Effects of moisture on CPLD

Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View
I have twenty Xilinx XC9572XL VQFP64. Their sealed package has been open two
months, and stored in an office with no temperature/humidity control. Now I
want to get these devices soldered in for a pre-production run.

If I put these in without carrying out a baking cycle am I asking for
trouble? What are the likely effects due to moisture, and what are people's
real-life experiences?

Many thanks,

Dave




Re: Effects of moisture on CPLD
Dave,

The packages may have absorbed moisture, and if you put them through a
normal solder wave machine, you will have popcorn.

The devices are prone to crack, and shatter due to the moisture turning
to steam, and having no where to go.

Parts may be baked before assembly to remove the water.
http://www.xilinx.com/bvdocs/whitepapers/wp192.pdf
details some of the procedures.

Austin

Dave Marsh wrote:
Quoted text here. Click to load it

Re: Effects of moisture on CPLD
Quoted text here. Click to load it
two
Now I
people's

Thanks Austin - It sounds like we we would definitely notice if there was a
problem then?! From the white paper it suggests a minimum of a 12 hour cycle
at 125degC is needed.

Dave




Re: Effects of moisture on CPLD
Dave,

Yes, you would notice a difference!  Not all parts will pop, and those
that do, may not even be noticed initially.  Later they will fail as
they will now absorb water like crazy from all of the cracks.

Austin

Dave Marsh wrote:

Quoted text here. Click to load it

Re: Effects of moisture on CPLD
Quoted text here. Click to load it
two
I
people's

Reflow soldering without baking them (probably 120 C for 24 hours) might
give problems. Hand soldering should be OK: I never have problems, anyway.

Leon
--
Leon Heller, G1HSM
http://www.geocities.com/leon_heller



Re: Effects of moisture on CPLD
Quoted text here. Click to load it
Now

Thanks Leon. That's interesting, as the first few are going to be hand
soldered (and I don't have a proper oven at the moment).

Dave






Re: Effects of moisture on CPLD
Quoted text here. Click to load it
open
anyway.

If you get a PCB assembly company to do the others, they should be able to
do the baking for you. They probably do it all the time.

Leon



Re: Effects of moisture on CPLD



Quoted text here. Click to load it
I also have been hand-soldering various Xilinx and other chips for years.
I've done Xilinx Spartan FPGAs in the PQ208 package without any problems,
and 9500 and Spartan parts in the PC84 also.

The chip never gets very hot in this process, maybe some local areas
around the
edge reach 100 C when I'm having trouble and clearing out some solder
bridges.  This is nowhere near the temperatures maintained when IR reflow
soldering boards full of these components.  Now, the lead-free stuff will
push these processes to even higher temperatures.

Jon


Re: Effects of moisture on CPLD
Quoted text here. Click to load it

I'm not so sure about that.  I bought a handful of microcontrollers
about a year ago and stuffed boards, and all was fine.  I never
resealed the bag (I don't have the facility) so they sat until I used
them a month ago.  I handsoldered one prototype and it failed in a
particular way.  After much gnashing of teeth (I hate shotgunning
parts), I removed the micro and replaced it with another from the same
bag, which worked.  I have since hand-built three more prototypes and
I've had a 50% fallout.  I guess I should've baked the parts...

-a

Re: Effects of moisture on CPLD
Quoted text here. Click to load it
anyway.

Thanks Andy. That's interesting - One of the assembly houses I've come
across on the web says the parts would need baking before they will hand
solder them . This seems to concur with your experiences.

Dave




Re: Effects of moisture on CPLD
Quoted text here. Click to load it

Perhaps one of those BlackNdecker toaster ovens will do the job since
they were mentioned awhile back as being useable for home based reflow
ovens in another thread on BGA pcb work.

regards

johnjakson_usa_com

Re: Effects of moisture on CPLD
Quoted text here. Click to load it

Yes, I was thinking about one of those too (just as long as they don't mind
running constantly for 24 or 48 hours.)

Dave



Re: Effects of moisture on CPLD
Quoted text here. Click to load it

I am sure any oven that will maintain the required temps will do.  But I
am not convinced that hand soldering without oven drying will cause
failures.  I have had many boards built by hand without any problems
that I can relate to moisture.  


--

Rick "rickman" Collins

snipped-for-privacy@XYarius.com
We've slightly trimmed the long signature. Click to see the full one.
Re: Effects of moisture on CPLD
I have real life experience with moisture effects with BGA parts, Bake them
at the recommended temp for the time specified on the bag, or yoiu will get
disconnected wires to the pins. I found that my assembler used parts stored
in an 'office environment' for several days, and *ALL* parts turned out to
have bad connections when the boards were done. The humidity issue is very
real, follow the directions on the bag, really.

A burned designer

Quoted text here. Click to load it
two
I
people's



Site Timeline