Order by: Relevancy | Date
Sep 6, 2002 | Peter, QC-calc: Verifying vision accuracy of your printer with calibration stencil and hundreds of repeats. If your boards are large and specially if you have finepitch parts on them you will find usefully to use QC-calc to measure board stretch/shrink.
Aug 30, 2002 | Search the fine SMTnet Archives to get started. We use 'glue' 'epoxy' 'adhesive' [without the ' of
Aug 6, 2002 | OK, I'll bite. How you can set a stencil down on a printed board and run a squeegee across it (even if it's a proflow head, it's still a squeegee, right?) without disturbing the printed paste?
Jun 20, 2002 | You're correct. It's a GREAT deal, especially when you match it up against those rip-off machines t
Jun 19, 2002 | The Seika SAWA is the thingy you're looking for. Go to
Jun 6, 2002 | but your stencils. AND IT WORKS.
Jun 6, 2002 | but your stencils. AND IT WORKS.
May 9, 2002 | I have no opinion on the accuracy and repeatability tolerances you should be looking for on the vision system and the actual alignment of the stencil. I expect Cp=2 from my printer.
May 7, 2002 | Almst quality of PCB with this pitch defined on used boards. Good board produses Fullmarks , look up to it , stencil parametrs isnt so critical but board material and layouts.
Apr 22, 2002 | Chances are your profile is fine. There is probably too much paste on the descrete pads. Consider reducing the aperture size of the stencil. Good luck.
Apr 12, 2002 | Equipment for laser cut stencil production Some suppliers of stencil cutting machines are: * Lumonics, 130 Lombard St, Oxnard, CA 93030 805.485.5559 fax3335 http://www.lumonics.com * Directed Light 633 River Oaks Pkwy San Jose, CA 95134 800-468-2326 408-321-8500 fax 8466 firstname.lastname@example.org A source of supplies is: Four Points PO Box 1530 North Falmouth, MA 02556-1530 508-563-9852 Fax: 5248 http://www.smtstencilsupply.com/ In order to make your own stencils, you either
Apr 12, 2002 | We use steel stencils. The adhesive manufacturer can give recommendations for squeegee type, material, pressure, etc. A lot of the tech data sheets include this information.
Apr 10, 2002 | How do you assure you "have squeegee pressure and speed controlled"? Search the fine SMTnet Archi
Apr 10, 2002 | I am curious how you measure your printed paste thickness. We are considering doing the same. As it
Apr 4, 2002 | What are the normal control limits in the industry, for a well controlled process, using a 6 mils stencil? Should they be different according to the surface finish (higher UCL for ENIG, Im SN, etc, lower UCL for HASL)? Thanks, Ioan
Apr 4, 2002 | Good points... Thanks everyone. ref back to Mr.Bob's/Dave's observation (not in order) on brick accuracy, position & placement, Stencil apperture geometrical opening, will feedback to my team to brain-storm further.
Apr 3, 2002 | Just one minor point to bear in mind, most stencils have tapered apertures. If you want to get really accurate volumes you will need to work put the volume based on the taper of the walls. Probably going to far but at least you can sound knowledgeable to the QA guy. Bob...
Mar 27, 2002 | Barry, If you are looking to set up a documented process with set parameters you might think about
Mar 20, 2002 | You based the aperture size on LxBxH. Where did you get the LxBxH? Obviously the thickness of the stencil is kinda fixed. Who gave you the other numbers? Consider searching the fine SMTnet archives for background on aperture design.
Feb 18, 2002 | what are advantages and disadvantages of the 2 type of printers against each other. And how to justi
Jan 28, 2002 | The product mentioned by SmartSonic (stencil cleaner maker) is from ScanCAD International. See http://www.scancad.com
Jan 16, 2002 | formula for calculating the necessary solder volumes for a given lead coplanarity: (Wp/W) x d x Hs x f(sh) = finished solder height Wp = Solder paste stencil width W = PCB solder pad width d = Stencil thickness Hs = Volume fraction of solder in paste ( Hs is about 55% with 90% solder metal) f(sh) = Shape 75% of the finished solder height, on the copper land provides a condition for stable and robust processing" will show how much non-coplanarity your process can handle. For a .020" pitch QFP, which uses a PCB solder pad width of .012", stencil width of .011", and stencil thickness of .006
Nov 20, 2001 | Dave, How do you try to contol the glue release? The information we've gathered so far indicates that this is controlled by the speed and distance of stencil separation. How do your defect levels compare to dispensed products? Thanks again, John S
Nov 19, 2001 | Printing paste with an �approx. 3mm (3000um) thick� stencil!!! Shirley, you jest!!! Please help us understand this better.
Nov 15, 2001 | Re: Avoiding Blood letting on stencil printer
Nov 12, 2001 | the growth (or shrinkage) it will have. Stretch also depends on the board house capabilities and controls and board thickness. The best way to minimize stretch effect is to group components that require tight tolerance into the central location of the PCB. Other contributing factors are: * Stencil stretch : 0.001" per inch for chem etched stencils was the best we could get a few years back. * PCB warpage: Contributes to the problem. * PCB solderability protection: The thermal gradients seen in the HASL process contribute to both warpage and stretch. If using a HASL finish, consider OSP or ENIG finish. * Screen print: Vision system on the printers? Optical alignment of stencil pattern (round half-etched fiducials on the bottom side of the stencil seems to work well) to board pattern is crucial. Of course foil thickness, aperture design, and squeegee material all play a role.
Oct 26, 2001 | get a misprint is when someone has let the paste level get too low. I would suggest setting up the inspection for the board only (not stencil and board). This speeds things up quite a bit and still catches any problems. One other nice point: Chase rails are adjustable for various size stencil frames . If you have old stencils for other machines, chances are you can still use them (you may have to add bottom side fiducials if the old stencils were for a top camera machine). Programming is a breeze. Lots of features are basically automatic to set up - touch a button on the screen, and that's it. I don
Oct 25, 2001 | I am about to purchase an automatic stencil printer. We have it narrowed it down to DEK. Can anyone tell me their appreciation of the DEK288. Our choice up to this point is a simple 265lt. Thanks
Oct 15, 2001 | rheopump, but if you plan a stepped stencil consider putting the steps on the board side of the stencil when using it. A metal squeegee is fine, step up or step down, either side. We used to do a lot of stepping, but do none now, because we understand stencil design [ie, area & aspect ratios] better . Two places to look for more information are: * IPC-7525, "Stencil Design Guidelines" gives good guidelines for keep-outs around steps, but only briefly touches on CCGA. * IPC-7095, "Design & Assembly Process Implementation for BGA's" give more information on printing paste for CCGA. � but since you
Oct 11, 2001 | . Therefore I can't say that the flux application is controlled very well. The BGA is actually 1 mm pitch, sorry. Balls are .024D and the pads on the pcb are .0157. We tried one stencil, 5 mil thick with .016 aps. After consulting with the stencil house yesterday, we are ordering a 4 mil stencil with 3 destructive profile. Now, they are giving us a couple of 3 pcb panels and 3 parts. once we get the stencil we will drill holes in the pb and bring 2 thermocouples up under each BGA on each PCB. We use a CircuitMaster Designs profiler with 6 thermocouples. Typical profiles we run have temp ramp rates of 1
Oct 10, 2001 | blocking off stencil apertures with tape Stephen, I don't understand this at all mate. 1. If you don't place a QFP and get bridging across the bare pads, you were gonna get absolutely horrendous bridging if you did put one down. That points to poor printer set up or stencil design or both or whatever. 2. I reckon non - populated ares without solder paste would look very strange. However I can see their point if you are using non HASL finishes. The non-pop areas stand out and any area with solder and no component is a fault. This seems rife with danger to me. What happens if you mistape the stencil and go merrily on your way? Ah, we
Oct 10, 2001 | What the heck are you doing having scotch tape in the plant? Isn't there a concern for ESD safety? B
Sep 17, 2001 | Please describe what was found to be optimal print parameters. I am also interested in hearing about stencil and design layout considerations. Thanks, Kevin
Sep 14, 2001 | please check the following also. in one of the cases we came across the second point was the problem. 1. the parallelisum of the conveyor. 2. the warpage of the board. 3. the stencil.(the differential height in the paste deposition of the two pads may also be cause)
Sep 6, 2001 | I may be wrong, but I'm thinking that nitrogen has less effect on solder bridging as does the amount of solder that is present. Nitrogen allows better wetting becasue there are no oxidation effects. If you have solder bridging problems, look at the size of the stencil apertures
Aug 27, 2001 | Hello there! Is there someone out there that knows of the name name of the company that was former named Conergo? Or even better if someone knows of a webaddress. They are making stencils for screenprinters. Could someone please help me? Best regards, Mattias Wennberg
Aug 3, 2001 | I have paste left on my stencil on the forward stroke. I adjusted the downstop pressure but it didn't help. Any suggestions.
Aug 3, 2001 | change of stencil fabrication, by having the problematic PCB pads, changed from one-opening Stencil, into twin-opening Stencil, and pls still retain the orginal, stencil opening area, of the respective problematic aperature.... Basic thing to do though, before you thrash into the bushes, with the above
Aug 1, 2001 | please look at trying lazer cut stencils. They have trapozoidal shaped apertures and this could assist with the paste releasing onto y the PCB
Jul 30, 2001 | by incorporating a step stencil. I have > successfully used 6 mil stencils for much larger > components for quite some time. Are you sure you > want to go that expense for a new stencil? There > are many parameters that affect the solderability > of the part. > > What steps have you followed in > your investigation that leads you to believe you > must increase the stencil thickness? > > Have you > considered other factors? Are you getting good > wetting on the part and the pads? Are the parts > getting knoked off by some other process? What > quality
Jul 13, 2001 | One of our board vendors recently switched their stencil design to home plate apertures. Since the change the quality and yield of their PCB's has went south, Could this process change be the cause?
Jun 13, 2001 | What kind of quality improvements could be expected by implementing MPM's Rheopump instead of using squeegee blades on a stencil printer?
May 5, 2001 | yeah, we use the low static stuff too... except when the purchasing assistant did the company a "fav
May 4, 2001 | I recognized the spoof. Where the heck does he find those links anyway? We only use the low stati
May 4, 2001 | Kapton tape is anti-static, that's why we use it so much in this industry. If you are seeing yellow
Apr 23, 2001 | Carri-all and Metro (materials handling) offer some very good solutions, at reasonable prices. Thes
Apr 18, 2001 | I would like input from anyone interested in a SMT Production Work Cart. What features should be included in such a system? I have been asked to spec one out from our machine shop. Are portable SMT workbenches out there with stencil storage? Thanks,
Apr 9, 2001 | We have some very nice cabinets for storage of our frames from Aerofeed. Mar 29, 2001 | Rob,
How does your chemistry stack up against the 440R? I see you mentioned ease of maintenance as
Mar 29, 2001 | Rob, How does your chemistry stack up against the 440R? I see you mentioned ease of maintenance as
Mar 27, 2001 | Nothing against Smart Sonic I just want to see what others are using and why. I have heard their che
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