(Sponsored) PCB Design for Manufacturing (DFM) Q&A with Sierra Circuits - Phil's Lab #158

The following is a recording of a conversation I had with Amit Bal of Sierra Circuits. Sierra Circuits are Californiabased PCB manufacturer and assembly house. Sierra Circuits very kindly agreed to answer some questions about design for manufacturing specific aspects to PCB design as they relate to manufacturing and I've recorded our conversation for you to watch and listen to in this video. Again, a huge thank you to Sir Circuits specifically to Amit and Lucy. Make sure to check out their website as well. They also have many handy tools which I'll link in the description box below. For instance, the bet DFM tool which is an online tool that can help check your manufacturability of your printed circuit board design. They also have many different handbooks, guides, often host webinars with PCB design experts and also have Sierra Connect which is a forum where you can ask questions and browse through various PCB related and electronics related posts. With that being said, let's get into the various questions and the recording. So yeah, I had this list of questions. I don't know. We can go through them if that's okay with you. There's no Yeah, I saw them. I saw them and uh they're great questions. They're very crossfunctional. You know, one thing interesting about uh manufacturing a circuit board and doing assembly, it's actually a very crossunctional thing. And in the US, uh it's mainly been PCB fab fabricators and then assembly fabricators. And they always were separate companies, I would say. Uh but now we see a little bit more of a consolidation. So Sierra is the same way. We build our own fabs and that's how we started and then we also do assembly. So questions like these are very crossunctional. Yeah. So that's great because it's I've heard I've attended some courses also from IPC and you always get various bits of information. The assemblers might say this, the manufacturers and designers might say different things. So it' be great to get your take on it. If you don't mind, I would also maybe share my ecat alum designer just so we can go through the design. Maybe that we can make it more visual in a way. I might also do some overlays in the video. So, I don't know how much Lucy told you about us. Um, so we are we are on a mission to educate as many uh PCB designers as we possibly can. That's something that, you know, is central to our uh mission as a company. That's great. Yeah, I really enjoyed the videos you did with Robert Feranic and also seen some of the webinars, at least the ones you posted on YouTube. Those were very interesting. And also actually read your DFM handbook and I noticed there were some answers to some of these questions in there already. there. So just with the first questions the first this is what I heard from an IPC C plus course uh relating to gasketing and stencil design. So I used to have for example on capacitors here essentially completely squared off pads. However the IPCC instructor said it's better to have rounded corners on pretty much all pads because that helps with applying solder paste stenciling and so on. I would like to ask you what your opinion is on that. Um I think it's a better way to do it and uh it's you're correct it will help with you know all the processes and you know a lot of the processes for PCB manufacturing are wet processes and so rounded corners you know rounded basically less right angles the better right so uh yeah I think it's a good idea both for the fab side as well as for the assembly side okay so you pretty much go with all rounded corners is that particular corner radius. You say the rounder the better. So, as far as you can get away with surface area, um that's how you round the corners. Okay, that's great. Okay, good. One thing that also I think also with beginners is solder mass expansions. So, some people say for example the solder mass layers you should just leave no solder mass expansion. Let the manufacturer for example edit the soldi render pads. For example, with components such as like a QFN packet where you have very closely spaced pads, very fine pitch. Sometimes what I'll do is because I like to define my own solder mask expansion that might be wrong with me is to then create for example a solder mask opening throughout the whole pad so that essentially there's no slivers which might not be able to be manufactured anyway left over. So how would what would you recommend designers do for that? Yeah, so I recommend you follow the manufacturer's guidelines for solder mask. So, for example, for us, we like a 4 mil solder mask web. Um, and we can go less, right? It depends on the design. So, it depends how much copper, it depends, you know, what surface finish. Um, those things do matter, but I would always recommend to have a solder mask web if your manufacturer can support that because that's going to be better for assembly regardless. Yes. Okay. So, that's what I try to do. Exactly. just if I can maintain that minimum web width for example in this design in this manufacturer this was possible but for some maybe solder mask colors that might not be and then I do for example maybe a fill and then get rid essentially of those webs is that a good practice or should I just essentially reduce the solder mask to be just the outline of a pad and let the manufacturer so to speak deal with it I think uh so I think that

the designer should be aware of the manufacturing rules around solder mask and you mentioned color that also is an impact, right? Cuz different colors expose differently and have different processing parameters, but uh I would leave it one with the pad even knowing what the manufacturing tolerances are because then that tells that signals the manufacturer that you know you're okay with them editing your mask. you have an area that you don't want the manufacturer to touch on the mask, then I would create your solder mask for that component or footprint and then I would say don't change the solder mask for this. Okay, so you would selectively do that and then have the designer add notes specific areas to say don't touch here and so on. Okay, another common very common question is for example something along the line of acid traps for example if you maybe have some odd entries and maybe I can't do it exactly here into the pads that you can maybe get these acute angles these triangular shapes is that still a problem I mean I try to maintain proper entries so vertical horizontal if needs be 45° into a pad but are acid traps a thing they are a thing uh again manufacturing is a wet process so um you know I have a virtual tour of our factory I can show you. But basically the develop etch and strip line is a horizontal for us it's a horizontal line and you have spray nozzles that come down. It's a wet process and um you know acid traps are real and you know if you have um the ability to teardrop or again remove as many 90° angles as possible I would do it. Okay. So even intersections like so where we have these sharp so to speak 90 degree angles that could even be a problem. I mean uh problem is a very big word. Um I would say better design practice is to teardrop. Yeah. And can an acid trap actually cause a problem? Well the answer is yes. But maybe your designs wouldn't you know fall into that category and you don't have to worry about it. But um we have absolutely seen acid traps cause an issue before. Okay. And what kind of issues did you see? Yeah. So like you know what you're talking about you can have you could end up having slivers. You could have a neck down in an area that you don't want. Um it could impact your signal integrity. You know all these types of those things can happen. At the end of the day, you the customer is sending us a design and it's not going to be 100% exact what is being manufactured because like I'll give you an example of edge comp, right? So, we take we'll take this trace and pad and we'll add edge comp to it. Um, which basically means that we know that when we go through our etching process, we're going to etch away a little bit more copper and it's going to go back down to what the designer is looking for. So it's a completely it's a wet process and a variable process. It's not exactly what you see on your screen is what we're going to build. Okay. So in terms of teardrops then would that be that the fab house does that or preferably or would the designer in the design tool add teardrops? Yeah. Um I think whatever is easier. Uh in this case I would say just add a note on your fab drawing. I hope people have fab drawings. Uh but uh fab drawing basically says you know add teard drops okay to add teard drops and then that gives the manufacturer a license to do that. Okay great and you do that both for SMD and through hole. Yeah, there's of course the whole electrical standpoint to it to filling essentially unused space so to speak with copper filled that to a certain net whatever but from a manufacturing standpoint there's always the copper balance aspect as well right I don't know if there's any rules of thumbs or when this might become a concern copper balance for example how unbalanced across the board stack does it have to be or is this even still a concern from what board sizes might this be a concern maybe it's hard to say as a general answer uh copper percentage um does matter per layer. You know, even today uh there was a very complex board that we were building and you know the customer said, you know, we sent this board to another fabricator and it came out warped. Um and what are you doing different? Right? Well, that's a hard answer. Uh but one thing that we do and is should be common practice among fabricators is to add a lot of thieving around the image um so not impacting the design of the designers. So as you build your boards on a sheet right th that we consider the copper area of the whole sheet and we try and balance as much copper as we can uh on the whole sheet. But if you have as a designer an opportunity to put copper pore, I would follow the you know design

guidelines of the manufacturer and do that. Um more copper the better. There's more copper to adhere to um in lamination um to help prevent DAM. Um it's a balanced construction so we can you know any manufact PCB manufacturer can um you know process the inner layers uh better um you know without you know I'll give you an example like it's an extreme example but let's say you had a 3M core and on one side you have 1 ounce of copper you know and it's like a ground pore and on the other side you it's a signal layer and there's just very few signals and not much copper that uh inner layer uh core would have the tendency to curl up and you know if something's curling up on you, you got to take measures to counter that. It's not standard. Um you could have cracks, you know, all these types of issues can happen. So um copper balancing your copper is a real thing both um on different layers in your stackup as well as on that, you know, layer and knowing what is the core. So what is this layer and then what's the opposing side of that core? What does that copper weight look like? and cover it. Okay, great. Okay, thank you. Yeah, from a manufacturing perspective, that definitely makes sense. It just my as a designer with copper paws is essentially always the cleanup of the copper paws. So, it's easy to just draw a polygon, but then you might have, you know, little islands that maybe aren't connected or with it might be difficult to get in there and that's the only trade-off I see for me. And also maybe impedance effects around that you have to do proper clearances and so on. Okay. But for manufacturing, you would say pretty much all the time you should aim for that. Yeah. Do copper pour and um honestly the CAM softwares that we have right now are very powerful so they can handle you know like a nice optimization or cleanup. Um so you could leave some of that to us. Uh the fabricator just I would say ask for your Gerber's back for approval. If you have a sensitive impedance area or RF area, you can always you should I think it's good practice ask for your Gerber's back for approval to make sure that you know that there's no extraneous copper where you don't want it and you know Okay. No, that's a great idea. So the next one would be about annular rings and annular ring capabilities. So the only at least what I've seen so far only place I've seen other than for example the IPC Courses is for example Euro circuits when you drill a bit higher or a larger diameter and then you plate down to the final hole diameter. So actually the annular ring calculation should include for example a larger drill bit and then you divide by two to get the annular ring. But most manufacturers won't state that or most calculations won't tell you about that. At least from what I've seen that might be completely wrong. So should annular ring calculations I assume should also take in the larger drill size for plating. So uh yeah so that goes back to you know how do you want to do things? own the design completely? Do you want to lean on your manufacturer? Follow their uh design guides a little bit. Um ask them talk to them because if you're building a standard product then what Eurosircuit said is fine. um you know standard copper weight you know standard surface finishes you know maybe enig things like that but when you get outside of the standard then it's really important to talk to your fabricator so for example I'll give you a couple examples the way you describe it is correct we we're going to drill bigger than what the finished hole size requirement is so on your fab drawing you should always specify the finished hole size and you should specify tolerance and so we are going to drill bigger than the finished hole size now what about the copper weight because as you plate on the surface, you also plate in the hole. So, if there's a little bit more thickness of copper that we're finishing at like 2 oz, then that changes the drill size that we're going to use. So, we're going to make it a little bit bigger so that as the copper gets plated on the surface, it also plates in the hole and uh you know the we can handle that you know based on the co the overall finished copper weight. So starting copper, finished copper weights play a role into what is the drill size that's going to be used um to actually drill your holes. So you have to be careful with how do you decide you know how you want to calculate annual ring. I personally think it should be um you know finished hole size plus whatever your fabricator says it should be. Okay. No, that makes sense. Yeah. Yeah, I just find it peculiar that usually that's not talked about and the only place I've seen are for example an IPC C or that Euroscircuit side. Well, it's not I don't think it's talked about because every manufacturer has their different rules of thumbs. Um but again, for a standard product, you know, considering that we're going to pick the next drill size that can accommodate, you know, maybe IPC requirements of copper and the via. So 8/10 is the minimum requirement. So if you can think okay I this is my finished hole size plus I need to drill it add 8/10 of copper you know what would

be the drill size at that point that's how we kind of figure it out and then if the surface finish is like a hassle um you know that takes up a lot of that that's very thick and so different from enig which is an electrolish process so a hassle surface finish would make us drill even higher so these are the considerations so it's not necessarily just cut and dry. It's up to the fabricator and what they've seen their processes and processes tolerances result in. Okay. Oh, great. That makes sense. What's often a problem when I'm for example footprint position files, component placement files, also when you're already defining or creating your own libraries for the footprints, defining essentially what is the base component orientation. Now it seems wherever I mean for example whatever manufacturer you go with they might have different standards at least from what I've seen where they define let's say where north is or rotations and so on. How would you should your for example component libraries be defined by how do you define orientations so to speak properly? Um I mean for orientations uh there isn't necessarily any one standard. So, I think that's the issue that you're referring to, but you know, we I would say that whatever you do, just be consistent. I don't know. That would be kind of like my generic answer on that. Um, I guess you could follow IPC guidelines as well. Um, but, uh, you know, there's really no one way of doing that. Okay. So there isn't, for example, a standard for pick and place machines that manufacturers or assemblers might use that rotate the component or have an orientation, a default orientation where, for example, 0 degrees is. There isn't something like that. I mean, you can do 0 degrees, but the pick and place machine doesn't really care. Okay. Yeah. If you're going to standardize on something, then just standardize on 0 degrees, but it's really not it's not a thing. Okay. So the essentially the common placement files, the pick and place files are probably always edited by the assembler beforehand. I mean if you it's a good idea that you mentioned to you know make sure that the zero rotation in the footprint corresponds to the feed direction um for the component that's in the reel. But I mean that's something that we take into account. Okay. And I think the next question is something I actually saw in your DFM guide. So I someone was wondering with having different drill sizes. of you know might have 0. 15. 3 or at least finished diameter hole sizes. Is there any cost difference or any benefit in reducing the number of drill sizes so just sticking with only 0. 25 I mean sometimes I guess they'll get rounded as well to the nearest drill bit or whatever you then plate to. Is there any benefit of reducing? Yeah. Um, so my perspective is that of a prototype manufacturer, someone who, uh, is doing, you know, lots of different part numbers per day and not that many. But if you're, you know, in the consumer market, um, and you're doing millions of pieces or tens of thousands of pieces, I would say that there is a benefit, um, in that scenario. But in a prototype environment or even in like a few hundred or a thousand pieces, it doesn't really matter. Yeah. What you're saving on is the time it takes for a drill machine to go and drop a drill and pick up another drill. And then, you know, our machines these days, they'll pick up the drill, they'll measure the size of the drill, make sure that's accurate, uh before it starts drilling. So you're saving on the, you know, that type of a, you know, a timeline just dropping and picking of a drill bit. Um, but other than that, there's really no um impact. And, you know, nowadays our drill machines have these big canisters at the back of the drill machine. So when there's a job that we're loading onto the machine, literally the, you know, the tooling is done automatically because all the drills and all the sizes and all the variations are built within the machine. So um there's really no kind of pre-etup extra charge and there's really no um cost benefit to you know minimize the number of drill sizes but in production it might make an impact. Okay. No that's great to know. Okay. So the next question would be related for example to futurial markers. So normally I would just do just a round exposed pad and then pull back the solder mask opening. I did however steal this maybe from Nvidia. I noticed on their graphics cards they use more of these cross fidial markers. Is there any manufacturing or assembly preference to what size or what um shape for marker is used? Uh I think so over the years our best practice for fidials is to uh have um you know three sides be uh round and then one side be a square. And that's really just so that we know the orientation and you know you're not getting the orientation wrong when you're putting that into an assembly machine. Okay. So actually having so you said three round one square it's actually four fidial markers on a PCB. There's this cross I mean I've seen that

on some Nvidia I think might have been it. It's just a an optical thing rather than having any use. Yeah it's just someone's okay. I thought it looked quite cool. So I guess that's anything. A lot of designers do things that look cool. So that's fine. Okay. All right. In terms of next thing would be for example rounding drill hole sizes. So sometimes especially if for example in Europe we're working with metric we might get um a US data sheet that has mill specifications for the drills and then underneath they'll have rounded it the drill maybe to 1. 02 mm. I typically would then round up taking into account of course tolerances and so on. But how would you maybe go about something like that? I think that uh I'm gonna go back to like kind of an just a gen generic answer. Understand that the tolerances for your fabricator are and usually very normal it's plus or minus 3 ms on a finished via for a nonplated via we can do a tighter tolerance of the hole because there's no plating in there. So that when you drill a hole, you're removing probably half a mil. And then so if someone says, "I can do a non-plated through hole plus or minus 2 mills. " Well, you know, you can do it even tighter than that because when you drill the via it, it really only removes about half a mil. So um you know, in terms of rounding, you can round up, you can round down. Just understand the you know, the tolerances of the drill, I think. So the next question would be polarity markings. There's of course many ways of marking the polarity. One indicator is it could be lines or dots or anything. Is there anything that assembly lines or assemblers fur marking the cathode or marking the anode and what shape that is or is that an odd question? No, it's not an odd uh question. I think it's a very important question. So um you know we have a DFA guide and that's like the number one DFA issue. So, you know, if you're I think, you know, having a you know, the actual symbol, you know, is the best thing to do, frankly speaking. You know, you do a plus or an A for the anode. That's fine. And a KRC for the cathode, but having the symbol also is the best thing. One point that I also often times get uncommon because normally I don't place, for example, component designators on silk screen. To me, it's more of annoyance, so to speak, trying to fit things in. And usually for denser boards you're going to have to produce the text size that's hardly legible anyway is other than unless you're of course doing prototypes and manual assembly but for actual automated assembly are do designators on silcreen add anything or as long as you have a good assembly drawing is that pretty much all you need. Um no I would say uh component designators are essential. um it prevents errors and again I live in the prototype world where there's literally hundreds of errors on every design that we get right so we're constantly giving the feedback and correcting those issues um and then you know you have manufacturing which you know is still um requires labor it's a there's humans involved in making um circuit boards so having you know proper silk screen you know Having proper component designators in silkcreen I think is a critical thing that you shouldn't skip. If a design is version number five and revision five and it's now in mass production, a mass production house might have a different answer, right? Nothing's changing um and nothing should change. Um so they might have a different answer, but from a development standpoint, which is what we do is we work with people early on in their design phase, there's always issues and there's always errors. So I think that that's a critical thing to have. Okay. No, that definitely makes sense. I was just remind of it because when I was doing an IPC EC course the instructor told us maybe very opinionated that not useless but there could be problems for example that silk screen that is too close to exposed copper and that could maybe overlap and then you get assembly issues and arguing that way but you say I mean yes for the prototyping it makes sense to add in the designators and that's less of an issue than for example silk screen registration alignment and so on. Yeah. So again, designers should know their manufacturing tolerances, right? So um you should have it and you should follow the guidelines of the manufacturer. What are the tolerances and you know what sizes you should use so that it's legible. Um and there's in our um front-end department, we clip the silk screen. So if a silk screen is falling on, you know, too close to something, you know, let's say too close to a pad, we will clip it. So you won't have that issue of silk treating too close to a copper pad or something but because we're going to clip it but then it now becomes useless for assembly. So uh you know follow the guidelines so that after the fabricator you know is done with their optimizations of your data that it's still useful for the AOI

machines at assembly. Okay. Topic of creating one's own panels as a designer. Is that something manufacturers even want example designers to do? To me, I would have thought that manufacturers would want to arrange on a panel. Depends maybe on volume or if they're putting it together on a sheet or a panel with other designs. What are your thoughts on that? Um, as a practice at Sierra, we haven't, you know, we basically design our own panels. The customers, you know, aren't really um we don't leave that as a burden on the customers anymore. And there's a couple reasons for that. So first of all, you know, there's the optimization on a full sheet on the PCB side. Uh and then there's also optimization in assembly. So you have to balance those two optimizations. I don't think a designer has all the information to make the best educated decisions. Um so for example, uh I'll give you a quick example. So in rigid flex PCB manufacturing to do an array really eats up a lot of real estate on a sheet. You need lots of spacing between parts. Sometimes, uh, fabricators will nest rigid flex boards, things like that, so they're not losing too much real estate. But regardless, doing a oneup and routing out the single up rigid flex board is more optimal space utilization for the fabrication side. Now, on the assembly side, you probably have to say, okay, well, assembling one board at a time is not optimal. Now in that case maybe the assembly will make a decision that we are going to generate a fixture properly hold the board the way we want to in assembly. You're basically if you optimize the PCB sheet and get the lowest cost PCB you're you could be then increasing costs on the assembly side and vice versa. So you have to make the decision a holistic decision and that's not the only thing that goes into making an array. I mean it's utilization. And it's also do you have any components that are overhanging in your array design and are boards spaced apart properly apart but you know so all those go into that decision process. So basically we don't want our customers trying to make those decisions because we end up correcting it anyway. So we basically do that for our customers. Um but in terms of general guidelines for creating an array I would there are some of course right like just but look out for you know overhanging components too close to the edge etc. And I would say that you know other common things in building your array you know I would say is you know make sure you have railings so that if you're going to build an array your assembly shop needs to hold on to the railings. um you know I would say there's going to be some guidelines around building arrays for example layer indices in copper so I will typically add for example just in copper just edged way just an index of the layer which I think is might be useful thing I don't probably not necessary but are there similar things that could be beneficial that the designer can do that maybe makes the manufacturer's life a tiny bit easier um so that that trick I've seen a long time ago it's like a really old trick and I think it's Great. Um on our sheet we do the same thing. So um you know we basically have uh these mechanical mechanisms so that we can't get the layer order wrong. um orientation wrong. All those things come into play on our sheets. So you don't really need it on the board anymore. Uh but it's nice. It's cute and I think it's doesn't hurt anything. And then I think that other than that, like there's really nothing like that on a fabricator side that they we absolutely need or want. I think the most important thing in my opinion for a designer is to have a fabrication drawing and to properly communicate anything special or what they're looking for um you know for from the fabricator. Fabrication drawing is universal and you know is key to building a board to specification. So, um that's what I would recommend is actually having a fabrication drawing uh more than anything else. And then in terms of like, uh we talked about copper pores and if you have any keep out areas, like that's important to outline in the gerbers. Um you know, a lot of fabricators will put their logo and date code, you know, right where they see an empty spot. And sometimes designers want that area to be free of any copper. If you want like a keep out, you should specify that in your on a Gerber layer. So these things are fab drawings or Gerber layers. I think communicating anything special is key on in that way. And in terms of fab drawings, do you prefer that if we're going with Gerber format be a separate Gerber layer or would you rather for example a PDF or any other form of documentation to document that? I think you should as a designer send it put in your gerbers and send a PDF both fabrication, fabrication drawings. So I

guess every designer or company has their own set of way of doing that. Is there maybe a template that people could use or maybe that's Sierra prefers in terms of which order or what the notes are. Is there something like that available? Yeah. No, we Yes, we definitely have our standard notes that we would, you know, I can send it to you if you want. Um or we can send you a link to it basically. But uh yeah, we have standard notes. Every designer should have a fab drawing and they should have those standard notes on the drawing. Yeah. Okay. Because I've I mean I have my standard which is a template as well, but that's kind of pieced together from repetition and finding out what works, what doesn't, and then having a standard set which might not be ideal. So yeah, if you have a link to that and that would be great. Thank you. I've heard quite a lot that the manufacturer does actually edit for example the FAB files quite a bit of course to compensate maybe for some warp or shrinkage or whatever the right term is. I guess the designer will have no influence over that or is there anything that the designer could do to aid the manufacturer and make that less of a pain painless process? Just understand that when we add etch comp now we have to etch through smaller spacing. So in manufacturing a circuit board it's the spacing between features that's the most difficult to deal with as a manufacturer. Uh so if let's say you had an option with a trace in space sit situation to have more spacing and a smaller trace that's the design decision I would make as a designer and that would help your fabricator to uh be able to build your board. For example, Gerber OB++ or IC format. Is there any preference? I mean Gerber seems to be the old standard that hasn't really been surpassed too much yet. As a manufacturer, what file format do you prefer? Yeah. So we prefer ODB and you know that being said if you send Gerber and ODB you can say use Gerber for the fab and ODB for assembly but in order to properly do flying probe test after assembly uh and to program the assembly machines you really need ODB data. And then there's the new format IPC 2581. More and more fabricators are supporting that format and I'm a full proponent of that format because it helps designers not get anything wrong. It's basically one package. It includes stackups. It includes your bill of material. It includes everything. So, um really understanding what needs to go in the package will be a thing of the past um with the 2581. And it also includes a birectional component to it. So, if we bring in your data um and we want to make a comment on a feature design that you've done, we could literally make a comment and you and send it back to you and you can import it back into your designer tool. So, there's a lot of advantages of 2581. So, first and foremost, I'm a proponent of 2581, but today we live in today and not every fabricator is going to support 2581. So I would say go with ODB and if you have a problem with just ODB and you want to use Gerbers for your FAB then say that say use Gerbers for fab and ODB for assembly and that works too. Okay. Is the majority of files you get still Gerber or what kind of proportions do you get these days? you know, uh, we we get about 50% ODB, which is huge compared to where it used to be 5 years ago. And we still get Gerber. So the other 50% is Gerber. And um, so yeah, we're getting both at this point. So it's the last question if that's okay. So for example for signal integrity and other reasons normally and also having less voiding in for example fills and inner layers usually I would remove unused pad shapes for example from vs or plated through holes and typically leave for example start and end layer pads. Is there any problem with for example removing maybe start and end layers or outer layer pads and just having for example one inner layer pad or a number of them or is there anything from a manufacturing standpoint that could go wrong? First of all, uh I would always remove non-functional pads. And that would be a fab note saying to the fabricator, hey, it's okay to remove non-functional pads. You know, especially if it's a heavy copper type of a situation. When the drill is going through your board, it gets deflected by all that copper. Um so you have to do things like slow down your drills. Um so they're spinning slower and feeding slower. and you might have to do a flip drill where you drill from one side then you flip the board over and drill again from the ne other side. So better to remove non-functional pads and it'll minimize deflection and then as per you know whether you know you should if you could have a pad on any layer. Yeah, go ahead. That doesn't really that doesn't Okay, so outer layer pads we can also remove if they're not needed. Okay, there's no Okay. All right. Again, a huge thank you to Amit and Lucy from Sierra Circuits for taking the time to answer these questions. And I hope these

answers and the discussion we had proves to be useful for your own PCB designs. Again, links to Serious Circuits and their very, very handy tools and guides will be in the description box below. Thanks again for watching this video and I hope to see you in the next one. Bye-bye.