Baked not fried chips.

[Ron Marcus]

I am just getting into reflow soldering the really fine pitched IC packages (like QLPs), and notice that a substantial amount of them need to be baked to drive off moisture prior to reflowing them. Has anyone dealt with this issue, and any tips?

Thanks,
Ron

[mister_e]

sounds weird to me.
What kind of machine are you using?
Wich temperature?
What kind of solder or are you using?
Lead-Free or not?

Usually, for smallest production AND when i was capable of, i did everything with my 2 hands, a solder pump, 0.062 solder, solder flux and, of course, isopropyl alcohol.

[Ron Marcus]

sounds weird to me.
What kind of machine are you using?
Wich temperature?
What kind of solder or are you using?
Lead-Free or not?

Usually, for smallest production AND when i was capable of, i did everything with my 2 hands, a solder pump, 0.062 solder, solder flux and, of course, isopropyl alcohol.

Ya know, I was that way too...Until I watched 40 plus parts (two QLPs with .5 mm lead spacing) solder and align themselves at the same time! And then...The thing worked!

I am using a Cuisinart digital convection oven, and it works fantastically. I have refrained from heating up the kid's Pop Tarts after using it with solder paste.
The Chipcon parts I am using are JEDEC class 3 for moisture susceptability.
I also want to use some large serial EEPROM memory in CASON8 packages, again with moisture warnings.

I have soldered a few with no problems, but I am having trouble with one. It seems that for the moisture sensitive ICs, they can actually explode from within, or fail from corrosion down the road. I am using lead solder at this time.

[mister_e]

how about using, even if i'm not a fan of it, some solder paste? I know Kester do some, but can't find the one i already used.. as now.

The Kester website may give some some great tips and info on that.

That's all i can say... sorry i've never met this kind of problem... as now

That's an interesting subject, i see some learning opportunuities here

[Bruce]

I was going to post this whole system on E-bay, but since there are a few people here looking for a surface mount soldering system, I'll give them first crack at it.

This is like new. I think it has a total of 10 hours total in use. We purchased a lot of other soldering tools shortly after this system, and we just don't need it any longer. It's in excellent shape, and I'll guarantee every peice of it.

ZT-1-CLS-MIL airbath, analog, 7.6 CFM Air Volume
ZT-2 AirPencil with variable temperature & air velocity w/5 stainless tips
ABC-1 adjustable board cradle, 3-rail
ZT-3-MIL AIRPICK with set of 4 esd safe suction cups

And a plastic smd bench top kit with 3 1/2 12g syringe's of no-clean solder paste, 4 smt stainless steel probe set, palm plunger, 2 metal + 47 plastic dispensing tips, 16 foot low melt desolder wire, anti-static foam swabs, 2 rolls of de-solder braid, and 2 jars no-clean flux.

I'll let the first person that contacts me have it for $500.00 flat. That's about what you would expect to pay for just the airbath & board cradle.

You can see it all here: http://www.zeph.com/directory.htm

This is a nice starter for someone just getting into surface mount assembly, and it's super easy to use.

[fanie]

Hi Ron,

I had such prblems a few times. The problem originates when the newly made PCB's are packaged while still having some moisture on them, in plastic. You'd tear the plastic off and when you dispense solder and place the components, during the soldering process the component like 1206 & smaller gets shot off the PCB - not all, but some. Looks real cool but very inconvenient seeing these fleas jumping off the board like their little feet are burning...

Solution was to bake / heat (+/- 50 - 70 deg thumb suck) the PCB's for a couple of minutes and then use the normal process.

What happens is the solder paste being almost like toothpaste traps tiny bits of water under it. When the water turns to steam it explodes as the solder becomes almost solid with heat and with the flux evaporating, so when the water pops the solder the component takes off.

[fanie]

Sorry, I forgot to mention.

We don't add solder paste for soldering those fine pitched jobbies, the solder being little balls (check with a microscope) cause shorts between the pins and you'll have to rework under a microscope. The PCB's we get come with the pads soldered (tinned) and is then cleaned with a hot air knife, so a tiny amount of solder is still left on each pad. To solder these use only flux on the footprint, be aware if you handle the chips by hand and the pins gets bent it's back to the microscope yet again.

[Bruce]

NOTE: The Zephyrtronics' hot-air soldering system I mentioned above has been sold.

[Ron Marcus]

Just an update... I've been using the new 16F690 in the (Yikes!) QFN (QLP)package. The convection oven works great, but I tried a technique someone may have posted here. I fluxed the board and IC pads, aligned it with a tweezer, and used a soldering iron with a relatively large ball of molten solder on it. Of course, the fine solder traces shorted with solder here and there as I moved the iron around the chip. When I was sure all pads and traces were coated with solder, I placed some very fine solder wick against the chip where the pads meet the PCB traces. I heated it with the solder iron, and low and behold, it pulled off all of the extra solder! I had the IC perfectly soldered in under a minute! If you haven't tried this technique, I highly reccomend it. I am actually looking forward to the next fine pitch surface mount build I have coming up.

Cheers,
Ron

[kallis]

it just taste better