Wire-Bondable MLCC with Stacked Capacitors
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Solution Overview
Problem
Existing multi-layer ceramic capacitors (MLCCs) occupy significant space on printed circuit boards due to solder fillets and limited packing density, as they require terminal connections at the ends, which restricts the number of capacitors that can be packed.
Innovation Solution
The MLCC device features vertically stacked capacitors connected via vias to wire-bondable pads on the top side of the ceramic chip, allowing for electrical connection through wire bonding instead of solder connections, reducing the footprint and eliminating the need for solder fillets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional solder connection methods are used for MLCC terminals, then reliable electrical connections are achieved, but significant PCB space is consumed due to solder fillets and required spacing
Solution Approach 1:
The patent replaces the mechanical solder connection system with a wire bonding system. Instead of using solder fillets to create electrical connections between MLCC terminals and PCB landing pads, the invention uses wire bonds to connect wire-bondable pads on the MLCC to corresponding pads on the PCB. This substitution eliminates the need for large solder fillets and associated spacing requirements, thereby reducing PCB space occupation while maintaining reliable electrical connections.
Solution Approach 2:
The patent transitions from a planar connection architecture to a three-dimensional wire bonding architecture. Wire bonds can be routed in three dimensions above the PCB surface, allowing connections to be made without requiring additional PCB space. The wire bonds extend vertically from the MLCC pads to the PCB pads, utilizing the z-dimension to achieve connections that would otherwise require lateral spacing on the PCB plane.
2Area of stationary object
If MLCC devices are packed closely on PCB, then space efficiency is improved, but solder fillet interference and unwanted connections between landing pads occur
Solution Approach 1:
By replacing the solder connection system with wire bonding, the harmful effects of solder fillets are eliminated. Wire bonds do not create the same interference problems as solder fillets, allowing MLCC devices to be packed more closely without risk of unwanted connections between adjacent landing pads. The wire bonds can be precisely controlled and isolated from each other in three-dimensional space.
Solution Approach 2:
The wire bond acts as an intermediary element that provides electrical connection without creating the harmful interference effects associated with solder fillets. The wire bond can be routed through air or insulation material, providing electrical connectivity while physically separating the connection paths of adjacent MLCC devices, thereby preventing unwanted connections even when devices are closely packed.
3Area of stationary object
If wire bonding is used instead of solder connections, then PCB space is reduced by eliminating solder fillets, but additional wire bonding process complexity is introduced
Solution Approach 1:
The patent merges the wire bonding process with the existing PCB assembly process. Wire bonding is performed as part of the overall assembly operation, combining the advantages of reduced PCB footprint with the established infrastructure of PCB manufacturing and assembly. This integration helps manage process complexity by incorporating wire bonding into the existing production flow rather than requiring completely separate processing lines.
Solution Approach 2:
The invention changes the connection method parameter from solder-based to wire-bond-based, which fundamentally alters the process characteristics. While this introduces new process steps, it also enables new capabilities such as reduced PCB space and improved device reliability. The parameter change is justified by the significant benefits in terms of space utilization and connection quality.
4Quantity of substance
If vertically stacked capacitor configuration is used, then capacitor density is increased, but wire bonding access requirements are imposed
Solution Approach 1:
The patent positions wire-bondable pads on the top surface of the vertically stacked capacitor structure, making them accessible from above. This three-dimensional arrangement allows wire bonds to access the pads vertically without interfering with the compact stacked configuration of the capacitors. The vertical stacking of capacitors is maintained while wire bonding access is provided through the top surface, resolving the conflict between density and accessibility.
Data Source
AI summary
A multi-layer ceramic capacitor (MLCC) device includes a ceramic chip having electrically conductive layers embedded within the chip that form one or more capacitors connected by one or more vias to one or more upwardly facing wire-bondable pads on the top side of the device. One embodiment includes electrically conductive layers that form at least two stacked capacitors connected by vias to multiple upwardly facing wire-bondable pads on the top side, whereby the MLCC device has a reduced footprint while avoiding solder fillets. The wire-bondable pads may lie in a common plane or be pyramidally stepped. Metallization on the PCB-facing bottom side and at least one of the ends of the ceramic chip of another embodiment forms a downwardly facing capacitor terminal.