Juha-Veikko Voutilainen

All Silk-Screen Printed Polymer-Based Remotely Readable Temperature Sensor

In this paper, we present the fabrication and characterization results of a remotely readable flexible temperature sensor. The sensor has been fabricated with screen printing technology and it consists of a polymer-based capacitor (ASAHI CR18-KTI polymer paste) as a temperature sensitive component added to the antenna coil (ASAHI LS411-AW silver paste) for remote reading purposes. The resonance frequency of the sensor (i.e., the formed LC network) is measured as a function of temperature. The sensor has been characterized in the temperature range of 0 °C-70 °C and the total sensitivity over this range is ~9 kHz/°C. The sensors normalized temperature response is independent from the polymer capacitors thickness and the effective capacitor area, which enables reasonable performance despite fabrication process induced inaccuracies. Due to the inexact nature of the resonance peak measurement, a dataanalysis algorithm was developed to enhance the accuracy of the measurement method. In addition, the sensor response to the misaligned reader and the sensor self-heating effect, due to the inductive excitation voltage, are considered. Finally, the calibration of such a sensor is discussed.

Reliability Study on Adhesive Interconnections in Flex-to-Flex Printed Electronics Applications Under Environmental Stresses

The reliability of conductive adhesive interconnections in flex-to-flex printed electronics applications under thermal cycling and cyclic bending tests is investigated in this paper. The components under study consisted of a backplane, having screen-printed silver wiring on polyethylene terephthalate film, fabricated in a roll-to-roll process, and a flexible functional component mimic stacked on top of the backplane. Each test component contained four daisy-chained conductive adhesive interconnections, and their reliability was monitored in situ with a four-point dc resistance measurement during tests. In addition, the effect of supportive nonconductive adhesives on structure reliability was studied in various configurations. The accelerated life test results proved that the long-term reliability of the studied components can be enhanced by adding supportive adhesive between the flexible layers. In both thermal cycling and cyclic bending tests, the most reliable method was found to be the configuration with supportive adhesive around the top layer sides, attaching the two layers totally together, whereas the configuration with no supportive adhesive at all showed the worst reliability. The failure analysis emphasized that the critical factor, in terms of reliability, was silver conductor delamination from the backplane surface at the interconnection area.

A prognostic method for the embedded failure monitoring of solder interconnections with 1149.4 test bus architecture

This paper describes the feasibility of accurate low frequency measurements in predicting the breakdown of modern lead free ball grid array (BGA) interconnections. In these measurements, performed partly with 1149.4 analogue boundary scan, ceramic BGA modules measuring 15x15mm in width, with 9x9 ball matrixes, were attached on an FR-4 printed wiring board (PWB) and thermally cycled over a temperature range of -40 to +125^oC. The condition of corner interconnections was monitored using the developed measurement methods and construction. In-situ measurements were performed with a datalogger during temperature cycling, accompanied with 1149.4 mixed-signal test bus measurements of corner interconnections performed between cycling intervals. In addition, the measurements were complemented by scanning acoustic microscopy and, X-ray. Monitoring corner interconnections by a simple, low-frequency voltage measurement method with embedded test constructions gives an early warning indication well before the electrical interconnection failures. Of two studied interconnection compositions, the ones with plastic core solder balls (PCSB) proved to be more reliable than the ones with 90/10 PbSn balls.

Fully printed memristors for a self-sustainable recorder of mechanical energy

Memristors have attracted significant interest in recent years because of their role as a missing electronic component and unique functionality that has not previously existed. Since the first discoveries of the existence of memristive materials, various different fabrication processes for memristors have been presented. Here, a simple additive fabrication process is demonstrated where memristors were deposited on a polymer substrate by conventional inkjet printing. The memristor structure was printed on a 125 μm thick polyethylene terephthalate (PET) substrate by sandwiching a thin layer of TiO x between two silver nanoparticle ink electrodes. Current–voltage (IV) characterization measurements were performed and they showed clear memristive behavior when voltage pulse amplitude varied between −1.5 V and 1.5 V. The corresponding resistance change is approximately between 150 Ω and 75 kΩ. In order to demonstrate the switching scheme in practical application, printed memristors and a printed voltage doubler were connected with a piezoelectric element. The element was subjected to impact-type excitation thus producing an electric charge that was able to switch the memristor between high and low resistive states. These results pave the way for an exploitation of cost-efficient, self-sufficient, all-printable memory elements for wide utilization in future electronics applications.

Current State of the Mixed-Signal Test Bus 1149.4

This paper presents the current state of the IEEE standard for a Mixed-Signal Test Bus 1149.4 and examines proposed modifications and alternatives. The standard was published in 2001 and got its first major update in 2011 which included description language support. Although the standard has not gained high usage in the electronics manufacturing industry, research has been undertaken to improve its usability. The main research topic has been the test methods for discrete components and analog circuits but the usage of the analog test environment for various applications has also been considered. The proposed modifications for 1149.4 aim to exceed the current limitations of the standard such as the inability to perform RF testing or to access problems in multichip packages. The alternatives for the standard are examined, focusing on other testability standards and also emerging standards such as IJTAG. The alternative test methods and standards cannot directly replace the 1149.4, especially on board level mixed-signal testing.

Screen-Printed Remotely Readable Environmental Sensor Pair

In this paper, we present the fabrication methods and the characterization results of a remotely readable flexible temperature/humidity sensor pair. The sensor pair has been fabricated with a screen printing technology, and it consists of a polymer-based capacitor as a temperature and humidity sensitive component added to the antenna coil for remote reading purposes. The sensor pair relays its operation to the double sensor structure in order to produce the environmental temperature and relative humidity readings. The resonance frequency of the sensor (i.e., the formed LC network designed to 13.56 MHz) is measured as a function of temperature and relative humidity. Temperature is sensed with the reference sensor with full lamination and the relative humidity with the active sensor with a lamination opening over the polymer capacitor. The sensor has been characterized in the temperature and humidity ranges of 0 °C-70 °C and 45%RH-95%RH, respectively. The simple data-analysis algorithm developed enables the calculation of both temperature and relative humidity from the corresponding measured resonance frequencies. The relative humidity sensitivity (ΔfRES/%RH) of the sensor was between 3.6-5.3 kHz/%RH in the temperature range of 30 °C-50 °C. The temperature sensor in the sensor pair had the sensitivity of 9 kHz/°C in the applied temperature range. In addition, the temperature compensation of the polymer humidity sensor is considered, based on the data-analysis algorithm. Finally, the calibration and the effect of the installation medium of such a sensor pair are discussed.

Solder interconnection failure time estimation based on the embedded precursor behaviour modelling

Abstract This article presents a method for estimating solder interconnection failure times based on nonlinear parameter estimation techniques in conjunction with the Levenberg–Marquardt Algorithm (LMA). The LMA algorithm is applied to precursor measurements, from which failure time estimations are deduced using nonlinear estimation parameters. An electrical behavioural model is also proposed for precursors indicating weakening of solder interconnections. This model is divided into three sections: linear region, conversion region and nonlinear portion. Results obtained from experimental studies are presented and discussed in detail. In addition, an error estimation of the results is conducted to obtain knowledge of the most critical parameters in the estimation problem. The results suggest that the proposed method is capable of predicting solder interconnection failure times in advance, provided that the precursor describing electronic fatigue damage in interconnections obeys the exponential growth model during the wear-out period of the interconnection life-cycle. The obtained prognostic distances (PDs) varied between 15% and 38%, and failure times were predicted 15–25% before the actual failure occurred with an error rate of less than 10%. To show the generality of the proposed method, experimental results are presented for several samples with both lead and lead-free solders.

A frequency mixing and sub-sampling based RF-measurement apparatus for IEEE 1149.4

This paper demonstrates the possibility of performing radio frequency (RF) measurements in the IEEE 1149.4 environment using a selected combination of mixing and sub-sampling as the method to down-convert the RF signal into a low frequency suitable for the analogue busses specified by the 1149.4 standard. Signals generated by RF signal generators (2 GHz) and a commercial VCO (3 GHz) were used to demonstrate the operation of the developed RF-to-LF circuitry in cooperation with Nationals SCANSTA400 IEEE 1149.4 analog test access device. The measured repeatability of RF power measurement through the whole system, i.e. from the RF input to the output of SCANSTA400, is /spl plusmn/0.15 dB and the measurement uncertainty of the RF frequency due to measurement instruments and signal sources is /spl plusmn/350 Hz. Interconnect measurements at 2.1 GHz were also demonstrated. Simple faults such as shorts, opens and missing components may readily be detected at the low-frequency output of the RF-to-LF circuitry.