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Aug 13, 2019 | Hi , Thanks for the reply. Yes CCGA was checked before placement and sending to reflow oven. The
Aug 7, 2019 | Hi I am having trouble getting solder bridges on TQFP-100 (0.5mm pitch) components. The boards are pasted on semi-auto printer using laser-cut 0.12mm stencil and SN63 NC257-2 T4 paste. The components are placed using Samsung CP40LV and tghen reflowed in Heller 1707 EXL oven. Thanks
Aug 2, 2019 | I don't get it. The liquidus of 80Pb/20Sn is like 280*C. Your reflow temperature got nowhere near th
Jul 30, 2019 | thanks dave .. I have one more query on the same CCGA. What are the chances of the CCGA lead get
Jul 4, 2019 | ://www.asahitec.in/inspection-templates.html BeamOn - http://www.beamon.com/inspection-overlay.php I-Source - http://www.i-source.com/smt-stencils -tooling-parts/#inspection Guessing --- Stencil fabs => Inspection templates
May 20, 2019 | Step-up stencil: recommendation thickness not connected to our PCB. Therefore, we would like to use a step-up stencil at 0.12mm everywhere (for the QFN) and at a higher thickness for this BGA module. This table is useful: https://www.7pcb.com/blog/stencil-thickness-calculations.php I was thinking about 0.16mm for the step-up. What's the maximum
May 9, 2019 | Hi, You can work on improving stencil design, having the perfect profile and other process improvements but it may be the paste itself letting you down. We have put a lot of work into developing our solder pastes to significantly reduce voiding. Your supplier should be able to help with choosing
May 6, 2019 | Hello! Do you have a better stencil design to reduce the large area of solder joint voids? Or is there a suggested way to set the reflow profile? Or are there other process improvements to make the solder joint at the LED pad less than 10% per void? Thanks a lot.
Apr 30, 2019 | QFN/BTC Pad Configuration Commonality for Solder Stencils . On the Pick and place side I name all the footprints using the device manufacturers names, generic QFN20 type names are simply not helpful. The best advice I can offer is when you encounter a new shape and get a stencil for it, you keep its vitals on a list somewhere, pitch, pins, pin width, pin length case size etc. the you can at least look that up before ordering an identical stencil to one you already have.
Dec 27, 2018 | Hi Prem, it will really help if you provide more pictures and metrics. Pad layout, part datasheet, stencil design and most of all picture of the misplaced part on the board. This looks like a very interesting case and I am willing to help you, but the facts that you provide are insufficient. Help
Oct 4, 2018 | 1. From your explanation it looks like you need more flux. Try to overprint a little or use 150um thick stencil 2. You should consider a little different profile - probably try to have a soak zone in the right alloy and flux range and give the part time to evenly preheat let the volatiles escape
Sep 15, 2018 | My second assembly order on ALLPCB.com is ready to finish soon. I need to provide HS CODE for the custom clearance process this time due to the large amount. Anyone knows the code for this ? At present, I know the ones for 1-2 layer should be 85340090, and for stencil it is 8479909090 And how about
Sep 19, 2017 | that was that we got a little too much paste in another location (if we had auto SPI I suspect we'd be seeing better than 100% TE) but we think we've solved that problem with a reduction in blade pressure. The next step will be to try a finer grained stencil w/o the coating to see if we can get around adding a day to stencil lead time and concerning ourselves with stencil washer detergent concentration more than we'd like to.
Mar 6, 2014 | Stencil, Electroformed * AGI, 177 Nick Fitcheard Rd, Huntsville, AL 35806; 256-858-3300 F256-858-3304 agicorp.com * ALPHA® Form™ alpha.alent.com * Chepaume Industries, 6001 Airport Road, Oriskany, New York 13424; 315-768-7001 F315-768-0270 Stencil, Colorado Springs, CO; photostencil.com Rachel Miller-Short, Global VP of Sales email@example.com 719-304-4224 * Stencils
Aug 11, 2011 | Franx: In response to your follow-up questions ... For the case 1: Q1: Should I apply the glue to the PCB with the same method as I apply solder paste? (with screen printer and squeegee). A1: Correct. Glue can be stencil printed, dispensed, or pin transferred. Q2: If so, I would guess that the stencil should be different from the stencil for solder paste in terms of the location and size of the holes for each component? A2: Correct. Generally, glue is applied at or in a pattern near the centroid of the component. For case 2: 'Q3': I think it cannot be applied to our case. Our board is all SMD
Nov 13, 2009 | machines are not suitable for stencil application, because they are not flexible and cannot provide the print/print mode. Only the print/print mode can be used with stencils, because the holes are completely open and it is necessary to prevent the paste from oozing out of the holes and dripping onto the substrate surface. For screens, the flood/print mode is used. Naturally, equipment is more desirable if it can function in various modes and can be used for both stencils and screens." [Surface mount technology: principles and practice, RP Prasad, Springer, 2nd edition, 1997] [snip] That aside, your issue
Sep 19, 2008 | Large Area Stencil Printing Four Points supplies materials to stencil fabricators. Four Points, SMT Stencil Supply: Standard Frame Sizes 8" x 10" I.D. Cast Aluminum 12" x 12" I.D. Cast Aluminum 15" x 15" I.D. Cast Aluminum 12" x 17" I.D. Cast Aluminum 15" x 15" I.D. Cast Aluminum 20" x 20" I.D. Cast Aluminum 24" x 24" I
Sep 16, 2008 | Stencil Design Here are some guidelines that you can go by: http://smt.pennnet.com/display_article/260261/35/ARTCL/none/none/1/Choosing-a-Stencil/
Feb 13, 2008 | Stencil Design Question , but soldermask seperates the ground plane from the rest of the PCB. I hope thats clear... We've been asked to try and print solder paste over this ground plane area so that it is completely covered after reflow. We are also using lead free paste. My question is regarding the stencil design. Does anyone have any ideas about how to design the apertures so that we can have sufficient paste depoist while providing complete reflow coverage and without severely weakening the stencil? Also, I understand that lead free paste does not really "move" during reflow, so i'm wondering if anyone thinks this is even
Nov 12, 2006 | One printer 2 smt lines = No problem, but then you will need 2 ovens. It is even sometimes a more valuable cost savings depending on what production you are into. At first the stencil printer with a divertion conveyor, then straight ahead into the 1 assy line, meanwhile you are setting up the next job in the second line or the secondary side of the product. A fast stencil printer will keep up with the production in 2 lines (assuming that you are not producing cell phones or simular). The drawback is that you need 2 ovens. We have this scenario with the DEK stencil printer and 2 smt
Oct 31, 2006 | SWAG is prolly right. You can verify the tactile sensor by watching the machine carefully. When finding the stencil height, make sure the board goes all the way up and touches the stencil to trigger the tactile. If it doesn't, then something is wrong. Also when leveling squeegees, each squeegee should touch your stencil twice. If they don not come all the way down check the tactile. You can open your I/O screen the verify the switch is not sticky or clitchy (high tech NASA terms). Software wise, make sure you programmed the right thickness board. I seriously doubt this, but may be worth
Mar 28, 2006 | not comprimise signal connections. Thermal via design - A grid of 1.0mm to 1.2mm pitch thermal vias that connect to a copper plane. The vias should be about 0.3mm to 0.33mm in diameter, with the barrel plated to about 1.0 ounce copper. Stencil design for pads - Select apertures for the pads to be 50 to 80 perecent of the size of the lead pad on the board. Here's an example: Part Type||Pitch||Aperture Width ||Aperture Length||Thickness range||Aspect Ratio Range||Area Ratio Range QFP||0.50mm (20thou)||0.22-0.25mm (9-10thou)||1.2mm (47.2thou)||0.125-0.15mm (4.92-5.91thou)||1.7-2.0||0.69-0.83 Stencil design for thermal pads - Use multiple small stencil openings [maybe 15 thou square], where total area approximately 50% of total thermal pad on the board.
Mar 26, 2006 | Hi We are running automatic stencil printers, open squeegees, stainless stencil, stainless blades, print speed 25-30mm/sec. We have a frustrating consistency issue printing .37x.3mm apertures on a 45pin LGA (11 pads each side, 1 large ground in middle) We get what appears to be random not to fold in air when exercising before putting on the stencil. What I am wondering is if the printing process itself is bringing air into the paste. At the start and end of the print stroke the blades lift, generating a slight peak. As the next blade comes in contact with the paste from the opposite side
Mar 18, 2006 | and process parameters below: Pad size: 0.508mm x 0.254mm Aperture size: 0.482mm x 0.229mm (12.5um reduction from each side) Solder paste type: type 4, particle size: 20um-38um Squeegee pressure: 5.4kg Squeegee speed: 50 mm/sec Separation speed: 20 mm/sec Stencil type: nickel, electroformed Stencil thickness found no issues with board to stencil matching. Squeegee pressure, squeegee speed and separation speed are adjusted correctly. Decreasing separation speed makes print quality the same or worse, apertures at that still remain blocked. One more thing I noted is solder mask opening. It is rather small
Dec 8, 2005 | Fine Pitch Stencil Design cause gasketing problems, which can lead to defects. How wide is are your pads? Next check your parts. J lead or Gull wing fine pitch. Are the leads as wide as the pads or smaller?Are there any large parts, like a TO-220? Larger parts may require a bit more paste than a 5 mil stencil can offer printing. Get to know your process. NOW, once you have all the above answered can you finally start thinking stencils.
Sep 24, 2002 | assembled for us by a contract manuafacturer. They�ve started out with a .005� thick stencil. On the first run of boards the LED�s were tilted all over the place. On closer examination it turned out the LED�s were designed with ONLY bottom solderable surfaces � no end, top or side metallization. I think adhesives on 0402 parts so we are persuing reducing the amount of applied solder � targeting somewhere around a .002� thick stencil. Are we going the right direction? What issues do we have to concern ourselves with when using such thinly applied solder paste. Is it preferred to reduce the aperture size of a thicker (say .005�) stencil? Any assistance would be appreciated. Gregg Temkin 206 286-1814
Sep 18, 2002 | . * Be wary of guidelines for pinching apertures without commentary about the size of the component lead and size of the pad on the board. * Consider IPC-7525 - Stencil Design Guidelines as a worthwhile input. * Stencil fabrication is a key variable affecting paste release. * Print independant variables dimensions and finish. * Component lead size and solderability protection. * Aperture dimensions, stencil thickness, fabrication. * Paste type and mesh. * Printer set-up. * Etc Finally, can you generalize about the bridging? Mostly: * Here or there. * On the side / sides of component leads. * On front
Jul 2, 2002 | Solder paste stencil life FIrst, be a doubting Thomas and never trust supplier propaganda sheets, do your own testing. How often do you knead the paste? We have a standing requirement that if the paste printer is idle for 30 minutes, we have a minimum of 4 kneads before printing. To test for stencil life in a recent the stencil, put the paste in a jar, then mix it with new paste the next day. Again, what works for us won't necessarily work for you. Set up a test matrix, execute it, and see what your results show you.
Mar 27, 2002 | "gap-hole" in between the 0805 component base & the PCB pad surface. We analyzed the solder paste as excessive for this pad size, paste height is measured along 7mils~8.5mils. We use a 8mils Stencil. We noted the paste print out, has "out of pad size" paste print. Stencil aperture is larger than the actual PCB pads. We can find that pads volume deposit is thus uneven in print. We will be changing to a new 6mils stencil, with aperture opened to match (might be smaller than)the PCB pads size. ~~~~~~~~~~~~~ Bottom line : We can not find the IPC-A-610C specs that dictates how much can a RES
Nov 26, 2001 | . The designer may have created a multi-purpose pad to accomodate several different parts. You can end up with too little or too much paste without considering the actual need. 2. Paste print "bricks vs. mountains" - Process variations cause this - consider squeegee type, speed, angle. Also stencil seperation rate from the PCB can lift the paste to a mountain shape. Poor alignment of stencil aperture to pads can cause non-brick shapes. Aperture geometry in the stencil will also misform "bricks". Paste viscosity (too cold, too hot), not enough or too much flux also affect "brick" shapes. 3. You are starting
Nov 20, 2001 | of the adhesive to get it to release from the long walls of the stencil. * Keeping aspect ratios less than 3:1. If process time and product suitability are the driving factors, I would (begrudgingly) print epoxy. Since you are setting-up a production line for this product, I assume you expect to run a large volume of product. We have never compared the defect levels of dispensing and printing. The comments made earlier, may be worth repeating: Factor||Dispenser||Printer Deposition control||High control over amount ||Difficult to control amount ||||Stepped stencils can be a nightmare ||||Stencil
Sep 19, 2001 | I�ll volunteer to answer this one for Jake. In order to prove the performance and capability of the stencil printing process, I think this level of inspection detail is required. However, in a production scenario where a known printing performance level has already been defined: * If the 3D first, by whatever means is possible and available in order to ensure high process yields. What I mean by �basic� is simple paste presence vs. paste absence where the threshold defining each can be uniquely defined. The vision systems on the advanced stencil printing systems offer these sort of basic algorithms in addition to checking the stencil apertures for blockage. This information can be monitored offline on a network PC, if set up that way, providing this sort of realtime health-check information on demand. Keep in mind the penalty for using the printer for inspection is longer cycle time
Sep 19, 2001 | ratios (i.e. smaller openings and/or thicker stencil) may see improvements in transfer efficiency from the enclosed printhead system, as this provides more direct pressure on the material to fill the apertures completely. 2. More efficient utilization of the solder paste material on the stencil with less waste generated. 3. Solder paste material is expected to have longer stencil life, since it is protected from exposure to the ambient in a sealed chamber. Further enhancements to the present day standard enclosed printhead system are expected to show better print definition and volume scatter
Sep 18, 2001 | questions to ask yourself are: a. Is the stencil designed correctly? b. Is the stencil damaged? c. Are the squeegees damaged? d. Is the solder paste rheology and formulation appropriate? e. Is the machine calibrated and operating properly? f. Are suitable printing process parameters being used? g . Is the board being fully supported with proper tooling? h. Is the under stencil wiping system working? i. When the board is printed the second time, is it still warm from the first reflow? Scenario 2: After placement? In this case the placement pressure is probably too high, causing paste to squeeze out
Aug 15, 2001 | it becomes squeezed out by the component will determine its size. Too much pressure or too much paste can also cause squeeze out. - Misregistration between the stencil aperture and the pad can lead to solder paste printing onto the board mask resulting in beading. - Operators can inadvertently transfer to float the component to the lands and straighten the component. - Worn equipment, stencils, and squeegees as well as warped boards or insufficient stencil wiping can also contribute to beading and micro balls as well.
Jul 12, 2001 | of the time no matter what paste, environment, or process parameters you use. The best way to eliminate them for good is to use the homeplate design on your stencils. It just plain works. It gets rid of the extra paste that gets squeezed under the part, but also holds the part to the board. Does not affect your solder joint at all. No need to requalify your paste, take a year to reprofile all your product or add any steps to your process. Call your stencil manufacturer and ask them to reduce the aperture openings 10% and homeplate all your Rs and C's up 1206. If you have solder balls on larger devices, you can homeplate them too, but go 1:1 and watch your stencil openings. You want to leave enough past there to hold the part to the pad.
Jun 27, 2001 | Manual Stencil Alignment Welcome. First, proper alignment can produce an order-of-magnitude increase in the number of boards that can be printed without wiping. The initial alignment can be made either by: * Peering through the stencil apertures at the board underneath and adjusting the board position to align with the stencil apertures. OR * Printing onto a clear, fixed film and aligning the board under the film. OR * Printing either onto the board itself or onto the board covered with clear adhesive tape, until the alignment is correct. Here, the print must be wiped off after each adjustment. Once acceptable
Feb 8, 2001 | is placed, less paste is squished under the part and doesn't ball out towards the side of the part during reflow. You should get a proper solder joint and no balling. Most stencil houses have a general homeplate they use and should be enough to get ya through. If your using hot air solder leveled boards , you might want to reduce the over all pad by 10% and use the homeplate design. Give it a try. all it costs is a stencil for a couple hundred bucks. If you don't like it, send it back for a refund and use your old stencil and use the formula someone is bound to post after this. I guess I just should
Oct 1, 2000 | Okay, you have only few different product. Smallest package is 0402 and biggest is 144 pins ic. So, maybe you don't need get high-speed machine. You must place about 12000cmp/hour. You can buy quite cheap placement machine. I can't tell what is good because i can't advertising here. Stencil MUST be steel. It's only GOOD stencil material. Good thickness is 0,15mm - 0,20mm. I use always 0,15mm. (I'm from Finland so i use millimeters). Laser cut stencil is good. Squeegees must be metal. Rubber is bad because it is too soft. If you have too soft squeegee then it wipe too much paste away. Paste
Apr 13, 2000 | 100 Resistor networks Our Process: 1st pass- "Bottom" Stencil Paste Glue dot Place Reflow 2nd Pass- "Top" Stencil Paste Place Reflow 3rd Pass- Insert Thru hole Mask Resistor Networks "Wonder Mask" wave solder The designs I am working with have not been designed for a selective solder palette . I have many of the resistor networks close to through hole leads. We use this process because we have had poor results during wavesolder with the resistor networks. I am wondering is it possible to use a special paste/conductive adhesive that could be stenciled on during the first pass creating
Jan 31, 2000 | SERIES, THESE DO GREAT SOLDER PASTE PREPARATION BY ALIGNING THE STENCIL ON THE MACHINE TO DO EFFORTLESS SOLDER PASTE APPLICATION FOR BGA AND CSP PRINTING. THE STENCILS ARE LOW COST AND IN STOCK WITH CUSTOM STENCILS BEING DONE IN A WEEK FROM A CREDIT CARD ON THE WEB. OLD BGA 3000 CAN BE UPDATED ALSO
Dec 10, 1999 | and quickly than you can (read that cheaper). The prepped part still has a visual indication of polarity, the short leads allow the LED to be inserted by automation, they are able to be fluxed and soldered by conventional equipment, it could be a no-clean process, and the assemblies might not need mass trimming after soldering. The amount you save by not wasting all that flux and solder on the long leads and not having to clean up the mess could pay for the prep work and more. Wouldn't the amount of solder on these trimmings make them toxic waste? John Thorup
Dec 6, 1999 | Christopher: Thank you for sharing your experience about the DPAK. Yes, out part has a heat sink at the bottom. Our stencil opening was 7 mils (in both X and Y) smaller than the pad size excepting that the stencil opening consisted of a series of zebra stripes across the diagonal of the rectangular (or square) pad. This certainly worked better than solid stencil opening. The zebra striped opening still floated the component. Placing glue under the component lifted the component body so much that we ended up seeing very little solder at the heel fillets (at the two leads of the D-Pak). Since
Dec 6, 1999 | "experts" at some of our sights don't even know what "VOC" stands for. Dave F writes: >I suggest that your customer is living in a land of washable >fluxes and has not kept currect with the vagaries of no-cleans >and your mission is to educate them of: >1 Costs of washing a no-clean and then trying
Nov 26, 1999 | Jeff, Ted, Stefano What Stefano is saying sounds reasonable. With entry-level systems its always a struggle to get sufficient results. The operators golden hand is needed. Better controlled advanced dispensing systems should do the work, unluckily I don�t have such a thing. Stencils worke quite well depending on that "golden hand" again, the work space left around the part and the equipment used. The rework equipment should be able to handle stencils that means position them safe and accurate. (could be a three head station, pick and place-, stencil- and reflow head ). It needs a bit
Nov 11, 1999 | 1. Most ionic testing is measured in NaCl, that is, the ionic residues are quantified in terms of NaCl equivalence. The test does not determine what the ionic residue is, just its relative strengh. 2. I use IPC cleanliness specs on OA fluxes but not on no clean fluxes. I've been away from no cleans for a while, but when I worked with them, the vendor freely admitted ionic testing would fail. In the case of that specific flux, it would easily dissolve in alcohol and yield a very high reading. But how often do your electronics function in an alcohol condensing environment? By the way
Nov 11, 1999 | ceramic substrate or microscope slides. Using the stencil described in paragraph 3 above. 4.2 Inspect the paste at X30 magnification. The shape of the deposit should be a "brick." Record the pitch that slumping became prevalent. 4.3 Bake the substrate at 150�C for 2 minutes. 4.4 Inspect the paste at X 30 magnification. There should be no slumping. Record the pitch that slumping became prevalent. Stencil description from 3: 3.1 Obtain a stencil with 15 to 20 rows of a series of 0.025 by 0.050 inch apertures spaced 0.050, 0.040, 0.025, 0.015, 0.010, 0.010, 0.025, 0.040, 0.050 inches apart. See
Nov 11, 1999 | Horace , We had a similar problem last year on an Ultra 2000 . We cured it by draining the pot , removing the wave forming ducts , pumps and nozzles and cleaning . Refill with fresh solder ( one third solder chips , two thirds solder bars - to get the pot up to temp quicker ) and the problem and clean every Saturday . The rotary wave you use - is it the "helix" type design ? . You can order a retrofit rotary wave with a helix design and open top which never clogs up - ask your Electrovert Rep. about this . Hope this helps .. just my tuppence worth .
Nov 9, 1999 | Could very well be your nitrogen diffusers are blocked. These have to be cleaned on a regular basis as well.Cleaning frequency for the diffusers is flux dependent as well as other factors but could be as little as one month of operation. Once the diffusers are blocked, the chip wave dumps
Nov 9, 1999 | Re: paste release from stencil, and volume calculation 1 Money IS an object, and my boss will be thrilled. The stencil manufacturer recommended ovals to facilitate better release. Seems likely to be true, but whether or not it's necessary I don't know. We have perpendicular walls on these (6 mil) stencils, but will be going to traps. for the next
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