Gideon Analytical Labs received several printed circuit boards (PCB) with fire damage on one and electrical overstress on the LTC4258CGW module when received. One good unit was provided for comparison. The objective was to find the cause and access the risk to the customer.
The LTC4258 can operate autonomously or be controlled by an I2C serial interface. Fault conditions are optionally signaled with the INT pin to eliminate software polling. External power MOSFETs, current sense resistors and diodes allow easy scaling of current and power dissipation levels and provide protection against voltage and current spikes and ESD events.
Gideon Analytical Laboratories received one failed optocoupler, along with two optocouplers for comparison. As a type of isolator favored by manufacturers, photocouplers
serve as noise protectors in many electronic devices. This optocoupler has a minimum isolation voltage of 5300 Vrms, a typical input voltage of 1.16 V, and a peak output voltage of 600V. The goal was to identify the cause of the failure.
The optocoupler was electrically tested. The input functioned normally with VF 1.
Gideon Analytical Labs received several PCB that opened up on several of the I/O metal dome pads.
The three black circles are the time, status, and menu pads. The metal domes came out when the two switches were separated. These buttons are connected to an output. The insulator cavity (the black spots) provides space for the metal dome. The metal dome makes contact when pushed from the top switch circuitry to the bottom switch shown later.
Gideon Analytical Laboratories received a single capacitor for failure analysis. The capacitor had a capacitance of 22µF, a voltage rating of 400 V, was ROHS compliant and had a vented bottom and the wound was exposed. The goal was to determine the cause of the failure.
The capacitor sleeve was not cracked and bulging was not apparent. This usually indicates the failure occurred during a minor period from onset of the pressure build up within the can.
Gideon Analytical Laboratories received a single MA COM MAAPSS0096 1 watt power amplifier for failure analysis. The device was thought to have some impedance issues.
The device was still attached to PCB on arrival, as displayed in the picture at the top left. The device was removed from the PCB and tested to find any indication of the condition of the internal circuitry. The MAAPSS0113 is a three stage power amplifier designed for Digitally Enhanced Cordless Telephone applications.
Gideon Analytical Labs received two 0805 MLCC capacitors mounted on daughter boards and several good capacitors for comparison. One capacitor mounted on a PCB had multiple cracks.
The pictures supplied indicated several horizontal cracks. The capacitor was cleaned and cut from the remainder of the PCB and mounted for horizontal to the PCB.
After analysis the conclusion was a combined affect of terminal fracturing and poor soldering wetting lead to over heating which in turn caused thermal cracks that lead to the EOS.
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 performed failure analysis on one opened splitter module LPF-200 PCB encapsulated in the black urethane potting material and housed in plastic. The PCB was burnt in one spot, and in that spot, a cavity existed under the carbonized epoxy of the PCB adjacent to the PTH. The trace line had a number of craters strongly suggesting an “electromigration” of copper. In order for electromigration to occur with copper a voltage, an acid and medium (moisture) must be present.
Gideon Analytical Laboratories performed failure analysis on good and bad Teapo electrolytic capacitors. A comparison leakage current test of the anode foil was set up. The leakage current over time is the best indicator as to whether the anode foil has an adequate crystal ratio of aluminum oxide forms to produce long-term reliability. The foil from the failed Teapo capacitors had multiple cracks like shown in the picture at the top left.
Gideon Analytical Laboratories performed failure analysis on several SM Syfer SM MLC Capacitors (also known as MLCC failures). The goal was to determine the root cause of these failures. Pictured on top left is the failed capacitor; it had an 11.5 Kohm resistance short.
The capacitors were cross sectioned. All cross sections of the new Syfer were in excellent quality. No voids, knit cracks, delamination, blow holes, or contamination was found.
