Cross-Sections of Components on PCBs

Gideon Analytical Laboratories received two printed circuit board (PCB) assemblies, each of which had a single multilayer ceramic capacitor (MLCC) suspected of failing. These MLCCs are Johanson Dielectrics PN 500T15W103MV4E. A PCB mechanically supports and electrically connects electronic components using conductive tracks, pads and other features etched from copper sheets laminated onto a non-conductive substrate. Components (e.g. capacitors, resistors or active devices) are generally soldered on the PCB. Advanced PCBs may contain components embedded in the substrate. Multilayer ceramic capacitors are fixed value capacitors in which ceramic the material acting as the dielectric. It is made up of two or more alternating layers of ceramic and a metal layer acting as the electrodes. There are various types of materials that could function as the dielectric in a capacitor. The goal was to determine the cause of the Johanson Dielectrics PN 500T15W103MV4E MLCCs failure.

Gideon Analytical Laboratories received four Printed Circuit Boards which had either opens or intermittent behavior on some of the P1 connector pins. A Printed Circuit Board (PCB)mechanically supports and electrically connects electronic components using conductive tracks, pads and other features etched from copper sheets laminated onto a non-conductive substrate. PCBs can be single sided,double sided,or multi-layered. An open circuit is an incomplete electrical circuit in which no current flows. Gideon Analytical Laboratories was asked specifically if the soldering on the PCBs was problematic.

Gideon Analytical Laboratories received four Spectrum Control Pi filters  N49927 Bus A (capacitor components FL1, FL2, FL3, and FL4). Capacitor-input filters (also known as Pi filters) are a type of electronic filter used to remove unwanted frequencies from a signal. Pi filters are primarily constructed of two capacitors and an inductor. They are used in situations where the ripple of a signal or the AC and DC currents within the signal are found to interfere with each other. Components FL1 and Fl3 had resistance measurements indicating that they were shorted. The goal was to determine the cause of the short.

Gideon Analytical Laboratories received two 153D8496G1 printed circuit boards (PCBs)for failure analysis. A PCB mechanically supports and electrically connects electronic components using conductive tracks, pads, and other features etched from copper sheets laminated onto a non-conductive substrate. Some of the electronic components that might appear on a PCB include semiconductors like diodes or transistors, discharge devices, power sources, resistors, and capacitors. The153D8496G1 circuit card assembly has 6 capacitors, 20 resistors, and 18 semiconductors all mounted to a printed wiring board. The capacitors on both153D8496G1 PCBs were open, and as a result of the leads disintegrating in the presence of voltage and flux. The goal was to find the reason why these capacitors on the PCBs were failing.

Gideon Analytical Laboratories received several Tusonix Pi filters that were failing in the field. Capacitor-input filters (also known as Pi filters) are a type of electronic filter used to remove unwanted frequencies from a signal. Pi filters are primarily constructed of two capacitors and an inductor and are used in situations where the ripple of a signal or the AC and DC currents within the signal are found to interfere with each other.

Gideon Analytical Laboratories received one failed relay with one good one for comparison. The failed relay was intermittent @ 2 KHz.

A reed relay is a switch that uses an electromagnet to control the turning off or on within a circuit. The contacts are of magnetic material and the electromagnet acts directly on them without requiring an armature to move them. Sealed in a long, narrow glass tube, the contacts are protected from corrosion and are usually plated with silver, which has very low resistivity but is prone to corrosion when exposed, rather than corrosion-resistant but more resistive gold as used in the exposed contacts of high-quality relays. Multiple reed switches can be inserted into a single bobbin and actuate simultaneously. The glass tube is wrapped in copper windings and closes the switch with an inductive action when the copper is energized.

Gideon Analytical Laboratories received three failed Kapton based flex circuits with opens in the trace lines. The origin of the open was not known. The opens in the trace lines were traced down on the Kapton to several eyelets where contact was supposed to be made.

No areas were distinguished and no anomalies were found suggesting a trace copper foil problem on any of the circuits received. A cross-section of the above trace line and eyelet demonstrates the trace line (the line in the middle) either has been dislodged from the barrel or was never connected.

Gideon Analytical Laboratories received one static transfer switch (STS) Main Logic printed circuit board (PCB) assembly with two chips onboard digital signal processor (DSP)’s that were non-functional. The thought was the DSPs may have ball grid array (BGA) solder joint integrity issues causing the failures.

Analysis ensued. The three DSPs were removed from the PCB and immersed into the green dye and the DSP was pried from the main circuit board to reveal any cracked solder BGAs. The pictures below show the front and back of the DSP; there were 67 solder balls that attached to the PCB more tenaciously than to the DSP when separated. There was no cracked BGAs nor evidence of poor solder joints.

Gideon Analytical Laboratories received 19 multilayered ceramic capacitors (MLCCs). MLCCs have a ceramic dielectric, a ceramic or lacquered coating, a metalized electrode, and connecting terminals. Ceramic capacitors, in particular, MLCCs, are ubiquitous in all kinds of electrical equipment. Some of the MLCCs Gideon received were to test quality control, some were to test process evaluation immediately after wave solder, and some were failures in the field. The objective was to determine where these failures were entering the product and the cause of the failures.

Gideon Analytical Laboratories received several PCBs with MLCC capacitors mounted near the circuit board edge. The capacitors had a polyurethane conformal coating passing class 2 IPC-A-610 inspection. Several of the capacitors had less than 3000 ohms leakage current when measured on an IR meter. The coating was removed and the samples were potted and cross-sectioned for further analysis. The capacitor shown is typical of a lot of failures.

These are flex cracks caused by PCB flexing or bending. These types of failures most generally do not show any signs of stress on the outside margin area and, therefore, cannot be identified visually under the microscope. This failure is clearly a handling issue associated with installation.

Gideon Analytical Laboratories received a PCB with possible failed capacitors in several positions. PCBs are used to mechanically support and electrically connect electronic components. They are used in almost every all but the simplest electronic devices, from GPS systems to laptops, from cell phones to microwave ovens. Several MLCC capacitors on this PCB had failed, and the goal of Gideon Analytical Laboratories was to diagnose the cause of the failure.

Gideon Analytical Laboratories received 100 capacitors and directed to analyze them via cross-sectional analysis. Capacitors store charges and frequently appear on PCBs. There are many types of capacitors; electrolytic capacitors are tantalum capacitors are fairly common. The goal was to discover any abnormalities or determine if there were no abnormalities.

Each capacitor was cross-sectioned and observed 15 to 20 times under 40-72x magnification during the sectioning process. At some point during the cross-sectioning process, pictures were taken to depict the internal quality of the ceramic structure and any cracks (mechanical, knit, Kirkendall voiding or other defects) that may be present.

Gideon Analytical Laboratories performed failure analysis on two printed circuit board assemblies (PCB) with fractured solder joints on the Hall Sensor interconnect. The assemblies were taken apart and the conformal coating was removed to reveal the solder joints of the Hall Sensor. Five out of six of the Hall Sensors were mounted flush against the Valox 457 mounting block.

A Hall Effect Device detects magnetic flux density and is used in both movement and position sensing. By integrating the sensing element onto the same silicon as its control logic and interface circuitry, Melexis, a maker of Hall Sensors has produced sensor chips with different degrees of intelligence to suit a vast array of applications, a pioneer in linear, programmable Hall Effect sensors, accurate rotary,and linear position indication. Incorporating memory and simple hood, safety,and drive-by-wire applications. Whether sensing actuator, pedal, throttle and steering wheel position, the rotation of camshafts or crankshafts in an engine or monitoring movement in motors, Hall devices offer a reliable, contactless method of movement and position detection.