Technical Library | 2020-12-07 15:26:06.0
Temperature cycling testing is a method of accelerated life testing done to PCCs that are exposed to normal operation temperature variations over its lifetime. During the testing, intermittent "open" failures can first occur at the hot and cold extremes of the test, exposing weaknesses in the design and assembly. A poor/weak solder joint fatigues, a via trace or barrel cracks, loose connections or a component fails all causing an intermittent open. When not at extreme temperatures, the PCC assembly relaxes, the "open" closes creating electrical connectivity. If you are monitoring the PCC under test in-situ you will know that an intermittent failure has occurred, and the test could be stopped for inspection. If in-situ monitoring was not implemented, you would not know if there were intermittent failures or not. The PCC gets powered up and works fine at room temperature.
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 | 2019-06-04 10:19:46.0
Interconnection technology relies very heavily on the ability of the conductors on a printed wiring assembly to maintain reliable signal integrity. Harsh environmental factors can precipitate a loss of conductivity due to oxidation and corrosion. Connections are typically soldered or inserted using pressure fitted connectors to obtain enough surface contact to meet the electrical conductivity requirements. In pressure contacts, surface integrity is especially critical where the abrasive effects of retraction and insertion can wear off the metallic finish from the contact area. This can expose the underlying copper or nickel and lead to increased resistance at the contact points. These types of conductors are frequently found in card edge connectors where the terminations are plated with a layer of nickel and gold (frequently referred to as gold fingers). A hard gold is typically used containing very small amounts of nickel and cobalt to increase the wear resistance.
Technical Library | 2010-01-13 12:34:10.0
Micro-sectioning (sometimes referred to as cross-sectioning)is a technique, used to characterize materials or to perform a failure mode analysis, for exposing an internal section of a PCB or package. Destructive in nature, cross-sectioning requires encapsulation of the specimen in order to provide support, stability, and protection. Failures that can be investigated through micro-sectional analysis include component defects, thermo-mechanical failures, processing failures related to solder reflow, opens or shorts, voiding and raw material evaluations.
Technical Library | 2022-03-16 19:48:18.0
Dendrites, Electrochemical Migration (ECM) and parasitic leakage, are usually caused by process related contamination. For example, excess flux, poor handling, extraneous solder, fibers, to name a few. One does not normally relate these fails with environmental causes. However, creep corrosion is a mechanism by which electronic products fail in application, primarily related to sulfur pollution present in the air.1 The sulfur reacts with exposed silver, and to a lesser extent, exposed copper. This paper will explore various aspects of the creep corrosion chemical reaction
Technical Library | 2015-10-22 17:37:28.0
The objective of this study is to evaluate conformal coatings for mitigation of tin whisker growth. The conformal coatings chosen for the experiment are acrylic, polyurethane and parylene. Also included in this paper are tin whisker inspection results of tin-plated braiding and wire that was exposed to an environment of 50°C with 50% relative humidity for over five years.
Technical Library | 2021-07-27 14:49:16.0
Conductive anodic filament (CAF) formation, a failure mode in printed wiring boards (PWBs) that are exposed to high humidity and voltage gradients, has caused catastrophic field failures. CAF is an electrochemical migration failure mechanism in PWBs. In this article, we discuss CAF, the factors that enhance it, and the necessary conditions for its occurrence. Published studies are discussed, and the results of historical mean time to failure models are summarized. Potential reasons for CAF enhancement solutions are discussed, and possible directions in which to develop anti-CAF materials are proposed.
Technical Library | 2022-12-19 18:59:51.0
Material and Process Characterization studies can be used to quantify the harmful effects that might arise from solder flux and other process residues left on external surfaces after soldering. Residues present on an electronic assembly can cause unwanted electrochemical reactions leading to intermittent performance and total failure. Components with terminations that extend underneath the package can trap flux residue. These bottom terminated components are flush with the bottom of the device and can have small solderable terminations located along the perimeter sides of the package. The clearance between power and ground render high electrical forces, which can propagate electrochemical interactions when exposed to atmospheric moisture (harsh environments). The purpose of this research is to predict and understand the functional performance of residues present under single row QFN component packages. The objective of the research study is to develop and collect a set of guidelines for understanding the relationship between ionic contamination and electrical performance of a BTC component when exposed to atmospheric moisture and the trade-offs between electrical, ionic contamination levels, and cleanliness. Utilizing the knowledge gained from undertaking the testing of QFN components and associated DOE, the team will establish a reference Test Suite and Test Spec for cleanliness.
Technical Library | 2009-11-05 11:17:32.0
Head-in-pillow (HiP), also known as ball-and-socket, is a solder joint defect where the solder paste deposit wets the pad, but does not fully wet the ball. This results in a solder joint with enough of a connection to have electrical integrity, but lacking sufficient mechanical strength. Due to the lack of solder joint strength, these components may fail with very little mechanical or thermal stress. This potentially costly defect is not usually detected in functional testing, and only shows up as a failure in the field after the assembly has been exposed to some physical or thermal stress.
Technical Library | 2015-06-22 16:39:47.0
Surface finishing is an integral part of any PCB fabrication. It is generally applied to exposed Cu connectors and conductors on the board. Surface finishing has numerous important functions. It serves as a protective layer for the Cu connectors during storage. The surface finish helps minimize or reduce tarnish of the Cu substrate. Additionally, since it is the layer that comes into contact with other components during assembly, it ensures good solderability between the PCB and the component during assembly. Furthermore after assembly, the finish helps prolong the integrity of the solder joint during use. A general review of common PCB surface finishes is presented. The advantages and disadvantages of each are discussed and compared.
