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Nov 29, 2007 | I really hate to ask but must. Are the components that are falling off, the components that don't have glue? Seriously not all the parts on the bottom are glued on? How do they stay on during the wave? The normal way is to run the top SMT as normal, and relow them, then stencil the bottom side
Nov 26, 2007 | I have been using it and noticed it seems to get runny after it has been out on the stencil awhile. Couple hours or so. At that point we've had some problems with the paste smearing on some fine pitch stuff(0.020"). I sped up my squeegee speed and it seemed to help solve the problem.
Nov 12, 2007 | Could be any one of the 3 you mentioned, need some details here, do you really think we can answer this question as it is? Now for your issue, what is the make up of the lead itself on the part? what is the reflow profile at this part? what is Paste type? what is stencil thickness? What
Sep 27, 2007 | Can anyone recommend an automated solder paste dispensing unit that works well and won�t break my company�s bank account? We are getting a bit pushed out by continuously purchasing one stencil after another. Thanks for any help any of you can offer from SMT land.
Sep 21, 2007 | this would be meaniung that somewhere in your documantation it should have spec called "repeatability" what this means is that when the vision aligns the stencil/board, the board will always be within "x" amount of the njominal xy "T" position, some printers cannot hold and repeat to the .4mm
Sep 19, 2007 | Hi,davef, thanks for your concern. The condition was the pasted printed off with around 0.8~0.9mm from the land pattern. This will easy observe at QFP area. At fiducial, the stencil seens aligned accurately. Once solder bridge happend, its easy to repair by do some simple touch up
Sep 15, 2007 | 220 should be plenty although if they're lead free you might need a little more heat. Is it possible that you've got a paste volume issue (stencil design, clogged apertures), or maybe the footprint isn't right for the part? I had this same problem with a QFP 100 a while back and it was due
Sep 10, 2007 | is tight on both ends. -Make sure the stencil is securely clamped. -Try slowing down the conveyor speed(not a true fix, but it could help)
Sep 4, 2007 | You probably could SMT it (standard Process)first, do your PTH and then wave solder using selective solder pallets. If you stick with your current method I would consider a mini stencil such as the ones used for BGA replacement to apply paste. This way you will get fast consistent pasting.
Sep 2, 2007 | Good day... Anyone please confirm that changing process to lead free => that I Can still use my old laser cut stencil that I used in leaded process? and also my wave pallet that I have used in leaded process? Your comment is highly appreciated for all lead-free transition recommendation and control
Aug 22, 2007 | Thanks for all responses really good feedback. I have placed a number of extra supports underneath e
Aug 14, 2007 | > pick/place head won't travel over the LED's, then you won't be able to proceed. I wasn't clear in describing my board layout; It is LEDs on one side and SMT components on the other side. I don't think we can get around the problem of stenciling the SMT side after the LED leads are sticking
Jul 14, 2007 | You can get laser cut stencils in mylar 3 or 4 mil plastic sheet. This company will cut one for you form $25 for a 4 sq inch mask. See http://www.smtstencil.com/. Apparently there good for one-off to small bactch production
Jul 5, 2007 | Hi BR, Are you screen printing adhesive to the bottom of the board? If so, have your stencil make put openings between the leads of the thru-hole part. SMT adhesive acts as a natural solder resist. So placing a small sliver between the pads works well. I do it all the time since we cannot
Jun 20, 2007 | works fine for 127/150um stencils. 1:1 BGA aperture is ok. BR, Pavel
Jun 18, 2007 | I need the passwords to mpm Up2500 Stencil printer. I have the supervisor one, but my coworker took the rest with him when he left. If anyone could give me the default ones, that would be great. I am trying to get everything done before vacation time. Thanks
May 22, 2007 | Hi All, I ran a prototype last week with one of the above mentioned connectors on board. During Inspection post reflow we noticed a solder ball had formed at the top of each leg. We used a 5thou stencil with 10% reduction on the width but it seems that we are applying too much paste ? anyone run
Apr 3, 2007 | Here's is a great thread Stencil Cleaners: http://www.smtnet.com//forums/index.cfm?fuseaction=view_thread&CFApp=1&Thread_ID=3026Message12325
Mar 30, 2007 | Question: Does this formula apply even for the small LGA:s like LGA36 6.5 x 3.5 x 0.6 mm pad size 0.35mm pitch 0.60mm? We use a 0.13 mm stencil thichess beacuse on the same board there is some P.I.P comps. The board dimensions is 35 x 50 mm on a panel with 24x these bastards. /Sincererly
Mar 30, 2007 | We have now ordered a another stencil with square apetures with 20% overprint just because it is so difficult to get the solder paste to stay on the pcb pads without to get it stuck within the apertures. We have set the print speed down, the separation speed down etc. etc. We are just going to try
Mar 1, 2007 | By used to you mean scraped from stencils and bucketed? If that's the case I'd check with the guys that recycle my dross. That's who did ours when we had volumes that justified it. Now we have so little it goes into the hazmat hamper with everything towels, tubes, etc..
Feb 14, 2007 | The challenge regarding the stencil was mostly due to the actual board layout and nothing having to do with the voids in the solder. It was my first encounter with 0.5 mm pitch on BGA and dealing with a LF solder paste with higher viscosity than tha leaded version previously used on the same
Feb 7, 2007 | Board vendors are always right. Unless you build yourself in their facility, at their price. Ways around this are half etch your stencil over the vias, open the resist (mask) on the vias, or use your own product (Sipad). The resist (mask) does appear to be rather on the thick side in your
Jan 25, 2007 | Force is definetely necessary. It really doesn't have much to do with board thinckness, if everything is programmed correctly. It is just the downward pressure applied to the stencil during printing. You are supposed to adjust this depending on your squeegee lenght and type. 1 lb. per inch
Jan 24, 2007 | Sounds like you need a support pallet to accommodate the narrow side clearance. Several pallet houses made pallets that work in screen printing that have flush board edge clamps that hold the board in the pallet yet allow the stencil to come all the way down flat. As far as Grid-loc goes, I
Jan 23, 2007 | Here's a good thread:
Jan 23, 2007 | Hi,
We have a UP2000 with grid lok installed on it. We run several assemblies that have component pads close the edge of the board.
The side clamps hold the stencil up off the board and we are either getting insufficients or excessive solder paste in those locations.
I am curious as to how others
Jan 23, 2007 | Hi, We have a UP2000 with grid lok installed on it. We run several assemblies that have component pads close the edge of the board. The side clamps hold the stencil up off the board and we are either getting insufficients or excessive solder paste in those locations. I am curious as to how others
Jan 22, 2007 | Thanks for the info everybody. As Real Chunks stated, a lot of paste is needed in order to solder
Jan 12, 2007 | Hi guys, Pin in Paste guidelines will be included in the IPC-7525A "Stencil Design Guidelines". This draft is being reviewed now and is scheduled to be released by February, (March at the latest). There are many other sources for these guidelines in the meantime. These would include some
Dec 16, 2006 | Hi all, Having been designing (3d modelling and programming) stencils and tooling (solderwave carriers,print support etc) for several years I am now investigating whether it would be possible to do this from home. I live in the UK and am therefore able to work when perhaps you guys
Dec 5, 2006 | How about a stepped stencil? Not ideal but ... As far as overprinting goes, try: http://www4.uic.com/wcms/WCMS2.nsf/index/Resources_44.html
Nov 30, 2006 | . The above checks are purely for Processing the board thru the machines. There are lots of other checks for stencil design etc. aj...
Nov 7, 2006 | We are using Kester Type R520A, Alloy SN96.5/A63.0/CU.5 paste which is applied using an MPM Accuflex machine. Our plant Humidity is 38 degrees. We are seeing insufficient paste post stencil on fine pitch parts. Could this be an environment issue? In the past we have not seen this issue.
Oct 25, 2006 | Bottom line is, If you have to pay a fee to buy spare parts then the company is not worth doing busi
Oct 25, 2006 | "Many manufacturers charge to register their equipment prior to selling parts or providing service."
Oct 5, 2006 | with this design you will have voids, you cannot trap the gas inside of via it has to go somewhere. These vias should be relieved from pad to prevent the scavenging of the paste during reflow. You may try a thicker stencil if you can to allow for the extra solder being scavenged by vias. May
Oct 3, 2006 | It's a consignment kit and we already have the parts. Otherwise I'd tell them to panelize the thing and we could build all 30 in one pass. I may be able find a 25 mil QFP on a stencil and hand print that one part if the apertures are long enough. Dispensing for the rest (SOT-23s and an SOIC16
Sep 13, 2006 | Hi If you are looking for a good solid reliable printer you might like to compare the Dek 248 and 1
Aug 25, 2006 | We use a single large pad on board and reduce stencil aperture 50%. If you mask/reduce the thermal pad the solder will not wet out to edges and you will still see the part standoff with the open joints. the purpose of reduction is to wet the paste out to edges causing the part to be pulled down
Aug 15, 2006 | Yes, when teaching fids and you get to the screen shows your fid (either board or stencil), hit the middle "roller button" labeled NEXT. This will toggle your bulb from regular to bright and vice/versa. If it's still very bright, the bulb itself may need replacement. Or you may have a lot
Aug 1, 2006 | It's been a while since I've built with 16 mil pitch, but I have to second the recommendation to go to 5 mil stencils. Night and day as far as release characteristics. The increase in aspect ratio opens up the window a lot. (read = covers up a multitude of sins)
Jul 10, 2006 | warping, discolouration or damage to the components. Is there anything is should be considering with regards to stencil design if it turns out we could do this. cheers Dougs
Jun 15, 2006 | Hi, I have a bad experience whenever assembling the PCBA that using SMD film capacitor as I encountered a lot of non wetting and tombstone. I did experiment on my reflow profile and stencil design and the result was improved but not totally solved. I'm looking for any suggestion or input from you
Jun 7, 2006 | first: what is your problem after reflow? second: a good rule of thumb is a tolerance of 1 mil. for example..if you got 5 thou stencil thickness then your range of thickness is 6-/+1 thou.. then you just improve after you get your height data and analyzed it through xbar r-chart..cheers..
Jun 1, 2006 | IPC a 610 has this info. An 0402 however mat require more solder than what IPC states (basically evidence of wetted fillet for class2). more paste = more flux = better wetting. Why don't you tell us what pad sizes and layout you have and stencil thickness. Russ
May 1, 2006 | I know from previous experiences that off contact printing have helped us reduce bridges and smears under the stencil. I am looking for ANY documentation regarding this topic in order to try to implement a change at our current factory. If anyone has a place to go and anyone to talk to would
Apr 20, 2006 | We had that problem with our printers we just drill and tap the top end of the stop and put a short screw in to allow us to adjust the top height of the stop and catch the board. Be careful not to make it to long or to could restrict the board from leaving the printer or dent\tear the stencil when
Apr 19, 2006 | Look at your paste specs, they give you recommended starting points relating to speed and pressure.
Apr 3, 2006 | I remember that. it was this thread here.
Mar 17, 2006 | Copper is the base material for the lead. It's tin/lead plated. I finally got profile. Here are the parameters"
Peak : 219
Max (+) Slope : 2.29
Max (-) Slope : -1.94
Time above 200 deg. C : 50s
Time 140C - 160C : 126s
Additional info :
Stencil thickness : 0.15 mm
Solder paste : Koki
Mar 17, 2006 | Copper is the base material for the lead. It's tin/lead plated. I finally got profile. Here are the parameters" Peak : 219 Max (+) Slope : 2.29 Max (-) Slope : -1.94 Time above 200 deg. C : 50s Time 140C - 160C : 126s Additional info : Stencil thickness : 0.15 mm Solder paste : Koki
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