Recently, a customer using solder spheres in a semi-automatic BGA solder ball placement machine asked if it was ok to leave these solder spheres for several days in the tray, or they should be removed and placed back in the jar after the production cycle was complete.
The reason the customer asked this question was because our solder spheres come packed in Nitrogen (N2), which keeps them from oxidizing. The oxidation procedure is not instantaneous but builds up after a long time, ultimately making the solder joints less reliable. By keeping them in N2, the solder balls can be kept for a long time (minimum shelf-life of Nitrogen-stored solder spheres is 1 year) in ambient or room temperature without the need for special treatment before use. However the time that it takes to build up an oxidation layer that is thick enough to affect the solder joint reliability is quite long, think in terms of months, not hours, days or weeks. Therefore our answer was that it was not necessary to take the solder balls from the trays after a production run, and then can leave the solder spheres on the trays for several days without fear of oxidation affecting joint reliability.
Putting the solder spheres back into the jars would be pointless anyway as they arrive sealed with a layer of N2, and to simply put them back in the jar with the lid on does nothing to prevent oxidation. On the other hand, CAPLINQ realizes that smaller customers prefer smaller package sizes, and recently introduced a new packaging of 250,000 spheres per jar instead of our previous 1 million spheres per jar. This allows customers to keep packages sealed before they need them.
For more information about Tin/Lead (Sn63Pb37) or Leadfree (SAC305, SAC387 or SAC405) solder spheres or any other of our products, visit us or contact us for more details.