Reflow soldering before xx hours of factory conditions

Other Hardware General Electronics
1

Hello all,

I have a sealed bag of 5 smd atmega mcu's. The warning label on the outside of it states that after opening the bag, I must subject the units to reflow soldering within xx hours.

I would much like to start by reflow soldering just one of them, to check and test my design before committing to solder the rest... Is there some way I can store the rest of'em, maintaining their 'reflow solderability'?

Thanks a lot in advance.

2

Do you know how they have been tinned ?
Chemical or hot ?

3

That's probably just for moisture control. If you seal up the rest in a airtight container with some dessicant pouches, you should be OK.

4

pwillard:
That's probably just for moisture control.

Yep.

5

If they have been chemically tinned, sealed or unsealed, normal recommendation is to solder within 6 - 12 months.

Edit
Apologies , I thought you were referring to pcb,s.

6

Just thought of something. Would pre-baking the parts (w/o solder -- just heated in the oven) work to remove moisture and... uh.. "freshen them up" for use?

7

So long as they are not actually wet the normal reflow profile should be all that is needed.

8

The reason for bakeout is to remove humidity from the epoxy so that the parts do not popcorn during reflow.

SirNickity:
Just thought of something. Would pre-baking the parts (w/o solder -- just heated in the oven) work to remove moisture and... uh.. "freshen them up" for use?

Yes. Baking is common for parts which have been exposed to humidity. J-STD-033 has bakeout times and temperatures for various parts.

9

I sometimes wonder about that when I see Maplins picking out of plastic drawers.
Only problem I have had is solder ability though.
Out of curiosity were those chips all in the same metal coated pouch ?

10

SirNickity:
Just thought of something. Would pre-baking the parts (w/o solder -- just heated in the oven) work to remove moisture and... uh.. "freshen them up" for use?

That's what digikey suggests on their moisture-sensitive device packaging. If the device has been exposed to too much humidity, they suggest baking at 120 - 130C for 48 hours.

11

JoshD:
That's what digikey suggests on their moisture-sensitive device packaging. If the device has been exposed to too much humidity, they suggest baking at 120 - 130C for 48 hours.

This is not the case for all components. It depends on a number of factors.

Digikey is a distributor, not a device manufacturer. I'd stick to the info agreed by the people who make the parts, not sell them.