Reliability of Lead-Free Electronics

[LTVibe]

As if we don't have enough to worry about! If you own any electronic item of any kind with the letters "RoHS" under a checkmark symbol on the packaging, this article will be a concern:

Within a whisker of failure

"The cause is becoming clearer. 'I believe the mechanism of whisker formation is now understood: it is due to compressive stress - caused by, say, diffusion of copper into the tin - being built up in the tin layer which breaks through the tin oxide barrier layer [to the air],' says Steve Jones of Circatex, in South Shields. Critics cite reports that solder substitutes - pure tin, tin-zinc, tin-silver-copper - simply cannot match the lead mixture for reliability, coverage ("wetting" terminals), and cost (silver is especially pricey). Therefore, the US military, Nasa and medical and high-level research equipment are exempt from what authorities view as untrustworthy commercial components."

 

[cosynthetics]

I'm still waiting to see the outcome of this. I work in the medical field and keep seeing part numbers changed for the RoHS.

 

[Pablo]

This is old news in my industry - but the drum beat of lead free continues. There are alternatives and if you choose the correct alloy for the situation you will be all right....but eutectic Sn-Pb (or even 60-40) remains the highest reliability. I know it's what is our satellites.

 

[Pablo]

Originally Posted By: cosynthetics
I'm still waiting to see the outcome of this. I work in the medical field and keep seeing part numbers changed for the RoHS.


Be EXTREMELY careful with some alloys! You don't want to be mixing Bismuth alloys with others, for example. This will create an extremely low mp .....

 

[Turk]

Pablo, do we have any more in common...?

I know Tin/Lead & Lead Free Soldering electronic components well.

63/37 Tin/Lead (Sn/Pb) or 62/36/2 where the 2 is Silver (Ag) is about the best. It reflows at 179 or 183 C. & wets well and is very compliant.

Lead free reflows at a higher temp, so you are exposing components to a higher temp that could induce failures.

Take away the Lead and all of a sudden components don't self-center on the pads - they stay put. If they're offset off the pads, that's the way they stay.

Tin whiskers is very well known.

SAC 305 (96%Tin/Silver/.05% Copper) is looking as one of the best alternatives to Tin/Lead.

The industry has been testing Lead free for a while now, but they are concerned with it. Some companies have "exemption" for a while and medical device companies are one of them.

What else would you all like to know?

 

[oilyriser]

My computer spontaneously powered down while reading the article, just after I scanned this part:

"The question is, are the products we are using now being affected by tin whiskers? When your computer stops working, could that be the cause? Certainly, some in the computer industry..."

 

[Colt45ws]

This is supposed to be why Xbox 360s give the RRoD. The solder holding the cpu to the board cracks with repeated thermal cycling.. Supposedly.

 

[Turk]

Solutions to that is Underfill if it's a BGA (Ball Grid Array) or Overfill if it's a TAB (Tape Automated Bonding) or other Gull Wing Device...

 

[Colt45ws]

It is BGA..

 

[Turk]

There's a lot to consider in BGA's & CTE's (co-efficient of thermal expansion). The body, the solder ball alloy, the substrate material and underfill.

X-RAY is the best method to find defects and micro-cracking.

I wonder if they do X-RAY? If not, they should...

 

[moribundman]

The cynic in me suggests buying a computer that's slapped together in China. It'll be full of lead solder. My iMac was made in Shanghai -- no whiskers!

 

[oilyriser]

Whiskers must be what makes old NiCd cells go short after a while.

 

[jsharp]

Originally Posted By: moribundman
The cynic in me suggests buying a computer that's slapped together in China. It'll be full of lead solder. My iMac was made in Shanghai -- no whiskers!

The Chinese bought billions of the RoHS and Lead Free stickers and they're slapping them on almost everything we buy now. As we know however, that has nothing to do with how they actually assemble the product.

We're still using conventional solder techniques here and waiting for it all to settle out. As one in the thread already mentioned, it looked like SAC 305 will ultimately get the nod.

In the mean time our customers prefer we run on the exemptions as we can and continue to make products that actually work long term.

Reliability is an issue when the product is the middle of an oil filed in the desert, or in a buoy in the north Atlantic...

 

[Turk]

jsharp,

Were you at APEX last week? I was there.

SAC 305 looks best so far. If you run both solder types, be very careful, run 2 seperate lines if possible as I'm sure you know...

Gee - we're only talking about Lead-Free, how about some Dendritic Growth??

 

[PandaBear]

Originally Posted By: oilyriser
My computer spontaneously powered down while reading the article, just after I scanned this part:

"The question is, are the products we are using now being affected by tin whiskers? When your computer stops working, could that be the cause? Certainly, some in the computer industry..."



Most likely due to [censored] Chinese capacitors rather than ROHS

 

[jsharp]

Originally Posted By: tpitcher
jsharp,

Were you at APEX last week? I was there.

SAC 305 looks best so far. If you run both solder types, be very careful, run 2 seperate lines if possible as I'm sure you know...

Gee - we're only talking about Lead-Free, how about some Dendritic Growth??

No APEX for me. Unless I'd have paid my own way. My boss is unhappy he's spent so much on new PCB layout tools in the last couple of years only to have me keep using my old software.

We run a conventional process in house for our through hole assembly and farm out all of the SMT assembly. We're just too small to purchase the equipment ourselves.

The same vendor that does our SMT work is all set up for SAC 305. So when ( if! ) we decide to change we'll just ship it to them. In the mean time we've cleared out all of the non-RoHS components we can so the chance of problems will be minimal.

We'll be running the old process for a long time though. A lot of the parts we use in older products aren't available as RoHS and will never be. So until those products finally die we'll keep building them the way we always have...

 

[Steve S]

Are people eating electronics?

 

[jsharp]

Originally Posted By: Steve S
Are people eating electronics?


No. The whole RoHS initiative is an example of people thinking "WE JUST NEED TO DO SOMETHING!!" even if it's not really required and is of no real significance. In this case it's driven my Europeans but it's the same mentality that got mercury batteries banned in the US.

The truth is in all of the exemptions. The the military, the auto industry, the aerospace industry, etc. All exempt. When they're all accounted for what's left is 5% of the total world lead and other element waste that we in the electronic industry generate.

The folks who generate 95% of the same waste get a pass...

 

[Pablo]

Very well said. People are so worried about losing freedoms and they are looking in one direction only....which IS a healthy concern....but it's the "do something" crowd that gets a pass! (and indeed have caused serious damage via "unintended consequences".)

 

[Shannow]

Lead paint, lead petrol lead solder in drinking wateretc. All were worthy of phasing out.

Lead free solder for electronics ?

Why ?

A joke.

I'm more worried about my smoke detectors in landfill than wanting lead free PCs.