Phil Zarrow: Brook, we've discussed handling solder paste from the refrigerator to the stencil printer, but there's a lot more to this story, particularly from the factory to the customer.
Brook Sandy-Smith: Right, when we talk about shelf life, we're usually talking about refrigerated shelf life. So, once your paste is in the refrigerator, how long can it sit there before you use it? But, a lot of times when we talk about that, we say storage less than 10°C, but there is this one little window, in the life of a jar of solder paste, where it's not at less than 10°C, and that's during shipping. So, when we prepare solder paste to be shipped out of our facility, we freeze it and we package up in a cooler with some ice packs, with the expectation that in the three to four days it usually takes for a package to be delivered, that the contents will never see ambient temperature.
Phil Zarrow: Right, now you're expecting three to four days, which is very reasonable, but there can be delays-customs; it could be shipped out on plane where upstairs the flight crew is having an altercation with a passenger, and the flight's going to be delayed-we know what happens… So, what's the impact on the solder paste?
Brook Sandy-Smith: So, when you receive a package of solder paste, and you're not sure what happened to it, but you know that it wasn't either delivered in three or four days, or it's especially hot where you're receiving the solder paste. If something unexpected happens, first, call us. We'll talk through the material that you're using, and the way it was shipped, and how many days you think it was exposed to temperature. We can also arrange to include temperature strips in the packaging, so that in future shipments you can tell whether or not the contents of the package reached a certain temperature. And then. further than that, you can look at the solder paste.
Phil Zarrow: Right, what are some of the symptoms that we're looking for?
Brook Sandy-Smith: Yeah, if you see solder paste with really excessive flux separation, that you can't stir back in, that's a big red flag. If you see any crusty parts, that's a red flag. Or, sometimes there can be like a skin that forms on the surface, kind of like if you leave pudding out-
Phil Zarrow: Right.
Brook Sandy-Smith: Exposed to air, it gets a little skin. And that would also be a red flag. Call Indium. See what I should do with this solder paste.
Phil Zarrow: Yeah, it all sounds very disgusting, so I think I'd resort to calling you guys too. Help! Help me out on this. Where can we find out more information on solder paste handling in general, Brook?
Brook Sandy-Smith: Well, you know we've talked about best practices for solder paste handling. You could also check out our application note on solder paste storage and handling guidelines, or I recently wrote a paper on what happens to solder paste in worst case shipping scenarios, which you can find on our website. Or, of course, you can just contact me directly at email@example.com.