Hi Jay! Good discussion! And yes, sometimes the practicality of teaming with your component fabricators is limited in assessing plating issues but it has been my experience that the level/effort of communication expended directly reduces the amount/severity of plating issues on printed wiring assemblies. With limited resources, being proactive is getting tougher. One of the toughest tasks is getting the communication/education down to the third tier supply level but those efforts also have the greatest payback. The information on the zinc whisker "heat treatment" is contained in an internal document but I'll check into the possibility of releasing the information to the TechNet community. All materials have their disadvantages - zinc plating included - but to totally eliminate their potential use without considering the use environment and application is equally as bad as their blind application. The NASA Goddard webpage is a great educational tool for the industry - keep up the good work. Dave Jay Brusse <jay.a.brusse.1@GSF To: [log in to unmask] C.NASA.GOV> cc: Sent by: TechNet Subject: Re: [TN] Zinc Plating Finish <[log in to unmask]> 09/12/2003 08:55 PM Please respond to "TechNet E-Mail Forum."; Please respond to Jay Brusse 2nd attempt to send (message bounced earlier)... Did somebody say "whiskers"? Zinc whiskers? Those who know me from this forum probably realize that the only time I cast in my two cents is when the topic of "whiskers" rears its ugly head. I help to maintain the NASA Tin and Other (aka ZINC) Whisker WWW Site at NASA Goddard. http://nepp.nasa.gov/whisker/other_whisker (for lots about ZINC whiskers) Regarding zinc and it's potential to grow unwanted whiskers, we have seen it very recently in a GROUND (non-flight) application. We believe this particular application of zinc plating (with possibility to form whiskers) is potentially so pervasive that we have issued a formal Problem Advisory via the US Govt and Industry Data Exchange Program (GIDEP) in August 2003. I suspect that many of you and your organizations may also be exposed to this problem without knowing it. I am not authorized to distribute GIDEP documents to a forum such as TechNET (i.e., no international distribution allowed... GIDEP participants only, etc.), but for an overview of the specific situation we have observed, you may view a presentation I prepared in April 2003: http://nepp.nasa.gov/whisker/reference/tech_papers/Brusse2003-Zinc-Whisker-Awareness.pdf The problem is one of zinc-coated structures used in the manufacture of raised "access" floor structures (commonly found in computer data centers). These tiles and the support structures they rest upon (pedestals and rails) are frequently made with steel that is zinc-electroplated for corrosion protection. In the case of the tiles, it is the UNDERSURFACE (the side you DON'T) walk on that is the potential source of problems. Over periods that may take months if not years, the zinc-plated surfaces may grow zinc whiskers. On one tile I retrieved from a data center, we estimate 10 MILLION whiskers growing on a 4 square foot area of a single tile. Many of the whiskers in excess of 2 millimeters. While they live below floor they pose essentially no problem. But when they get dislodged from the tile or rail/pedestal... they become an airborne NIGHTMARE. The subfloor space of many raised floor structures is commonly pressurized for cooling of the electronics in the room. Tiles with holes or floor vents are strategically located about the center to distribute the cool air. The problem is that when someone lifts a tile (they are called "ACCESS" tiles after all) and slides it across the floor or drops it back in place or pulls electrical cable under floor, the Zn whiskers become dislodged and away they go merrily blowing about the room. The fans on the equipment in the rooms are quite efficient at pulling in air to keep them cool. Along with the air comes a fog of conductive zinc whisker debris... Result... intermittent glitches... catastrophic shorts... and as Joyce Koo remarked...the bullet that killed the beast is so difficult to see due to small size or gets melted during the event... or gets blown away from the crime scene... that detection of this problem is HARD!!! This is not a "rare" situation as I have seen it myself in at least three different data centers in the last 8 months and in researching the matter I have talked to many (at least 7) others who have faced this beast as well. In my review of this problem, I have spoken with more than one manufacturer of electronic equipment who have told me that they too have dealt with zinc whiskers growing from the Zn plated equipment racks or from the Zn-plated chassis housing their system. The fact that this type of problem isn't PUBLICLY reported is often a matter of each company's choice to go public or to quietly address the problem internally. I think I am echoing Joyce Koo's comments here. Dave Hillman's suggestion to work closely with your supplier is a good idea, but is frequently impractical. The company I buy a bolt from may not be the one doing the plating. The company I buy the relay from may be using Zn-plated structures INSIDE of the relay that they buy from somewhere else (by the way Zn whiskers have grown from inside of such devices leading to field failures). Dave also mentioned that Zn plating can be rendered immune to Zn whiskers by "annealing". I am very interested to learn more about that this practice and to find out if such practices are indeed industry standard approaches. Also as Joyce remarked, I know of no accepted test methodology by which one could evaluate a particular product's propensity to whisker in 1 year, 2 years, 10 years, etc. The floors in many of our facilities have been in use for 30 years or more in some cases. Just to cloud the whisker issue a bit further, I've recently seen pictures of Zn whiskers from Hot Dip Galvanized Steel (albeit rarely). Just this week during an audit of a manufacturer of electronic components, they told me they had recently received a survey from a major client asking them about whether their products may be prone to "tin whiskers" through the vendor's choice of pure tin finishes. The vendor, clueless about what a tin whisker is, responded... "Not a problem for us" because they interpreted the question to mean are they using pure tin "solder" to make solder joints. Of course the vendor does NOT use pure tin SOLDERs but they do use pure tin-plated terminals and other mechanical items in the construction of their product. Buyer Beware! Cheers, Jay -- Jay Brusse QSS Group, Inc at NASA Goddard 301-286-2019 --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------