Pass-Through-Hole Standoff Chassis Grounding in Potted Field Devices
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Solution Overview
Problem
Field devices used in industrial and hazardous environments face challenges in maintaining reliable chassis grounding and minimizing electromagnetic interference (EMI/EMC) while withstanding corrosive, explosive, and vibrational conditions, often requiring additional mechanical fixing processes and external housings.
Innovation Solution
The implementation of a pass-through-hole standoff configuration that extends the PCB outline to establish a chassis ground connection from the PCB to a field mount housing, allowing for soldered mounting screws to contact the housing through a through-hole without threads, facilitating a potted 'hockey puck' design that eliminates the need for external housings and reduces EMI/EMC interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional PCB mounting methods are used in potted configurations, then the device can be sealed and protected, but chassis grounding becomes unreliable and additional mechanical fixing processes are required
Solution Approach 1:
The grounding post is integrated directly into the PCB structure, merging the electrical grounding function with the mechanical mounting structure. This eliminates the need for separate grounding connections and mechanical fixing processes, resolving the contradiction between grounding reliability and assembly complexity.
Solution Approach 2:
The grounding post serves multiple functions simultaneously: it provides chassis grounding, acts as a mounting anchor, and establishes electrical connection between PCB layers. This multi-functionality eliminates the need for additional components and assembly steps, addressing both reliability and complexity concerns.
2Object-affected harmful factors
If external housings are used to protect field devices in hazardous environments, then mechanical protection is improved, but EMI/EMC interference increases and device complexity increases
Solution Approach 1:
The grounding post extends through the entire PCB thickness and protrudes beyond the copper layers, extracting the grounding function from internal PCB structures and making it externally accessible. This eliminates the need for external housings with grounding provisions, reducing EMI/EMC interference while maintaining protection.
3Reliability
If PCB outline is extended to accommodate grounding connections, then chassis grounding is improved, but manufacturing complexity increases
Solution Approach 1:
The grounding post is designed as a separate structural element that can be manufactured independently and then integrated with the PCB during standard manufacturing processes. This segmentation allows the grounding feature to be added without requiring complex modifications to the overall PCB manufacturing workflow.
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 configuration ensures proper chassis grounding without additional assembly processes, minimizes EMI/EMC interference, and prevents potting material issues at screw contact areas, enhancing the field device's reliability and operational safety in harsh environments.
Implementation Method 1
The pass-through-hole standoff can be soldered to the first PCB to allow a mounting screw to make contact from a top side of the field device to a field mount housing (e.g., a DIN Rail) through the pass-through-hole standoff
Data Source
AI summary
A field device apparatus includes a field device that includes a first PCB (Printed Circuit Board) based on a PCB outline of a PWA (Printed Wiring Assembly) and a second PCB based on the PCB outline. One or more pass-through-hole standoffs can be configured with respect to the first and second PCB's in a configuration, wherein the PCB outline is extended to mount the pass-through-hole standoff to the first PCB and the second PCB. The pass-through-hole standoff can be soldered to the first PCB which is connected to a chassis ground that allows a mounting screw to make contact from a top side of the field device to a field mount housing through the pass-through-hole standoff, thereby effectively providing chassis ground connection through mounting screws to the external world. The pass-through-hole standoff can include a through-hole, but does not contain a thread therein.