stencil apertures

"stencil apertures" search results in the Electronics Forums

5337 results found for "stencil apertures" in the Electronics Forums

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QFN84 Solder Printing Issue (QFN with Inner LGA Pad)

Nov 15, 2017 | IMO – Look into nano-coatings for your stencil and radius all square apertures This should help out with solder paste releasing from the stencil helping with insufficient solder QFN LGA aperture design, try a stencil cut with a few different aperture designs to test. I have had success with aperture reductions in “pad” width and increase in “pad” toe (almost 15%) to take care of bridging For the larger ground center “pad” window pane aperture should aid paste to allow outgassing. Also reduce the ground aperture about 40%, check the volume of paste under the QFN ground, if the volume is too

IPA versus Stencil Cleaning Solution

Jun 15, 2017 | Hmmm.... When I clean my stencils after I run a job, it is to clean the paste off the stencil so it doesn't dry out in the apertures and on the stencil surface while it is being stored. Wiping the stencils during production is to clear the paste off the bottom of the stencil. Not wash . Personally I am a little dubious about wiping cleaner up into the apertures then screen printing solder paste through them and wondering what that is doing to my flux chemistry......?? We dry wipe highly complex stencils (daily) with a multitude of micro apertures. No problems. I'm not the SPI IPA versus Stencil Cleaning Solution

Help understanding something about stencil orientation when printing

Nov 3, 2016 | Help understanding something about stencil orientation when printing Hi, I am struggling to interpret correctly the following statement: "An aperture oriented with its long axis in the same direction as the blade stroke does not fill as well as an aperture oriented with its short axis to the blade stroke." If I am printing a rectangular aperture

Auto calculate Aperture are on stnecils

Jun 6, 2016 | Valor mss process preparaton has a stencil tool module that can do just what you want as well as alarm you if for a defined thickness what apertures need attention Is template driven so can save your stencil processing and settings.. Is powerful tool to get first time right stencils... Auto calculate Aperture are on stnecils

Auto calculate Aperture are on stnecils

May 20, 2016 | Hi All I have a need to calculate the Aperture area in a stencil with in a very short time without going in to a CAD viewer. I need that when I insert solder paste file in to a certain software application and that application software calculate the area of each Aperture in the stencil and output a Auto calculate Aperture are on stnecils single value of the total area covered by the Apertures. Thanks in advance for any information, Milroy

Aperture shape for DPAK

Sep 23, 2013 | Hi, just for the package you have you will see 20 different designs for the ground pad. Some will be 1:1 with the part some will be 3 times bigger than the part ground contact. I would always print according to the part and will always do a windowpane design for the apertures on the stencil. Aperture shape for DPAK

Is there any good articles to read on solder paste?

May 30, 2013 | I have another idea. Would you check the apertures on the stencil? May be they didn't cut the right size apertures there. If you have smaller aperture you can't get the right amount of paste.

Fine Pitch Printing Issues

May 20, 2010 | What is the area ratio for the aperture? What size paste are you using? Stencil thickness & aperture size?

paste release

Feb 7, 2010 | The ratio of aperture opening area to aperture wall area is a critical evaluation measure for the release of the printed solder paste. The stencil thickness has the biggest impact on area ratio.

Stencil thickness

Sep 25, 2009 | 0.5mm pitch QFP's are typically mixed with large components on all of my boards. I usually use a 6 mil stencil with a minimum aperture width of 10 mils. Normal aperture size is 10 x 50 which causes shorts about 20% of the time. A recent purchase of a used LSM height measurement system shows paste height of 7.3 to 8.2 mils. To compensate for the additional paste height, I could go to a step stencil for the QFP, reduce the aperture to 10 x 40 or go to a 5 mil stencil and take a lot of time increasing the paste on the rest of the parts. What are you doing to solve this problem. Stencil thickness

Vapour phase soldering - problem

Aug 20, 2009 | reduce the stencil aperture to prevent tombstoning in vapor phase process. from my experience a 6 mil thick must be at least between 20 to 30 % aperture reduction for 0805's and below. cheers!

Stencil Design

Sep 16, 2008 | I am a doer myself but with the turn around and cost on EFORM stencils I prefer to be right and starting with math is always the best way. We have played with reducing apertures even stencil thickness as low as 4 mil. On the side that this component is on we have over 3500 apertures in a circuit Stencil Design

stencil apertures for BGA

Apr 11, 2008 | stencil apertures for BGA Hi Andrzej, We are using for BGA (0.8 pitch) square apertures size 0.4 mm (rounded corners r = t) and stencil thickness t=5 mils. So area ration-> w/4t=0.8 Regards Jan

stencil apertures for BGA

Apr 11, 2008 | stencil apertures for BGA I have a question concerning stencil apertures for BGA. In my case we have 0,8mm pitch BGA - plastic casing. I have found an information that paste reduction diameter should be 2mils. Is that correct ? In my case aspect ratio = r/2t = 0,76 > 0,66 Is it ok ? Is it overprinted r - radius of stencil aperture - 9mils ~ 230um t - stencil thickness - 150um Other data : diameter of soldermas - 26mils Diameter of pad - 18mils Diameter of stencil apertre - 18mils Pitch - 0,8mm ~ 31mils What stencil aperture for BGA do you recommend ?

Inspecting a new stencil

Feb 18, 2008 | Print paste through the new stencil with a piece of mylar [or other clear plastic sheet about the thickness of paper] between the board and the stencil. Dispose of the mylar according to local practice after confirming proper aperturation of the stencil. Inspecting a new stencil

BGA Aperture

Jun 20, 2007 | Hi All, Just a quick question in relation to BGA Stencil Aperture Design - We currently use 1:1 ratio - are there any rules or benefits from over printing the PCB Pad ? Replies appreciated. aj... BGA Aperture

Kester paste problems

May 24, 2007 | We have a similiar problem with kester em907, a pb free paste. You say that your AOI system picks up blocked apertures, do you mean that the printers own camera looks at the stencil and sees apertures blocked? Or, is it picking up insufficient paste on the pads? When we set up our printer to check the stencil after a print, we seem to always get some blocked apertures, up to 40-50%, but have noticed that the print quality is never really effected by this(assuming we never leave the paste long enough to dry into the apertures). If this is the case you may just want to turn off your stencil inspection, I think it's a rarely used option anyway(if the apertures really are blocked you'll get insufficients )

0402 aperture design lf

Apr 12, 2007 | Hi all, What stencil aperture designs do you use for 0402 components? Thanks in advance for replies. aj... 0402 aperture design lf

LGA Processing

Mar 29, 2007 | PCB land to part land ratio - 1:1 Stencil aperture size - 1:1 with PCB land Stencil aperture shape - same as PCB land

Invar Stencils

Mar 16, 2007 | I am not sure what the smallest aperture is that I have. I can tell you that I remember the area and aspect ratio (for apertures) being quite a bit lower than standard on quite a few stencils. We only order Invar on stencils that fall below ratio.. Your stencil house should be able to advise you Invar Stencils accordingly. BTW...We have never had the need for an electroformed stencil.

Stencil design question.(BGA Apertures)

Apr 4, 2006 | Stencil design question.(BGA Apertures) I did the apertures 1:1 using an Invar foil material. I will post and let you know how it works out. Thanks

Stencil design question.(BGA Apertures)

Apr 4, 2006 | Stencil design question.(BGA Apertures) 10mil square apertures should be ok with your 4mil stencil.

Stencil apertures IPC design

Feb 28, 2006 | Stencil apertures IPC design The key driver to aperture design is to assure a fillet of the proper height for the component temination and the reliability of the end-product customer use environment.

Stencil apertures IPC design

Feb 24, 2006 | Stencil apertures IPC design What is the IPC norm wich drives the IPC stencil aperture design? The contest is: a stencil for the deposition of solder pastes on bare boards Thanks

stepped stencils

Feb 23, 2006 | stepped stencils Depends what is adjacent to the step. 1206 chips could reside closer than say a 16 mil fine pitch. Larger apertures are more forgiving to height variations than small apertures.

Tombstoning 0306's

Sep 11, 2005 | If 0 or 180 degr. make v-shape openings to each other left & riht, if 90 or 270 degr. top/ bottom, on the stencil apertures; well, you understand... We use this and 87 % reduction of stencil apertures for 0603:s and 0402:s. 0.127 mm stencil thickness. We have no problem with tombstoning and solder


Apr 3, 2005 | What is the recommended stencil aperture opening ,stencil thickness and aperture shape for CCGA?We are seeing high reject for Open solder joint.

BGA question

Feb 9, 2005 | First off how thick is your stencil going to be? I have printed .5mm pitch with .009" apertures with a 6 mil stencil. A 5 mil would have been better but the 6 worked just fine. Pitch is not necessarily the deciding factor for paste type. it is the aperture opening that determines what mesh you will need. Use an area ratio to determine what you need (area of aperture opening vs. area of aperture wall).

Pasteproblemater aftersoldering

Feb 8, 2005 | have you had any reduction in aperture size though, we generally use a 6 mil stencil thickness with a 10% aperture size reduction for chip components and leaded components ( SOIC - QFP ) and a 1:1 ratio for BGA components without any problems.

Stencil Thickness

Dec 15, 2004 | I read with interest in September Circuits Assembly magazine an article entitled "Reducing Variation Through 'Intelligent' Stencils. In this the authors propose that by REDUCING stencil thickness from 0.005" to 0.004", the paste deposit volume will INCREASE by 76%. The test aperture was a 0 .010" circle. Their argument,(which I don't doubt), is that by reducing stencil thickness the transfer efficiency is increased by increasing the aspect ratio. In a nutshell - the thicker the stencil the more paste stays in the aperture, the thinner the stencil the more paste goes on the board. This would seem to make sense to me, particularly when you get down to 0.005 - 4 stencils. I very rarely use circular apertures and would be interested in any feedback from "mounties" in production facilities. Anyone tested it? What were the results etc. Cheers, Darby. P.S. Chicago was spectacular Dave.

Step stencil troubles

Sep 17, 2004 | You are right, playing with apertures is how to ensure release. Making a stencil thinner or thicker is "playing with apertures" It all relates to aspect and area ratio calculations and what you need to do based upon the numbers you get. Russ Step stencil troubles

HASL Plating Thickness

Jul 27, 2004 | How does the HASL finish and stencil match ? I have seen ocasions on fine pitch devices where the HASL can protrude into the stencil aperture either pulling paste down on the snap off or completely blocking the aperture and getting no paste.

Cleaning of stencil

Apr 20, 2004 | Hi Everyone, I am trying to stencil print chipbonder. The problem I am having is with the cleaning of stencil. The apertures are gettting blocked and cleaning with alcohol is not helping. Could anyone suggest a better way of cleaning the stencil. I appreciate your help. Cleaning of stencil

Stencil Printers

Feb 18, 2004 | I'm looking for a shareware software that I could use for specifying stencils (we are stencil users not manufacturers). I would like to enter some preliminary spec in a software form, such as: the smallest pad geometry on pcb (possibly selected from a library), % aperture reduction, if needs step -down, etc. Next the sofware do its calculation (using aspect ratio and other rules...) and provides the suggested stencil spec, such as: thickness, aperture shapes, type of aperture wall, if electropolished or electrofomed, etc. Thanks for your help Mauro Stencil spec software

Stencil Aperture Sizes

Jan 21, 2004 | Stencil Aperture Sizes Depending on how you frame the question, either of you could be correct. Neither of you mentioned stencil thickness, which together with aperture opening [and stencil fabrication technology] define how well a paste will release. So, the key measures are: * Aspect ratio * Area ratio Search

stencil thickness for bga

Oct 13, 2003 | stencil thickness for bga Aperture size should vary with the component [pitch]. That size should be the same a the pad size. So, generally pinching is not required. Indium discusses BGA apertures on their site [ ]

Stencil Aperture Aspect Ratio

Jun 24, 2003 | Stencil Aperture Aspect Ratio Bruce, I have a spread sheet, in Excel, that helps in determining stencil thickness, based on smallest aperture size. If you are interested, I can email you this.

Stencil Aperture Aspect Ratio

Jun 17, 2003 | Stencil Aperture Aspect Ratio Aspect ratio = width of aperture divided by height. E.G. 6 mil stencil at 9 mil wide = aspect ratio of 1.5. Value should be 1.5 min. Area ratio - use when length and width of pad are roughly same dimension like for BGAs and 0805 and smaller R-nets this is the ratio of contact area of aperture opening and the surface area of the aperture walls. E.G. 30 mil aperture at 6mils thick gives area ratio of 1.25 Value should be greater than .66 Russ

Blocking stencil apertures (on purpose)

May 1, 2003 | Blocking stencil apertures (on purpose) Dave: After the stencil was made with apertures for a connector on this PCB, it was discovered that the connector would have to be handsoldered after SMT reflow. If the solder deposits are left to reflow on the pads, it makes it difficult for the operators to handsolder the connector on later and keep the connector level, since they cannot reflow all the connector leads at one time. (it's a long connector) We've used Kapton tape to mask off the apertures on the underside of the stencil, but the thickness of the tape creates a gasketing problem on a nearby fine pitch part. kelly

Blocking stencil apertures (on purpose)

May 1, 2003 | Blocking stencil apertures (on purpose) ehess Why do YOU want to block apertures to keep solder from pads?

Blocking stencil apertures (on purpose)

May 1, 2003 | Blocking stencil apertures (on purpose) Why not fill the apertures with paste and let the paste dry-out? We have found that a hammer and chisel are very effective for removing dried paste.

TSOP40 Lead pitch 0.50mm recommended aperture sizes?

Mar 6, 2003 | What are the recommended stencil apertures for a TSOP40. Lead pitch 0.48mm & lead width 0.21mm. And direction of squeegee print over the aperture? Recommended Stencil thickness? Recommended aperture reductions? Recommended pcb pad sizes? Recommended Printer settings - pressures & speeds, or any TSOP40 Lead pitch 0.50mm recommended aperture sizes?

0402 stencil design

Feb 4, 2003 | Greetings, I am pretty new to SMT production, and have learned much from this forum. I am getting ready to build a CCA with many 0402 parts that are really close together. I consider these fine pitch. The board also has two QFPS, so my stencil design at those locations uses trapezoidal apertures reduced down to 80% of the pad size. I plan to use a 5 mil laser cut stencil. What are some good guidelines for the 0402 parts? Should I use home plate apertures, reduced apertures, or just leave 1:1? TIA for any links or helpful info. 0402 stencil design

Solder Paste and fine pitch components

Sep 18, 2002 | steps are straightforward. If design factors are incorrect, either fix the design or you are forced to find work arounds that may compromise your ability to produce a defect free product. Secondly, pay close attention to your stencil apertures. Oversized or 1:1 ratio apertures in 15 mil pitch can that encourages defects during reflow. Fourth - back to design of PCB. Are there solder dams of mask between the pads? If yes, that helps. If not, pay close attention to stencil aperture width and be sure that the aperture deposits less paste by 1-2 mils per pad, centered on the pad. Next - paste volume from actually paste deposit measures. Too much height or blow out on the sides of the deposit indicates squeegee pressure not optimized, aperture not aligned to pad, etc. 5 mils stencils work well with fine and ultra fine pitch parts. Normally I use 6 mil because of consideration for the rest

Reliability of U-shape appetures

Jul 5, 2002 | I have seen the U-shaped aperture on a customer site, being used with success. However, the problems with the stencil and the �loose� tabs where reportedly a reason to search for different aperture designs. Before this company could test their ideas of using two pads and four small circular apertures, two on each sides of the pad towards the component center, the company went out of business. Please let us all know, if this works.

pasteprinting D.O.E.

Jun 4, 2002 | Factors to consider are: * Squeegee speed * Squeegee pressure * Separation speed * Stencil thickness * Stencil aperture fabrication method * Stencil aperture shape * Paste type * Stencil under-wipe frequency Search the fine SMTnet Archives for a thread on printing DOE done on CSP by rpereira.

Cpk Variables Control for Paste Printing

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.

CCGA and overprinting?

Oct 15, 2001 | I hate getting "roped" into math stuff, but here I go again ... Area of aperture = volume of paste / stencil thickness = {[5000 mil^3] / 5 mil} = 1000 mil^2 Side of the square aperture = Sqrt of the area = [1000 mil^2]^1/2 = 32 mil Diameter of aperture = 2 * Sqrt of the [area / pi] = 2*[1000 mil

blocking off stencil apertures with tape

Oct 10, 2001 | blocking off stencil apertures with tape What the heck are you doing having scotch tape in the plant? Isn't there a concern for ESD safety? Ban the scotch tape, then they won't have something to block the apertures with.

blocking off stencil apertures with tape

Oct 10, 2001 | blocking off stencil apertures with tape Why not quantify the amount of time spent taping apertures every time you want to use the stencil vs. the cost of a new stencil (about $300, usually)? Look for problems that are created by the blocked aperture method - is there rework down the line that could have been avoided? Include that rework cost into your justification. You could probably prove a return on investment rather quickly. If that don't work, poke a hole in the stencil and force 'em to buy a new one. Don't quote me on that!!!

Reflow Ovens thermal process improvement

Selective Solder Wetted Nozzles