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 Jul 10, 2003 |
Micro BGA pads, adhesion to laminate A reading of the pictures is: A1: Looks like pad [B1] is smaller than the other pads. It�s weird that the pads are such different colors. A2: Looks like pad [B1] is smaller than the other pads. Solder mask opening [B1] is misregistered and seems smaller than other openings. Solder mask seems very thick, relative to the pad thickness. B1: Silk screen is closer to the pads than A1 and C1. B2: Silk screen is closer to the pads than A1 and C1. B3: All solder ...
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Mar 25, 2002 |
... the solder paste out to the sides of the print, and, if you are not careful, 0.4mm spaced pads short together very easily, becoming 0mm spaced pads. ;-) Also, the location of microvias in the LGA pads can cause opportunities for rework. If the out-gassing of microvias is violent enough, solder can bridge between pads when the microvias on adjacent pads are positioned in the same location on pads. Staggering of the location of microvias reduces, but does not eliminate, the problem. As mentioned ...
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Jul 19, 2005 |
... bottom-center pads. It is on the bottom outside-bottom pads. Notice curious fuchsia color that's in "stipes" on raw solder and dots at the edge of some silk screen legend. There is some raw solder off the bottom pads. 0408%20Missing%20Solder%2003.jpg - Paste is not missing from the upper-right-center and lower-right-center pads. It is on top of the component and on the outside and left-center pads. Paste that originally was on the left-center pads is on the outside left pads. Curious fuchsia ...
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Oct 19, 2008 |
... x 1". The pads are in the bottom of the PCB and it goes on the Top side of the mother board the pads of the RF board are like a BGA (square pads)and we have troubles to make the proper welding in the pads of the RF board with the pads of the mother, the problem is just with one pad not all of them. between two pads there is a via hole, I do not why is the reason of this hole, one of the pads that is just beside of this hole is the one with the issue with not proper welding between pads. Any help ...
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May 8, 2002 |
... aperture openings b) PCB (Au/Ni) pads sizes and found the two coverage areas are mis-register, when superimposed on each transparency. E.5) the PCB pads have "up/down/in-out" Pads irregular pad layout; even when the gerber data shows all the Pads are supposedly equal in Pads dimensional lengths and equal dimensional PCB layouts. E.6) the stencil was generated using customer supplied gerber data of the silk-screen layer. this gerber supplied to us assumes all pads are of equal layout and ...
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Apr 3, 2003 |
BGA attach eval. R1: Contacting Altera to find out if the BGA pads are gold. D1: Bet money the pads were ENIG. R2: Contacting Altera to find out if they use abrasives. D2: If abrasives were the problem, you�d see it in many pads, especially those close to the problem pad. R3: Could one expect to see a flat pad with a forcible removal? D3: We�d be surprised not see lifted pads. Lifted pads are flat, right? Lifted pads indicate a good solder connections. Mmmmm, flat non-lifted pad doesn't ...
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Jul 2, 2009 |
BGA pads lifting from PCB On first glance it looks like those particular pads were not attached to any traces. If I had to guess I would say that your rework profile got hot enough to melt away the glue holding the pads to the board and they came away with your part when you lifted it off the pads due to surface tension with the solder. This can be a problem sometimes because those pads are not attached to any other copper they heat up more quickly. I would recommend attaching a thermocouple to ...
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Sep 28, 2008 |
... to 210�C at 1�C/sec, > then peak. another thing: are the hot air > blowers of your oven running at the correct > speed? too much air flow on the small pads will > exhaust the flux more rapidly. > small pads like 0402 tend to get hot quite > easily. looks like excessive heat is your problem > here. pads are wetted, component leads are not. > this means solder paste flux on top layer was > exhausted before entering in reflow. your profile > is the 'in-between ...
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Aug 20, 1999 |
... solder mask between qfp pads | | | | | | One of the DFM suggestions I've seen is to remove the solder mask web, i.e. the mask between pads on 20-mil QFP devices. The rational is that if the mask is thicker than the pad the mask can prevent the stencil from making intimate contact with the pad and allowing solder paste to squeeze under the stencil and encouraging solder bridging. Another school of thought seems to be that the solder mask prevents bridging between pads. Anyone have experience ...
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Jun 2, 2009 |
... pads caused voiding. Your supplier is correct that the pads on the board should be the same size as the pads on the interposer, but this is to improve reliability issues. Search the fine SMTnet Archives for more on BGA voiding. Finally, we're not wild about your supplier using solder mask defined [SMD] pads on the interposer. * Motorola did a study in 1996 that indicated that nonsolder mask defined [NSMD] pads were significantly more reliable. * 3.1X Life Improvement of NSMD over SMD Pads [
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Apr 4, 2009 |
BGA Rework - Pads being lifted Cause: Solder between the pad and the BGA on the pads being lifted has not melted. So, when you lift the BGA, you also lift those pads with the unmelted solder with the BGA. These pads are probably sinking the heat to a large copper plane in a inner layer of the board. Solution: You may want to add more heat to the board prior to lifting the component. Do this through: * Longer preheat * Increased bottom side heating * Longer soak Each component on each board may ...
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Aug 17, 1998 |
... pad and terminations during replacement all the pads should be flat prior to replacement. Solder wick may be used with a soldering iron or a vacuum de-soldering tool with a flat ended vacuum tip. A flat blade soldering iron tip is also a good method for pad flattening. If there is no evidence of spiking on pads due to the correct use of flux, solder removal may not be necessary. Removal of the solder to flatten the surface does make life easy. Pads may be re-coated with flux prior to placing the ...
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May 10, 2004 |
... definitions, the two main types for solder masking near BGA pads are: 1 Pad, Non-Solder Mask Defined. In circuit board design, pads with spacing that does not allow solder (usually bumps) on the pads to contact the adjacent solder mask. [After reflow, this ends-up being a potato shaped ball, when looking at a section.] 2 Pad, Solder Mask Defined. In circuit board design, pads with spacing that allows solder (usually bumps) on the pads to contact the adjacent solder mask. [After reflow, this ...
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Jul 9, 2003 |
Micro BGA pads, adhesion to laminate Our company applies solid solder to surface mount lands. While processing a micro BGA design we had some pads fall off, peel, whatever you might call it, from the surface of the board when touched "GENTLY" with the tip of a blade to remove a small squeeze out. The pads fell off so easily it seems like it may have been a clad copper to laminate issue. Most of the pads in the footprint were soldermask defined, a larger trace with the soldermask opening creating ...
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Sep 18, 2002 |
... 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. I had the exact opposite experience with solder dams on 15 mil pitch. When the board shop tried to put solder mask between the pads, the pads were too small. We couldn't make the aperatures smaller than those pads because there would be no opening left if we had. The result was pads smaller than ...
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Aug 6, 1998 |
... vigorously failing the products at final test or during goods receipt if products are contracted out. If the surface of the pads are to be used for interconnection then any contamination may not be acceptable. Contact strips, LCD interconnection or key pads are examples where solder contamination may cause mechanical connection failure of intermittence. This would have cause be related to the position and the size of the spots. It is however much easier to just reject the products than make a ...
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Jul 16, 1999 |
... 1 was originally required. Round test pads near this area will be used to complete this circuit rework, however these test pads are not the proper size. 1 end of each chip component will share a single test pad, the other ends of these chip components will be soldered to separate pads. Tomb stoning will result during automatic solder reflow unless the pads are trimmed to the proper size. The question is what should the relative size of these 3 pads be to eliminate tomb stoning. 1 pad will share ...
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Oct 14, 2004 |
Soldermask Defined BGA Pads We are experiencing a problem with soldermask defined BGA pads not accepting solder during the reflow process. The paste is there when the boards come off the printer but after reflow, no paste. Some other pads in the same pattern are fine. Here is the really weird part, we only saw it on 3 of 6 boards. The other 3 were fine, 100% coverage. Opening sizes are .012 round. Our process reflows the boards without components so we are expecting a meniscus of paste on the ...
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Apr 11, 2002 |
... these defects, but multiple factors that need to be tuned to work well together. PAD DIMENSIONS * Some SM-782 pads are a bit archaic. 7525, Philips, and Topline pads are more in touch. Suppliers are the best source of information. Go there first. Everyone else is sheep. Baaaa. * At some point of development, the gap between pads is probably more critical that the size of the pads. Pads that are closer are better than those further apart. Something like 18 thou is better than the more common 25 ...
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Oct 3, 2001 |
... we have a lot of opens after reflow. We checked our profil by installing thermocouples on the pads of the component and everythings seems OK. We checked the coplanarity of the leads and it seems OK too. We noticed that the pads width are at the edge of acceptability (0.010" according to IPC-SM-782) and the board as a poor HASL.Pads are not all at the same height.Also I have solder mask between the pads. Those things migth be the cause of the problem or maybe not. Does anybody experienced the ...
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Aug 18, 1999 |
REFLOWING WHITE TIN PLATED PADS WE ARE CURRENTLY HAVING PROBLEMS REFLOWING BOARDS WITH WHITE TIN PLATING. WE ARE NOT GETTING GOOD WETTING ON THE PADS. WE HAVE CHECKED THE REFLOW PROFILE AND TRIED DIFFERENT PASTE'S. WE THINK THERE MAY BE CONTAMINATION OR OXIDATION ON THE PADS. IS THERE A WAY OF CLEANING THE BOARDS WITH OUT HARMING THEM? ANY IDEA'S OR SUGGESTIONS? THANKS, GREG DENHAM
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Feb 23, 2000 |
... be reworked. Are my concerns justified? Am I missing anything? One of the primary reasons of using SMD pads is to increase the surface area between the copper and the resin to reduce the possibility of damaging pads during rework, correct? Believe me, I'm not about to ignore this possibility as we have had pads damaged when BGAs have been replaced on a couple of occasions but can't we also decrease the risk of damage by using a higher Tg material (maybe Tg=210 or so)in the fab of the PCB's? I ...
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Feb 23, 2000 |
... be reworked. Are my concerns justified? Am I missing anything? One of the primary reasons of using SMD pads is to increase the surface area between the copper and the resin to reduce the possibility of damaging pads during rework, correct? Believe me, I'm not about to ignore this possibility as we have had pads damaged when BGAs have been replaced on a couple of occasions but can't we also decrease the risk of damage by using a higher Tg material (maybe Tg=210 or so)in the fab of the PCB's? I ...
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Nov 14, 2007 |
... micro-vias in 0805 and larger pads, with no issues. But my most recent project had vias that were larger than the 0402 pads that the via was in. To the point that for a number of the lands, there was no visible pads (a couple of them...you could actually see a sort of outline where the pad would have been, but all of the plating was taken up by the ring of the via). The determination was that the designer definitely used vias that were too large for the pads that he used them on. I couldn't give ...
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Oct 8, 2007 |
... on this board (if the answer is yes, this is a good thing! no need to troubleshoot the mechanics of the unit.) 2. Are you using fids or pads for alignment? If you are using pads, try the following "teach vision" method; Enter teach vision and delete all models. Find two devices on opposite corners of the board which will allow you to see at least two of the pads on the monitor screen. (a 20 or 25 mil pitch QFP is VERY good to use!) Center the end pad of the device in the cross hairs and hit next ...
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Mar 24, 2007 |
... a QFN but it has no surrounding pads. It just looks like a uBGA with pads instead of bumps or balls. I forgot to mention that the device has 4 outer oval dummy pads (~1.15mm away from each corner) and the size of these is 0.7 x 0.35mm. The PCB has oval solder pads for these 4 oval outer dummy pads as well. I guess that will help a littlte bit to self center. But I'm still not sure how to do the process properly. So totally: LGA 36 + 4 outer oval dummy pads which I don't understand the need for ...
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Aug 17, 1998 |
... tests were conducted using the Multicore Must 2 wetting balance incorporating a micro globule to test surface mount pads. Two methods were evaluated on sample copper pads measuring 0.050" x 0.040" finished with a nickel/gold finish. Samples were removed from a circuit board featuring a series of five pads and finished so that the edge of each of the pads extended to the edge of the board. The board sample was then placed in a modified holder to allow the board sample to be lowered at ...
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Sep 20, 2000 |
Contaminated Pads I am sure that this is a problem that will never be solved, but something that I am seeing in increased numbers. Often refered to as "Black Pads". After production, returns from the field coming back with contaminated pads under various components. They have a blackish tinge to them and solder will not adhere to them. I know that I am being very vague, but there is so much information surrounding this I hardly know where to start. Any ideas? Have already looked into the PCB ...
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Oct 19, 2009 |
UIC GSM and NiPdAu pads We have a problem with QFN IC's with NiPdAu plated pads. Our ULC's don't see the pads due to the almost ideal reflection. Vision sees the pads almost black. As we don't have OAL-cameras (which can help in this case, I assume), I am thinking of back-lit nozzles, as QFN's have pretty good defined case outline and then center using MELF algorithm...? - Deni
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May 12, 2009 |
conformal coating - masking problem with ammonia We do a conformal coating for a customer with copper-nickel-gold pads on his board. The pads are masked prior to coating with a standard gel, containing ammonia. After thousands of boards, being processed like this, now the gold pads seem to be less solderable and the pads have dark/brownish areas. Can anyone help me? What has happened here? Any known chemical reaction with copper seems possible but what is so critical in NiAu-processes ...
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Jun 18, 2008 |
Criteria for Min Thickness regarding Large and Small pads Does anyone know of an established guideline for thickness requirements? Our smaller pads continue to receive a thicker solder deposition when we measure by the larger pads for process accessibility and vice versa for the larger pads when we measure by the smaller ones ...
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Nov 21, 2007 |
via under a smd pad ? From info I have been told from design standpoint, via in pads helps with managing EMC issues with working design, in particular for high speed digital/dense populated type PCB's. We had a manufacturing customer that had very low yield because of this via in pads was two big and solder was drained away from the pads - 1000s of pads on design - lots of rework. It can be done but via size has to be as small as possible, or preferably plugged vias used with solder. This all ...
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Jul 10, 2007 |
... tape adhesive Hi All, We are producing PCBA with COB process. We are using kapton tape to protect the COB pads from solder splashes/stains. Questions: 1) Is kapton tape an industry accepted way of protecting gold pads from solder splashes? 2) What are the chances of the kapton tape adhesive leaving behind silicone residues on the COB pads? 3) If silicone residues are left behind, how to get rid of it? 4) What are the other options of covering the COB pads aside from kapton tape? Thanks a lot ...
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Sep 19, 2005 |
... a customer that produces RF based assemblies. We are building several board types for them, all of which have an "RF" area of the PCB. This RF area does not have any mask to define pads. There are also several issues with components sharing pads, unequal thermal mass between pads and via's on some of the common pads that "thieve" the solder. The net result is an unacceptable amount of tombstones and shifted components. We have worked extensively to develop a profile that minimizes thermal delta ...
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Dec 9, 2004 |
... mask? We did this for BGA pads, but have not thought about other types. So, this may or may not apply for those. Pad defined by:||Advantages||Disadvantages Non-solder mask||No point-of-stress concentration at edge mask and solder ball||Smaller pads have poorer adhesion strength, performance in rework and multiple reflows, and heat dissipation ||No CTE mismatch at edge mask and solder ball|| ||More space for routing traces between pads|| Solder mask||Larger pads have better adhesion strength ...
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Nov 6, 2003 |
... with no solder on the pads. Generally, any device that has bare pads under them that attach to corresponding pads on the board qualifies as a land grid. Third, watch out for LGA with a thermal "slug" under them, like a QFN [and the drains on your MOSFET]. The slug really limits the options if overprinting. If the opening for the thermal slug is too great when using blades (not a pump), the blades can "scoop" paste from the center of the deposit for the slug. Since the pads do not get scooped ...
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Jan 17, 2003 |
BGA PCB Pad size How do 0.5 mm pads on the board help paste release from the stencil? Paste release from the stencil is a function of: * Paste * Printer operation * Stencil design You have no obligation to made your stencil apertures the same size as the pads on your board. You should deign your stencils with the area and apect ratios described in the fine SMTnet Archives to get good release. You should make the pads on your board according to suggestions of your component fabricator. We don't ...
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Aug 29, 2002 |
OSP / Paste Printing Problems Problem description: pads of PCB:s seems to "reject" solderpaste. Problem is more easy to identify on larger pads where the paste forms a double layer of paste on the other end of the pad and on the other end there is no paste at all. On smaller pads, on same boards where we have problems also with bigger pads, there is no paste at all on some areas of the PCB ...
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Oct 5, 2001 |
Solder on gold LCD pads I have had an issue where solder has contaminated gold plated pads (fingers) where it is not acceptable. The pads must remain perfectly coplaniar for a LCD zebra strip to lay accross them. Does anyone know of a way to remove the marriage level of solder (tin/led) from the pads without damaging the circuits on the PCBA? I have looked into reverse electroplating, but I have concerns about pumping current into the board. Dan Steffler Quality Process Specialist e-mail:
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Aug 4, 1998 |
... the larger thieving pads I've never seen a bridge on a 50-mil pitch SOIC. One other thing about SOIC pads that you can do to reduce the bridging on the bottom, is to make the pads .020" wide, it's a little narrower than what IPC calls out, but it reduces the chance of shorts when wave soldering. Also, if you're only gonna put the pads on the trailing edge of the SOIC, be absolutely sure of what that direction is gonna be, it would suck a little bit to lay the pads out for one direction and ...
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Sep 1, 1998 |
... 196 I/O count. The problem seems to pop up without warning & disappear in the same manner. | | | Our pad design is .020" diameter pads with .025" solder resist diameter. The center pads on the PCB are all tied together as a ground plane, therefore, the pads are solder mask defined and are .025" diameter. The shorts mostly occur on the center pads on this ground plane. | | | One thing that is strange, is that there is another 144 I/O BGA very close to this one on the PCB, with the ...
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Aug 31, 1998 |
... with a 196 I/O count. The problem seems to pop up without warning & disappear in the same manner. Our pad design is .020" diameter pads with .025" solder resist diameter. The center pads on the PCB are all tied together as a ground plane, therefore, the pads are solder mask defined and are .025" diameter. The shorts mostly occur on the center pads on this ground plane. One thing that is strange, is that there is another 144 I/O BGA very close to this one on the PCB, with the same ...
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Dec 28, 1998 |
Wavesolder Bridging We have a new PTH board that utilizes lap pads on the B/S. Some of the pads are paired closely together and are aligned at angles (30,45,60 degrees)to the boards direction of travel through the wave. The pads most always bridge together. I realize that this is a design issue, but the customer is unwilling to change the board design. We have resorted to masking off the troublesome pads but this leaves a significant amount of hand soldering. I am wondering if I can do anything ...
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May 7, 1999 |
... pads This is not strictly a surface mount query but any input welcome I am thinking of using surface mount solder thief pads for a through hole connector. The connector is two rows of 0.1" pitch pins and on waving there is often a bridge on the last two pins. To ease the layout overhead, we want to put the pads at either end of the connector to enable the PCA to be layed out/ reflowed either way round. Does anyone have any experience of doing this, what would the implications be of putting pads ...
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Aug 18, 1999 |
... solder mask between qfp pads | | | | | One of the DFM suggestions I've seen is to remove the solder mask web, i.e. the mask between pads on 20-mil QFP devices. The rational is that if the mask is thicker than the pad the mask can prevent the stencil from making intimate contact with the pad and allowing solder paste to squeeze under the stencil and encouraging solder bridging. Another school of thought seems to be that the solder mask prevents bridging between pads. Anyone have experience ...
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Aug 16, 1999 |
Re: solder mask between qfp pads | | | | One of the DFM suggestions I've seen is to remove the solder mask web, i.e. the mask between pads on 20-mil QFP devices. The rational is that if the mask is thicker than the pad the mask can prevent the stencil from making intimate contact with the pad and allowing solder paste to squeeze under the stencil and encouraging solder bridging. Another school of thought seems to be that the solder mask prevents bridging between pads. Anyone have experience ...
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Aug 24, 2000 |
... De-wetting on the smt pads and componenent termination on the bottom side after top side procssed through reflow. Board finish is immersion silver. ? Any recommendation on what we should check & verify * Problem is random in nature. Not component related * De-wetting only on the bottom side after top side reflow * De-wetting only on chip components/pads * There are vias on pads but the problem is not correlated with these pads * No apparent contamination on the pads * Have not verified the ...
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Feb 19, 2002 |
... in use for Au finger connectors on a regular basis). Via Pads (underneath BGA) - On Top The via pads on the top (underneath) the BGA should be covered to prevent the solder from wicking into the PTH. The via pads on the top side cannot be used anyway since they are covered by the device ...
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Jul 18, 2008 |
... solder on all the pads, My plan was that a LITTLE solder on the center pad would wet and center the device (using a gel flux) with our BGA hot air rework station. Then we would touch each pin with a tiny iron to make the pad connections. Well we had it nicely lined up on the gel paste, then reflow was good, but it shifted (nice and square) ONE SET OF PADS offset. Rev two of this attempt will be to put less gell flux on, and a tiny dab of paste the pads, hoping to have the PADS do the alignment ...
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Apr 6, 2007 |
... a way to share some pictures... * Pads on pcb are very very strange: It varies from a non uniform pattern but after we measure these I would say ~0.22 - 0.24mm dia. Haha, We have never discovered such a strange way the land pattern is done: After looking in the microscope we find out this: Tha PCB pads are actullay "a little bit" higher(!) than the solder mask! Not much but the surrounding soldermask ring look almost like a well. The leads is between the pads. PCB: 35 x 50 mm 6 layer 1.6 mm ...
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