The letter below was dated December 13, 2006 from Kester's Senior Market Development Engineer. I guess since then they have moved production back to Mexico. We no longer use EM907 as our primary Pb-free paste so I haven't seen any containers in a while.
Prior to this issue we experienced with the paste turning into a brick, we had had an issue with its viscosity being too low. The print would bridge on fine-pitch components because it was being squeezed out between the foil and PCB. ----------------------------------------------------- ----------------------------------------------------- Gentlemen,
Kester recently experienced an issue with lots of EM907 made with a now known bad lot of a rheological agent. This raw material is a thickener that helps in areas of slump resistance and print definition. As with most raw materials in no-clean solder paste flux, outside of rosins/resins, this thickener sublimes as heated and is not present in anyway in post soldering flux residues.
The issue with the lot of thickener is that it experienced a very limited shelf life and hardened in a short period of time. Any issues experienced with the troubled lots would be purely on the print side of the process and will not affect the solder joint integrity or long-term reliability.
A recall of the lots in question was performed but unfortunately some of the material fell through the cracks. Kester apologizes for the mix up and we are doing all that we can to make sure that the issue will not happen again. Additional incoming QC checks have been implemented to ensure that the thickener is within specification limits. Full production of EM907 has also been transitioned back to our US facility.
I hope this is the information that you were looking for. Please let me know if you have additional questions or comments. -------------------------------------------------------- --------------------------------------------------------
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