electrodes second side. A first transient liquid phase sintering conductive layer is the first side and in electrical contact with each first electrode; and a second transient liquid phase sintering conductive layer is on the second side and in electrical contact with each second electrode.