Conductive anodic filament (CAF) is a failure mode in printed wiring boards (PWBS), which occurs under high humility and high voltage gradient conditions. This paper aims…
Conductive anodic filament (CAF) is a failure mode in printed wiring boards (PWBS), which occurs under high humility and high voltage gradient conditions. This paper aims to review the history of CAF from its identification in the 1970s to the statistical analysis of its failure mode and the factors that enhance its formation.
Charts the chronology and details the developments of CAF over the last 30 years.
CAF is a conductive copper‐containing salt created electrochemically that grows from the anode toward the cathode sub‐surface along the epoxy/glass interface. It can also grow from the anode on one layer to a cathode on another. CAF was first discovered in 1976 and was identified as a catastrophic failure mode. It is enhanced by high humidity during storage or use, by high voltage gradient between anode and cathode, by certain soldering flux ingredients, by hole drilling, multiple thermal cycles during processing, and by higher processing temperatures associated with lead‐free solders. CAF is a copper hydroxy chloride salt and is a semiconducting material.
Our analytical tools today are far superior to those of these early researchers. Early data were obtained from chart recorders and manual plotting. Today we have computers for automated data collection and analysis and the sensitivity of the scanning electron microscope has improved significantly. The researchers of the 1970s and early 1980s characterized the basic factors associated with CAF and in many ways we are just repeating what they have done.
Vantage Circuit Products, Bolton based suppliers of speciality chemicals and materials to the electronics industry, have agreed with Du Pont to supply soldering products, notably the ‘Solderel’ range and the ‘Sipad’ system into the UK market.
‘Fluxing and Cleaning in Electronics Soldering’ The Grosvenor Hotel, London, 22 February 1989. ‘To clean or not to clean?’ ‘Aqueous or solvent cleaning?’ ‘What is the future for CFCs and other chlorinated solvents?’ The electronics assembly industry is ringing with such questions that make the cleaning of electronic assemblies the key issue for 1989—an issue that urgently requires answers that have the stamp of authority based on fact rather than speculation. This BABS seminar was therefore very timely and attracted a large audience to listen to eight presentations from speakers representing the cleaning equipment manufacturers, flux manufacturers, MoD quality assurance, and users' experience, as well as background on solvents in the environment.
The title of this review may be slightly misleading because Lannion is really a few kilometres from Finisterre, but it certainly seemed as if we were getting to the end of…
The title of this review may be slightly misleading because Lannion is really a few kilometres from Finisterre, but it certainly seemed as if we were getting to the end of the world travelling there in a fierce equinoctial tempest, one of the worst for several years! Fortunately, the weather cleared up for the opening of the conference the following day and revealed the beauty of the Britanny landscape. Nevertheless, the remark must be made that Lannion was a peculiar choice for an International Conference in view of the fact that it is 500 km from the nearest international airport. A number of participants complained of the difficulty of communications and it is known that others abstained from participating purely because of the difficulties of reaching such an isolated spot. However, some 210 delegates arrived by all possible means. Let it nevertheless be said that the organisation was impeccable — one of the best conferences I have ever attended from that point of view. As just one example, Lannion is essentially a small, mediaeval market town that has outgrown its clothes by the advent of modern technology and the enterprises that surround it. The result is a severe lack of modern hostelries capable of lodging an influx of a couple of hundred or more persons. However, there are an adequate number a few kilometres away, in Perros‐Guirec, a small town situated over three picturesque coves on the Pink Granite Coast. The organisers had the forethought to ensure coaches were always available to shuttle the delegates between their hotels and the various events. They also engaged the services of a caterer to produce lunch and dinner each day, probably otherwise impossible if the delegates had to make their own arrangements.
The Electronic Industries Association (EIA) has announced the release of EIA‐364–71, Solder Wicking Test Procedure for Electrical Connectors/ Sockets (Wave Solder Technique), formerly Standards Proposal No. 2185‐A. The object of this test is to determine whether a connector can be wave soldered to a printed wiring board without sustaining damage caused by solder wicking onto the contact surfaces or other areas that might alter its operating characteristics.
‘The Joining Environment’ Dates: 14–15 October 1992 Venue: Forte Posthouse, Coventry, England This Conference will provide a venue for discussion on advances in joining technology, and papers will cover a wide range of scientific and technical developments, focusing in particular on soldering, brazing and diffusion bonding practices which may involve environmental considerations.