Technical Library | 2021-02-20 00:55:47.0
Customers must be able to rely on accurate humidity indication as an assurance of SMD quality and fitness for processing and use. Without it, they might accept SMDs from suppliers that have already been irreparably damaged by moisture during storage or transit. Or, they might approve for processing SMDs that have been improperly or insufficiently heat-dried. Beyond the processing questions, there are financial questions: Where did the dry pack problems originate and who--supplier, customer, shipper--is financially responsible for the damaged SMDs? In response, Clariant, the originator of the color change humidity indicator card, and a member of the JEDEC's Subcommittee 14.1, "Reliability and Test Methods for Packaged Devices," created a new "non-reversible" halogen and cobalt dichloride free humidity indicator card. This HIC combines two reversible indicators (5% and 10%) with a new non-reversible (60% RH) indicator spot. (Figure 1) The 5% and 10% reversible spots work the way similar indicators do: they change color from blue (dry), to lavender, to pink (wet) to indicate humidity exposure at the indicated levels. If humidity levels drop, they will gradually revert back to blue.
Technical Library | 2020-11-09 16:59:53.0
A customer contacted ACI Technologies regarding a high failure rate of their assemblies. They provided assemblies to be X-rayed and inspected for the purpose of identifying any process related issues such as (but not limited to) solder and assembly workmanship and evidence of damage due to moisture related problems during reflow (a.k.a. "popcorning"). Moisture damage usually appears as physical damage to the component. The first indication of moisture damage would be externally observable changes to the package in the form of bulging or fractures to the outer surface of the component, an example of which is shown in Figure 1. Internally observable indicators of moisture damage typically include fractures to the die inside the package and lifted or fractured wire bonds. These conditions would be apparent during transmissive X-ray inspection. Another symptom of moisture related damage would be inconsistent solder joint sizes that result from package deformation during the liquidus phase of the reflow process. None of these indicators of moisture related damage were present on the customer samples.
Technical Library | 2019-06-11 09:36:13.0
An experiment was recently performed ACI Technologies for a customer that was interested in comparing the wetting of lead-free solders with varying temperature profiles and atmospheric conditions. In order to deliver an objective measurement of solder wetting (in addition to subjective inspection analysis), a simple wetting indicator pattern was added to the solder stencil in an area on the test vehicle that had exposed and unused copper.
Technical Library | 2019-06-21 10:39:15.0
Recently, an ACI Technologies (ACI) customer called to discuss failures that they had observed with some through-hole capacitor parts. The components were experiencing failures following vibration and accelerated stress testing. Upon receipt of the samples, ACI performed three levels of inspection and Energy Dispersive Spectroscopy (EDS) testing to investigate the root cause of the failures. These analyses enabled ACI to verify the elements comprising the solder joints and make the following recommendations in order to prevent future occurrences. The first inspection was to investigate the capacitor leads using optical microscopy, and no anomalies were found that could indicate bad parts from the vendor or improper handling prior to assembly. However, vertical fill in the barrel of the plated through-holes was too close to the IPC-A-610 minimum specification of 75% to determine a pass/fail condition, and therefore required further investigation.
Technical Library | 2019-07-11 11:07:08.0
Affordability is not exactly the primary word which comes to mind when discussing the use of design of experiments (DOE) principles, but is generally accepted as a necessary part of the engineering activities required in the development of a product or process. However, a number of studies have indicated that the cost savings derived from a well deliberated experimental design can be substantial in the initial stages where the conditions or parameters of a process are determined. Some studies have shown a greater than 50% cost savings compared to the more conventional means of trial and error approaches to process development. At ACI Technologies (ACI), we have found the use of DOE techniques fundamental in eliminating extraneous costs otherwise spent on unnecessary testing.
Technical Library | 2021-11-03 16:52:47.0
This paper proposes the integration of pulsed photonic sintering into multi-material additive manufacturing processes in order to produce multifunctional components that would be nearly impossible to produce any other way. Pulsed photonic curing uses high power Xenon flash lamps to thermally fuse printed nanomaterials such as conductive metal inks. To determine the feasibility of the proposed integration, three different polymer additive manufacturing materials were exposed to typical flash curing conditions using a Novacentrix Pulseforge 3300 system. FTIR analysis revealed virtually no change in the polymer substrates, thus indicating that the curing energy did not damage the polymer. Next, copper traces were printed on the same substrate, dried, and photonically cured to establish the feasibility of thermally fusing copper metal on the polymer additive manufacturing substrates. Although drying defects were observed, electrical resistivity values ranging from 0.081 to 0.103 Ω/sq. indicated that high temperature and easily oxidized metals can be successfully printed and cured on several commonly used polymer additive manufacturing materials. These results indicate that pulsed photonic curing holds tremendous promise as an enabling technology for next generation multimaterial additive manufacturing processes.
Technical Library | 2008-10-23 15:36:58.0
As part of continuous process improvement at KEMET, most failure modes caused by the capacitor manufacturing process have been systematically eliminated. Today these capacitor manufacturing-related defects are now at a parts per billion (PPB) level. Pareto analysis of customer complaints indicates that the #1 failure mode is IR failure due to flex cracks.
Technical Library | 2021-03-10 23:57:29.0
Latent short circuit failures have been observed during testing of Printed Circuit Boards (PCB) for power distribution of spacecraft of the European Space Agency. Root cause analysis indicates that foreign fibers may have contaminated the PCB laminate. These fibers can provide a pathway for electromigration if they bridge the clearance between nets of different potential in the presence of humidity attracted by the hygroscopic laminate resin. PCB manufacturers report poor yield caused by contamination embedded in laminate. Inspections show ...
Technical Library | 2016-10-20 18:13:34.0
Pad cratering failure has emerged due to the transition from traditional SnPb to SnAgCu alloys in soldering of printed circuit assemblies. Pb-free-compatible laminate materials in the printed circuit board tend to fracture under ball grid array pads when subjected to high strain mechanical loads. In this study, two Pb-free-compatible laminates were tested, plus one dicycure non-Pb-free-compatible as control. One set of these samples were as-received and another was subjected to five reflows. It is assumed that mechanical properties of different materials have an influence on the susceptibility of laminates to fracture. However, the pad cratering phenomenon occurs at the layer of resin between the exterior copper and the first glass in the weave. Bulk mechanical properties have not been a good indicator of pad crater susceptibility. In this study, mechanical characterization of hardness and Young’s modulus was carried out in the critical area where pad cratering occurs using nano-indentation at the surface and in a cross-section. The measurements show higher modulus and hardness in the Pb-free compatible laminates than in the dicy-cured laminate. Few changes are seen after reflow – which is known to have an effect -- indicating that these properties do not provide a complete prediction. Measurements of the copper pad showed significant material property changes after reflow.
Technical Library | 2012-12-14 14:28:20.0
This paper examines the potential failure mechanisms that can damage modern lowvoltage CMOS devices and their relationship to electrical testing. Failure mechanisms such as electrostatic discharge (ESD), CMOS latch-up, and transistor gate oxide degradation can occur as a result of electrical over-voltage stress (EOS). In this paper, EOS due to electrical testing is examined and an experiment is conducted using pulsed voltage waveforms corresponding to conditions encountered during in-circuit electrical testing. Experimental results indicate a correlation between amplitude and duration of the pulse waveform and device degradation due to one or more of the failure mechanisms.
