In the early thick film days, resistors were designed using one mil squares and often ended up in a variety of shapes as serpentine, or? In those days, we used air abraiding techniques (sand blasting) to "trim" the resistors to the correct value after the resistor ink was screened and cured on the substrate. Much depended on the thermal coefficient of expansion of the ink after cure and after being subjected to many tests. Not much has changed in the process, from design through acceptance, but for markedly improved inks that are much more stable, and the laser trimming process. Where this applies in some PCB designs is when using resistive inner layers as "Omega" ply types. In some instances the same concept is used to trim the resistors to their intended value and required tolerances. MoonMan --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------