Is melamine more abrasive than e-glass? Actually, I have not found any difference, in terms of front taper/margin land wear, between aluminum clad entry/backer vs. melamine clad entry/backer. Whereas, with a spec limit of .003" TPR, in a 3 high stack of .062" and using a .0145" tool at 2000 hits, we saw CpK values for top panel accuracy of .99 and 1.03 for aluminum clad and melamine products, respectively. CpK's for bottom panel accuracy were, .76 and .85. (These findings were substantiated in a study previously conducted by a lEading drill mach. manf.) I'm not sure that enough holes were measured to capture the effect of alum. galled on the point of the tools... But, that's something else to consider. These two materials were the better performers in a group of 8 different products studied. So, I too, would be interested to know more details of how these CpK values were derived. ______________________________ Reply Separator _________________________________ Subject: RE: FAB: Drill Wander Author: [log in to unmask] at INTERNET Date: 05/08/97 2:16 Mark, I was reading your response and become curious about the stated CpK = values. What was the true position used to calculate the CpK and what = type of drill machine were used? Ed Cosper Graphic Electronics =20 ---------- From: Mark R Ford[SMTP:[log in to unmask]] Sent: Thursday, May 08, 1997 6:03 PM To: [log in to unmask] Subject: Re: FAB: Drill Wander In response to drilbert's drill wander reply: Having worked with the largest PCB manufacture in the US for 6 years, I tend to use them as a "barometer" for what does and does not work effectively in producing printed circuits. I have a great deal of confidence in the Cpk values for DTP using an aluminum clad entries (Cpk: 1.80 to 3.50). I would be very interested in what kind of Cpk values you achieve with melamine cladded entries over 2500 hits with a #80 in a three high .062" 6 layer board with 1.0 oz inners. My biggest concern with using melamine entry is abrasion. melamine is one tough customer to drill (that's why we like to use it for counter tops in our kitchens). Regardless of whose tools you use, they tend to abraid faster and, more importantly, farther down the margin of the tool creating a detrimental front taper condition. This equates to reduced hit counts, more stock removal at repoint, fewer repoints and ultimately, higher drilling cost. However, the entry that I originally spoke of was solid phenolic or melamine (.008 to .024 thick) which are being used by some PCB manufactures. And lastly, not to beat this subject to death, penetrating a "hard entry quickly" can be misinterpreted as utilizing unconventional chip loads.=20 There are tool geometries available that allow for extremely "high" chip loads but, this does in fact cause drill wander - no if's, and's, or but's. If the goal is to reduce drill wander, chip loads have to be carefully scrutinized to assure that you are not penetrating the work piece too rapidly. =20 *************************************************************************= ** * 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] = * *************************************************************************= ** *************************************************************************** * 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] * *************************************************************************** *************************************************************************** * 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] * ***************************************************************************