Design for Manufacturability (DFM) and Assembly (DFA) tips with Jay Colognori

Get Design for Manufacturability (DFM) tips from Jay Colognori, Director of Business Development at Electronic Instrumentation & Technology (EIT). DFM and Design for Assembly (DFA) are important to engineers who know you can’t just design a PCB and throw it over the wall to manufacturing. Early and proactive optimization of all the manufacturing functions from fabrication to assembly of the final system is key. Listen to Jay and Judy discuss high-yield designs, EIT’s value-added engineering services and the latest state-of-the-art inspection technology and test capability.

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Show Highlights:

• Jay was educated at Virginia Tech where he attained an EE Degree, followed by a Master's in Electrical Engineering at the University of Virginia.
• He spent  most of his career in the mid-atlantic and his career spans from board level electronic design to applications engineering doing custom microelectronics for a couple of years, eventually ending up in PCB Design first at TTM and now at EIT.
• EIT has been in existence for 42 years, and specialize in electronic manufacturing services, turnkey builds, box builds, and demand fulfillment and consider their Engineering value add as part of their DNA.
• EIT has three facilities on the East Coast, consisting of over 200,000 sq ft. They have a facility in Danville Virginia, headquarters in Leesburg and another in Salem, New Hampshire. Altogether they have eight surface mount lines.
• The Danville facility is designated as the low-cost center of excellence and is also a 100% vertically integrated location - it is built for box builds.
• Leesburg and Salem are high-tech facilities with the latest state-of-the-art universal equipment, as well as the latest and greatest inspection technology and a full suite of test capability - with a lot going on and a story that needs to get out - it’s almost been a secret!
• New EIT website

DFM Tips:

• 2 objectives - 1) to design so that it can be fabricated reliably and with high yields, and 2) so that it can be assembled
• VM Pad requires a wrap plating process to provide a reliable button around the via.
• This process requires more copper which can wreak havoc with fine line design, so be sure to plan upfront and move those fine line geometries to the inner layers.
• Overlapping via structures can’t be made. They need to be stacked and sequential, not overlapping.
• Sit down with your PCB Fabricator at the time of stackup development, before you even start that router and make sure everyone’s happy with the stackup.
• FR4 has too high a Dk for high speed designs today and new materials such as teflon or ceramic-filled laminates are becoming more .
• If you work with a new material, consult with your PCB fabricator to see how the rules have changed with that new material for the speed you desire.

DFA Wisdom:

• Pads - so close together that they touch, rather than routing a thin signal from pad to pad is a problem. We don’t want them to physically share the same space which will cause loss of control over the solder flow.
• Keep the pads apart and just run a small solder trace between them.
• The via in the pad has to be filled, it must be plated over and planarized.
• Sometimes the planarization isn’t done properly and even a little dimple, with a BGA on top, will cause the gas trapped beneath the solder paste, to expand ferociously and blow all the solder out of the pad at reflow.
• Always use non-conductive filler it’s much less expensive.
• The benefit of using conductive fill from a thermal point is negligible and is too expensive for the return.
• Thermal conductivity is defined in Wattmeters - if you use a conductive fill, you only get 6 more wattmeters which is rather pointless because the copper is already doing all the work.
• When a thermal via is located in a big plane, with a copper button around it - the button will be in contact with the plane and this is a big no-no. It compromises the solder flow again.
• Do a sprocket arrangement around that thermal via button. This will create a gap between the button and plane and sprockets simply act as traces surrounding it - very good design practice, frequently missed. Especially on backplanes with active components, this will require retooling to enable manufacturability.
• Why has design migrated as a service inside many EMS companies? What is the value to the customer?
• It’s a benefit to both the customer and the EMS. We want to do more for the customer than just assemble the circuit cards. We want projects going through without a hitch, no delays. What we all want is production of electronics.
• Why did EIT choose Altium over other tools? Firstly it’s an all-inclusive package. It’s schematic and design, we like the ECAD and MCAD interface which makes it easy to do 3D fit models. We love the room creation capability that allows you to reuse previous designs. It has very solid DFM rules capability which are set up in advance - that’s a nice piece of insurance. It’s reasonably priced compared to the other high-end tools as well.
• Engineers After Hours: Big hiker, especially the Rocky Mountains. We’re going to do 3 national parks this summer.
• Unique hobbies? Jay has been a dart player since the age of 19. Played in a couple of US opens. Pro advice: 2-3 beers is the sweet spot for optimal dart throwing performance.

Links and Resources:

EIT Electronic Instrumentation & Technology Website

Jay Colognori on Linkedin

EIT on Linkedin

About Jay Colognori

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Transcript:

Hey everyone, this is Judy Warner with Altium's OnTrack podcast. Thanks for joining us again. I appreciate everyone that's following, we are spreading like wildfire and we thank you for all your comments and opinions and we always look forward to hearing about things you want to hear - so reach out to us on Twitter; I'm @AltiumJudy, or you can connect with me on LinkedIn or Altium is on LinkedIn, Facebook, and Twitter.

So today I have a longtime friend and ex colleague, Jay Colognori and Jay is the Director of business development at EIT which is Electronic Instrumentation and Technology in Richmond Virginia, and you're gonna have fun just listening to Jay because it's like talking to Matthew McConaughey!

So you girls out there? We're gonna just have fun listening to Jay talk...

Just kidding, but he does have a nice Southern drawl.

So Jay, thanks so much for joining us today, and we look forward to talking to you about DFA and some technical stuff today. So thanks for joining.

Thank you for having me. This is an exciting time at EIT we just added on Altium capability and so I'm delighted to get to the word out, and what better way to do it than talking to you?

Well, you know when you suck up to your friends at Altium, you get on the podcast. That's how it works around here.

So Jay, Why don't you start out by telling our listeners a little bit about your educational background and your professional background sort of set the stage for us?

Okay sure. I picked up an EE Degree at Virginia Tech and then a Master's EE at the University of Virginia. So you could say I'm a son of Virginia for sure. I managed to spend most of my career here in the Mid-Atlantic and my career spans from board-level electronic design to integrated circuits, VLSI design, and then kind of jumped over to the other side of the table and became an Applications Engineer, doing custom microelectronics and had a few years running a rep firm making some commissions along the way, and then I ended up in the printed circuit board business working for DDI and VIASystems, now TTM, and one of my customers was a company called Zentech which was an Electronic Manufacturing services company, and I went to work for them. And now I work for EIT who is also situated in the Mid-Atlantic. I do want to correct one thing you mentioned. I live in Richmond, Virginia, but EIT is based in Leesburg, Virginia where we have two other facilities, I can talk some more about that.

Alright. Thanks for correcting me there.

So with all that variety of background why don't you tell us a little bit about where you are now and about EIT and what their expertise is, and what kind of technology makes they handle and so forth?

Yeah. Okay, so I joined EIT back in March, very happy to be there. This is a company that's in its 42nd year of providing...

Wow.

Yeah - Engineering services which then led to electronic manufacturing services. So we do both; engineering is very much in our DNA, we consider our engineering value-add to be an important part of most of our customer relationships.

So, you know, the thing about being in the electronic manufacturing service is that it's kind of a commodity when you look at it from the standpoint of just picking and placing with machines. So, we're looking to engage customers at additional levels, including engineering, turnkey builds, turnkey testing solutions, of all manner, box build if necessary, demand fulfillment, soup-to-nuts… so that we're doing more than just using those machines. And EIT has three facilities on the East Coast. Altogether we have over 200,000 square feet of brick and mortar which makes us pretty big for a small company. We have a facility in Danville, Virginia. Our headquarters is in Leesburg. And then another in Salem, New Hampshire. Altogether, I've got eight surface mount lines to keep busy.

Danville is what we designated our low-cost center of excellence. It's also a 100% vertically integrated location because they can do any kind of metalwork, cabling wire, box build. We have all that in place. It's a purpose-built facility to support the box builds, which we like to do for our customers. We don't do metal stand-alone, although occasionally I'll build a heat sink or something for somebody. We tend to allocate that factory towards our customer box builds.

Okay.

And then Leesburg, and Salem New Hampshire are high-tech facilities, they both have the latest state-of-the-art universal equipment, so we can back each other up if something goes wrong and they both have a full suite of the latest and greatest and automated inspection technologies and a full suite of test capability.

Wow that sounds impressive!

It's a heck of a lot going on, and a story that needs to get out; it's kind of been a kept a secret lately so yeah...

I haven't heard of them. I mean I'm on the left coast, of course, but I had not heard of them, but they sound like a really great facility with a really good… going all the way from true engineering to box builds. That's nice.

So… and we'll make sure to share the link, by the way, for any of you listeners who are looking for a good EMS or engineering service or whatever. We'll be sure to share that link on the show notes.

So yeah, and please do, because we're launching a new website next week, so I want to get that out.

Okay. Hopefully the timing for that'll work out.

Okay. Alright good. We'll send you some traffic for your new website. So Jay, because of the breadth of your knowledge and experience and background I thought it'd be great for our listeners today if you shared a few tips from, you know, being that you came from some of the largest board manufacturers and certainly in North America and almost the world - maybe three tips or so, on bare boards and then a few on DFA to help the designers in our audience, and engineers in our audience, that might want to learn a few tips and tricks from a pro?

Okay, you know I came up with a few of each, you know, really when you're looking to design a printed circuit board, you have two fundamental objectives: one, to design it so that it can be fabricated reliably and with high yields. And then two; so that it can be assembled. So there's mistakes that can be made that can affect both key processes.

So first of all, let's talk a little bit about PCB design issues that affect PCB fabrication and reliability and, you know, none of these I think are gonna be earth-shattering, but it's interesting to see the same mistakes being made a lot over and over again.So, we just kind of keep - we're banging the drum and we hope everybody gets the message sooner or later.

So, I guess beginning with VM pad. There's more and more VM pad today, by necessity, and VM pad, in order to be done reliably, requires a wrap plating process. Without getting into specifics of what that does, what the purpose of it is, it provides a reliable button around the via. Without the wrap plating process. It's an unreliable arrangement, but that requires the addition of more copper on the outer layers than you would see otherwise, and this wreaks havoc with the fine line design.

So, if you're at 3 mill tracing space or below, you really can't tolerate that extra copper; so it requires planning upfront. Understand, if you're gonna need wrap plating and if so, maybe move those fine lines geometries to the inner layers where that won't come into play.

Okay, that makes sense.

And it'll get you, I mean, you think your design's done and then the next thing you know, your fabricator says, well you know, you realize I'm going to add this much copper to the outside and now you're violating tracing space.

I've seen this happen too when there's multiple on RF and microwave boards too and you have... when you're doing sequential LAM or whatever, and you keep plating, plating, and people don't, when they do their simulations, don't add in those extra layers are getting extra copper too. So you really can throw you off.

All right. That's a good one.

Here's another one that you know, I'm told we're still seeing a lot of it in the market by the guys that I used to work with at DDI, and that is, you know, they'll see overlapping via structures where the designer has put a via from say, level one and three, and another one from level two to eight; that can't be made. They have to be stacked; they have to be sequential. They can't be overlapping but believe it or not. You see it.

I've seen it many many times, but you know, to be fair, sometimes when I look at those cords and figure out how they're gonna be stacked up, it… you know. I get confused too. So...

Well, I mean, I'll say this again and again: sit down with your PCB fabricator at the time you develop your stack up and your basic via structure and basically your structure is going to be driven by the toughest part of the design.

Maybe it's a BGA with a finer pitch than you've ever used before. You're not even sure how to route it, you're probably going to have to stack some micro vias, or at the very least, have some blind or buried vias to get the job done. Sit down with a fabricator, before you even start that router, and make sure that everybody likes the stack up and that it looks manufacturable.

Yep, very sound advice. Okay, that's another good one, got another one for us?

One more I want to talk about, because this is happening more and more, you know, all the designs are getting faster and faster. I mean, high speed digital is now in the radio frequency and, FR4 is just has too high a dielectric for most of the new designs now, so many PCB designers are going to have to work with materials they haven't worked with before, the more exotic, more expensive materials, and when you start talking about fabricating a PCB with Teflon versus FR4, you're talking about different processing altogether.

So, when you go to a new material, consult with your PCB guy as to which material would be suitable for the speed you're looking at, and ask them, okay, how have the rules changed with that material? What are your limitations?

And you can ask the EMS provider the same question, because the parent circuit board is the foundation upon which all of our business is done. So we understand PCBs, but I think especially with materials you want to talk to the fabricator.

Yeah, it's true and when I worked for an RF and microwave shop once, I told them, I said: you know, sometimes when you see a piece of Teflon material and a piece of... I don't know, Rogers 4350, until you strip the coffer off. You can't tell it's different, but inside the board shop that Teflon can turn into bubble gum, it's not reinforced. But when you take the copper off and you go like this [motions] it like flaps in the wind where 43-50 will remain rigid so, kind of gives you a visual sense of, this is radically different. And the way that it processes inside the shop, and how, the way it interacts with chemicals, moisture, heat, so it is true - the closer you can be when you go into those materials, to your fabricator. Okay, those were three good ones. All right how about DFA wisdom?

Okay, well one we see quite often, and I guess it's tempting for the to do this, because he thinks he's kind of found a shortcut and a way to use less PCB area, but you see a lot of guys trying to use what we call pads, and these are pads that are so close together that they touch, rather than routing a thin signal from pad to pad.

So these pads do share the same signal, but we don't want them to physically share the same space. That causes us problems with controlling what the solder does once it flows, so keep those pads apart, and run a just a small signal trace between them. And then we'll let the solder mask do the rest, and we can control the flow of the solder. So that's a real simple one, but we run into it a lot.

Okay.

I talked before about VM pad, we see a lot of designs where people don't fill that via. If the via is in the pad, it's got to be filled, and it must be plated over and planerized. Sometimes that's done properly sometimes it's not. There's a little dimple there...

Yup.

If there's a dimple in that pad and I place a BGA ball on top of that gas, it's gonna get trapped underneath the solder paste that I apply and there'd be a little air in that dimple and heated gas expands; it expands ferociously. It doesn't want to stay where it is and it'll blow all the solder right out of the pad at reflow time and you know I have customers argue with me against it, it is expensive to fill and planerize via, but it's the right thing to do. You have to do it if you want reliable BGA connections. These are leadless that we can't inspect visually, we have to use x-ray.

It's not really practical to use a hundred percent x-ray inspection except on high-reliability applications like military, maybe medical. So we lot, we lot-sample these BGAs with X-ray and if we don't see any problems with a lot we carry on.

So, I can't emphasize that enough, to fill those vias and fill those vias properly. And I would add further, that there's no point, you know, we have some people that are using thermal vias, these are vias really which are designed, not necessarily to conduct an electrical signal, although they do, but to conduct electricity from a hot part from maybe a ground plane, might be an inner layer or wherever, and you run into people who call out… so there has to be a filling to fill those vias before they're plated over.

Right.

And there's two types of filling: there's conductive and there's non-conductive. I strongly recommend never to use conductive. Non conductive is much less expensive. The benefit of using conductive fill from a thermal point of view is super minimal. I mean, the copper's doing all the work...

Okay.

-and if you need to draw or pull more current or more thermal energy, just create more thermal vias because the copper's doing all of the work. I mean, I'll give you some numbers: thermal conductivity is defined in wattmeters, a typical via is going to give you over 600 wattmeters of conduction, if you fill it with conductive fill you only get six more wattmeters. What's that compared to...

Oh, yeah.

-380 I'm sorry, 380's what the copper gives you. The non-conductive only has point six wattmeters.But the point is both of those are in the noise compared to with the copper's doing.

Right.

And last but not least. Good luck trying to get a printed circuit board fabricated in China with conductive fill they don't do it over there.

Really?

Right so well, maybe somebody's doing it but we're having a hard time finding any.

Interesting hhm.Why is that?

Because it's not, it's not...

They just don't like it? It's not important so we're just not doing it?

I don't think anybody should be doing it, it doesn't make sense to me, it's too expensive for the return.

Interesting, I'd never heard that before actually, but it makes sense with those numbers. I'm kind of surprised it took root for a while.

We recommended as far back as five years ago, at DDI, not to use conductive fill, I think it's a dinosaur that it's day has come and gone, but there's probably some engineers out there right now, going no!

Huuu! [laughter]

We'll see...

Yeah well show me the data, you know, and when when there's enough good research out there and data people stop doing it. I'm sure.

Okay, so along the lines of thermal vias, here's another tip. A lot of times a thermal via will be located in a big plane so you'll have the via, and the copper button around it will actually be in contact with the plane - this is a no-no. This makes it very hard to deal with the solder flow again. So what we ask our customers to do; is do a sprocket arrangement around that thermal via button and so basically that button will exist -  there'll be a gap between it and the plane around it, and then the sprockets are simply traces above, below, and the right and left and that - it's an arrangement of the sprocket - very good design practice, frequently missed and, it's not unusual that we have to go back and retool the board to add those in order to make it.

Especially back planes with active components; you see a lot of that and they have to retool to add that feature to make it manufacturable.

Well, these are good tips. You were concerned you didn't have good tips. I think these are really good tips actually.

Well glad you do.

I do, not that I spend all my days, you know, pondering DFA these days, but that's good.

You know Jay, you and I worked together for a small bit of time and something I've noticed over the years I don't know... maybe five, ten years, it seems like there's been a migration of more EMS shops that go in to have PCB designers in their shop and not so much I guess, fabricators - at least that I've noticed, they may be there, of course they do with larger shops, but why do you think that is and why do you think that's a good idea?

Well, I think it's a great idea for both the customer and the EMS. We, as I mentioned before, we want to do more for the customer than just assemble the circuit cards and if a customer, an Altium customer, finds themselves in a position where they need to outsource some of their design, maybe they you know, their designers are saturated, maybe they just need the resources.

What better place to do it than at a guy that knows how to assemble the cards and really understands the issues about fabrication and about assembly. Your chances are that the design from your EMS provider is going to go right through new product introduction without a hitch, whereas if you do it internally and you're not aware of some of the issues you know, it won't go through it without a hitch. We may not catch the problem until it's too late. And we may see several tooling iterations, and you'll see a delay and nobody wants to delay during new product introduction - everybody's in a hurry to get their prototypes.

And nobody wants to waste money because that's going to be expensive too -

Yeah, but we think there's a lot of serendipity between that particular engineering function and getting to what we all want. Which is production of electronics.

Well that does make sense in that, we both know Mike Brown, and Mike I trusted implicitly to know about fab and assembly and he would catch all that stuff so he did have a broader understanding than maybe, somebody who just does, you know has a consulting firm say, that does designs because he's around it all the time all, day long so there's certainly a lot of exposure there. So that makes sense.

Well, first of all, welcome to the Altium family! You told me recently that your designer on-boarded Altium Designer 18, that's exciting for us. So thank you for that. What made you - I'm gonna go for a little pat on the back for Altium right here. I want you to tell us why you, why EIT chose to go Altium Designer over perhaps another tool?

Okay. Well, we think some of the key features of Altium; first of all, it's an all-inclusive package so it's schematic capture and printed circuit board design. You don't have to worry about working with two different pieces of software.

We like the fact that there's an e-CAD m-CAD interface which makes it really easy for us to do three-dimensional fit models once we place the components. We love the room creation capability which as I understand it, allows you to take a previous design, a piece of it, and then just kind of cut and paste it right into your new design.

Yeah.

So you don't have to reinvent the wheel. I think that's pretty strong and then, last but not least very solid DFM rules capability that you know, is really going to help us get to where we need to be. I mean the fact is these boards need to be designed to IPC standards and the fabricators have tailored their process to meet these standards; and when you send them something that's outside those bounds, the mechanism sort of locks up. It just doesn't work. You'll get a 'no-bid' or bells will go off, so those design rules are critical and that you have the ability to set them up in advance is a nice piece of insurance so; I think it's a reasonably priced tool compared to the other high-end tools as well. So we're pleased to have it.

Good. Well, thank you again we're happy to have you on board and I'll needle you later about sending your designer to AltiumLive because we're gonna have a really good conference with some good training coming up. So your designer will probably enjoy going if you guys have the time and budget to do that.

Well, keep me posted on when and where.

I will it's coming up in October. So Jay, we're kind of wrapping up here, but if you've listened to these podcasts before, you'll know that sometimes I like to ask designers or engineers like yourself, what you like to do after hours, and we call this portion of the podcast designers after hours. So, I know you have a couple interesting hobbies...so why don't you tell those to our listeners because I think they're kind of fun?

Well, I'm looking forward to 10 days in Montana and Wyoming this September, I'm a big hiker, and nothing is more fun than hiking up in the beautiful Rocky Mountains. So we're gonna hit three national parks; we're gonna do about two to six hours of hiking a day or as much as my legs can give me and just have just an awesome lifetime outdoor experience and hopefully not run into a grizzly bear along the way… my wife's really worried about that, by the way [laughter].

Bring your grizzly repellent!

And then, I know you wanted me to talk about one other thing...

My favorite...

Yeah, as you know, we business development types are very competitive and what better setting to compete against each other than you know, in a pub throwing some darts.

So I've been a dart player since I was 19 and took it very seriously for a while, and spent way too much time on it. Actually traveled every weekend to tournaments all around the United States and played in a couple of US Opens. But that was a long time ago, now I just play for fun on Monday nights.

That cracks me up. You are the one and only competitive traveling dart player that I know... Okay, but my favorite part is - tell about the beer to success ratio of a good dart player.

Oh yeah, so so we're throwing a 27 gram projectile at a target about the size of a dime and turns out, that if you get nervous or you try too hard, you're not going to be very successful with that. So, it turns out that, that second or third beer really kind of smooths out your stroke and you generally shoot a little bit better. At least that's what we rationalize.

And what happens if you go over three?

Yeah, that's that's a slippery slope indeed. You've got to be careful...

That is so funny oh my gosh. Okay well, that is like one of my favorite, I think, designer after our hobbies yet.

So when I come out, we'll find a place and throw a few.

Okay. Alright, I'll get my three beers ready

Okay!

No, actually for me, I'd be like half a beer, like three beers you'd be putting me in an Uber and sending me home. I'm a wimp.

So Jay, thanks so much for your time. These have been great tips and it's good to see your face my friend, and I wish you all the success at EIT, and we will certainly share all the links in the show notes and we'll also put the link to AltiumLive in the show notes and we'll encourage your designer to come out and join us as one of the new new beasts of the Altium family. So we'll include that as well.

So thanks again for joining and we'll talk to you soon, my friend.

Thank you Judy, it was my pleasure. Thanks again for listening to the podcast.

This has been Judy Warner with the Altium OnTrack podcast and Jay Colognori from EIT, and we look forward to seeing you next time. Until then always stay on track.

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