Hi All! Just want to "muddy the waters" a bit... How many of you that use metal squeegees, and pretty much have your stencil thickness down (as far as specifying thickness for a given pitch) have found that it is really "crucial" to measure your paste thickness? I for one, have found that when I spend the time and the money on equipment to measure paste thickness, when using metal squeegee blades, and having a solid set-up procedure, that I'm spending a bunch of time and money measuring things that are always good...meaning that time could be spent better elsewhere as long as you use metal squeegee blades, and have a good procedure in place ensures that the printer is set-up correctly..which is not rocket science... Am I over simplifying things? It's always worked for me since the advent of metal squeegees...I don't know how you can go wrong with a metal blade. Look at the gerbers you're given, see if they match the pad geometries, and then get the stencil made. Things are pretty straight forward after that... -Steve Gregory- > Howard, in the past, I was forced to use to use and invest in smaller, less > expensive systems (I've since been lucky to have nice EXPENSIVE > toys-teehee). One of my favorite tools has always been the benchtop > Cyberoptics unit. I don't remember the model name, I'm sure it's on their > website, or a price figure. But I do know it was cheaper than most systems. > The beauty of it is it shoots a laser at an angle, laser is viewable on > monitor and is deflected by paste height. You line up the reference lines > on the screen and get pretty true paste height. If your using 1:1 apertures > or if you're doing aperaure reductions, you can calculate your volume. > Hope I've helped. > > Jason Gregory > SCI Systems, Inc. > Software Specialist - NPI Group > (256)882-4107 x3728 > [log in to unmask] > > > >>> [log in to unmask] 07/31/01 11:49 AM >>> > Hi Howard, > > I've always found measuring solder paste volume to be very difficult. Yes, > numbers can be generated, but even taking large amounts of data doesn't > guarantee the correct impression. Generally, regardless of equipment used, > the best results one can hope for are for trends, which at best could be > described to be of the order of -1 or +1 from true. It's not a bad thing to > try but don't expect absolute results. > > Best regards, > > Andrew Hoggan > BBA Associates Ltd > www.bba-associates.ltd > -----Original Message----- > From: TechNet [mailto:[log in to unmask]]On Behalf Of Howard Watson > Sent: 31 July 2001 14:47 > To: [log in to unmask] > Subject: [TN] Solder Paste Measurements > > > > Dear Technetters, > > My question is: how do you measure solder paste height and volume > accurately? My situation is with using the VisionMaster Model 150A, I am > having trouble obtaining reasonably accurate measurements. The VisionMaster > is a small bench topsystem that uses a template consisting of a "region of > interest" (the solder paste), and reference regions (the areas on each side > of the pad). Because there are inconsistencies in the PCB (HASL finish), > like raised areas from traces, valleys surrounding the pad, and > irregularities in the solder mask, the readings I get cannot possibly be > true. Many times the measured readings for weighted average height are over > 7.5 mils using a 6 mil screen and 9.5 mils using an 8 mil screen. The > process specifics are Multicore NC-40 paste, shore 94-97 polyurethane > blades, DEK 265 Infinity, and correct squeegee pressures, print gap, etc.. > I believe the bricks are good, I just ca! n't use the measurements for SPC > as it shows the process to be out of control. > > In theory, polyurethane blades should "scoop" if anything, leaving a > shorter brick than the stencil thickness. It seems logical to me that the > best way to obtain accurate measurements would be to use the pad as a > reference region and measure the height from the pad, but the VisionMaster > system does not allow me to do this. Does anyone have knowledge or > recommendations on what I can do here? How do the more expensive systems > measure solder paste? Oh yea, spending $$ on new equipment is not a real > good option at this point! > > Thanks in advance for the assistance, > > Howard Watson > Manufacturing Engineer > AMETEK/Dixson