Charles, Thanks for reeling-in the conversation back to the details of the NTSB report; it was quickly degrading into an emotion debate over personal favorite car makers; Off-Topic. How easily we all slip.
Encapsulation does almost nothing to stop whisker growth. That approach has been tried by many without much success. At best it delays the inevitable by a year or two, but the wiskers always win.
@ Connectr .Great point. Why do you think most of gadgets built in China,Korea, or any "inexpensive" countries die after a few month? Why all phone companies offer you a new phone every year , or two?
Answer is simple: whiskers! I found them on routers, modems,computers,tablets, card readers amplifiers ...too many to mention.One of our shuttles almost did not start , because on a last review they discovered whiskers on the mounting slides for PC boards. Lead was surely saving us from most of the problems.Military does not use ROHS anymore and some other industries are considering dropping it.All the lead hype came from plastics and paints more than solder. There is so much of disinformation out there. We need to believe scientists .
Whiskers grow on every metal and unless this is an alloy that contains whisker inhibitor (like lead in solder)they grow always, not "on couple samples".Like I wrote in your previous post: tin, silver ,copper can grow in 24 hrs or less. Whiskers are not a coincidence - there are books on metalurgy that contain "whiskers" in many chapters , if not a whole book.
I have an '02 Ford F150 with 125k, and outside of tires and brakes and tires, I have not had issue. I had a 94 F150 that at 50k miles needed a new universal assembly and a new clutch cylinder at 80k. Sometimes, I think that it is a crap shoot on vehicle quality.
I have yet to own an import and I am still holding on to my beloved '96 Caddy even though I recently bought a low mileage '03 F-150. I have stayed away from imports because they didn't have enough torque to pull the hat off your head and you have to remove half a dozen components to get the alternator out of the engine compartment. The torque ratings probably have improved since they do make a V8 now. Don't know about the alternator thing though. But with that said, I haven't been just thrilled with my F-150 either. Don't get me wrong, its a fine truck, but there are things like lack of sound deadening and slow shifting transmission that I think could have been improved. Maybe there is a "J" factor that isn't seen in America. Heck, an F for an asian student is an -A.
Tin whiskers are not a new phenomena, but we used to have a bit of lead in our solder which prevented it. But with everyone going RoHS compliant, this is one of those results of the law of unintended consequences.
Keep in mind, when RoHS was first proposed and adopted, the primary usage of lead in electronics, was a pigment fixative in plastics. The darker the color, the more fixative was used. In the average consumer electronics equipment, something like >90% of the lead was in the plastic.
RoHS was never originally meant to touch our solders, because that was considered (at the time) too little a percentage to be worthwhile. If memory serves, the day that RoHS was adopted, Nokia dropped their 5 year warranty to 1 year because they were afraid of tin whiskers. Ahh, how times change!
Charles, I hate to tell you "I told you so" , because I did comment on your previous blog where you definitevely rejected a possibility of whiskers "because NHTSA said so". Few cases in 1.7 million cars? Just a good cover-up.Most of customer have no idea what a dealer is doing to a car that was left for "car mat replacement".Anyhow , why would I take a word of NHTSA agains NASA? Only one of them consists of really credible scientists (no pun intended to the other one)It is a serious problem and it has to be addressed as such.A driver of a car does not quite know what to do in a panic situation.Sorry to say that but after seeing thousands "whisker cases" in many other devices I would dismiss car mats...
I have thought of the encapsulation method myself, such as a spray on coating after assembly, but am not sure if this would prevent whisker growth. Perhaps someone with direct experience with the issue could chime in and answer the question. The real scary part of this is that any commercial aircraft built in the last 30 years are controlled by fly-by wire systems.
The typical method is to use a voltage divider so that a short to either rail or an open is an invalid reading. monitoring for noise is also used to determine if the connection is intermittent, which is what will happen when the sensor starts to fail. They usually open in the throttle position that is used the most, like at a highway cruise or idle.
I am interested to know how the computer can distinguish between a throttle position giving a certain resistance and a tin whisker coincidentally producing the same resistance.
Would not encapsulation of soldered areas solve this problem?
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