BGA soldering and ground plane

Try etching away most of the outer layers, making them effectively a grid of pinholes (to the frequencies of interest). I suspect you should be easily able to remove 50% of the heat absorbing problem, without altering the shielding effects.

Are they leaving enough time for the heat to propagate through the "thermal mass" to the component side? Is there a problem in letting the components cook for a bit longer?

-- James

On Wed, 5 Nov 2008 15:09:23 -0800, CBFalconer wrote (in article ):

Are you forced to use ROHS? It stinks. Safety critical and aerospace systems are exempt -- tin whiskers and all that.

(Does elemental lead actually hurt anyone?)

-- Charlie Springer

Hi,

Use another manufacturer. I suppose he uses an old infrared reflow oven. For this setup, you get best results with vapor phase soldering. We often have such setups, and it is no problem.

best regards Thorsten Trenz

--

Much of ROHS is disproportionally strict, and it's implementation and integration has caused endless problems. But many of the restrictions are for good reasons (environmental protection, and human safety) - "lead-free" is only one aspect. It's the part that causes most trouble for manufacturers, but it is other ROHS-banned substances that are more poisonous. Also note that although elemental lead is not a danger (unless you *eat* old pcbs), it reacts with all sorts of other gunk in landfills, and seeps into the water table as compounds which *are* poisonous.

The real problem with ROHS (and similar initiatives in the far east and parts of the USA) was the implementation - the powers behind them had a naive and childish belief in the power of capitalism and "the market" to solve any problem given enough advance warning. If they'd done the research first, *then* made the rules, we'd have had a far more reliable and economic solution.

Yes. It affects mental development in children. Same reason it was removed from fuel and paint.

Peter

uhhh, those both had lead compounds - not elemental lead

Do you think elemental lead stays that way indefinitely?

Peter

And how does one measure mental development of children with any accuracy?

Even when you do find correlation between lead content of children and lack of mental development (which some but not all studies have found) how do you determine that the lead was causal and not that lack of mental development or more likely other factors which led to mis-measurement of mental development causes an increase in lead content of children?

Not exactly proof but try

Peter

Very little point in arguing with flat-earthers, tobacco company apologists, etc. As they do not understand epidemiology they are best left to their happy stubborness. Still, "lead epidemiology" in Google won't persuade them of anything (4.9M hits).

Pity Bush seemed to be the same, playing games with the planet's climate but at least had a financial motivation.

a) No, but AFAIK, pure lead is less toxic that the removed compounds. b) the original question was about 'elemental lead'.

That's true as far as it goes. I suppose Peter answered the question that *should* have been asked, rather than the one that *was* asked - he probably assumed that everyone knows that potentially hazardous waste in landfill dumps do not stay neatly packaged in elemental form for long.

Pure lead is not toxic - but only if it stays that way. It has traditionally been used for roofing without trouble. It has also been used for water pipes, and *does* cause problems - if there are corrosive impurities in the water supply, people end up drinking lead compounds.

Then he probably should have qualified his answer, somewhat. :-)

Not real likely. :-)

May get a little lead oxide in the ground. :-(

That's why cities that still have lead water pipes have to add chemicals to the water to force a coating on the pipes, IIRC what I have read.

More info:

Roman lead coffins are occasionally found, e.g.

Lead in water pipes is more of a problem if the water is very soft, apparently, but even then it's only a problem because all the water is in constant contact with the lead, directly before it is used for drinking. A few hundred pounds of solder joints in a landfill isn't going to hurt anybody, though it is a wicked waste of resources.

JS

Until acidic rain dissolves it and carries it into the ground water. May take a few years, but it will happen.

"acidic rain" = either the acid formed from sulpher emmissions from smoke stacks or the weak acid formed between water and CO2.

Or nitric (or is it "nitrous"?) acid formed from NO2 from car exhausts and lightning.

Of course, lead is just one of the substances banned or limited by ROHS that gets into the environment like this - some of the others are worse, although the quantities are lower in typical pcbs.

On Tue, 11 Nov 2008 06:23:53 -0800, David Brown wrote (in article ):

I have plenty of mercury and silver in my teeth - maybe that is my problem. I have plenty of mercury and silver in my teeth - maybe that is my problem, I have plenty of mercury... probably not. The amalgam is stable and any leaching of soluble compounds is minute and happens over 20 to 40 years.

We get lead from lead compounds in the ground. Who could be opposed to returning it to Mother Gaia? Modern land fills in the US have clay basins and clay caps. Someday they will be resource rich deposits of rare metals and hydrocarbons.

Since the tin whisker problems in aerospace applications I have tried to avoid ROHS (the labels are on practically everything now). What else of import is restricted? Tantalum caps I would assume. I never liked their failure modes.

I was thinking more of the new conditions under which people can solder and such. Since I spent about 50 years with a soldering iron, I'm not crazy about higher temp ROHS soldering and I'm not convinced of the benefits. How many car batteries wind up in land fills?

-- Charlie Springer

Thanks, I do not want to go down the path of removing or changing the ground plane, expensive as it will also involve emc retesting. I was beginning towonder whether solid ground plane on the outer layers of a PCB was good for EMC in principle but a manufacturing problem in practice.