Dear Steve: The only important difference I am aware of between sodium carbonate and potassium carbonate is related to the concentration at which they are employed. DuPont literature recommends a 1.0% by weight sodium carbonate solution for developing. Note that the molecular weight of sodium carbonate is 105.99 and the molecular weight of potassium carbonate is 138.21. The carbonate ion exhibits a molecular weight of 60.01 and therefore comprises a larger percentage of the total molecular weight of the sodium salt versus the potassium salt; hence a 1% by weight solution of sodium carbonate is STRONGER than a 1% by weight solution of potassium carbonate. For example: SODIUM CARBONATE 10 g/L x 1 mol Na2CO3/105.99g = 0.094 M CO3 POTASSIUM CARBONATE 10 g/L x 1 mol K2CO3/138.21g = 0.072 M CO3 Note: A 1% by weight solution is equivelent to 10 g/L. Keep in mind the g/L realtionship to % by weight is NOT LINEAR as the salt content increases in concentration (ex: 40% by weight K2CO3 = @540 g/L)!!! Keeping this in mind, it may be necessary to make corrections at make-up to operate at the desired concentration. It is also my understanding that sodium (Na+) and potassium (K+) are "spectators" and do not participate chemically in developing. We have performed numerous SEM sidewall studies on virtually all types of resists developed in both sodium and potassium carbonate. It has been our experience that the pH of the developing solution is the critical variable (within concentration ranges of 8-12 g/L) regardless of the salt employed. Please feel free to call me at 612-479-6525 if you have additional questions. Ted Stern Circuit Research Corp. Steve wrote: > > Besides solubility what are the differences between potassium and sodium > carbonate developing solutions for aqueous dry films. Does the potassium > ion play a role vs. Na? Interested in finding out diiferences, if any? > > Thanks *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************