Conductive anodic filament failure analysis caf preventlab. Conductive anodic filament caf is a failure mode in printed wiring boards pwbs, which occurs under high humility and high voltage gradient conditions. Ready and turbini 2000 identified this copper salt as the cu2oh3cl, atacamite compound. Catching and correcting this potential failure can substantially lengthen product. Conductive anodic filaments may be composed of conductive salts, rather than cationic metal ions. Caf dendrites can form between adjacent plated through holes pth, or between a plated through hole and a. Conductive anodic filament caf failure is copper corrosion within a printed board. Conductive anodic filament caf formation is defined, in ipctm650, method 2. Conductive anodic filament failure is the growth or electromigration of copper in a printed circuit board. Citeseerx document details isaac councill, lee giles, pradeep teregowda. May 22, 2002 pbfree reliability workshop 2 outline background.
Caf formation is a process involving the transport of conductive chemistries across a nonmetallic substrate under the influence of an applied electric field. Guide to pcb caf issues mcl millennium circuits limited. Development of a standard test method for evaluating. Applying the silane coupling agent to the surface of the substrate creates. Download file pdf conductive anodic filament growth failure isola group thank you for downloading conductive anodic filament growth failure isola group. The filament, a copper salt, grows from anode to cathode along the epoxyglass interface. Electrochemical studies have shown that both cucl and cucl 2. For example, trialkoxy groups of the silane may react with exposed silanols on the glass to form a siloxane, which is further polymerized to form a silane polymer barrier layer on the exposed glass fiber ends. Conductive anodic introducing the next filament monitoring. It was drafted to provide guidance regarding implementation of the user guide for the ipctm650, method 2. Caf is metal filaments that can grow from copper viahole plating along the glass fibres embedded in pcb materials such as fr4.
Nov 11, 2009 conductive anodic filament caf is a failure mode in printed wiring boards pwbs which occurs under high humidity and high voltage gradient conditions. Technical development headquarters dvances in the highdensity wiring of electronic parts have been accompanied by insulation degradation stemming from. Gives guidance regarding implementation of the user guide for the ipctm650, method 2. As a followup to previous work published in 20111, the high density packaging users group hdpug consortium evaluated an additional 12 materials in two constructions each for holewall to holewall conductive anodic filament caf performance. The migration occurs through the pcb laminate and not on the. To date, there has been a lack of information on standardized. This test determines if a material is prone to growing a conductive path between adjacent conductors. Conductive anodic filament, also called caf, is a metallic filament that forms from an electrochemical migration process and is known to cause printed circuit board pcb failures. Pdf microstructure of conductive anodic filaments formed. The migration occurs through the pcb laminate and not on the surface which is considered a different defect mechanism. It is a electrochemical process, and initially caused by anodic cu corrosion. Calce research and labs offer solutions to conductive anodic filament formation problems. Applying the silane coupling agent to the surface of the substrate creates surface silanols, which are implicated in conductive anodic filament caf growth.
Conductive anodic filament monitoring system following over 2 years of intense research and development we are proud to introduce the next generation instrument used to measure surface insulation resistance sir and conductive anodic filaments caf. Caf testing conductive anodic filament testing nts. In 2002, ready identified caf as atacamite, cu2oh3cl. Ready and turbini identified this copper salt as cu2oh3cl, atacamite. Conductive anodic filament caf formation, a failure mode in printed wiring boards pwbs that are exposed to. Standardizing a test method for conductive anodic filament growth failure clarissa navarro isola abstract the increase in board density, decrease in spacing between holes and features and the increased requirements for printed circuit boards to perform in high temperaturehigh humidity environments have led to increased concern on. A novel test circuit for automatically detecting electrochemical migration and conductive anodic filament formation. Abstract conductive anodic filament have been increasing concerning about pcb reliability in the last few years. Nov 16, 2015 conductive anode filament caf caf formation inside the pcb is an important failure mode for electronic circuit. This material is advisory only and its use or adaptation is entirely voluntary.
Conductive anodic filament caf formation was first reported in 1976. Initiation for caf to occur there must be a source of copper, a electrical bias and a glass reinforcement fibre in the same locality. Increasing board densities, decreasing spacing between holes and features and the growing requirement for printed circuit boards to perform in high temperaturehigh humidity environments have led to renewed concerns about possible reliability problems caused by the growth of conductive anodic filaments caf. Us8974888b2 preventing conductive anodic filament caf. Technical development headquarters dvances in the highdensity wiring of electronic parts have been accompanied by insulation degradation stemming from ion migration. Wo2011107418a1 hydrophobic silane coating for preventing. Nov 11, 2014 isola completes testing of laminate materials for conductive anodic filament resistance data supports the development of cafresistant materials for electric vehicle applications email print. Caf test boards fabricated from three resin types were reflowed five times following either eutectic snpb or pbfree profiles. This document is the product of the ipc electrochemical migration ecm task group. Ipc, the trade association for the circuit board and electronics assembly industries, has a standard test procedure for caf resistance titled ipctm650 method 2. Yung, phd, associate professor pcb technology centre, department of industrial and systems engineering, the hong kong polytechnic university abstract.
Pdf abstract conductive anodic filament caf formation was first reported in 1976. Caf is a copper containing filament that grows inside a pcb under the presence of moisture. As the caf filament grows copper ions migrate along the glass fibreepoxy interface towards the cathode, an environment of neutral ph is quickly reached. This unintentional growth typically bridges two oppositely biased copper conductors resulting in a short circuit. Evaluating the caf conductive anodic filament resistance of. Conductive anodic filament caf enhancement with leadfree processing temperatures dr. In the present work polyethylene glycol peg and polyethylene propylene. Maybe you have knowledge that, people have search hundreds times for their favorite novels like this conductive anodic filament growth failure isola group, but end up in infectious downloads. Conductive anodic filament how is conductive anodic. Despite the projected lifetime reduction due to caf, field failures. Conductive anodic filamentation is a subsurface failure mode in woven glassreinforced laminate fr4 materials, where a copper salt filament allows bridging between via walls and other copper.
Conductive anodic filament formation caf o conductive anodic filament formation caf, is a failure observed within the glassreinforced epoxy printed wiring board pwb laminates o it is an electrochemical process involving the ionic transport of metal under the influence of an electric field 27. Conductive anodic filament formation is when electrochemical migration of copper occurs between two barrel vias as shown in figure 6. Conductive anodic filament growth conductive anodic filament failure involves the growth or electrochemicalmigration of copper in a pcb. Evaluating the caf conductive anodic filament resistance. A materials perspective, proceedings of the 3rd pacific rim international conference on advanced materials and processes, 1998 6 l. Often electrical applications are requested to function in. The purpose of this work was to evaluate the conductive anodic filament caf growth susceptibility of three common pwb laminate systems under both eutectic snpb reflow and pbfree reflow conditions. Conductive anodic filament caf failure conductive anodic filament caf formation is a wellstudied phenomenon that is driven by chemical, humidity, voltage, and mechanical means. As the caf filament grows cu ions migrate along the glass fibreepoxy interface towards the cathode, quickly an environment of neutral ph is reached. Conductive anodic filaments are coppercontaining corrosion. The five stages in the formation of a conductive anodic filament are described below.
Calce researches solutions for caf formation center for. Thus copper precipitates as an insoluble copper salt left hand edge white region in pourbaix diagram, and it is this build up of coppers salts that constitute a conductive anodic filament. Ready and turbini 2000 identified this copper salt as the cu 2oh3cl, atacamite compound. Conductive anodic filament caf resistance test electrochemical migration testing 1 scope this document is the product of the ipc electrochemical migration ecm task group. S1921 standardizing a test method for conductive anodic filament growth failure clarissa navarro isola abstract the increase in board density, decrease in spacing between holes and features and the increased requirements for. Electronics industries user guide for the ipctm650. Conductive anodic filament caf formation is a wellstudied phenomenon that is driven by chemical, humidity, voltage, and mechanical means. With the addition of the os to the composites, the contact angle between epoxy resin and glass fiber decrease notably. This work has investigated the influence of polyethylene. Ipc 9691a2007 user guide for the ipctm650, method 2. Conductive anodic filament resistance test conducting a test of a boards caf resistance helps to ensure its overall quality and reliability.
The barrier layer effectively seals the glass fiber bundles and eliminates the conductive anodic filament caf pathway between pth vias. The combination of biasvoltage and elevated humidity initiates caf failures. The boards were subjected to a 600 hour, 100vdc caf test. Conductive anodic filament caf formation has been studied for a number of years, but the mechanism of its formation has not previously been defined. Another type of corrosion that reportedly occurs on pcbs is called conductive anodic filament caf boddy et al. Following over 2 years of intense research and development we are proud to introduce. Normalized water sorption by gravimetric measurements showed that the interfacial debonding time of composites with the os can be. Our filament is shipped in a vacuumsealed package with a desiccant packet. The effect of flux chemistry,applied voltage, conductor spacing, and temperature on conductive anodic filament formation 1209 tracks, two pths, or a pth and a surface track. Its caf conductive anodic filament time this brief but important series of images is provided courtesy of the folks at the georgia institute of technology, at the time they were there first image below.
Conductive anodic filament caf is a failure mode in printed wiring boards pwbs which occurs under high humidity and high voltage gradient conditions. Because conductive graphene pla filament is mechanically stronger than abs and pla, it can be used to 3d print functional parts such as. Pv inverter accelerated testing for highhumidity environments. The materials tested include two high tg phenolic fr4 materials, six halogen free fr4 materials, some of which might also be considered midlevel. Conductive anodic filament caf enhancement with lead.
Electronics industries user guide for the ipctm650, method. Xy axis date 0416 revision b originating task group electrochemical migration task group 532e material in this test methods manual was voluntarily established by technical committees of ipc. Sep 01, 2006 conductive anodic filament caf is a failure mode in printed wiring boards pwbs, which occurs under high humility and high voltage gradient conditions. The role of epoxyglass adhesion by seth binfield, dr.
It was drafted to provide guidance regarding how the ipctm650, method 2. The effect of flux chemistry, applied voltage, conductor. It is characterized by a sudden loss of insulation resistance that happens internally in the pcb. Susceptibility of glass reinforced epoxy laminates to. The silane coupling agent is applied to the surface of the substrate for coupling the substrate to a varnish coating. Conductive anodic filament caf formation was initially thought to have little impact upon service lifetimes. Amolen 3d printer filament, conductive black pla filament 1. An enhanced substrate for making a printed circuit board pcb includes a hydrophobic silane coating of a silane composition intermixed with a silane coupling agent applied to a glass fiber substrate. Thus copper precipitates as an insoluble copper salt lefthand edge white region in pourbaix diagram, and it is this buildup of coppers salts that constitute a conductive anodic filament. Us9351405b2 hydrophobic silane coating for preventing. Conductive anodic filament caf formation tspace repository. The subsurface deposits of corrosion byproducts emanate from the anode and eventually progress toward the. Improvement of interface interaction and conductive anodic.
Evaluating the caf conductive anodic filament resistance of multilayered pwbs akiko kobayashi, yuichi aoki, keiko to espec corp. Nathan blattau all glass fibers used in glass ply production have a form of sizing applied before the weaving process to ensure sufficient lubrication and prevent fracture. Conductive anodic filament caf formation is a reliability concern that has dogged the electronic industry for decades and remains a concern even with board materials that suppliers claim to be cafresistant. Nov 11, 2009 conductive anodic filament caf formation has been studied for a number of years, but the mechanism of its formation has not previously been defined. Conductive anodic filament caf testing in california usa. It is electromigration of the copper from anode to cathode between two conductors of different potential, whereas growth from cathode to anode is a dendrite. Conductive anode filament caf caf formation inside the pcb is an important failure mode for electronic circuit. To meet miniaturizing needs and satisfy higher performances, a more and more mayor pcb density is forcing pcb design toward closer conductors, smaller pitches, singleply dielectrics. This brief provides a detailed insight into conductive anodic filament issues though saying little about its prevention even though the.
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