On Feb 22, 8:34 pm, "Martin H. Eastburn"
wrote:
One of many issues is the thermal expansion of component and boards.
Most of the time it is close, but he tin-lead gave some stretch.
This lead free is harder and causes parts to come off.

I have to debug my weather station - the outside unit has several
TSSOP packages - small thin leads that Gull-wing out the sides.
These traditionally spring off the pcb in massive thermal ratios,
but across the country they are in failure mode and I suspect
the packages should have been BGA or SSOJ with the J lead that pretends
to be like a ball.

I went through a lot of engineering and stress testing - you should have
seen my oven - Hot & cold oven about the size of my office - walk in -
and put entire computers within - have them cycle up and down in all sorts
of temps - and see if any part starts to creep or spring up.

Martin

Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
TSRA, Endowed; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal.
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member.http://lufkinced.com/

wrote:
I'd like to know where he came up with that $280B figure.

I don't know, exactly, but in my assembly business, the time taken by
our assemblers to place a component on a circuit board using lead-free
pure tin solder is about twice as long as with tin/lead solder. So,
that may be where the amount came from. The machine placed components
using a paste of tin-silver-copper takes the same amount of time. The
pass through the convection oven is also about the same time.

The scary thing is what two of our customers reported in the last
couple of weeks. That is a perfectly soldered lead-free component,
soldered to a silver plated circuit board using tin-silver-copper
solder paste, popped off the circuit board, leaving a trace of copper
from the component where it had been soldered.

The actual lead-free plating on the copper component leads detached
from the component.

I have read that lead-free wave soldering will always begin to
dissolve the copper board trace into the molten solder. Same thing may
happen with lead-free solder paste and a convection oven when the time
of the paste being liquid is too long. I have not read about the
component tinning/plating also causing copper problems in the
component.

This happened on one component on one board out of many for two
different customers. Not the same component manufacture, either.

Paul

Thanks for the heads up on the possible thermal problems. We just
build them as the customer requires, but very few customers even knew
lead-free was required for export to Europe. So, they are still in
catch-up mode! When and if we can get in on the engineering phase of a
product, I will suggest we look at the larger component packaging to
see if the leads or pads will allow for movement caused by expansion/
contraction.

For the edification of the other posters, most, if not all, circuit
boards with surface mount components will have at least one hand-add
that is either surface mount or through-hole. Also, most current
production surface mount components are ONLY available lead-free. No
choices.

Thanks, Paul