Tech Talk - Chemical Etching for Bipolar Plates - Fuel Cell Technology Explained - Hyfindr Montoya

Tech Talk - Chemical Etching for Bipolar Plates - Fuel Cell Technology Explained - Hyfindr Montoya

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Hello my name is Steven. Welcome to Hyfindr Tech  Talks, where we aim to understand the technology   that makes the hydrogen economy work. Today we  are going to be looking at bipolar plates again   chemically etched bipolar plates. And for this  topic we've reached out to a company that has a   50-year history in this area, it's called Elcon Precision. They've worked in several areas with   this and are now providing this for the hydrogen  economy as well. And from Elcon Precision I am  

very pleased to welcome a lady, who's a process  engineer there, who's driving this forward and   helping to make it more efficient for fuel  cell applications, electrolyzer applications   or wherever these things may be used. So I'm very  particularly pleased to welcome Aurelia Montoya. Welcome to Hyfindr Tech Talks Aurelia. Hi Steven,  thank you for having me. Yes and in fact I do  need to mention, that you are joining us today via  

Zoom, because you're based in California and we'll  be talking in this way. So thank you for taking   the time and let's go right into it. Aurelia,  what are chemically etched bipolar plates?  So as I'm sure you know, bipolar plates are  chemically conductive or electrically conductive   plates, that are used in the fuel cell stacks.  So when they're chemically etched the channels   and any other features that are critical  to the application are chemically etched. And just for understanding, when you  mean chemically etched, what is etching? Etching is a subtractive manufacturing process,  in which corrosive chemicals attack and dissolve unprotected material, that's left  unprotected by photosensitive film.

I'll go into all of that as we move forward. Okay good, unprotected aggressive chemicals,  well let's see how that goes. Then please take   us deeper help us understand what the process  of chemical etching for bipolar plates is. Yeah,   so the chemical etching process for bipolar plates  can be broken up into eight general steps and so   you can see those on the screen there. I'll be  going over each of these individually as we move   forward, so unless you have any questions about  this slide I can move forward to the first one.  

So the first step is material selection. Material  selection is how we start the process for bipolar   plate etching. The material selected for bipolar  plates in particular needs to be electrically   conductive and low gas permeability, but you  also have to make sure the material that's used   is etchable. So the metals you see listed here,  like copper and its alloys kovar, molybdenum,  

hafnium and tungsten are all etchable, but  the only ones that are typically used for   bipolar plates are aluminum, titanium and  stainless steel. And I do have an example   of a stainless steel sheet here to show  you, so this sheet is stainless steel. It's roughly 0.6mm thick and this can be used  to make a bipolar plate. So this will kind of   give you an idea of what we start with and what's  moving through the process. So on the slide I see   all those metals, is this correct? Yes. Okay all right  

So moving on to the next step is cleaning.  So cleaning is a really important process   because it helps prepare the metal surface for  lamination, which I'll talk about after this. In the video here you can see the operator is  going to dip that metal sheet into a tank, so   it gets dipped into tanks of degreasing solutions  and mild acidic solutions, that help take off any   oils and any contaminants on the surface of the  metal. That will allow the film that I'm going to   talk about after this adhere, so that we can  print the image that we need to and continue   with the etching process. So there it's getting  rinsed with water and it'll get dried and then   ready for the next step. The step after cleaning  is lamination. With lamination you can see here in  

this small diagram, that with your metal sheet you  have two layers on either side, so it's sandwiched   between that protective photosensitive film that  I mentioned earlier, so we'll see how that gets   laminated onto the sheet. In the video here you  can see that the operator is feeding that metal   sheet that's already gone through cleaning,  through two rubber rollers and it's getting   coated or laminated with that photosensitive film. Those rollers are applying pressure and they have   a temperature of I believe at least 120°C, so  that it can properly adhere to that surface. This   film is really important because it allows us to  image what we want to etch, but also protect the   areas of the metal that we don't want to etch. So  here you can see it coming out of the other end,  

it's been fully laminated and so that metal is  now sandwiched between that photosensitive film.   After lamination our next step is digital  imaging. With digital imaging you can see here,   that film that we just put on the metal surface is  going to be hit with UV light, to print the image   that we want to etch essentially, that pattern.  Here in this video, you'll see the panel that's   just been laminated get placed onto that stage  with a direct imager and it'll go through that  process of printing the pattern. There you can  see the operator setting it down, making sure   that it's flat. It's going to start moving in  that X/Y stage, to start lining up the image with   that panel. We're going to get a couple different  views here, so you can see what's happening inside  

the machine. In this area here, this print head  there is used for alignment, so this part here is   aligning the image that we're transferring over  from a file on the computer to the panel and we   want to make sure that we have good alignment  between the top and the bottom side. What I   didn't mentioned before is that when you're  printing, you're only doing one side at a time,   so right now it's going to do this top side  and eventually we'll see them flip the panel   and image the bottom side Aurelia if I can  just ask. You have applied the film and this light now has a - projects what you  want onto that surface, basically,   and it only lights up the areas that you wanted  to get exposed, is this correct? Yeah exactly,   so you make a drawing using some CAD software and  then that's the image, the pattern that you want   to etch. So then that gets transferred onto here  and with this direct imager it only lights up the  

areas that you want to protect essentially, and  the rest of the areas as you'll see afterwards   gets peeled away, so that you can have your  etched dimension or your etched features.   As the video continues, you can see,  that - so this is helping with the   alignment of it. In a second you'll be able  to see those three rectangles of blue light,   is UV light that is hitting the panel directly  and it's imaging at the same time. So they're   moving in synchronized motion, to image that  pattern onto that laminated metal surface. As you continue watching the operator is flipping  the panel over to the other side and so now that   panel is ready to be printed on the back side.  Using direct imaging technology is really   critical as well, because it helps us maintain  good alignment between the front and the back,   which is important for precise features  that are required for bipolar plates.  

As we move forward to the next step, after imaging  we move on to developing. The next step here for   developing, as you can see, that the material on  the surface that photosensitive film that's been   hit by the light will remain on the material and  the rest of it will be washed away. As you can   watch on the video here, the panel gets placed  into a machine, so it'll be placed on those   rollers there you see on the left side over here,  it's moving through these chambers and it has a   mild alkaline solution that's called a developer.  Spray it on both the tops and the bottoms of the   panel and it's essentially breaking down the film  that wasn't hit by the light, so that it washes   away and you're only left with the areas that  you want to protect. As it's rolling out of here,  

these lighter gray areas are the metal that's  peeking through that film. The rest of it,   with the majority that's blue greenish, is that  protective film that we want to keep on there.   So now you see this is the image that we're  going to be seeing and etching - that goes   on to etching and only that silver area here is  going to be attacked by those corrosive chemicals.  Understood, so if a chemical comes on there  it'll start eating away at those lighter   areas we saw on the plate. Yes exactly. So  after developing is done the next step is  

etching so now we're at like the main portion of  it photochemical etching, the thing that we do.   So with etching I have an example here and we'll  see a couple of different ones after this too,   but you can etch different types of designs  if you want and you have the ability to   etch on both sides. As you can see, generally  what happens is you have that etching solution   which is that liquid on that top area here, that's  hitting both the top and the bottom sides. It's   not eating all the way through the metal, which  is typically what will happen for bipolar plates,   since you have channels that are running through  both sides, but they don't meet. They'll have some   features that do, but for the most part channels  are a certain depth not going all the way through.   So as we put it through the etching machine, this  machine works very similarly to that developing   machine that we just saw. The metal sheet that's  ready for etching is placed on the conveyor belt,  

it starts to move through the chambers and in the  chambers you have that etching solution that is   hitting both the top, it's not in the video, but  it also can be hitting the bottom and it's eating   away at that metal, so it's corroding it away. As  it's moving through, obviously this is simplified   but you can see that the etchant is causing those  holes to open up and those channels to etch as   it's moving through. Then when it comes out the  other end that darker brown, red-ish chemical you   see there is the ferric chloride, that's used  to etch the stainless steel in this example. Ok, understood. Can I ask one  or two questions around that? This chemical that eats away, how do you control  how much it eats away? Doesn't that go really   quickly and then you have a hole? Especially  when you say you don't want to create a hole,   you want only a certain depth of  a channel. How do you do that? You control how much you're etching away, by  controlling the speed of that conveyor belts   movement and also the pressure at which those  sprayers are hitting the panels with the etchant.  

The higher pressure is going to cause faster  etching rate and a slower speed will also cause a   faster etching rate, because it's a longer time in  the chambers, before it comes out the other end.   Sometimes they require a couple of passes, but  that's how you would gauge whether you want to   etch a hole all the way through or just a  channel like you would for a bipolar plate. Okay, and just to understand, how long does  that take? Is it like 2s or 3s and then you   already have a channel or are we talking minutes,  are we talking hours before you get any depth?   It's minutes, it really depends on the material  that you're etching, some of the materials etch   a little bit faster than others, like stainless  steel. Those kind of ferrous materials tend to   etch a lot faster than titanium for example  or molybdenum, but it really depends on the   metal. But it's more like minutes. Okay, and  how do you ensure, that the one side isn't   etched more than the other? Maybe this is  such a basic question, but looking at that   process I asked myself, how do you ensure the  channel that has the same depth everywhere?   So with process controls in the  process, you have the ability to know how fast you have to run the conveyor, to  understand how much is going to etch. With  

your etch chemistry for example, with the ferric  chloride etchant, when it's like a fresh new bath,   it's at its strongest, so it's going to have  a much faster rate, so operators would know to   etch at a much faster speed, because that etchant is going to be a lot stronger. So there's a lot   more of those active ions in there, that are  going to be oxidizing that metal surface and it's   etching at a much faster rate. With those  process controls there is how you get an idea   of roughly - okay I understand that for stainless  steel I'm running it at this speed and it's going   to etch away about 0.5mm - or whatever the  case is. So you have a lot of variables   there so you have to know how much you've run  through that particular solution. That's quite   complex chemistry you need to manage there,  obviously. Definitely and it's only been  

learned after doing it for so many years. It's  really important for the bipolar plates that   you can maintain those tight depths, because  you don't want to have a huge range across one   panel or across one plate. So can you say -  we saw it on one picture it's called etchant,   I quite like that word. What are those? You mentioned ferric chloride or so what are they? So I have a couple more  slides here, so I can come back to these.

Here's a general overall chemical reaction  that's happening when that material is being   oxidized. The etchant is working as an oxidizing  agent basically, so that ferric chloride etchant   that's like the main component that's driving  this reaction and it combines with the metal ions,   so that iron substrate you see in the front there.  When the etchant is oxidizing the metal surface,   it dissolves that away into a soluble salt  and then it goes into, basically, the product,   which is that reduced chemistry now, which  is ferrous chloride now and it's that spent   etchant. That has to continuously be  moving so you need a lot of agitation  

in there which is why the sprayers really  help with that, because you need a constant   rotation or a constant change in the chemistry  hitting the metal surface, so it continues to   drive that reaction. Like I mentioned before too, these couple slides here, we have the ability to   etch one side if you want, both sides if you want  and you can control how much depth you want to do.   So you have the ability for a single side etching  where you only etch one side. You could do it all   the way through if you wanted to potentially  or just to a certain depth. You can also do   double-sided etching all the way through, similar  to that first image we saw, where it had remaining   material except here, they continued they  met and you have a hole on the panel.

After etching we move on to our next step, which  is stripping. At the stripping portion it's   basically that etched plate without that film  on there because we don't want the protection   film anymore it's gone through the process and  done what we needed it to. When the material   gets stripped, it gets dunked into a tank of  an alkaline solution, that's strong enough   to remove the rest of that protectant film. It  dissolves away the rest of that blue film you see there and when it gets agitated with the sprayer  and when it gets rinsed it just washes away from   the metal surface, and you're left with your  finished piece. So then that brings us to our  

last step here, which is inspection. The last  step of making a bipolar plate with etching is   doing inspection. So here we have a bipolar plate  sitting on a optical inspection tool stage and so   the way this inspection tool works, is by using  light to measure any important features that are   important to the application. So you'll measure  things like the channel depth, the channel width,

the size of those holes anything like that to  make sure that it's to the print and that you're   making what you went out to make. And I do have  an example of finished plates here to show you.   That metal sheet that I pulled out before, once  it's gone through that entire process will end up   looking something like this. So this is an example  of a etched bipolar plate, you can see that   there's channels here, like those grooves that  are moving through the major center portion of the   panel and those through features that you can see  at the end here. So you have the ability to type any text or anything like  that on here and really you   have a range of different features you can add. We have like a much larger size panel too, just  so you get an idea of how different panel sizes   can be or the types of bipolar plates that are  etched. So this one's a whole lot larger, like  

three four/times the size of the other one and it  has the same general idea for a bipolar plate. You   have the channels going through the center, you  have the through holes that are here on the side,   like these squares, and those holes there. Just  to give you an idea. Well okay, that's quite   impressive how big that is. Maybe just at that  point we were discussing earlier - obviously you  

work for Elcon Precision, but your sister company  PEI, that is also mentioned here, they make the   bigger ones. The expertise is sitting within your  organization there. Yeah right. Very impressive   Aurelia, just two or three questions to add to  this. When you compare etching of bipolar plates,   you know that we have other methods of  making those channels into bipolar plates.  What would you say from a etching point  of view is an advantage to this process?   Etching definitely has its advantages, when  compared to other manufacturing, like metal   manufacturing processes, like hydroforming  and stamping. One of the key features with  

etching is it has a low tooling cost, so you don't  have to make a die to get those features. It's   just a subtractive process, like we saw it eats  away at those channels. Because of that as well   it's really easy to make different designs fairly  quickly. You're able to just make a new design, transfer that image file over to the direct  imager and make a whole new plate without much   time in between. In addition to that, you're  also able to prototype and move to a volume   production fairly quickly, because you're  able to create a lot more panels without   having to require additional tooling. We also  have the ability with etching, to create finer   geometries. I just remembered too that we have an  additional slide here for that. This is basically  

just summarizing what I'm going over. We also have  the ability to create finer channel geometries, so   we're not dependent on how small a feature can get  with a die, since we can just etch that and remove   away from the material. We can also do different  patterns and different depths on a single side, so   we can add complexity to a design without adding  additional costs. And with etching you get a flat,   burr and stress-free part, so it's essentially  ready for stacking without any further processing.   Okay, so wow okay. That's very interesting to see  that way. Just one particular thing on the cost. I   mean we're always talking about the cost of things  in the hydrogen industry and we have bipolar   plates there, which are part of the stacks, which  are one of the more expensive components in that.  

So what is it about etching that is expensive?  What makes that process expensive - if it is   expensive? Or what's like the most expensive  step? So one of the most costly parts of  doing like a bipolar plate or a chemically  etched bipolar plate is really the material,   so with etching, like I mentioned before,  there's no tooling that you have to worry   about adding that cost, but you're really kind  of dependent on how expensive a material is.   So depending on whether you're using titanium or  stainless steel or kind of what the application of   the bipolar plate is going to be, that's just  going to add a bunch of costs at the start,   because they tend to be pretty thick plates as  well and that's really what's driving like the   high cost for photochemically etched plates.  Okay, I have two more questions and one is   about - I mean these are probably aggressive  chemicals that that you're handling there and   can you tell us a little bit about that? I mean  obviously that is also something that you need   to know how to handle? Do you use a lot of those  and can you reuse them or how how does that work?   Yeah, so there is a lot of very harsh corrosive  chemicals that are required to make etching happen  so there's definitely a lot of  regulations and laws in place,   about how you handle all of that chemical  or all those chemical solutions and all   that equipment as well. Whenever you're  working with an etchant for example,   you're able to regenerate to a certain point, by  adding additional like chloride ions for example,   to turn that ferrous chloride back into ferric  chloride, but it can only do that so much to a   certain point and then at one point you just  have to replenish or create a whole new bath. 

So then you produce hazardous waste and  there's regulations at the city state   and federal levels, especially in the United  States and in California, about how much waste   that you can be producing and basically getting  disposed of, how you get disposed of that waste,   if it's diluted enough, for example we have waste  water that's produced at the facility through all   of the processes that we have and that's dilute  enough that we can discharge it to our regional   wastewater facility, but it has to be analyzed  for any metal ions, to make sure that we're not   above any acceptable limits. But with something  that's a lot more dense or a lot more hazardous,   like the chemical etchant for example, we have  to have licensed hazardous waste facilities, that   come and pick up that waste for us and dispose of  that properly. Okay so that means it's all sort   of taken care of, also in terms of regulations  to make sure that this can go back to nature.

Yeah, very tightly regulated. Okay the last one  Aurelia, because I think we're running out of   time. Just when you look at - I mean you you're  pushing you're driving this forward and obviously   you have seen some changes in the last years. Can  you give us a bit of an outlook what development   you're seeing in the etching space and what we  can expect from there in the next years? Yeah,   I think definitely seeing an increase in how  complex all of these designs are getting,   so all of these bipolar plate designs,  adding sometimes two or three depths on a   single side and that's luckily really easy and  set up for the photochemical etching process,   because you're able to get those features and  also being able to test new designs I think   will be important as we're figuring out what's  more efficient. Designs are quickly changing   so being able to prototype fairly quickly is  important and with photochemical etching you   can do that well. I also see volumes growing and  with that we have potentially larger format plates   like you have here with this larger size one and  also more efficient designs and factory automation   to help bring costs down and for example like  some fuel cell powered aircrafts are in early   stages now of what hopefully in the next few  years is going to have exponential growth,   so there's going to be a higher demand for  bipolar plates. Wow okay, that's a very  

positive outlook and at least for me I picked  up one point and that's the quick prototyping,   which I think is very useful for the industry  that is evolving, so people now know who can do   that and obviously have learned how that is done.  Aurelia it's been an absolute pleasure talking to   you about this I've really learned a lot and see  how these complex words formed into action. Thank   you very much for taking the time and thank you for all those who watched.   If you like this please give us a like in our  channel here or connect to us on social media. Also below the video you will see all the  links to the industries involved in this.  Thank you very much for watching. Thank you  Aurelia for taking the time and we look forward  

to have you sometime in the future. Please watch  another video. Thank you. Awesome thank you!

2023-09-23 20:45

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