So welcome everybody my name is Kevin Palowski i will be your host today in our webinar selective spray conformal coating optimizing for maximum output so the idea here what we're going to be talking about is how to optimize your process because you're not in the business of just coating boards you're in the business of making money hopefully coating boards so we're going to help you maximize that.
So first quick introductions like i said i'm Kevin Paulowski i'm a marketing manager application specialist over at Chemtronics i'm a good person to know if you have any questions and you call in there's a good chance you'll get me on the phone if you do a on our website you go chat you're getting chances are you gonna get me and i can generally answer a whole lot of questions i've been at this about 18 years so i can offer a lot but i'm not a chemist but luckily we do have chemists on staff so speaking of which we have Pierce Poland Pierce is a is a senior field engineer at ITW and he's he's formulated a lot of these coatings but also he's our field engineer so he's out there trying to make things work right for you so if there's any problems he's the one that j ps on an airplane and gets over to you and he's been in the industry about 18 years as well and has been very active at IPC SMTA and just out there also you may have seen him at any of these events speaking and so on the screen there you'll see his email his phone number and of course a special guest John Urcard with pba now Pierce covers the chemistry side John's covering the equipment side so between the two of them we've got it all covered okay and so that's the whole point of this is get the experts together and let's talk about how to make your process work as good as it can get.
John's a director of global applications engineering and so similar to Pierce he's the one he's one of the people that are there to help you get your job done okay if you're running into any spray problems if you're trying to spec in some new equipment there's a good chance you're going to talk to John as well let's just go over a quick informal overview and what conformal coatings do and do not do a little bit of the chemistries and then John will obviously work on the equipment side and we're going to kind of tag team back and forth through this presentation so just a little bit about just conformal coatings in general when our laboratory team or any of the the other coating manufacturers create these coatings they're designed to protect your pcbas and your assemblies from any environmental exposure in their service areas and just basic typical characteristics of any conformal coating it will conform to the contours of the board it will get on and all the nooks and crannies where it needs to go it will coat very evenly and it goes in between the gaps between the components if the settings are correct and you've chosen the correct chemistry they're very lightweight they're very flexible and for the most part they are h idity and temperature resistant they are not waterproof so let's bear that in mind so why do you want to code well first and foremost it will increase the reliability and the workings of your PCB and your final assembly in the service environment.
Well how does it do this? Okay well it it'll provide protection from any environmental and physical contaminants whether it's gaseous whether it's chemical splashes whether it's uv invasion fod just about anything that you can think of if you've chosen the right coating it will prevent any kind of current leakage that may be going on if you get moisture invasion it insulates any heat sensitive moisture sensitive components to a degree it prevents arcing if you get moisture invasion under the coating it will help to to prevent that so let's go over a couple of the of the application methods and the first is is obviously a manual method it's usually a lot of times for very small areas for touch up for prototyping there are a lot of there's some pros and a lot of cons to brushing it's totally reliant on the operator for consistency every operator will brush a little bit differently even one operator will brush one board one way and another board slightly different there's always always a risk of contamination from handling the assembly or if your tools are not clean if there's a breeze coming from air registers whatever there's always that that potential for having fod land on that coating there's obviously increased housekeeping with it you'd have exposure to the operators from the chemicals that you're using from the solvents and the coatings when you do brush we always recommend using natural hair bristle brushes nothing synthetic because some of the cheaper brushes will dissolve in the coatings so be very careful about that if you have some drying of the coating on the brush if the operator gets up and takes a break and doesn't put it back into a solvent cup it could accumulate on that brush and then deposit on the board grosser the bristles are the bigger the bristles are those can entrain air as you're dipping in as you're wiping off it can entrain air between those bristles and then when you make your pass across the board it will deposit those bubbles on that substrate sometimes they'll come out sometimes they won't.
Brush direction can be very very important relative to the coverage that you're getting in a specific area or on a specific component and generally these are used as i mentioned before for prototyping for touch upping if you're RNR'ing or removing and replacing a component you'll you know take the component off you'll clean the area again where you re-solder on and then you can just touch up with a brush so that's that's brushing if you're dipping this can be done obviously manually they do have automatic systems where you can dip it's pretty much a robotic system there's a large bath for the coating and on the larger systems the more automatic systems logan those can have a nitrogen blanket on there that can prevent it from drying out and where you have a lot of viscosity issues from start to finish over a project or over a shift you do need to monitor that monitor that withdrawal speed and the reason being is that your withdrawal speed is the only thing that's going to determine your wet film thickness contrary to what you may think the slower you withdraw it the less what film you have and the faster you withdraw it the more what film thickness you'll end up with it does comply or complete provide complete coverage of the board you just have to have that residence time in the coating to allow that to go everywhere it needs to go it can be anywhere from a low vol e to a high vol e depending on if you're doing this manually or it's an automatic system and it's generally an offline process in other words it's not conveyorized over to this they take it from solder to cleaning to the dip coating process areas.
One of the this was the final and most common methods to manually apply formal coatings is the spray method and by spray i'm referring to manual spray using either an aerosol can or a hand spray gun when you're doing that your boards will need to be masked for any areas that don't require coating and the masking will also need to be removed after cure the process will need to be performed inside of a spray booth or a ventilated booth of some sort usually with filters so that you're taking any overspray or vapors from any solvents away from the operator and you know like any other manual method you know the work area's got to be kept clean you know there's also you know a lot of risk for you know contamination from dust and dirty tools and all that so you know housekeeping is key and you know while manual spraying is quite an effective method there's a lot of handling with you know masking d masking and you know consistency of the finish and the thickness you know still relies heavily on the operator so now we get into a selective process so when you're when you're applying foam coating selectively you know you're applying the coating in a specific pattern using a robot on a board typically using one or more types of applicators and it's applied in a single wet layer that will dry to your target thickness don't typically use multiple layers to apply selectively but it's i've seen it done in some special situations with selective systems you do get the benefit of optimized coating usage due to no overspray you know essentially you're programming exactly where you want the coating to go you're not necessarily spraying off the sides of the board you're also getting a very repeatable and usually improved process compared to you know your manual methods and it's also a safer and much cleaner process for your operators so if you've got a product that you're planning to you know start coating selectively.
Here's a kind of a question i get asked a few times years how would i design a board how would i lay it out for selective coating if you do have the luxury of working with a product designer and you can talk about you know designing for manufacture you know here's here's you know a kind of a short list of guidelines to use for layout to just help enable a selective coating process and allowing to be successful you know some of the key points you know you want to allow you know two to three millimeters would be great around no coat zones or keep out areas this just allows any variation in coating flow it's good to group any of your tall components together but with that being said you also want to leave enough access so your applicators can get around any large components or if they got to get coating underneath tall components you want to play place connectors away from your coated areas if possible you know like anything just give yourself enough room between the muscle and no code areas any connectors being used it's always good to use a type of connector that has a sealed lead or it's got a sealed socket.
This just prevents coating from wicking inside should you have to coat around the base of the connector or connector leads it's always good to plug unused vias that way you prevent coating from seeping through or wicking through to the other side of the board you know you want to leave enough edge clearance on the board typically five millimeters is smeama spec to allow for you know smooth conveyor transport and then you know you want to clearly define what you want what must be coated and what must not be coated and then you know when it comes to inspection you know make sure you understand the limitations of the process in other words you know what thicknesses can and can't be achieved what sort of coverage can can't be achieved and how does it look be sure to to make sure your qc people understand that you know when you're planning for automation you know there's a few things to consider based on your board design this helps determine you know how large of a coating machine do you need does it have the proper clearances to allow the boards to transfer properly how will the products be handled will it be handled manually do they need to be in a carrier or a pallet of some sort will they be transferred on a shuttle or conveyor and also what type of application method will be used.
You know can a product be fully selectively coated or do any areas require you know a tape dot or a masking dot applied you know and also do the applicators require special clearances or extra reach around tall components does the coating system have enough axes of motion to complete the task in other words can you do the simple three axis machine or do you need a four or five axis machine to access all areas of the the board and you know how how will the product be cured you know this will lead to how you set up your curing and we'll talk about this briefly a bit later this is one item i like to always comment on if i'm talking to somebody about you know setting up a new process is you know make sure your doc entation clearly outlines you know what you're trying to achieve and where you're trying to coat in this example that i just you know threw together from just a random concept you know if you see the image on the left obviously we get a lot of drawings in black and white and you see a lot of different types of cross hatch and x's and everything else and it's kind of tough to determine what you must must not coach so if you take a look you know can you can you find nine keep out areas easily in that whole drawing you know it's not always that easy if you can do something like the image on the right you know and i've might be easier said than done but just adding a little bit of color makes a huge difference you know you want to lay out three different types of call outs for coverage in the green you've got where the coating is absolutely required in the white areas the coating is optional and the red areas show where you absolutely must not have any coating so this helps minimize you know any questions or issues in determining you know what is a properly coated board and you know one additional thing in this sort of layout is the image on the right could actually come in handy if you're trying to set up an aoi system so you know you can clearly define what regions the cameras need to be looking for i have a quick question so i'm seeing this coating optional area so it looks like on the image to the right you're building in some tolerance also into the the keep out area.
So yeah that kind of goes along with the idea i mentioned earlier about you know if you can you know design or have input into layout of a board you know can you have two to three millimeters for you know clearance from your must coat your no-coat areas again that's just to allow you know variations in coating flow should they come up okay now i have one more question now i don't want to get us too far off track but you've mentioned axes machines that have three access points or four to five now i i know length width depth but what's what are we talking about with access points once you get to four to five so you know when you're getting beyond three you've got x y and z you know left right front back and up down vertical but then you've got rotational so you might be spinning actually about the z axis and then the fifth you know fourth or fifth could have a servo or pne atic tilt so now you've got the ability to coat the sides of components underneath components you know just get into hard to reach areas that just the vertical type approach can't get to all right when it comes to processing liquid coatings you know machine providers typically you know group them into you know two different categories you know we'll say you've got either solvent based or 100 solids product this helps us guide the choice of what sort of applicator or group of applicators to use helps define the processing method and you know gives us an idea of how we're going to cure the product for solvent-based coatings you know typically low viscosity typically under 100 centipoise often they require dilution for processing if they don't already if they're not provided already diluted you know during cure you're going to lose quite a bit of wet film thickness just due to the solvent evaporation and you know sometimes you can apply multiple layers of solvent-based coatings but typically you're applying again.
Selective you're typically applying a single wet layer that that you know the solvents evaporate off to get your thickness and you know some typical examples you see in like acrylics or solvent-based urethanes the other category you'd say you know typically say 100 solids coatings and these are you know products that have no solvent carrier in them and they tend to be higher in viscosity you know up to you know three you know thousand to three thousand centipoise in some cases even higher you know because there's no additional solvents required to process these there's very little or no loss of the film thickness when they're cured these coatings are almost always applied in a single layer and you know there's multiple curing options you know depending on the type of product so in other words you know you might be curing with just h idity or moisture in the air or you might be using strictly heat only or you might be using a uv cure type of product now you'd mention 100 percent solids but Pierce i think i heard you mentioned that that's sort of a can be a misnomer can be sort of a marketing term it can be some of the companies will say and this is a lot of times generally for where you see or where we've seen it mostly with silicones is that they'll say that it's it's 100 solids yet as as the raw material the raw polymer comes in the door it already has some some solvents in it just to make the polymer flowable so you know if you really want to call it 100 solids they really shouldn't have anything in it you know as far as solids or solvents go so so just something to bear in mind if the spec requires 100 solvents or there's further dilution involved you know and it may be best to know what's in that of course that would should be on the sds right for the most part the new ghs format leaves a lot to be desired in my opinion things that that had to be listed on the old ansi format are not required anymore now so you may don't don't take it for granted that you're getting complete formulation information on that sds when in doubt contact a chemical supplier absolutely electronics.
Okay very good thank you you know when it comes time to setting up equipment you know and and choosing the tools to use you know it helps to have a very basic understanding of everything we just talked about what's you know what's the coating how are you trying to apply it where are you trying to apply the coating on the substrate so on and this helps guide you know what the coating system needs in order to complete the task again you know we mentioned coating machines can be simple three axis robots with a spray head fed from a pressure pot or you can have you know much more involved configurations using four and five axes of motion multiple applicators fluid monitoring barcode reading on and on and on you know all these different tools you know integrated into the system help you know keep process on track getting into some of the types of applicators is typically four types of applications so the first type and probably most common is an atomized spray applicator you know anime spray valves are pretty much the all-around option for applying liquid formal coatings and you're using a low vol e low pressure spray which allows you to provide a selective pattern you're not using a high vol e spray gun where you're getting this mist and cloud of material that goes everywhere it's a very gentle soft application of the fluids where it needs to be you know selected atomizing can be used for fully selective applications or even you know mask and spray you know automating a mask and spray type process you know if you're using a solvent-based coating just be sure the coating is diluted to the proper ratio or use a slow evaporating solvent and that helps keep the spray heads clean and keeps them from drying too quickly atomizing is also typically a choice for achieving the lowest film thicknesses that are required for a lot of coating operations you know often you know get as low as 25 to 50 micron films and even thinner with you know highly solid compositions you know there's there's a choice of you know fine narrow spray and wide spray patterns available and you know a combination of head sizes or types can be configured to fit the process and applicator speeds are typically in the you know 100 to 204 you know sorry 100 200 millimeter per second range 40.
We'll say four to six or four to eight inches per second rate the second type of applicator is an airless spray valve oftentimes refer to this as a film a film coating valve a curtain coating valve flow coating valve and this type of valve relies on the viscosity rheology of the coating to create a solid fan or a film pattern which lays down a very defined stripe of the coating onto the substrate this type of applicator works really best in solvent based coatings kind of the sweet spot is around 50 to 65 centipoise but usually you know anything under 100 centipoise can be run there's other tools that can be used to to help higher viscosity products work with this but you typically want a very very low viscosity coating to apply in here you know the applicator speeds are much higher you're in the 350 to 500 millimeter per second range so you're anywhere from i think you're about you know 14 12 14 inches up to 18 inches a second range but you know be aware you know even though it is fast because of the high speed you've got a risk of possible splashing from the coating bouncing off certain component geometries if you do find something like this happens often you can prevent this by maybe shifting the path slightly in your program or even just try changing the direction of the coating path the third common applicator used in selected heads or selective process are needle dispenser battles and these typically are very commonly used to complement you know the work that a spray valve might do and you know the needle valves are used to typically apply coating around or under tall components you can use it to draw and outline around a coating area or you're applying a line or a dot of coating onto a component or component leads for maybe some extra coverage or to get into hard to reach areas between tall components in cases where the coating requirements or the product design doesn't exactly allow a fully selective process a lot of times needle valves are used to apply a liquid peelable mask in select areas before coating hey i've got a question on the liquid peelable mask if you're applying it with the needle is there a sweet spot for viscosity or something like that i've seen it you know anything as low as 10 000 up to we'll say 30 40 000 obviously and this is just saying if you're applying from just a reservoir you know using air pressure needle you know the needle valves can apply much higher viscosity products but then you have to use a p p of some sort to move it so anywhere in the 10 to 40 000 centipoise you can do higher viscosities if maybe they're thixotropic but that's usually the sweet spot yeah and one caution that we've run into on the on the chemtronic side is the sheer curing that can occur with some masks so they're there's especially in the natural latex is what a sheer cure is is under pressure like if you have some in your finger and you squeeze it it actually cures as you do that and of course the the pressures get pretty high as you get to the end of that needle so it could run into problems there so as you're if you're specking a mask for a process like that and you know you could be plugging up on you well just thinning it down may not do it you need to take a look at that so here's a just kind of an application tip you know if you're using a needle valve you know if you've got a maybe a high viscosity version or a gel version of your coating use the needle valve to draw a dam next to a keep out or around a connector you know prior to your spraying i mentioned earlier about you know using a certain connector design to prevent wicking but you know if you're a contract coating house or contract manufacturer you've got to use what you're given and you've got unsealed components on sealed connectors it's always good to be able to use something that's got high enough viscosity you can apply it around the connector prior to using your low viscosity coating and it prevents anything from going inside you know typically you will see this with a lot of surface mount type or through-hole type connectors you know besides connectors a lot of times you'll see using something like that for plugging open vias again to prevent coating from working through to the other side of the board.
Then the the fourth kind of common applicator used in selective application and selected machines is the micro or the jet spence valve you know these types of valves they apply a very small amount of coating either in a dot or a line or some very defined pattern often you know around keep outs or even coating individual components these types of valves are what we'd call a non-contact type applicator and you know not necessarily spraying the coating but you're just kind of letting dots or streams of liquid exit the nozzle as it sits above the circuit board the main benefit of using a jet you know is being able to really precisely deposit coating in very small amounts you know from a distance of some cases you know up to almost half an inch away from the substrate depending on the substrate size so you've got something very small you know a jet or micro valve alone might be all that's needed you know an example of this would be like on flex circuits micro pcbs using mobile devices or medical products you know something to note is to be careful of the the coating thickness that you end up applying using this sort of method while jetting provides a very defined XY placement of the coating if the coating viscosity is too high and the thickness applied is too great you know it might not lay down and create a spin of film as if it was sprayed so you know this could lead to potentially future cracking issues when it's under stress in the coating or you know possible assembly problems with you know intricate and small tolerance designs when you're feeding the coating systems you know often a simple pressure pot will will work you know you're just putting air on a tank sends material out to your applicators and then things are great but that doesn't always work for everybody sometimes people want a more hands-off approach maybe it's got issues with pressure fluctuations in the factory you know whatever it may be you know there's there's feed systems available often you know using gear p ps or similar types of p ps which can provide coating you know right out to the applicator in some cases you know in this example here we use the solvent-based coating with airless applicators where we'll actually circulate it out to the valve we'll run it through a heater you've got warm coating at the valve and then it recirculates back through the system and continuously p ps through so you do two things here you you raise the temperature of the coating so you know it's consistent you also provide a much consistent thickness because the viscosity is not changing and because you're using the p p to move the coating it minimizes the risk of getting bubbles inside your tank because you use at that point you need a very low amount of air pressure on the tank itself you're just letting the p p move the coating and not the air pressure on the tank and another device that's used and this is something we call continuous film calibration this is often used with your airless applicators and it's a measuring device used to calibrate the spray pattern as it exits the valve and you know while it's measuring it it also also is tied to the control system to adjust the pattern the spray pattern with to compensate for any variations typically seen with viscosity fluctuation using this type of device you know it's very fast it only takes you know a few seconds two to four seconds to take that reading and while it you know it not only measures the film width but it also measures and very well doesn't measure but it verifies that the film is actually continuous across the entire spray pattern so this ensures that there's no breaks and that the strike that you're putting out is consistent okay so you're going to be preparing the chemistry so you have everything set up and it's ready for the delivery system well the first thing that you're going to have to do is transfer the coating fluid from the packaging container into your pressure vessel well first and foremost always use clean containers clean tools just to reiterate what John has has tried to hammer in on the the housekeeping one way to prevent a lot of cleaning on the pressure vessel is to use liners in there those liners are disposable once it's empty if you're either adding material you can change out the old liner put in the new liner add add materials works very well if you're switching from one coating to another as well as having to clean your lines and your applicators you do want to work in a well ventilated area because those solvents are just raw at that point so you need to protect your operators as you can see from the picture and maybe that's just the way the picture was taken or designed but the pressure vessel is tilted and then your someone's pouring in from the packaging format there you want to pour in very gently to minimize the turbulence because that just creates a lot of bubbles and then you've got to sit there and wait for the bubbles to to come to the surface and go away think about pouring a beer into a glass just pour it down sideways and not not create a head or or any turbulence to the liquid at the bottom if you need to dilute stir it in don't shake the the vessel mix it till you get to the desired viscosity you can check using various viscosity cups there's four there's on it's based on a time on how long it takes to drip out the orifice on the cup when you do this please make sure that you clean the cup thoroughly including the orifice because it can it can affect one or two seconds on your on your answer like i said if you do have some errand train in here let the bubbles come out naturally and never ever ever pull vacu with a solvent boring coating in your in your pressure vessel or just even even if it's just a holding vessel because all that's going to do is force the coating to start curing out inside your vessel hey i got a question for you Pierce does this cover maybe a misunderstanding out there you know let's say you've got you know you you clean but you don't clean that well there may be little pieces of coating won't that just dissolve and you know it's the solvent the same solvent dissolved in the first place won't it just dissolve again it can some solvents really are very chemically resistant once in solution they kind of tend to stay in solution but then you gotta work pretty hard to get them back into solution to dissolve epoxies urethanes are very common for this so chances are it's just going to sit there the piece it's just going to sit there and it could it could it could foul some of your lines you know which just messes up your delivery system okay some little tips and hints if you're diluting well if you've got an old-time operator or old-time engineer you're going to hear this somewhere down the line we've always deluded because well because in years past most of the bulk coatings that were on the market were considerably high solids and the delivery system for the applicators at the time really could didn't have a wide operating range they had to get it down to a nominal level before they could consistently and repeatedly deliver these these coatings so they had to dilute but nowadays the nozzles and the delivery systems are much more advanced they can they have a wider operating window but also check with your coating manufacturer because what 10 years ago they may have offered an only one viscosity option they'll have the same product but they they a lot of times will offer it in a high or a medi or a low viscosity option depending on what your needs are
So as i said the newer nozzles or applicators they can also handle very low viscosities now like down to 10 centipoise where in the past it would almost pour out of the applicators they really couldn't contain it very well but as John couldn't kind of test there's been a lot of advances in the engineering on these on these nozzles or applicators now bear in mind when you dilute it will increase your overall cost the the diluent or your diluting agent may be very inexpensive but it's going to cost you time okay your coating will go further because you've diluted it but what you have done is you've decreased your viscosity but in the meantime you've just you've also decreased your percent solids in that mixture so your film build will be not as as great as it was basically your your price per board will go down but your total cost for the manufacturing goes up and by diluting it will increase the ability for the coating to flow by lowering that viscosity but if you go a little too low then you're gonna it's just gonna start wicking or flowing into your keep out areas whereas before you're able to keep it within the parameters of your drawings so be very careful when you delete okay curing methods the cheapest most inexpensive way is to cure it in ambient conditions okay it's slow it's the curing rate or or the speed at which it cures it's going to be dependent on your coating thickness your wet film thickness as well as the temperature in that facility or curing area as well as the h idity okay it's generally okay for solvent-based and moisture curing coatings like rtvs we recommend always using an enclosed cabinet rather than just racking them there because some coatings if you're going to rack them vertically which you almost have to do some coatings have a tendency to sl p a little bit and you could find them after cure and some keep out areas where they weren't there when you coated it but an enclosed cabinet you're laying them down horizontally just the same way that they were they were coated you want to use an exhaust in there to limit your operator exposure obviously but it also limits depositing fod on that fresh coating you know whether it's lint fuzz in the air or stuff coming through your your ventilation system or your air conditioning registers so there's a lot of a lot of pluses to doing ambient cure the big pro or the big con is that it's extremely slow so you know when you want to accelerate the cure of again usually solvent-based coatings you can do this with heat cure and you know some rtv type coatings but you know typically when you've got a solvent-based coating you want to accelerate it you know we typically use ir elements as the energy from from the ir infrared is a really good choice as you know it's warming the substrate from the inside out so you know someone may say well i've got an old convection oven i'm going to use that well it will work it can be done i've seen people do it but you know you've got to be careful to use a very gentle ramp to your cure temp to avoid you know skinning the board or skinning the coating too fast on the board which can potentially you know trap some solvents still trying to come out and that ends up leading to air bubbles in the finish.
And you know when it comes to you know selective process again you know the ovens used are typically conveyorized there's there's a range of links depending you know lengths of the oven depending on production amount of cure required and you know most often you know for an inline process most often you want the coating to be tack free you're not necessarily baking it but you're getting tac-free and solid so that if you know the board can be handled for any next steps in the assembly or testing process and you know if someone is handling the substrate then you don't get drips falling off the board or you don't get fingerprints and it helps us minimize you know any any contaminants getting to the substrate at that point and then you know it's always good to to run profiles you know using your production a production substrate in order to get a very accurate reading of how the board is heating up and then just a couple you know example profiles you know showing the difference between using you know something that does have salt and coating that does have a solvent versus something that's strictly a heat fewer products you know in this case the heat cured product was 100 solid silicone if you notice the image on the left you've got a much more gradual slope up to temperature and again this is to avoid you know a skinning over of the coating or trapping of the solvents you know you want to allow the solvent's time to generally exit out of coating as the cross-flicking linking starts to happen and the image on the right you know as i mentioned silicone you know it shows a very fast ramp to temp but you know too much can also be a bad thing you know again too hot too fast you still could generate bubbles you know maybe appearing around leads or underneath components because you're trying to just you're just trying to hit it or shock it too fast and any any air pockets are just trying to get out you know creating leading to a bubble situation so you know if you do see something like that where where bubbles are generated you know immediately after or during the cure cycle you know lower your ramp rate if necessary then lastly you know another curing method and this is you know wholly dependent on the type of coating you're using and you know if you're using the ultraviolet keyword coating you know you want to determine are you do you need a spot cure do you need a flood are you using a focused cure do you need a focused beam or you're just trying to cure an entire substrate you know again with selective systems these are all inline conveyorized ovens you want to make sure the light can get all into all the necessary coated areas to at least start the cross-linking process if there are shadowed areas on your board where nine times out of ten it usually is you know you want to check to make sure your coating has some sort of secondary cure mechanism whether it's you know a heat cure secondary or moisture exposure which will help provide you know complete cure in your shadowed areas all the time.
You know just check with your coating supplier to understand you know when the coating will actually reach full properties before you do any stress testing and like with any oven you know use the proper calibration tools in this case a radiometer periodically to just ensure that the oven is providing proper output then you know lastly you know once you've got all your pieces in place you know here's one example of an inline you know medi to high rate process to coat both sides of the substrate you know including a flipper a couple cue stations aoi for inspection inspection cue and for an entry level process you might only just need a single coating machine and a batch configuration may be all that you need for very high vol e production features such as dual lane conveyors multi-head tooling you know multiple applicators you know can be added for in multiple machines could be added for processing you know multiple boards at a time and just maximizing throughput okay so what can be some or actually the main causes for coating defects and this slide is actually pulled from our coating defects webinar which i believe Kevin has provided a link for so i'm not going to go into really any detail but cleaning application and curing are the three main causes for coating defects okay now there are categories within each of those and i do want to point out that there are some defects or process indicators that can be can be caused by more than one of these for instance voids and bubbles can be caused by a curing i can also be caused by some of the application errors so i urge you to review that that webinar or the slides for the webinar i think you'll find a lot of good information on there in defects if you weren't able to attend so that's all i'm going to say about that one cleaning your pcba before you code well coatings love clean okay but some of these areas below will resolve a lot of your coating issues okay if you clean your pcba before posts are actually post solder and pre-coating very common for a variety of causes just because of fod and other contaminants that are on the board such as fish eyes de-wetting delamination these these are very common commonly seen in uncleaned or improperly cleaned assemblies flux residues that are left on the board can absorb moisture they can cause corrosion even underneath the coating it's actually called a triangle so we always recommend that you're that your assembly should be cleaned before the coating process this includes no clean fluxes.
Just a real quick note here the way no cleans work is that doesn't just because you don't have to clean them because of lack of dendritic growth doesn't mean that you shouldn't clean them prior to coating it depends on how good your cleaning process is but you can avoid these failures due to a lot of these surface contaminations flex residues mold release agents on your components silicone contamination which can come from almost anywhere so it's very migratory material adhesive residues like from kapton that's just a generic term scoring dust any other fat that may come and land on that board before you coat okay so the impact of cleaning well the whole idea of cleaning essentially n ber one you remove the residues but you do that because coatings love clean and it has to be able to adhere to the surface of the substrate otherwise you're not going to get any functional projection it's just going to either lift off peel off delaminate de-wet and it's it's just not going to be a good process so a lot of the residues fluxes thought oils greases they all affect the ability of that coating to adhere to the substrate and like i said it could result in de-wetting could result in delamination if it's a big relatively big piece of fod it just blocks the substrate from being coated and overall you'll just get better integrity of that interface between the coating and the substrate and it will allow that coating to protect the assembly the way it's designed to do by adhering to the substrate all right.
So I'll take it from here thanks John thanks Pierce great job on that you know our job is to make your job easier to make your process more effective and more efficient because like i'm like i said you know you're not in the business of coating you're in the business of making money by coating so so you know our job is to help you do that so please reach out to us if you need anything and again John Pierce great job i appreciate all your work