In a message dated 97-05-09 02:37:20 EDT, you write: << Could anyone explain to me what is the difference between screen coating and curtain coating? and also, I would like to know what is the difference between convection( batch and tunnel) oven and turbine ? if I extend tack dry time, while keep the same temperature setting at 170F, Would it be more chance to leave ink in the holes? I think the epoxy polymer only can be activated at much higher temperature 300F. What impact could have, if panels are over backed at final cure stage. Thank you all in advance! >> 1) Screen coating can be applied on specific areas and/or one can flood coat using 60 to 80 mesh screen and squeegee. The curtain coat is is pumped from a fountain and flows down an apron which spreads the coating over an area that is usually wider than the board. The excess is collected an reused as one does with screening. In the case of curtain coating, this process is easier to automate. 2) Convection batch and tunnel dry is usually associated with poor air distribution and dead spaces where coatings may not dry properly. the addition of turdry promotes extreme air flow which greatly assists removal of unwanted solvent that normally would be retained in the film. 3) Extending tack dry time at the same temperature could create a developing problem not only in the holes, but leave an invisible film on the copper areas that you want to develop off. This could/will cause a solder problem later. 4) Overbaking at the final cure stage should not hurt provided the board has been totally and correctly processed. *************************************************************************** * 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] * ***************************************************************************