RF Shielding Coating for IC Substrates Preventing Shorting
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Solution Overview
Problem
Current RF shielding methods for integrated circuit devices and modules are inefficient due to space constraints, high costs, and susceptibility to Electro-static Discharge (ESD) and shorting issues, particularly when applied to exposed die components and non-encapsulated modules.
Innovation Solution
A system and method involving a substrate with metal traces, a non-conductive coating to cover exposed metal areas, and a conductive coating applied to ground pads or a ground plane to provide effective RF shielding while preventing shorting and ESD, using techniques like laser removal or saw cuts to expose metal traces for grounding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal shield is directly attached to the semiconductor package substrate, then RF shielding effectiveness is improved, but the risk of shorting to other components and susceptibility to ESD increases
Solution Approach 1:
A non-conductive coating is applied between the conductive RF shielding material and exposed metal surfaces on the substrate. This intermediary layer prevents direct electrical contact that would cause shorting, while still allowing the conductive coating to provide effective RF shielding when connected to ground pads through non-conductive pathways.
2Reliability
If a conductive coating is applied directly to exposed metal on the substrate, then RF shielding is achieved, but shorting occurs
Solution Approach 1:
The coating structure is designed with different electrical properties in different locations: non-conductive coating covers exposed metal surfaces to prevent shorting, while conductive coating is applied in specific areas to provide RF shielding. The conductive coating is strategically positioned to contact only ground pads, creating localized conductivity where needed while maintaining insulation where critical.
3Reliability
If external shields are soldered to the motherboard, then RF shielding is provided, but additional board space is required and the process is costly and low yielding
Solution Approach 1:
The RF shielding function is merged with the substrate structure itself. Instead of adding separate external shields that require additional soldering processes and board space, the conductive coating is integrated directly onto the substrate, utilizing the substrate's existing ground pads and metal traces as part of the shielding system.
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 enables efficient RF shielding for exposed die components and non-encapsulated modules, reducing the risk of shorting and ESD while optimizing space usage and cost, by applying a conductive material to grounded metal pads or planes, thus effectively managing electromagnetic interference.
Implementation Method 1
a non-conductive coating is applied to cover exposed metal areas on the first surface of the substrate
Implementation Method 2
a conductive coating is applied to the non-conductive coating, and electrically contacting ground pads exposed on the substrate
Data Source
AI summary
An integrated circuit module has a substrate having a plurality of metal traces. At least one semiconductor package is electrically coupled to at least one metal trace on a first surface of the substrate. At least one electronic component is electrically coupled to at least one metal trace on the first surface of the substrate. A non-conductive coating covers exposed active surfaces on the first surface of the substrate. A conductive coating is applied to the non-conductive coating, and electrically contacting ground pads exposed on the substrate.