This Photo Gallery contains examples of EEE Parts and related hardware that have grown tin or zinc whiskers.  This photo gallery is by no means a complete archive of the types of parts that have been known to whisker, but instead contains only those part types for which NASA GSFC has been able to obtain photographic evidence.  In the literature, numerous other part types have also been reported to grow whiskers including diodes, transistors, microcircuit leads, printed circuit boards, plastic film capacitors, etc. The growth of whiskers is NOT unique to a specific part type but rather is related to the materials and processes used to plate the components as well as the subsequent environment/handling conditions to which the parts are exposed.  As such, users are urged to exercise caution when selecting components that are plated with materials and processes that are prone to whisker formation.

Photo of the Month Archive

UPDATED Nov. 19, 2002
The hermetic relay shown below (age ~14 years) has an iron armature that has been plated with PURE TIN.  The armature is INTERNAL to the packaged relay and cannot be seen by the user unless the device is destructively opened for analysis.  As noted by the images, numerous tin whiskers are clearly visible (even via naked eye inspection) growing from the armature.  Some whiskers are approaching 3 mm in length which is more than sufficient length to create a short internal to this device.

The Relays shown below are plated with pure tin.  This plating exists over the entire case, header and the hook terminals that will normally have stranded wire soldered to the end of the hooks.  Whisker shorts can occur due to whiskers growing from either the case, header or the terminals.  Even when terminals have wire soldered to the hooks, whiskers have been observed growing from the base of the terminals near the glass to metal seals.

Photos Courtesy of NASA GSFC

Photos Courtesy of Space Systems Loral

These commercial (size 0805) ceramic chip capacitors have pure tin plated terminations over a nickel barrier layer.  The user mounted them using conductive epoxy (i.e, not reflow soldered) and after thermal cycle testing discovered the tin whisker farm.  After thermal cycling max. whisker lengths of 100 microns were observed.  HOWEVER, after additional room ambient storage (6 - 8 months) the whiskers continued to grow with some in excess of 200 microns (max. length ~240 microns).  It has NOT been experimentally shown whether soldering these parts to the board would have eliminated the whisker concern through either reflow of the terminations or mixing of "most" of the termination surface with the mounting solder (typically tin/lead based).  See NASA GSFC Experiment #5 for more info.

Photos Courtesy of I. Hernefjord & NASA Goddard

Terminal Rings

The terminal rings shown below are plated with pure tin.  These terminal rings are commonly used in "crimp" type applications where a stranded wire is inserted into the barrel and crimped in place.  The ring terminal portion is most often mounted using a nut and bolt to adhere the ring to a conductive surface such as a chassis.  These photos are of "unused/loose piece" terminal rings taken straight from the manufacturer's shipping containers.  Almost all of the whiskers photographed were found "inside" the crimp barrel of these parts.  A few very short whiskers were also observed on the external part of the barrel in the "seam".

Photos Courtesy of NASA GSFC

Hybrid Microcircuit

The photo below is of the package lid of a hybrid microcircuit.  The lid was plated with pure tin. This whisker was found growing on the on the surface of the lid that was facing INSIDE the of the device.  Other whiskers were also found on the lids with some as long as 2 mm.  
In previous (unrelated) reports, whiskers similar to the one shown below on hybrid package lids have been reported to cause field failures in Phoenix Missiles¹ and F-15 radar systems² 
1) L. Corbid, "Constraints on the Use of Tin Plate in Miniature Electronic Circuits", Proceedings 3^rd International SAMPE Electronics Conference, pp. 773-779, June 20-22, 1989.
2) B. Nordwall, "Air Force Links Radar Problems to Growth of Tin Whiskers", Aviation Week and Space Technology, June, 20, 1986, pp. 65-70

Photos Courtesy of NASA Goddard Space Flight Center

Photos Courtesy of Peter Bush (State University New York at Buffalo)

Test Points

The test points shown here are "bright" tin-plated phosphor bronze loops.  They are commonly installed on PC Boards as access points for attaching test leads/probes to monitor signals and voltages during board level testing.

Connector Pins

The connector below is an octal type connector with circular cross-section pins on the plug-in side (left side of first image below) and rectangular cross-section pins on the right angle mount solderable contacts (right side of first image).  The pins are pure tin-plated.  Tin whiskers were found on the rectangular cross section pins while performing an inspection of a module reported to have failed in a commercial electric power utility application due to tin whisker shorts originating from a microcircuit also used in this assembly.

Raised Floor Tiles and Support Structures with ZINC Whiskers

The whiskers below are ZINC WHISKERS.  They were found growing on the zinc-coated steel underside of raised floor tiles.  In these examples the floor tiles were part of a computer room in which zinc whisker debris was shed from the floor tiles especially during maintenance activities within the data center .  The conductive whisker debris was distributed around the room via the air cooling system.  Ultimately, some whisker debris was drawn inside of the electronic systems (e.g., servers, routers, disk arrays) operating in the data center resulting in catastrophic and/or intermittent short circuit failures.
See the presentation:  "Zinc Whisker Awareness:  Could Zinc Whiskers Be Impacting Your Electronics?" for More about Zinc Whiskers

ADDITIONAL GALLERY of Zinc Whisker Photos on Raised Floor Structures

Photos Courtesy of NASA Goddard Space Flight Center

Zinc-Plated Steel Bus Rail (Documented in 2001)

The images below depict ZINC whiskers found growing on a zinc electroplated steel bus rail.  This rail also has a yellow chromate finish which obviously did not inhibit whisker formation.  Whiskers up to several millimeters long were observed.  The user of this bus rail determined the zinc whiskers were the root cause of catastrophic electrical shorting failure during a thermal vacuum test.

ADDITIONAL GALLERY of Zinc Whisker Photos on this Bus Rail

Tin-Plated Flange of a Waveguide (Documented in 2004)

The images below depict tin whiskers found growing from the tin-plated flange of a Ka band waveguide.  The high density of whiskers, some approaching 5-mm long, were found within several weeks of receipt of product by the waveguide user. In the end application whiskers of this size and density produced signal reflections and losses that affected the electrical performance of the waveguide.

ADDITIONAL Tin Whisker Images of this Waveguide

DISCLAIMER:
This website provides information about tin whiskers and related research. The independent research performed during the past 50+ years is so vast that it is impractical to cover all aspects of tin whiskers in this one resource. Therefore, the absence of information in this website about a particular aspect of tin whiskers should NOT be construed as evidence of absence.

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