Whiskers - Θα δουλεύουν τα τωρινά μας μηχανάκια σε 10 χρόνια?

[Yiannis_B]

Metal whiskering is a phenomenon which occurs in electrical devices. Tin whiskers were noticed and documented in the valve (tube) era of electronics early in the 20th century, in equipment which used pure, or almost pure, tin solder in their production. It was noticed that small metal hairs or tendrils grew between metal solder pads causing short circuits. Metal whiskers form in the presence of compressive stress. Zinc, cadmium, and even lead whiskers have been documented.[1] Many techniques are used to mitigate the problem including changes to the annealing process (heating and cooling), addition of elements like copper and nickel, and the inclusion of conformational coatings.[2] Traditionally, lead has been added to slow down whisker growth.

The European Union banned the use of lead in most consumer products in the early 21st century due to health problems associated with lead and the "high-tech trash problem", leading to a re-focusing on the issue, see Restriction of Hazardous Substances Directive (RoHS).

http://en.wikipedia.org/wiki/Whisker_(metallurgy)

http://nepp.nasa.gov/whisker./

 

[Yiannis_B]

Τα νέα είναι σχετικά καλά, αλλά ποιος ξέρει τι ακολουθεί η κάθε βιομηχανία?

"The new process does, indeed, use similar chemistry to that found in the circuit board industry. The initial trials carried out in the process of testing this patent-applied-for process used an electroless nickel chemistry. In the testing carried out with nickel as a tin whisker elimination coating, it was found that a coating thickness of 0.2 microns is needed to eliminate the phenomena of whisker growth [1].

In the testing, a FULLY ASSEMBLED board was electroless nickel plated by placing the assembly into the plating bath. Once removed, the board was rinsed off and dried in a process similar to that already in use in both the bare board fab and assembly industries.

Before immersion in the chemistry the areas of the board not requiring plating such as gold connectors and edge contacts were masked off using standard masking materials. The result is shown in the photograph below. Every metal surface on the assembly is now coated with nickel, and tin whiskers will not be an issue--they have not been mitigated, but eliminated.

The board above works just fine after the treatment and, thanks to the nickel surfaces, will continue to work reliably without the doubt of a tin whisker induced failure. So far, not one assembly to which the process has been applied has failed to function after the process exactly as it did before.

The benefits of the process are many in the drive to eliminate whisker growth in a high-reliability electronics assembly; some of these are outlined below:

• 
  
  
  • Eliminates BOM scrubbing and testing components for Pb-free Sn at receiving.
  • Solves termination finish whisker problem with COTS assemblies.
  • Permanently suppresses whisker growth (Kim et al. > 5 yrs for 200 nm Ni [1]).
  • Applicable to all electronic assemblies (mask, add a few components later if necessary).
  • All tin is covered/no shadowing /hot aqueous immersion.
  • Risk of damage to assembly function, reliability and legibility negligible.
  • Fixed and maintenance costs negligible.
  • Small equipment footprint.
  • Process inherently safe--doesn't use exotic chemicals (i.e., not already in use in electronics industry). Long history, wide use of electroless Ni.
  • Training of work force simple--expect broad process window.
  • Quick, so no bottleneck: Time requirement ≯ 5 minutes/assembly.
  • Process can be performed immediately after cleaning and before conformal coating; no additional cost for masking.
  • Easy cleanup of assembly for next process step--water and steam, dry.
  • No interference with rework; masking allows components to be added later.

The trials continue on this new process. The industry is currently carrying out many trials and hopes to work with a number of OEMs to run side-by-side trials with fielded units of both untreated and treated products.

Given the long history and current use of electroless nickel, both on circuit board bare fabs and components, along with the historic tin whisker testing on nickel coated components [1], it looks like the search for an effective, easily-reworkable, easily-implemented, cost-effective process for the elimination of tin whiskers is over. "

http://www.pcbdesign007.com/pages/zone.cgi?a=71147

 

[Yiannis_B]

Τώρα θα βγει ο Sansui - man....

...πάντως ένα mail στον James Tanner θα το στείλω...

 

[Zizik]

Μα τα παλιά είναι πήχτρα στο μολύβι. Πεθαίνεις εσύ, όχι τα μηχανάκια.

 

[Yiannis_B]

Μα τα παλιά είναι πήχτρα στο μολύβι. Πεθαίνεις εσύ, όχι τα μηχανάκια.

Αν ήταν να μπεις σε ROHS πύρ(κ)αυλο θα το ξανασκεφτόσουνα......με τα αεροπλάνα τι παίζει?

http://en.wikipedia.org/wiki/Galaxy_IV

 

[Zizik]

http://twbrewing.com/

 

[VLASSIS-S]

Αυτο ειναι σαν τα ακαρια στο στρωμα ???

 

[Yiannis_B]

Αυτο ειναι σαν τα ακαρια στο στρωμα ???

..η επιστροφή...

 

[JOHN MARKOU]

Τώρα θα βγει ο Sansui - man....

...πάντως ένα mail στον James Tanner θα το στείλω...

Να το στείλεις και να του πείς και χαιρετισμούς.

 

[JOHN MARKOU]

Μα τα παλιά είναι πήχτρα στο μολύβι. Πεθαίνεις εσύ, όχι τα μηχανάκια.

Γι"αυτό εσυ τα χάρισες όλα , για να μην πεθάνεις από το μολύβι ε?

 

[Zizik]

Ναι. Πιό έμπρακτα δε γίνεται.

 

[JOHN MARKOU]

Και επειδή είσαι και ουμανιστής , είπες , ε! ας πεθάνουν οι άλλοι.

 

[Manos58]

Δεν το ήξερε τότε βρε .

Spoiler

Αν το ήξερε θα τα πούλαγε