So what's the truth about lead-free solder ?

[PeteS]

Don't look to this newsgroup for factual info on lead free! Instead
look at actual test results in the trade publications such as SMT
magazine:
http://smt.pennnet.com/home.cfm
They have published numerous tests comparing various lead free
materials and processes with tin-lead. Some lead free materials and
processes are better than others (no surprise) and picking the best
one for your situation is non-trivial.

My nutshell summary of the published test results is that lead free is
significantly harder to do right than tin-lead, requiring tighter
process controls, but if done right it can be more reliable than
tin-lead for non-shock situations. Lead free is harder, stronger and
more brittle than tin-lead so tin-lead will deform plastically under
high shock when lead free will break, however lead free will withstand
more hot-cold cycles than before failure than tin-lead (better fatigue
resistance). So you need to know what the significant failure
mechanisms are in your design to pick the most reliable materials.

Glen

Another major issue is tin whiskers. We have hard evidence at
$WeBuildAvionics (where I am currently consluting) that the current Pb
Free / RoHS solder mixes have significant problems with growing
whiskers, leading to wonderful issues such as short circuits developing
under BGAs a few months after production. In a Flight control computer
(don't laugh - in a fly by wire environment it's the ONLY flight control
and virtually all late model airliners use it) this is Not a Good Thing
[tm].

The whole RoHS / Pb free thing is a political issue - the processes for
Pb Free use more hazardous substances than they get rid of.

Typical EU beauraucrats - unelected, overpaid and have to find something
to regulate to justify their existence. [1]

Cheers

PeteS

[1] Their existence, even from birth, might not be justifiable.

 

[Arfa Daily]

On my PC I have voice control, I can just say:
show BBC1
show ITV1
show ARD
show RAIuno

and in a second or so (as the motorized dish moves to a different sat)
I have it on the 1680x1050 LCD (no not yet 1980).
All it needs is a PCI card and a satellite dish.

Aha ! So you are comparing wide bandwidth high bit rate satellite
transmissions, displayed on your high res PC screen, with an analogue PAL
signal. That is not quite the same as a low bit rate highly compressed
digital terrestrial transmission, displayed on an ordinary household TV set.
I do not have an issue with a setup such as yours producing comparable - or
even possibly superior in some instances - subjectively viewed pictures. But
that was not the comparison that I was making, when I voiced the opinion
that the digital pictures ( now being foisted on the public via the
terrestrial TV transmission network ) did not compare to the analogue PAL
pictures that we have been used to.

Arfa

 

[Arfa Daily]

Another major issue is tin whiskers. We have hard evidence at
$WeBuildAvionics (where I am currently consluting) that the current Pb
Free / RoHS solder mixes have significant problems with growing whiskers,
leading to wonderful issues such as short circuits developing under BGAs a
few months after production. In a Flight control computer (don't laugh -
in a fly by wire environment it's the ONLY flight control and virtually
all late model airliners use it) this is Not a Good Thing [tm].

The whole RoHS / Pb free thing is a political issue - the processes for Pb
Free use more hazardous substances than they get rid of.

Typical EU beauraucrats - unelected, overpaid and have to find something
to regulate to justify their existence. [1]

Cheers

PeteS

[1] Their existence, even from birth, might not be justifiable.

It's good to hear at last from someone involved in the avionics industry,
and it's also good to hear that this particular industry is identifying
serious problems with the technology, as that might at least help to
maintain their exemption for some years to come. I really hope that the
industry has sufficient strength to stand up to this legislation, and to
continue to maintain their position of refusing to use it on safety /
reliability grounds. With my daily dealings with lead-free solder, and all
of the problems that it has brought to consumer electronics, the thought of
being held seven miles up in the sky by equipment using the same technology,
is truly worrying to me.

I cannot agree more that this whole thing is a poorly thought through
example of 'bandwagon politics' and job justification.

I would be interested in hearing any other input that you may have on the
subject, with regard to the avionics industry. Both anecdotal and factual
would be welcome, and I am sure that Graham (who started this thread) would
like see more from you, as well.

Arfa

 

[Eeyore]

Make no mistake, I am not trying here to compare a good digital signal - say
Sky Movies Premiere - with a poor noisy anlogue signal. What I am saying is
that the general public is being 'sold a pup' with the digital terrestrial
channels, where even the best quality transmissions, struggle to produce a
picture subjectively as good as that produced on a *good* analogue TV with a
*good* analogue PAL signal going in.

I agree with you.

The same holds for DAB too.

Graham

 

[clifto]

Nope. If you tune the signal, you get ALL of the data. You must exceed
more than ten percent bit error rate for a dropout to occur, and it is
bit error rate that matters most for a "tuned" channel.

I get regular breakups on cable, on multiple channels, at all times of day;
picture plus sound, picture only, and sound only. Picture loss includes
pixelization, cessation of action with partial pixelization, full loss of
action for seconds at a time. A visit from the cable company can fix that
for three or four days at a time.

The video reproduction is very reminiscent of the old 16-bit PC video
cards, especially in low-light scenes when it starts to look like the
video has about 16 brightness levels (four-bit video).

I used to get far better picture quality with rabbit ears from stations
a hundred miles or more away. I can take the snow when I don't have to
tolerate all the nasty artifacts in a digital picture.

 

[Spurious Response]

Thanks for playing. It is like taking candy from a baby though.

You're an idiot, and have yet again said absolutely nothing.

 

[Spurious Response]

Interesting you should say that. There must be tons of gear out there that's
'legacy' so-to-speak PAL.

Read it again. He said PROFESSIONAL, and NEWER equipment is inferred.

 

[Spurious Response]

I think you can still buy toy composite mixers, try BHphoto etc and
the camera control units (CCU) all had the usual PAL ScH and timing
adjustments, but rarely used, and don't forget that the (almost
obselete) Betacam SP format recorded in YUV anyway.

The PAL outputs are great for preview monitors, ie non critical, and
less wiring.

PAL is a very robust transmission format, but absolutely sucks in a
production setting

Spot on.

It is akin to a high end HD digital video card also carrying a composite
output jack.

 

[Eeyore]

Read it again. He said PROFESSIONAL, and NEWER equipment is inferred.

Since when did PROFESSIONALS not use PAL ?

Don't talk about stuff you have no experience of. It makes you look even more
retarded than normal. I was the technical manager for an editing equipment hire
company some years back. I do know what I'm talking about.

Broadcast TV isn't as wealthy as it once was and don't expect equipment to be
'upgraded' on a whim.

PAL (and especially UK PAL) produces a far superior picture to NTSC btw just in case
you're getting confused.

Graham

 

[Spurious Response]

Really? Could I have a model number and manufacturer?

US Digital. WalMart. Made by Hisense, model DB-2010. ($200) Broadcast
only, NOT capable of the cable format. Ready for a single antenna,
multi-channel subscriber reception planned for the future in some cities.

Every source I've
seen says that to date there is absolutely no such thing in existence,
and is pessimistic about the appearance of such before the deadline
and/or at a price anywhere near the ridiculously low projections for
price of such items.

It has been out for over two years now, and it looks amazing on an old
standard set, not to mention on an actual HD set.

Broadcast digital reception is flawless, and should be the standard...
Oooops... to late... It is!

It has component out and composite, and SVHS.

Two channel audio only.

Great reception with either a standard set top antenna or a
preamplified unit, not to mention a rooftop job.

The "several" remark was just an assumption, but one would think that
others would include such a feature in their units.

 

[Spurious Response]

MORE reliable? Please elaborate.

SHOCK.... and AWE!

 

[Spurious Response]

It's all very well saying that compression artifacts are a product of
available bandwidth, but that bandwidth is much limited with terrestrial
digital,

Both terrestrial broadcast, as well as satellite uplinks are 6MHz wide
STANDARD channel slots and transponder slots. That was one of the rules
of the game back when all this started.

So, on "terrestrial", one can expect the best picture, as it is "single
channel per carrier" (SCPC), whereas a satellite uplink from a service
provider is going to be a "multiple channel per carrier" (MCPC)
implementation, in 99.9999% of the cases.

Artifacts are a product of bit error rate. If the bit error rate of
your reception in zero, you WILL get ALL of the data.

The other source of artifacts are pre transmission compression.

In the old MCPC setup, only 6 or 10 channels per carrier could be
pumped, and it was an MPEG-2 compression schema and a 480i schema.

Now, they put up to 12 channels per carrier (per transponder) into the
uplink for 24 or 64 channels per transponder total.

With HDTV, much more data per frame needs to be dealt with. FEC is
your friend.

 

[Spurious Response]

For the most part, however, I would agree with you
that this is not an issue with the satellite transmissions,

Bullshit. That is EXACTLY where the multiple channel per carrier thing
gets implemented.

In terrestrial schemes, it is only ONE channel per 6MHz wide carrier.

Your tuner may say that there are 3 PBS channels on the number 15, but
the actual frequencies of those channels are all on separate 6MHZ wide
slots with MAYBE only one which as actually on the channel 15 assigned
frequency.

 

[clifto]

US Digital. WalMart. Made by Hisense, model DB-2010. ($200) Broadcast
only, NOT capable of the cable format. Ready for a single antenna,
multi-channel subscriber reception planned for the future in some cities.

Thanks. I'll have to take a look.

Broadcast digital reception is flawless, and should be the standard...
Oooops... to late... It is!

HDTV sucks, at least the little I've seen. The artifacts are too distracting
for me to watch the picture. When you can get a camera to stand still while
focused on a still object, so the compression isn't blurring everything,
there's improvement in sharpness and no snow and, if you're lucky, a
minimum of aliasing. When you get off the still life and start watching
conventional programming, the picture goes to hell. I watched a bit of a
football game while sitting in a furniture store and got a headache from
seeing the crowd go into and out of focus.

Great reception with either a standard set top antenna or a
preamplified unit, not to mention a rooftop job.

Wouldn't do me any good. I couldn't get a permit for the fifty-foot tower
I couldn't afford to put up. Far too many buildings between me and the
transmitting antennas at Sears Tower.

 

[Eeyore]

Bullshit. That is EXACTLY where the multiple channel per carrier thing
gets implemented.

In terrestrial schemes, it is only ONE channel per 6MHz wide carrier.

Your tuner may say that there are 3 PBS channels on the number 15, but
the actual frequencies of those channels are all on separate 6MHZ wide
slots with MAYBE only one which as actually on the channel 15 assigned
frequency.

'Arfa' is in the UK. There is no 'PBS' here.

We do have the BBC though, although it's been degraded terribly in the last few
years on the cross of 'political correctness'.

Graham

 

[clifto]

SHOCK.... and AWE!

Aw, not so shocking.

 

[Spurious Response]

Make no mistake, I am not trying here to compare a good digital signal - say
Sky Movies Premiere - with a poor noisy anlogue signal. What I am saying is
that the general public is being 'sold a pup' with the digital terrestrial
channels, where even the best quality transmissions, struggle to produce a
picture subjectively as good as that produced on a *good* analogue TV with a
*good* analogue PAL signal going in.

You must be in a different multiverse location.

Satellite service gives you 300 plus channels by putting up to 12 6MHz
wide "channels" into each 6MHz wide slot.

http://www.tech-faq.com/mcpc.shtml

http://www.webopedia.com/TERM/M/MCPC.html

 

[Spurious Response]

Don't look to this newsgroup for factual info on lead free! Instead
look at actual test results in the trade publications such as SMT
magazine:
http://smt.pennnet.com/home.cfm
They have published numerous tests comparing various lead free
materials and processes with tin-lead. Some lead free materials and
processes are better than others (no surprise) and picking the best
one for your situation is non-trivial.

My nutshell summary of the published test results is that lead free is
significantly harder to do right than tin-lead, requiring tighter
process controls, but if done right it can be more reliable than
tin-lead for non-shock situations. Lead free is harder, stronger and
more brittle than tin-lead so tin-lead will deform plastically under
high shock when lead free will break, however lead free will withstand
more hot-cold cycles than before failure than tin-lead (better fatigue
resistance). So you need to know what the significant failure
mechanisms are in your design to pick the most reliable materials.

Glen

Another major issue is tin whiskers. We have hard evidence at
$WeBuildAvionics (where I am currently consluting) that the current Pb
Free / RoHS solder mixes have significant problems with growing
whiskers, leading to wonderful issues such as short circuits developing
under BGAs a few months after production. In a Flight control computer
(don't laugh - in a fly by wire environment it's the ONLY flight control
and virtually all late model airliners use it) this is Not a Good Thing
[tm].

The whole RoHS / Pb free thing is a political issue - the processes for
Pb Free use more hazardous substances than they get rid of.

Typical EU beauraucrats - unelected, overpaid and have to find something
to regulate to justify their existence. [1]

Cheers

PeteS

[1] Their existence, even from birth, might not be justifiable.

Damn. You actually made a post that I agree with 100%.

Seems one must fully encapsulate a finished assembly in transformer
varnish under vacuum to lock out the whisker growth.

Serviceability... right out the door.

Stink factor... worse than it was.

The whole fucking thing stinks.

 

[Spurious Response]

I get regular breakups on cable, on multiple channels, at all times of day;
picture plus sound, picture only, and sound only.

That is your fault for not calling them and complaining about your
obviously poor strength feed. That or the dopes actually think they can
send it out that way from the head end to everyone. That would be really
sad, and point toward the need for a class action suit. started at a town
meeting, and including the City Manager.

 

[Spurious Response]

The video reproduction is very reminiscent of the old 16-bit PC video
cards, especially in low-light scenes when it starts to look like the
video has about 16 brightness levels (four-bit video).

That is referred to as "posterization".

Remember posters that were of "photos" or "pictures", but could only
give you a 16 color palette? Distinct lines of separation to "create" a
gradient.