Why is Spread Glass popular? Chris Hunrath from Insulectro
Why is spread glass popular? What can you use instead of FR4? Listen and learn from industry veteran Chris Hunrath, who joins us from the San Jose Insulectro facility for a deep dive into what material sets are used in printed circuit board assembly and manufacturing. Get expert insights and learn about new materials on the market to help with your PCB design before going to fabrication and assembly.
Links and Resources:
Chris Hunrath on Linkedin
Understanding Glass Fabric by Isola Group
Hi this is Judy Warner with the OnTrack podcast. Thanks again for joining us. Once again I have another amazing guest for us who is the go-to guy in PCB laminates.
I am with Chris Hunrath today but before Chris and I get started I would like to please invite you to subscribe, or to favorite us on your RSS feed, or you can connect with me personally on LinkedIn. I share lots of stuff relative to engineers and PCB designers and on Altium I'm at @AltiumJudy and Altium is on Facebook Twitter and LinkedIn.
So please give us a subscribe and a connection and we’d love to interact with you and hear more about what you'd like to hear on this podcast but I'm sure you're going to enjoy today's guest.
Chris is the VP of technology at Insulectro and I'm gonna let Chris go ahead and tell you a little bit about Insulectro for those three people on the planet who might not know who Insulectro is. So, welcome Chris and tell us about Insulectro.
So yeah Insulectro has been around over 50 years. We supply materials to the circuit board industry - actually multiple industries - but mostly we've been focusing on electronic materials. Everything from laminates, prepregs, flex materials. copper foils, conductive inks. Different kinds of plastic substrates used with conductive inks, process chemistries, imaging materials, drilling materials, lamination materials. Also we have 11 stocking locations. We just opened one up in Toronto and we have nine branches. So I'm based in the San Jose branch in the Silicon Valley area so that's a little bit about Insulectro.
Yeah nothing going on there in San Jose?
Lots yeah, so since the San Jose facility is one of the four branches where we do fabrication on master sheets and master roles of prepreg and laminate we do cutting, tooling, vacuum packing, and will also do that on the lamination materials, the release films, and the press pads and things like that. So we do that in four branches…
I'm going to ask you more about that later because you just told me about that yesterday and I had no idea you guys did that. Actually I saw you more as a distribution channel. But before I ask you about that, why don't you give us a little bit of background on your history in the industry and how you came to this? I always say no and no one does this on purpose, unless you're an EE right?
So yeah those printed circuit boards - those of us that got pulled into the industry ,, have been here a long time. So I started actually back in 1983, I was going to school for chemistry and one of the shops back east, actually in New Jersey, was looking for someone to work in plating on the night shift, and ,, the rest is history as they say. I got pulled into the business and the next thing I knew I was coming to California to to work with our sales team. So that's how I got started in this, and then I joined Insulectro in 2001 and it's been great being with this company. So many different materials we get to work with and so many different customers.
I think you're a familiar name and face - being the VP of Technology but you also do trade shows and stuff. You present a lot and are really articulate explaining the technology of laminates because it's gotten a lot more complicated than it used to be back in 1983. I started in ‘84 by the way, and it used to just be, we'll get some FR4 some, prepreg and you're off to the races.
Right yep, back then it was FR4 and polyimide. A little side note, actually the company I worked for made multi wire circuit boards so we also had an adhesive to embed the wires and that's a whole nother story for another time. Primarily it was FR4 and and polyimide and now there are so many different materials and then if you add the Flex materials on top. There's a lot to to work with, it's a lot of complexity but also a lot of opportunity. I mean electronics are going into everything and we're seeing that with our printed electronics products as well ,. A lot of interesting applications from wearables to medical to consumer electronics so that's been pretty cool to be a part of that as well.
Yeah so tell us about what you're seeing on the front lines of current technology and marketing trends that are having an impact on laminate suppliers - ultimately since our audience here is mostly engineers and PCB designers - how that's sort of flowing down and what the impact is?
Yeah so big question sorry.
Yeah that's okay, that's all right. It's become a bigger opportunity - a big part of our business - but if you look at materials in general, everybody knows people are looking for higher speeds and high-speed digital and they're looking for lower loss in RF applications the Internet of Things also even data communications and those types of things; car electronics, radar, self-driving cars. All these things need low loss materials. One of our challenges - and again - it's an opportunity as a supplier to the industry; is having the right stuff available for customers and certainly the Bay Area. It's always been a quick turn market, but it's that the time window has shrunk and one of our challenges is supplying all these different materials to our customers, and of course with every laminate system, every resin system you have the different core thicknesses, the different copper weights and then you have the prepregs with different thicknesses, and resin contents. Add to that also spread glass. It’s becoming very popular I'm sure most of the people who watch this will be familiar with the spread glass systems. They have electrical and fabrication benefits but but again, it adds to the part numbers, the variety of materials we have to stock. So we we currently have here, just in San Jose, we have a hundred and seventy-five rolls of prepreg we cut from for customers. And ,, it always seems like our customers need something we don't have in stock.
It's the one thing they need for that application. But you know we try and up our game here and have the right things. And that comes from going to our customers and talking to the people in their design group, in their sales department and asking them; what do you see? You know, years ago we used to work on forecasts. Customers would have a very predictable usage on materials and they'd have forecasts out for some time. We would base our stock on that and we do forecasting today but it's not the same thing anymore. I mean customers may get an order and they have four days to turn it and they don't know what the build’s gonna be until the stackup’s done and and that creates those challenges. But you know, we try again, we try and improve what we stock and what we have here and get better and better at that. It's just never boring that's for sure.
Yeah right, you gotta have a big crystal ball…
Yeah just talk a little about spread glass.
Yeah spread glass now that kind of puzzles me in context of high speed so I'm curious. Teach us about spread glass?
So there's different kinds of glass, what they call standard E glass and then of course the low dielectric constant glass. I'll talk a little bit more about that in a few minutes. But the spread glass is basically that the the fibers, instead of having a crossover and a weave - like you would in a fabric for like clothing - the actual filaments and the weave are spread out, so you don't have open areas and crossover areas, or areas of higher density glass and that makes the system more electrically uniform. So when you have traces that go through the PCB they’re not either going through high resin content areas, or high glass content areas because they'll have different signal properties so you want to make it more uniform.
Are they more in glass spindles - are you saying it's not woven?
Well it is woven but instead of having a high concentration of glass with open areas of just pure resin, the filaments are spread across so you're filling in the open areas.
Okay so they're kind of fanned out you're saying?
Yes exactly there's different terminologies there’s mechanically spread, there's flat glass, but but basically what ends up happening is, the crossover areas where you would have what we call glass knuckles, they're thinner and of course, the open areas now have some glass. So again the system is more uniform it's a composite. So the composite’s more uniform and and like I said that has signal benefits, especially for differential pairs. If you had one trace and a diff pair running over mostly resin, and one running over mostly glass, they'll have different propagation velocities. So you'd have different electrical results, so the spring glass is better for that. It is better from a drilling standpoint, either laser or mechanical drilling. Because you're not going through high concentrations of glass where the crossovers are so there is a benefit there. There are some caveats though, to how it works with filling ground planes. Because the resin doesn't easily move through the glass fabric - you could have some problems filling, so we have to offer not just the spread version, we have to offer the standard versions as well because very often, designs - if they're strip line - you'll have a reference plane on either side of a signal and those reference planes could be heavy copper and they require a certain amount of fill. So you need the standard fabrics to use as well in a stack up. So you might have a mixture of those types of systems - so yeah it does add some complexity.
So now we're not only doing hybrid materials now we're doing hybrid prepreg you're saying?
Well there are different varieties I guess you have to do it that way anyways because if you're doing hybrid you're matching the materials to the bond ply that you're using anyways I suppose, but now you're adding in this kind of third layer almost.
And then we also have standard copper foil and then we have HVLP or VLP copper and low-profile coppers, so so yeah so it adds. And then of course, all the different copper weights - really everything from 5 micron through four or five/six ounces, so it's all over the place. But yeah actually going on the hybrid thing too we are seeing a lot of mixing the resin systems. In other words you would never mix B-stages in the same layer in other words you wouldn't have one kind of resin melt but you can mix cores so you could have one type of resin system as long as it's fully cured adjacent to another kind of resin system and we see that with RF, because very often what you do is, you have your low loss layer on the outside and then you would have your - whether it's high-speed digital or just DC - you would have that in the other layers and that system would be mixed and there are challenges there too even if you're not mixing the B-stages. Some materials require higher lamination temperatures and if you're not using a standard material that can withstand that, you would have issues or you would have to use a low loss material that has normal laminating temperatures. And typically when we say normal laminating temperatures, we're talking in the 375 degrees Fahrenheit range. Whereas some of the more exotic PCB materials - the filled PTFE systems LCP FEP - they require much higher laminating temperatures more like 550 to 600 Fahrenheit.
For a while I was at an RF - it really never took took flight - but I'm sure you remember not too many years ago, we got on the fusion bonding bandwagon. We thought that was going to solve all our problems but I remember being at a shop where I think we were running our lamp press at like 700 - 800 degrees Fahrenheit for 12 hours with some crazy profile. That's not very sustainable but it was homogenous DK and it had some great performance benefits but it really never took flight. So my gosh let's talk about hybrid a little bit more because I left the industry for a while to raise kids, and when I came back it was like Rumpelstiltskin waking up to all this high speed stuff and I was like wow! And what I did see was an awful lot of hybrids. So can you talk a little bit about what you think - certainly RF and microwave is an obvious one - but talk about what is driving the demand of high-speed digital RF and hybrid technology overall?
Well it's - in very broad terms - it's about electronics, doing all kinds of different things from a design standpoint though it's about mixing, mixing proper material properties in composites that's what you do. You choose one material over another because of its properties and you separate those layers out to get what you need out of a design. So it's driven by cost, some of its also driven by how you would fabricate. In other words, if you had a material that was hard to laminate you could use that as a double-sided low loss layer and then bond the other layers. Conventionally that would run the DC or other signals you would have in the design. We do have some new materials, so one thing I didn't mention earlier is that we distribute for both Isola and DuPont.
Isola does have a suite of laminates that are low loss, some of them even with DKs close to the Teflon range, and they laminate at normal temperatures. So making a composite build is a lot simpler. You don't have to do two separate laminations, unless you had buried micro vias. But you wouldn't do it because of the materials. You would do it because it's for the design but you can do it in one lamination cycle so that's one thing we're trying to bring to market and that's something that's been a growth item for us. Some of these new materials like Tera MT40 for example, the Astra MT77. Astra has the lower dielectric constant - a dielectric constant of just under three - that's for certain, for RF designs, whereas the I-Tera is for the mid-DK, what we call the 3.4 - 3.5 DK range but they're both low loss and they’re both laminated. Again at normal temperatures, so that seems to be getting some good traction.
How do they stand up cost-wise against some of the traditional high speed laminate providers?
Well as a resin system PTFE is expensive and then if you're reinforcing it with ceramic or fiberglass, that adds cost as well, so we actually stack up - no pun intended - pretty well with the PTFE-based product. It's not as well-known, many of the designers are familiar with the PTFE based laminates for RF applications so, they go with what they know very often, until they have a need and then they start looking at alternatives. And there's so many different, projects coming on with our customers, we're quite busy trying to keep that education process going.
So I'm putting myself in a designer's shoes today and I was talking to Lee Ritchie yesterday and he was talking about how the speed curve has gone up near vertical in the last five years and I think you and I would both agree that we've seen that trend. I'm putting myself in a designer's shoes, so how do I get educated fast enough to keep up with all these moving pieces? Because like I said, when I left the industry and came back it was completely like a waterfall as far as onboarding all the different laminate manufacturers and then learning about matching bond, prepregs and bonding systems and cover weights. And then, let's just throw in, that we might have this on an aluminum carrier or whatever. How can we do a good job other than hosting a podcast so I get people educated?
I think the IPC design councils are helpful for that. Some of our folks have presented, I presented, our other people presented. Certainly, if you're an OEM or a designer and you get boards from a board shop, reach out to the board shop and say, what are my options? The board shops have to live and breathe this stuff and certainly, folks like myself and folks at DuPont and Isola will also support the board shop in that effort. In fact that's becoming a bigger part of what I do. I travel with my customer to their customers and talk about their options and the pros and cons because you would think, in theory you would want the highest performance at the lowest cost but, it's not just single performance. It could be mechanical performance, it could be thermal performance, there are a lot of different attributes that you would need in the design and you don't know unless you talk, unless the designers were talking to the folks that have the materials background. You can't put all that together and I've seen projects where people have used the same old stuff and then they get unexpected results and so that's what we're trying to do. It's better for everybody if we hit it right the first time. So, that's what we do, we go in and we say, these are the options, this is when you use fired glass, this is when you use standard, this is when you go for the lowest loss possible, this is where you go for a better economy. We have a material called high speed that's very economical and it's pretty low loss, it's a 006 loss tangent and it's compact. It's not as cheap as FR4, but it's close to a lot of the other materials out there. So it's a nice scale of economy. Now it's not for every design but those who have been using FR4 for a long time and want to upgrade to a total low loss system, it might be a good next step. And that product has actually doing pretty well for us. The 4UIS has been growing pretty well and then the high-end products are growing pretty well. The products in between not so much, but, I think it's just a matter of what people need and the design.
All right, that makes sense. Does Insulectro and/or DuPont and Isola put out resources online that designers can get a hold of?
Yeah both companies, obviously all three of us actually, have websites with links to connect slash sheets, tech data sheets, and other things but I don't know if a website will ever be a good substitute for actually having a conversation with someone who's knowledgeable. Certainly that's a good place to start. The other thing too is sometimes a design will have some IPC slash sheet numbers on them, the specification sheets for different materials, and sometimes you're locked into that. So we've seen that with our customers, sometimes they're locked into a particular material set and it may not be the best. And again that goes back to having a conversation with the people involved. And sometimes they’re willing to change and sometimes not. Sometimes they have no choice. Certainly all old legacy military designs are examples where people are really stuck on very old old systems. And there's definitely a better mousetrap in those cases. But like I said, there's no substitute for having the conversation.
So Insulectro for instance, we were just at IPC Apex and I'm sure Chris, you were doing presentations there. I assume that going to trade shows also, there would be opportunities to have face-to-face conversations?
Yeah certainly, seek out - if you're buying boards - seek out your PCB shop. The folks at those trade shows, or sit in on some of the technical sessions, and then certainly, if Insulectro, Solar DuPont are there, great place to go get some information on materials.
Well I know I sound like I repeat myself often about this, but I've often said, and I used to blog on Microwave Journal to tell people, please go talk to your workshop, please go to your workshop because I think it kind of all ends and starts there and and because, like you said they have to deal with so many laminate and resin systems and all these things every day. A lot of times they could be helpful, it's just sometimes I think designers are so strapped for time. Sometimes they're doing the jobs of two people and so I'm always trying to help the designer get resources as best they can.
Yeah and it's something we appreciate, and what we see happening too, is they'll pick up a data sheet and they look at differences there - sometimes there are very minor differences between resin contents and electrical performance. You don't know the dielectric constant of a loss and they'll pick the lowest on the datasheet, but that might not be the best for the fabrication and having the right material to make the board come out right, yield well, do well after assembly, do well in the field. You're not really giving up anything even if the loss is very minor, higher in loss, but yet the board performs well it's definitely a good trade. So that's part of the problem, sometimes some of the designers who are pressed for time will pick a particular material set. Yeah it might have the lowest numbers, but it may not be the best fabrication. If you can't build it, or if the board shop doesn't yield well, it doesn't do anybody any good.
So I was just talking also to Kelly Dack, Chris.
You would probably recognize his face. Anyways we were just talking about this and it's like what looks good on paper is... First thing, it isn’t always this linear process when it comes to design and fabricating. So, back to the hybrid designs. What would you say for someone that's designing hybrids, some of the the challenges are of those boards and some of the benefits? Obviously performance is one of the benefits.
Yes performance and cost, because very often the very low loss materials, come at a premium, because of the resin systems - the cost of the resin systems - and the cost to make the materials and so on and so forth. So that is another benefit - it can be a challenge for the board shop and it really depends on the materials. The challenges are more often in fabrication than they are in the actual design part of it. Yeah, like I said before, it just varies so much, I mean one of the requirements usually for an RF design is to have a certain level of precision when it comes to forming the circuitry. When we say forming, it could be a plating and etching, it could be just print and etch, depending on the the technology used. And then you would laminate that into a standard FR4 system, and sometimes those materials aren't really compatible. So yeah, that goes back to being able to have materials that have the right CT properties, the right adhesion the right lamination properties.
But you look at some of these high speed materials and sometimes they can be more fragile. I mean they might for instance - and correct me if I'm wrong here - this is second-hand knowledge here, but they might survive the fab process, and lamination cycles, or even multiple lamination cycles, because then you introduce buried and blind vias. And then there's multiple thermal excursions and then you take it to assembly and you've got through-hole and surface mount part and they have to go through another two thermal excursions. And so that it all adds up and it it's not obvious at the outset right?
Yeah those are all good points, all things that have to be considered in the fabrication and use of the part and there's a lot there too. One of the things I'm seeing, is copper is a really good moisture barrier. So one of the things that we try and preach to our customers and their customers or the assemblers if it's a CM, is you have to bake the parts prior to assembly and you can't underestimate that. There was a really good paper put out around 2011 - 2012 at IPC that showed just how long it takes for the moisture to get around because if you have a strip line construction, or if you have a reference plane and RF design, that moisture has got to go around that copper plane. It can't go through it and I've seen people underestimate the baking and end up with with scrap. It's kind of a shame because if moisture is the only reason why you're doing the laminating and assembly it really is avoidable yeah sometimes it's a pain did it bake a board for two, four, six, sometimes 24 hours but, that's what it takes to yield well but it's it's still worth it and that’s something that comes up a lot.
Well I know that I worked for a smaller art shop and we had the case where we were doing kind of pre-production quantities and the board was cooking along, no problem, and then one day it wasn't working. Guess what, it had rained for a week and we didn't have them in an airtight storage or whatever, so we had to completely look the way we were storing and make sure we were baking this, because in California, it doesn't rain that much and it wasn't first and foremost on our brains and when it came down to that, it was like what? Yeah didn't see that one coming at all.
I've seen that happen yeah, I've seen that it where customers or assemblers, they don't bake for years and think everything is great and they want to know what's changed and it's well material’s the same...
Had a heavy winter...
Yeah and it turns out it was something like that, it's always best practice to bake and it varies so much by design - ground planes are a problem. In fact there was a great study done recently with HD Paragon, I don't know if you if your listeners are familiar?
Maybe not, but we’ll put that link below in the show notes. Because they're an amazing asset to our industry.
So they did a great study on crosshatch ground planes on flex so there's some performance trade-offs to the crosshatch ground planes, but they do create a window. Moisture will get in more easily but it can get out more easily and when - as opposed to a solid plane - there is a frequency cut off where that is usable and one of the things the study looked at was diamond-shaped versus round openings in the ground plane. But I always like to put, or recommend putting, openings in the ground plane when you can afford it - just as a moisture egress.
Hmm, that’s new to me, so neat but it completely makes sense right? if you're locking in moisture inside of the laminate because you're capping it off, you're trapping it right?
Right, and a lot of the PCB processes are water based or aqueous based chemistries, even up to the surface finish. You know, Enog one of the most popular surface finishes, it sits in a hot bath for 30 minutes, actually two hot baths. The gold bath in the NIP and the nickel plating bath or high temperature what, 180 Fahrenheit - 190 Fahrenheit for 20 or 30 minutes in each bath. That's a big opportunity for the moisture uptake on the part, and if you can imagine, that's near when the part is finished. It usually gets routed and cleaned and electrical tests and a few other things. But then it goes out to the company that does the assembly some assemblers require the board shop to bake, which is okay if you put it in a moisture proof bag, but even that's not a guarantee because the workshop loses control over when it was opened and how long it stays in the atmosphere before it gets assembled and so on and so forth...
-or just before it gets bagged.
And it may already be present and you're just vacuum sealing a moisture-laden board. It’s so many moving pieces, I always say, I wish my dear friends that were printed circuit board designers or engineers that are designing boards now understood the complexity of board manufacturing because you and I've been talking this whole time about just the laminates this is not drilling, laminating buried and blind vias, filling vias. There's so many moving pieces and I think sometimes copper bond treatments? Yeah all of that and I think in this day and age, a bare board is a line item on your bomb. It's not like pulling a component off the shelf and so I think the closer board fabricators and engineers can get together the better for both actually. Because sometimes I think the board fabricators also get exasperated with designers, but the technology is being driven in a certain way. And they're gonna be the first ones to see it and can actually help enable the board manufacturers in many cases so it kind of goes both ways
An experienced designer will know what the board shop needs and that's again - that comes from communication - things like minimum clearances, designed for manufacturability, those types of things, and in fact all the board fabricators I know are very good about working with their customers to try. And again it's in everyone's best interest to yield well and have a part that survives.
Absolutely, and back to Kelly Dack, we had a long conversation - actually two people here at Altium, all of our AEs and FEs here - are required to take the CID course and so two guys here recently took it and for the first time I got to look through the workbook. Holy cow this thing is like this thick and a huge percentage of that is the DFM things. It's understanding, so to hopefully save time and money and headache on the end of the designer.
Well Chris, I know we've only got started but we need to do this again clearly, because the other thing I want to talk with you about is flex, because flex is on the rise and I know you'll have a lot of insight there and I would love to ask you more about that. But before we go I always do this thing at the end of the podcast called ‘designers after hours’ because most people in our industry usually have some kind of interesting hobby. or a lot of us, even though we kind of act left brained, we have a pretty active right brain too actually, so sometimes we're creative or do something interesting. So do you have anything that you enjoy doing after hours, sort of unique?
Yeah so actually I've been I've been diving, gosh since the late 70s…
Diving? Oh scuba diving I thought you said dieting, okay!
Yeah so actually I started back east when I was living in New Jersey I actually did some shore diving and some wreck diving and that was a lot of fun. Now in California, when I was living in Southern California, it was Catalina Island and the Channel Islands and so on and so forth. But here in northern Cali the best place to go is Monterey. I've done some abalone diving up in Mendocino, but that's free diving that's not scuba. But, in fact, I've taken my sister my niece there. There's divers also and we've gone down to Monterey and I've done that so that's one of things I like to do. It's something I don't get to do as often as I like of course.
I know we're all so busy. Well speaking of free diving for abalone my mom and dad grew up here in San Diego - I grew up in in Orange County just about two hours north of here - but my mom, when she was a teenager used to free dive for abalone in La Jolla Cove. So about a year ago I moved down here and I'm itching to go get certified and do diving here because there's some really neat dive spots here. But we went to the area where my mom used to free dive and my daughter came up from snorkeling one day and pulled up two abalone shells, which is so rare.
Well down here it's so picked over it's like there's divers out every weekend so it's really rare to find live abalone anymore. But anyway, she brought up a couple of shells.
Interesting fact about La Jolla, you can find electric rays down there so Rays are capable of delivering an electric shock.
Yeah well check it out they're pretty cool - but don't touch them - yeah, they're pretty cool.
Yes my interest in electronics and nature stops. Well thank you Chris, so much, this has been fascinating and I want to ask you 50 more questions but if you will say yes we'll do this again in a month or so and we'll talk about flex.
Okay thanks so much Chris.
Again this has been Judy Warner and Chris Hunrath with the OnTrack podcast. Thanks for joining today, we look forward to you tuning in again and until then, remember to always stay OnTrack.
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