Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Joe

#12799

Moisture Sensitivity and Package Cracking | 25 January, 1999

Greetings,

We are discussing what should and what should not be baked and vacuum packed. Should we just concentrate on the fine pitch packages and the bga's? What about those components which come on blister tape, should they get baked and re-packed? We are a subcontractor and are running different boards constantly on our lines, if I had to follow every rule on each MS component marking I would'nt be doing anything else than baking and vacuum packing. Can anyone help?

Where can I find the standards behind all this moisture sensative handling process?.

Thank you

reply »

Dave F

#12800

Re: Moisture Sensitivity and Package Cracking | 25 January, 1999

| Greetings, | | We are discussing what should and what should not be baked and vacuum packed. Should we just concentrate on the fine pitch packages and the bga's? | What about those components which come on blister tape, should they get baked and re-packed? | We are a subcontractor and are running different boards constantly on our lines, if I had to follow every rule on each MS component marking I would'nt be doing anything else than baking and vacuum packing. Can anyone help? | | Where can I find the standards behind all this moisture sensative handling process?. | | Thank you | Joe: We/ve had problems with tantalum caps, in addition to the devices you mentioned. Plastic parts take-on moisture. Check out J-STD-0331, Packaging and Handling of Moisture Sensitive Non-Hermetic Solid State Surface Mount Devices - Chair, Steve Martell, Sonoscan in the link below

TTYL

Dave F

reply »

Chris Fontaine

#12801

Re: Moisture Sensitivity and Package Cracking | 1 February, 1999

All of our moisture sensitive components are shipped to us in vacuum sealed, desiccated bags with a moisture indicator. When the parts are removed from the bag (this is done at either SMT setup, or in the stockroom) the indicator is checked. If it is within spec than the parts are processed, if it is not the parts are either returned to the vendor, or baked. In either case, the vendor is notified of the shortfall. After the bags are opened the parts are stored along with the indicator in either a dry box, of a new vacuum sealed, desiccated bag.

Here at Sanders a majority of our parts are of the non-moisture sensitive military style ceramic type, however we have a growing number of commercial type plastic parts. It is my understanding that moisture enters the component through the lead seals, and not the body itself. I am not an expert on package design, however I would expect that most plastic bodied parts would be "moisture sensitive" candidates.

As for a solution to your moisture sensitive dilemma, I recommend working with your suppliers to receive properly sealed, desiccated, and indicated parts. Process the parts assuming they are moisture sensitive, and view the baking as a rework procedure. If you are doing a lot of baking, than there is a shortfall in your handling/stocking process.

Chris Fontaine Manufacturing Engineer, Circuit Card Assembly Sanders, a Lockheed Martin Co.

reply »

justin.medernach@flextronics.com

#12802

Re: Moisture Sensitivity and Package Cracking | 2 February, 1999

| Greetings, | | We are discussing what should and what should not be baked and vacuum packed. Should we just concentrate on the fine pitch packages and the bga's? | What about those components which come on blister tape, should they get baked and re-packed? | We are a subcontractor and are running different boards constantly on our lines, if I had to follow every rule on each MS component marking I would'nt be doing anything else than baking and vacuum packing. Can anyone help? | | Where can I find the standards behind all this moisture sensative handling process?. | | Thank you | First of all, never accept moisture sensitive material in tape and reel. You're a CM, you're building, lay that rule down and make sure it is followed. Otherwise, you're looking at some serious problems, especially if this is a consigned kit. Who knows how long the customer had the reel sitting out in some unfriendly condition. Focus on the vendors. That's how MSDs must always be handled. It's not a package thing. Saying that all QFPs must be baked or all BGAs must be baked, will land you in the toilet. There will just be too many jobs put off because of baking. Check Jedec standard JESD22-A112-A for the levels of moisture sensitivity. Follow the table for exposure times and bakeout procedures. Also, Terra-Universal sells dessicant cabinets for component storage. these things are pretty short money and worth their weight in gold. They only consume about 1 5028 cuft. cylinder of liquid N2 a month.

Regards, Justin Medernach

Regards, Justin Medernach

reply »

Lead Free Wave Solder - 1 Click SMT

SMT equipment