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Development of Low-Mass Flex PCB and Nanowire Interconnect Technologies for HEP Module Integration

Abhishek Sharma, Atul Gorane, Petra Riedler, Julian Weick

TL;DR

The paper tackles the challenge of low-mass, high-performance detector packaging for high-energy physics by pursuing two complementary approaches: ultra-thin flex PCBs with double-sided pad access and nanowire-based thermal/electrical interfaces. It presents a wafer-scale fabrication workflow for circular ultra-thin flex circuits (~17 μm), including dense pad/via features, strict solderability tests, flip-chip zones, and current/voltage tests, together with trace-impedance modeling comparisons to guide design. It also investigates nanowire bonding strategies—glue-supported and sintered—for both electrical interconnects and thermal paths, reporting an initial mechanical viability with pull tests above ~80 N and ongoing evaluation of multiple interconnect technologies. Together, these results provide quantitative data and process insights toward minimal-mass, scalable, robust packaging suitable for HL-LHC-era detectors.

Abstract

The development of lightweight flex PCBs and nanowire-based thermal interfaces for low-mass, high-performance detector modules are presented. A novel manufacturing approach targeting flex circuits with double-sided pad access, assembled using ACF and gold studs. Signal integrity was simulated and validation trials conducted on test structures. For thermal management, sintered nanowire interfaces were evaluated. These results contribute quantitative input relevant to minimal-mass, scalable packaging in HEP detectors.

Development of Low-Mass Flex PCB and Nanowire Interconnect Technologies for HEP Module Integration

TL;DR

The paper tackles the challenge of low-mass, high-performance detector packaging for high-energy physics by pursuing two complementary approaches: ultra-thin flex PCBs with double-sided pad access and nanowire-based thermal/electrical interfaces. It presents a wafer-scale fabrication workflow for circular ultra-thin flex circuits (~17 μm), including dense pad/via features, strict solderability tests, flip-chip zones, and current/voltage tests, together with trace-impedance modeling comparisons to guide design. It also investigates nanowire bonding strategies—glue-supported and sintered—for both electrical interconnects and thermal paths, reporting an initial mechanical viability with pull tests above ~80 N and ongoing evaluation of multiple interconnect technologies. Together, these results provide quantitative data and process insights toward minimal-mass, scalable, robust packaging suitable for HL-LHC-era detectors.

Abstract

The development of lightweight flex PCBs and nanowire-based thermal interfaces for low-mass, high-performance detector modules are presented. A novel manufacturing approach targeting flex circuits with double-sided pad access, assembled using ACF and gold studs. Signal integrity was simulated and validation trials conducted on test structures. For thermal management, sintered nanowire interfaces were evaluated. These results contribute quantitative input relevant to minimal-mass, scalable packaging in HEP detectors.
Paper Structure (3 sections, 7 figures)

This paper contains 3 sections, 7 figures.

Table of Contents

  1. Introduction
  2. Ultra-Thin Flex PCB
  3. Nano Wires for Pad Interconnection

Figures (7)

  • Figure 1: Sketch of typical module to mechanical support layer stack.
  • Figure 2: Flex PCB with dedicated test features produced on 4" silicon wafer substrate (left). 17 µ m flex thickness measured with micrometer (centre). 25 µ m diameter vias and 10 µ m traces with 5 µ m gaps (right).
  • Figure 3: Successful solderability of 0603 SMD component on bottom pads (left). Minimum trace width tests including current evaluations on titanium (centre). 8 µ m small feature production tests (right).
  • Figure 4: Relative difference between obtained widths for Z0 = 50$\Omega$ compared to the 2D FEM method for LineCalc, Hammerstad and Jensen, and Full FEM models.
  • Figure 5: Trace dimensions obtained for Z0 = 50$\Omega$, for 3D analysis methods.
  • ...and 2 more figures