RF Circuit Ground Potential Stabilization via Buried Solder
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Solution Overview
Problem
Manufacturing tolerances in radio frequency circuits can lead to unstable ground potential of metal films, resulting in deteriorated signal propagation characteristics due to inconsistent coupling between the grounded base metal and metal pillars.
Innovation Solution
A radio frequency circuit design featuring a multilayer substrate with a grounded base metal, insulating layers, and wiring layers, including a metal pillar with a height lower than the distance between the grounded base metal and the upper substrate, and a solder buried in a through-hole to bond the metal film to the ground wiring layer, ensuring stable ground potential even with manufacturing tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal pillar is used to couple the grounded base metal and metal film, then electrical coupling is achieved, but manufacturing tolerances cause unstable ground potential
Solution Approach 1:
The patent introduces solder as an intermediary material that fills the through-hole to create a reliable electrical connection between the metal film and ground wiring layer. This mediator compensates for manufacturing tolerances by providing a compliant bonding interface that ensures consistent electrical coupling despite variations in pillar height or positioning.
Solution Approach 2:
The patent changes the electrical coupling parameter from direct metal-to-metal contact (metal pillar to metal film) to a solder-mediated connection. This parameter change allows the system to tolerate manufacturing variations while maintaining stable ground potential, as the solder provides a consistent electrical pathway regardless of precise alignment.
2Reliability
If the metal pillar height is increased to ensure contact with the metal film, then coupling reliability improves, but manufacturing complexity and tolerance requirements increase
Solution Approach 1:
The solder acts as a mediator that eliminates the need for precise height matching between the metal pillar and metal film. By introducing this intermediate bonding material, the system achieves reliable coupling without requiring complex manufacturing controls on pillar dimensions.
Solution Approach 2:
The design anticipates manufacturing tolerances by incorporating solder as a cushioning element that absorbs dimensional variations. This beforehand cushioning approach allows the metal pillar to be of fixed, simpler dimensions while still ensuring reliable contact through the compliant solder interface.
3Reliability
If through-holes are used to embed solder for bonding, then ground coupling stability improves, but substrate complexity increases
Solution Approach 1:
The through-hole serves multiple functions: it provides a pathway for the metal pillar, contains and positions the solder, and establishes the electrical connection between layers. This multi-functionality reduces the need for separate structural elements, thereby limiting the increase in substrate complexity while achieving stable ground coupling.
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 stabilizes the ground potential of the metal film, suppressing unnecessary radio wave emission and improving signal propagation characteristics by ensuring reliable coupling between the metal pillar and ground wiring layer, even with manufacturing tolerances.
Implementation Method 1
a solder (56) buried in the through-hole (36) and bonded to the metal film (42) and the upper surface of the metal pillar (24)
Data Source
AI summary
A radio frequency circuit includes, a multilayer substrate having a grounded base metal and a plurality of insulating layers and wiring layers formed over the grounded base metal and having a recess surrounded by the plurality of insulating layers and wiring layers over the grounded base metal, an upper substrate having a through-hole penetrating the upper substrate, a first semiconductor chip mounted on the upper surface of the upper substrate and electrically coupled to a metal film formed on the lower surface of the upper substrate, a metal pillar formed on the upper surface of the grounded base metal in the recess, and a solder buried in the through-hole and bonded to the metal film and the upper surface of the metal pillar. The metal film is bonded to a ground wiring layer electrically coupled to the grounded base metal among the plurality of wiring layers.