Performance degradation analysis and reliability statistical inference of PCB

PurposeTo present and discuss open trace defects uncovered in an FR4 assembly during electrical testing.Design/methodology/approachThis paper presents open trace defects observed in FR4 assemblies and analyses the distribution of defects. The paper also discusses possible root causes for their occurrence.FindingsThe open trace defects that occurred during printed circuit board (PCB) fabrication should have been observed by the board manufacturer. It appears that the PCB manufacturer did not perform automatic optical inspection (AOI) and electrical testing during the manufacturing of the boards. The cost due to the rejected PCBAs was approximately 3x times that of the PCB cost.Originality/valueThe paper highlights the costly impact of uncovering a PCB defect after assembly. Based on the results of this study, the implementation of electrical testing and AOI for PCBs is recommended.

Traditional life evaluation theory established on the basis of mass failure data, the phenomena of little or naught failure put forward challenges for existing life evaluation theory. The performance degradation data provides useful information for products' life and reliability, and gives feasible way for life evaluation. The limitations of existing stochastic process models for performance degradation are analyzed; a new approach based on performance degradation amplitude is brought forward, the calculation methods based on degradation amplitude analysis are given out. For degradation product with large amplitude size, by way of fitting the reliability of every moments, the performance degradation rule can be got and the products' life can be forecast; for small amplitude size, the degradation path is selected in accordance to engineering experience and products' failure mechanism, the products' expected life and reliability is evaluated based on appropriate distribution model. An example of laser device with performance degradation data is given out to validate the effectiveness of the method.

Channel loss is a dominant factor for the signaling performance of high-speed I/O's. Some platform design guides clearly specify the printed-circuit board (PCB) loss requirement. During the initial design stage for PCB material selection, platform designers would like to have the accurate and efficient insertion loss measurement to meet the channel requirement because the PCB material contributes largely to the platform cost. In this paper, a comprehensive study on PCB design and analysis by different industrial methodologies for insertion loss characterization was conducted. Delta-L 2.0 methodology result is correlated with 2x-Thru results and it is good to utilize this for PCB electrical characterization. The de-embedding structure by 4 inch and 2 inch with handheld probes is validated in the accuracy, efficiency and compact test coupon size, compared with the design with 10 inch and 5 inch by SMA.

Increased use of sensors and controls in automotive applications has resulted in significant emphasis on the deployment of electronics directly mounted on the engine and transmission. Increased shock, vibration, and higher temperatures necessitate the fundamental understanding of damage mechanisms which will be active in these environments. Electronics typical of office benign environments uses FR-4 printed circuit boards. Automotive application typically use high glass-transition temperature laminates such as FR-406 glass/epoxy laminate material (T g = 164.9°C). In application environments, metal backing of printed circuits boards is being targeted for thermal dissipation, mechanical stability and interconnections reliability. There have been several studies on electronic reliability for automotive environments [Lall 2003, Syed 1996, Evans 1997, Mawer 1999]. However, none of the previous studies address the damage mechanics of electronics on metal backed substrates. Published data on crack propagation has targeted ceramic BGAs [Darveaux 1992, 1995, 2000] and plastic BGAs on glass-epoxy laminate [Lall 2003]. In this work, the effect of metal-backed boards on the interconnect reliability will be evaluated. Other failure mechanisms investigated include – delamination of PCB from metal backing. The test vehicle is a metal backed FR4-06 laminate. Metal backings investigated include – aluminum and beryllium copper. Three adhesive have been investigated for metal backing including – arlon, pressure sensitive adhesive and pre-preg. The use of conformal coating for reliability improvement has also been investigated. Component architectures tested include – plastic ball grid array devices, C2BGA devices, QFN, and discrete resistors. Reliability of the component architectures has been evaluated for HASL and electroless Ni/Au finishes. Crack propagation and intermetallic thickness data has been acquired as a function of cycle count. Reliability data has been acquired on all these architectures. Material constitutive behavior of arlon and PSA has been measured using uni-axial test samples. The measured constitutive behavior has been incorporated into non-linear finite element simulations. Predictive models have been developed for the dominant failure mechanisms for all the component architectures tested.

The characteristics of performance degradation data are analyzed. The disciplinarians of numerical control machine tool performance degradation data with time are analyzed, the reliability assessment methods with performance degradation data based on performance degradation distribution is presented. The performance gradation data contain abundant numerical control machine tool reliability information, the reliability and lifetime of numerical control machine tool can be evaluated with performance degradation data availably, even if the failure time cannot be obtained by life testing.

A printed circuit board (PCB) is an essential element for practical circuit applications and its failure can inflict large financial costs and even safety concerns, especially if the PCB failure occurs prematurely and unexpectedly. Understanding the failure modes and even the failure mechanisms of a PCB failure are not sufficient to ensure the same failure will not occur again in subsequent operations with different batches of PCBs. The identification of the root cause is crucial to prevent the reoccurrence of the same failure. In this work, a step-by-step approach from customer returned and inventory reproduced boards to the root cause identification is described for an actual industry case where the failure is a PCB burn-out. The failure mechanism is found to be a conductive anodic filament (CAF) even though the PCB is CAF-resistant. The root cause is due to PCB de-penalization. A reliability verification to assure the effectiveness of the corrective action according to the identified root cause is shown to complete the case study. This work shows that a CAF-resistant PCB does not necessarily guarantee no CAF and PCB processes can render its CAF resistance ineffective.

The THz gap has been a significant research objective for photonics and electronics for decades. This work introduces a fully integrated frequency modulated continuous wave (FMCW) radar sensor with a center frequency of 0.48 THz, realized in a silicon-germanium (SiGe) technology. The sensor consists of a THz MMIC integrated onto a front-end printed circuit board (PCB) with FR4 substrate used for frequency synthesis and IF signal amplification. A dielectric polytetrafluoroethylene (PTFE) lens is mounted above the MMIC to act as transmitter (Tx) and receiver (Rx) lens as well as a physical protection for the bond wires of the MMIC. A back-end PCB generates the supply voltages and control signals, and its analog-digital-converter (ADC) samples the IF signal. The whole sensor is just 4.9 cm by 4.3 cm in size and is cost-efficient due to its design with FR4 PCBs. The MMIC reaches an output power of up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-9$</tex-math></inline-formula> dBm. In FMCW operation with the full sensor, a tuning range of 49 GHz is reached along an equivalent isotropic radiated power (EIRP) of up to 22 dBm. Distance measurements were successfully tested for distances of up to 5 m, and a radiation pattern is presented. In summary, this article demonstrates the potential of SiGe technology in the THz range for applications like localization, material characterization, and communication.

Purpose – The purpose of this paper is to verify how solder joint properties correlate with soldering profile set-up. These characteristics act against each other. All observed properties may significantly affect the quality and reliability of solder joints. The purpose is also to design recommendations for manufacturers of electronic assemblies. Design/methodology/approach – The samples for experiment were reflowed by using a laboratory reflow oven. A LEXT laser confocal microscope was used for wetting angle and intermetallic compound (IMC) thickness measurement. The ionic contamination was measured by using a contaminometer. Findings – The appropriate choice of soldering profile is very important for the reliability of electronic assemblies. The higher temperatures or longer preheating and soldering times improve the wetting angle. Likewise, there is also the activation of all the fluxes. The result is low contamination with printed circuit boards (PCBs). On the other hand, we must not forget that higher temperatures and longer soldering time also affect the thickness of the IMC. The outer limits recommended by the manufacturer were selected for the soldering profile set-up. Even within these limits, it is possible to achieve an improvement in the wetting angle, an improvement in levels of PCB contamination and an increase in the thickness of the IMC. This paper presents the results achieved for solders Sn42Bi57.6Ag0.4, Sn96.5Ag3Cu0.5 and Sn97Ag3. Originality/value – The gained knowledge on the correlation between IMC thickness, solderability of PCB and PCB contamination caused by different soldering profile set-ups can help to prevent reliability problems because each of the named effects has a significant influence on reliability.

Electrical interconnection, mechanical support and electrical insulation are basic function requirements for printed circuit boards (PCB) in all of electronic products. The current trend toward miniaturization in electronics industry has forced a continuous reduction on conductor spacing. This fact has brought a greater reliability challenge to insulating properties of PCB. Short failure had become one of the most common PCB problems in field. In the present study, the various short failures had been summarized and classified into four typical categories: (1) quality defects of PCB; (2) foreign conductive metal residues on PCB; (3) electrochemical migration (ECM, conductive anodic filament (CAF) is regarded as one type of ECM) (4) ionic residues. The fault features, analysis methods, failure mechanisms and preventive measures were discussed through comprehensive analysis on the real short failure cases of each type. It is suggested identifying fault features first, which is helpful to choose proper analysis methods, then find out root failure causes accurately, and put preventive measures specifically from electronic auxiliary materials controlling, PCB quality controlling, PCB layout design or electronic assembly management.

Computing environmental life of electronic products based on failure physics

A high-performance S-band power amplifier fabricated on a low-cost 20-mil-thick FR-4 printed circuit board (PCB) for S-band radar applications is demonstrated. The amplifier consists of a single-ended driver stage and a balanced output power stage utilizing Wilkinson power dividers/combiners with quarter-wave transmission lines. Under 10-V and 2.45-A dc bias condition, the S-band power amplifier with 23-dB small-signal gain, 38-dBm 1-dB gain-compression power with 25.6% power-added efficiency (PAE) and 3.9-dB noise figure can be achieved. In addition, excellent linearity with a 48.73-dBm 3rd-order intercept point is also measured. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 311–313, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20620

This paper presents an L-band patch antenna with linear polarization for mobile device application. This patch antenna is constructed with two-sided structure and fabricated on FR4 printed circuit board (PCB). It is fed by 50-Ω subminiature version A (SMA) connector with the patch size of 2.38 × 3.57 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Experiment results demonstrate that the patch antenna has a suitable operating frequency around 1.98 GHz for mobile device application. In addition, it provides linear radiation patterns with 4.6-dBi antenna gain. The patch antenna has been successfully design, fabricated, and demonstrated. From the measured results, it found that this patch antenna is well suitable for mobile device applications.

In this paper, design and implementation of a 4.25Gb/s optical fiber transceiver for Gigabit Ethernet (GbE) applications based on IEEE802.3z standard using Multi Mode Fiber (MMF) is described. Transmitter consists of an 850 nm Vertical-Cavity Surface-Emitting Laser (VCSEL), laser driver and transmission lines and receiver consists of a PIN photodiode, amplifiers and transmission lines. Differential microstrip lines and single-ended Conductor Backed Coplanar Waveguides (CBCPWs) on a FR-4 Printed Circuit Board (PCB) are implemented. To evaluate the performance of the implemented optical transceiver, as the results, the measured eye diagrams and Bit Error Rate (BER) measurements at the transmitter and receiver outputs are presented.

This study proposes a compact 5-GHz front-end module with embedded antenna on a low-temperature co-fired ceramic substrate, which is to be used for the IEEE 802.11a wireless local area network applications. The module comprises an embedded inverted-F antenna, a bandpass filter, and a low-pass filter. Both the proposed filters possess transmission zeros at out band for suppressing unwanted signals. A double-pole double-throw bare die transmitting/receiving switch is mounted on the surface of the substrate. The interconnection between the bare die switch and the buried circuits is established by bond wires. The effect of the bond wire is considered by incorporating its equivalent inductance into the design of the filters. The overall size of the antenna front-end module is only 6.2 mm times 5.4 mm times 0.98 mm with most of the space (near two-thirds of the volume) reserved for the antenna so as to have a better radiation performance. Also, to avoid the potential close proximity coupling among the buried circuits and the antenna, numerous metal vias connecting the top and bottom grounds in the module are designed for shielding. Since the radiation of a small antenna is influenced by the nearby circuit ground due to induced ground current, the developed antenna front-end module is tested on two FR4 printed circuit boards (PCBs) with different sizes (i.e., 55 mm times 20 mm and 80 mm times 46 mm). It is demonstrated that the antenna module performs well on these two grounded PCBs. The achieved 10-dB return-loss bandwidths are near 900 MHz for the transmitting and receiving paths. The measured radiation patterns are quite omnidirectional with peak gains (including the losses of circuit components) at approximately 0 dBi for the transmitting path and -1.7 dBi for the receiving path.

This article describes the design methodology to achieve reflective diode-based parametric frequency selective limiters (pFSLs) with low power thresholds ($P_{th}$) and sub-dB insertion-loss values ($IL^{s.s}$) for driving power levels ($P_{in}$) lower than $P_{th}$. In addition, we present the measured performance of a reflective pFSL designed through the discussed methodology and assembled on a FR-4 printed circuit board (PCB). Thanks to its optimally engineered dynamics, the built pFSL can operate around $\sim$2.1 GHz while exhibiting record-low $P_{th}$ (-3.4 dBm) and $IL^{s.s}$ (0.94 dB) values. Furthermore, while the pFSL can selectively attenuate undesired signals with power ranging from -3.4 dBm to 13 dBm, it provides a strong suppression level (IS > 12.0 dB) even when driven by much higher $P_{in}$ values approaching 28 dBm. Such measured performance metrics demonstrate how the unique nonlinear dynamics of parametric-based FSLs can be leveraged through components and systems compatible with conventional chip-scale manufacturing processes in order to increase the resilience to electromagnetic interference (EMI), even of wireless radios designed for a low-power consumption and consequently characterized by a narrow dynamic range.