A Chip Integrity Monitor for Evaluating Moisture/Ion Ingress in mm-Sized Single-Chip Implants

Akgun, Omer Can; Nanbakhsh, Kambiz; Giagka, Vasiliki; Serdijn, Wouter A.

doi:10.1109/tbcas.2020.3007484

Cited by 7 publications

(5 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Due to the small size of cochlear implants, helium leak testing is inapplicable making soak test necessary to examine the resilience of AIMDs against ions and fluids. These tests confirm delamination to be a major failure mechanism [ 23 ]. Based on these criteria, the following materials and investigation methods were chosen.…”

Section: Methodsmentioning

confidence: 82%

“…Before this, life testing methods were heavily based on increasing factors of temperature and electric current in amperage and frequency. With better knowledge of the processes of interface diffusion and delamination, new factors of HALT open up [ 23 , 31 , 32 ]. Furthermore, a first estimation in ratio of diffusion rate between bulk and interface could be made marking interface diffusion up to 5 times faster than in bulk.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Predicting Corrosion Delamination Failure in Active Implantable Medical Devices: Analytical Model and Validation Strategy

et al. 2021

View full text Add to dashboard Cite

The ingress of body fluids or their constituents is one of the main causes of failure of active implantable medical devices (AIMDs). Progressive delamination takes its origin at the junctions where exposed electrodes and conductive pathways enter the implant interior. The description of this interface is considered challenging because electrochemically-diffusively coupled processes are involved. Furthermore, standard tests and specimens, with clearly defined 3-phase boundaries (body fluid-metal-polymer), are lacking. We focus on polymers as substrate and encapsulation and present a simple method to fabricate reliable test specimens with defined boundaries. By using silicone rubber as standard material in active implant encapsulation in combination with a metal surface, a corrosion-triggered delamination process was observed that can be universalised towards typical AIMD electrode materials. Copper was used instead of medical grade platinum since surface energies are comparable but corrosion occurs faster. The finding is that two processes are superimposed there: First, diffusion-limited chemical reactions at interfaces that undermine the layer adhesion. The second process is the influx of ions and body fluid components that leave the aqueous phase and migrate through the rubber to internal interfaces. The latter observation is new for active implants. Our mathematical description with a Stefan-model coupled to volume diffusion reproduces the experimental data in good agreement and lends itself to further generalisation.

show abstract

Section: Methodsmentioning

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Predicting Corrosion Delamination Failure in Active Implantable Medical Devices: Analytical Model and Validation Strategy

et al. 2021

View full text Add to dashboard Cite

show abstract

“…The dielectric sensor was diced and separated from the other test structures on Chip-B to ease wire bonding and sample preparation required for the long-term accelerated in vitro aging. The custom-designed sensor is capable of measuring IMD resistance values in the 10 14 Ω range with the sensitivity to detect changes at a sub-MΩ resolution 45 . This sensor was designed and tested with two goals in mind: 1) to verify if a complex CMOS circuit could operate when fully submerged in PBS solution at 67 °C, and 2) acquire more sensitive measurements of the dielectric changes and capture a 3D mapping of the possible moisture/ion penetration pathways into the chip.…”

Section: Resultsmentioning

confidence: 99%

Longevity of Implantable Silicon-ICs for Emerging Neural Applications: Evaluation of Bare Die and PDMS-Coated ICs After Accelerated Aging and Implantation Studies

Nanbakhsh,

Idil,

Lamont

et al. 2024

Preprint

Self Cite

View full text Add to dashboard Cite

Silicon integrated circuits (ICs) are central to the next-generation miniature active neural implants, whether packaged in soft polymers for flexible bioelectronics or implanted as bare die for neural probes. These emerging applications bring the IC closer to the corrosive body environment, raising reliability concerns, particularly for long-term clinical use. Here, we evaluated the long-term electrical and material stability of silicon-ICs from two foundries, after one-year accelerated in vitro and in vivo animal studies. The ICs featured various custom-designed test structures and were partially PDMS coated, creating two regions on each chip, uncoated "bare die" and "PDMS-coated". During the accelerated in vitro study, ICs were electrically biased and periodically monitored. Results demonstrated stable electrical performance for at least a year, suggesting that bare die ICs can function in the body for months. Despite electrical stability, material analysis revealed chemical and electrically driven degradation of the IC passivation in the bare die regions. In contrast, PDMS-coated regions revealed no such degradation, making PDMS a highly suitable encapsulant for ICs intended for years-long implantation. Based on the new insights, guidelines are proposed that may enhance the longevity of implantable ICs, significantly broadening their applications in the biomedical field.

show abstract

“…Though this relationship only considers contamination already present at the gate oxide and does not consider the role of temperature in accelerating diffusion of such species from the external environment. The authors have recently introduced a new platform fully integrated on a CMOS IC, which can be used to detect potential ingress of moisture/ions through the ICs metal layers [68]. This ingress will manifest itself in the form of changes in the resistance of the interlayer dielectrics, which can be picked up by the platform.…”

Section: Current and Future Ageing Testsmentioning

confidence: 99%

Silicone encapsulation of thin-film SiO_x, SiO_xN_y and SiC for modern electronic medical implants: a comparative long-term ageing study

et al. 2021

Self Cite

View full text Add to dashboard Cite

Objective. Ensuring the longevity of implantable devices is critical for their clinical usefulness. This is commonly achieved by hermetically sealing the sensitive electronics in a water impermeable housing, however, this method limits miniaturisation. Alternatively, silicone encapsulation has demonstrated long-term protection of implanted thick-film electronic devices. However, much of the current conformal packaging research is focused on more rigid coatings, such as parylene, liquid crystal polymers and novel inorganic layers. Here, we consider the potential of silicone to protect implants using thin-film technology with features 33 times smaller than thick-film counterparts. Approach. Aluminium interdigitated comb structures under plasma-enhanced chemical vapour deposited passivation (SiO x , SiO x N y , SiO x N y + SiC) were encapsulated in medical grade silicones, with a total of six passivation/silicone combinations. Samples were aged in phosphate-buffered saline at 67 ∘ C for up to 694 days under a continuous ±5 V biphasic waveform. Periodic electrochemical impedance spectroscopy measurements monitored for leakage currents and degradation of the metal traces. Fourier-transform infrared spectroscopy, x-ray photoelectron spectroscopy, focused-ion-beam and scanning-electron- microscopy were employed to determine any encapsulation material changes. Main results. No silicone delamination, passivation dissolution, or metal corrosion was observed during ageing. Impedances greater than 100 GΩ were maintained between the aluminium tracks for silicone encapsulation over SiO x N y and SiC passivations. For these samples the only observed failure mode was open-circuit wire bonds. In contrast, progressive hydration of the SiO x caused its resistance to decrease by an order of magnitude. Significance. These results demonstrate silicone encapsulation offers excellent protection to thin-film conducting tracks when combined with appropriate inorganic thin films. This conclusion corresponds to previous reliability studies of silicone encapsulation in aqueous environments, but with a larger sample size. Therefore, we believe silicone encapsulation to be a realistic means of providing long-term protection for the circuits of implanted electronic medical devices.

show abstract

A Chip Integrity Monitor for Evaluating Moisture/Ion Ingress in mm-Sized Single-Chip Implants

Cited by 7 publications

References 42 publications

Predicting Corrosion Delamination Failure in Active Implantable Medical Devices: Analytical Model and Validation Strategy

Predicting Corrosion Delamination Failure in Active Implantable Medical Devices: Analytical Model and Validation Strategy

Longevity of Implantable Silicon-ICs for Emerging Neural Applications: Evaluation of Bare Die and PDMS-Coated ICs After Accelerated Aging and Implantation Studies

Silicone encapsulation of thin-film SiO_x, SiO_xN_y and SiC for modern electronic medical implants: a comparative long-term ageing study

Contact Info

Product

Resources

About

A Chip Integrity Monitor for Evaluating Moisture/Ion Ingress in mm-Sized Single-Chip Implants

Cited by 7 publications

References 42 publications

Predicting Corrosion Delamination Failure in Active Implantable Medical Devices: Analytical Model and Validation Strategy

Predicting Corrosion Delamination Failure in Active Implantable Medical Devices: Analytical Model and Validation Strategy

Longevity of Implantable Silicon-ICs for Emerging Neural Applications: Evaluation of Bare Die and PDMS-Coated ICs After Accelerated Aging and Implantation Studies

Silicone encapsulation of thin-film SiO x , SiO x N y and SiC for modern electronic medical implants: a comparative long-term ageing study

Contact Info

Product

Resources

About

Silicone encapsulation of thin-film SiO_x, SiO_xN_y and SiC for modern electronic medical implants: a comparative long-term ageing study