Automated Application Questions
▶ Q1: Our company has been using HumiSeal coatings and applying them via manual methods. We are investigating automated application and need to know if HumiSeal´s coatings are compatible with this type of equipment. If so, can HumiSeal make any recommendations regarding the equipment types?
HumiSeal works very closely with all the major manufacturers of selective robotic application equipment. As a result, all of HumiSeal´s coatings are compatible with the majority of automated application systems on the market. For further information please contact HumiSeal directly at our Contact Us page. Thursday, 11th March 2010
▶ Q1: Our design and prototyping work is done in one location but we have production facilities in several different countries. Is HumiSeal available globally?
HumiSeal enjoys a presence on over thirty countries globally. Please check for the location nearest to your facilities at our Global HumiSeal page. Wednesday, 17th October 2007
Conformal Coatings Questions
Typically, there are three main approaches to avoid coating wicking into press-fit connectors (and other keep out areas). Wicking is a phenomenon caused by a combination of low viscosity of conformal coating material and strong capillary forces generated by the low standoff gaps in the SMT process.
- Use of masking materials. Masking materials are typically available in liquid, tape and dedicated rubber push on ´boots´. Simply apply the masking material (let it dry if liquid) and then you should be able to apply the coating as normal. Sometimes, especially in dipping processes, where the complete immersion increases the opportunity for masking materials to leak, it may be necessary to use a combination of masking materials.
- Use of thixotropic gel versions of standard coatings. Some suppliers can supply a thixotropic gel version of the same coating you are using, which can be dispensed directly around the keep-out area, and due to thixotropic nature, material will not flow or wick into components and coating can be applied over and around the dispensed gel.
- Use of a higher viscosity UV curable material. The combination of higher viscosity and snap cure will prevent the material from being able to wick into the component. Care must be taken however, to ensure the viscosity of the coating material is above 500 cPs or so, or else the material may be prone to wicking.
In this case, I would say that the key is to choose a soft coating to enable ease of push-fit and avoid risk of damaging the connector. Acrylic materials are generally used by most people doing this kind of assembly, although some softer urethane coatings can work with a bit more effort, especially if the connector is fitted as soon as the material is touch dry. UV cure materials are generally pretty tough after UV curing and so are less suitable (in general) for this kind of assembly. Monday, 14th April 2008
▶ Q3: We are currently purchasing your Conformal Coatings in one gallon containers. Does HumiSeal offer other packing sizes and if so what are they?
HumiSeal offers the majority of our Conformal Coatings, Thinners, Stripper and other products in a variety of package sizes. These package sizes include; US Quart, US Gallon, 5 US Gallon Pail and 55 US Gallon Drums. Dependent upon your global point of purchase, we also offer a full range of metric package sizes. Please contact HumiSeal directly so that we may assist you with the selection of the package size that best fits your needs. Tuesday, 16th October 2007
▶ Q4: We have been using HumiSeal Conformal Coatings for quite a while. Lately we are coming under more and more pressure by our local regulatory agencies to reduce the level of VOCs and HAPs we are emitting. Does HumiSeal offer any products that will enable us to meet these requirements?
Yes. HumiSeal offers a full range of environmentally friendly Coatings. These Coatings have been specially formulated to retain their full reliability while addressing today´s more stringent environmental regulations. HumiSeal offers Conformal Coatings and Thinners that are low in VOCs and HAPs, as well as a full compliment of VOC and HAPs free products. Please contact HumiSeal directly so that we may recommend the product which best fits your particular requirement. Monday, 17th March 2008
▶ Q5: My customer has requested that we apply a Conformal Coating to their assemblies. We have never used a Conformal Coating before and were hoping you could provide us with some information about the different types of coatings.
A good place to start would be HumiSeal´s comprehensive Conformal Coatings Handbook, available on this web site. Additional information can be obtained via the IPC´s CC-830 Conformal Coatings Handbook. This is available from the IPC at www.ipc.org. Friday, 27th July 2007
▶ Q6: There are so many different Conformal Coatings available, how do I know which one is right for my particular application?
Selecting the best Coating for your application can be challenging. To assist you we have a self-help "Decision Tree" that will help identify the right process for you. We also suggest that your review HumiSeal´s comprehensive Conformal Coatings Handbook available on this web site and additional information can be obtained via the IPC´s CC-830 Conformal Coatings Handbook, available from the IPC at www.ipc.org. Monday, 10th April 2006
▶ Q7: Conformal Coatings protect against moisture. If I use a Conformal Coating is my assembly waterproof?
All Conformal Coatings can be described as semi permeable membranes. Although they protect the assembly from the negative effects of high humidity environments and water vapor, Conformal Coatings DO NOT render electronic or printed circuit assemblies waterproof against standing water. With a properly applied Conformal Coating an electronic assembly MAY be able to withstand full contact with water for a short time. However this is NOT RECOMMENDED. Wednesday, 16th January 2008
▶ Q8: We are required to use a Conformal Coating that is UL recognized. Does HumiSeal have any UL recognized Conformal Coatings?
Yes a great many of HumiSeal´s Coatings are recognized under the Component Program of Underwriters Laboratories, Inc., File Number E 105698. The product tables contained on this website clearly state which of our products meet these requirements. You may also view a complete listing of HumiSeal´s UL recognized Coatings on the UL web site. Once there simply insert HumiSeal´s name into the company name space, hit search and our file will come up. Wednesday, 15th August 2007
▶ Q9: Our customer requires that we coat their boards with a Conformal Coating that is military qualified. Does HumiSeal have any coatings that meet the military specification?
Yes, in fact HumiSeal has more products qualified to the Military´s MIL-I-46058C specification than any other Conformal Coating Manufacturer. The product tables contained on this website clearly state which of our products meet these rigid requirements. You may also view the Military´s Qualified Products List (QPL) for this specification on their website. Tuesday, 12th February 2008
▶ Q10: We apply Conformal Coating to a small portion of our work and at this point do not want to perform the coating application in-house. Can HumiSeal provide information on contract coating services in my area?
HumiSeal is aware of many quality contract firms who apply our coatings. To provide you with the latest information please contact us directly for information on contract coaters in your area. Monday, 10th August 2009
▶ Q11: We are using a “No-Clean” assembly process. Do I still need to clean my boards prior to the application of a Conformal Coating?
There are a wide variety of "No-Clean" products on the market and unfortunately not all are of equal quality. Therefore, HumiSeal strongly recommends checking the compatibility of your "No-Clean" process with any Conformal Coating prior to starting production. Additional information about cleaning requirements can be obtained from the IPC at www.ipc.org, by reviewing HumiSeal´s Conformal Coating Handbook and by checking for any technical papers on this website that may pertain to cleaning. However for maximum long term reliability, the best practice may be to follow the old adage "When in doubt - CLEAN. Monday, 12th January 2009
▶ Q12: Problems with bubbles in conformal coating We operate a troubleshooting, repair, fabrication facility. The circuit cards we see are between 5 to 10 years old. They are exposed to extremes in weather and humidity. After repair/rework we apply low VOC silicone as a conformal coating. Our problem is bubbles.We´ve tried heating the boards to varying degrees, as well as keeping them cooler. We used various types of brushes to apply the coating, but continue to have bubbles between and behind the legs of surface mount components. Can you suggest low cost ideas we can try to reduce bubbles as the coating cures?
The reason that you have bubbles between and behind component legs is probably due to the viscosity (high) and thickness (100²m +) of the material applied. What tends to happen is the coating dries on the surface and solvent is trapped in the coating, if this coating contains solvent. This is also probably accentuated by the fact the coating is not flowing under the device due to high viscosity and is trapping air under the device. I would suggest a water based coating, acrylic or polyurethane, if you need low or no VOC, or a solvent based coating if solvents are not an issue for you. The lower viscosity combined with a reduction in coating thickness will eliminate the bubbles. I presume the original boards are coated with silicone, if not I would only suggest using a silicone coating if the units that you coat have a continuous operating temperature over 150°C. Below 150°C and if the original boards are not coated with silicone I would suggest acrylic if only moisture protection is required and polyurethane if moisture and chemical protection are required. Wednesday, 17th March 2010
▶ Q13: Contamination Prior to Conformal Coating When moving PCB assemblies through the factory we use a tray that is not made of anti-static material. In order to minimize static issues we will place a layer of pink antistatic bubble material on the tray placing the boards on it. There is a “rumor” that the pink material can leave a residue on the PCB creating a contamination, inhibiting good adhesion of conformal coating. We have contacted several suppliers of this pink bubble material and none of them believe this could be a problem. Has anyone seen evidence of this problem or have some data to support or deny this rumor? Thanks for any help.
The most likely source of contamination from this type of material would be either plasticizers used in the production of the film, or something like a release additive used to enable easy handling of the film in production. In my experience, both of these issues are less likely to cause issues than other materials used in manufacturing the bare board and other chemistries used in assembly such as fluxes and staking compounds etc. The specific type of conformal coating and application method are also factors that will have an impact on the adhesion. In general, high surface energy is the key to good coating adhesion. This is an easy thing to test and a Google search of dyne pen test will give you plenty of information such as can be found at www.accudynetest.com/adt_introduction.html. In my experience, 35 Dynes/cm would be the minimum value I would feel comfortable with prior to coating. I prefer to see numbers in excess of 40, which is achievable, but depending upon your board shop, can become an issue to be worked through. This is a huge area, and like most engineering questions, the answer is ´it depends"... It may be easier to handle offline in a phone call - please feel free to contact us directly. Monday, 8th March 2010
▶ Q14: Re-plating lead-free components for tin/lead assembly We work with an aerospace manufacturer on a PCB assembly that includes Pb-free components (no BGAs). The device is processed using SnPb (60-40) solder, but this does not solve the issue of Sn plating on the leads and the risk of tin whiskers. According to information on this website http://nepp.nasa.gov/whisker/ tin whisker formation is an issue on the exposed component leads outside of the solder region. Is there a process that can be used to re-plate component leads to add Pb?
As you are an aerospace manufacturer you may be conformally coating the boards. If so, you may be interested to know that HumiSeal has just completed a study with the NPL (National Physical Laboratory) into the interaction between tin whiskers and conformal coating. Results show that conformal coatings will abate tin whisker growth and although various conformal coating chemistry types perform in different ways with tin whiskers, they all abate growth. Please contact us if you would like full information on this project. Wednesday, 10th March 2010
▶ Q15: Which to Use – Rosin Flux or Water Soluble? What are the major differences between rosin based fluxes and water soluble fluxes? Assuming we have up-to-date equipment and cleaning systems to handle either process, under what circumstances should we use one process over the other?
Rosin based fluxes use natural rosin as the activator to clean the metals so that the liquid alloy can coalesce and wet to the solder pad. ROL0 (Rosin Low activation) is generally used in no clean applications. Water soluble flux. There are basically two types Water washable Water soluble. Water washable - flux may contain rosin and in addition a surfactant to remove the flux residue after reflow. Water soluble generally uses organic acid activators as the flux and every component in the flux system should be soluble in water and therefore clean with only water. These types of paste are generally high activation flux. Why use one or the other ? It depends on what you are making. If you need high reliability for a long term then it is a good idea to use a water soluble paste as it has high activation flux and after cleaning there will be no residue or contamination left on the board. If you are conformaly coating the board you should either use a cleaning process after soldering, chemical or water, or test the compatibility of any no clean flux used with the conformal coating. At HumiSeal we can provide a compatibility test service for no clean flux residues. Monday, 15th February 2010
▶ Q16: Epoxy Bonding Problems on RoHS Boards We are having problems with epoxy bonding components to RoHS circuit boards. We never had this problem on non RoHS boards. We´re sure the epoxy has not changed. Is there something about RoHS compliant boards that makes them more difficult to bond to? The boards look sparkling clean to the eye!
This is related to the surface energy of the solder resist. High surface energy is good, low surface energy is bad. For example a non stick frying pan is low surface energy, not easy to paint! There are many different types of solder resists and the surface energy varies with all of them. Over curing solder resist tends to lower the surface energy as silicones can be forced to the surface. I suggest that you get a set of dyne pens, these are inks of a known surface tension. The point at which they wet will indicate the surface energy of the board. As a guide 36 to 38 dynes is average, a no clean assembled board would be about 32 dynes and anything less than this bad. These levels are what we (HumiSeal) consider good, bad and average for conformal coating purposes. You have probably moved PCB manufacturer or are now using a different solder resist to the one you are used to. Wednesday, 20th January 2010
▶ Q17: Affects of Silicone Migration We are researching the affects of silicone migration onto electronic circuitry. We have heard of military contractors not allowing silicone materials in certain parts of the factory. Are you familar with any potential hazards to health or long-term product reliability due to products exposed to silicone materials?
Silicone conformal coatings have been linked to relay failures due to contamination over time. Silicones also have a tendency to contaminate other surfaces affecting the wetting and surface adhesion of conformal coatings. As coatings move away from solvent based systems due to VOC reduction directives in Europe wetting issues are more obvious. This is due to the fact that VOC free coatings are 100% solids or water based and lack the quasi cleaning ability of traditional solvent based coatings. We would generally not recommend that a conformal coating process is close to any silicone process. Thursday, 8th October 2009
Parylene Coating Questions
▶ Q1: We have reviewed your website and can find no mention of a Parylene coating. What is it and do you provide it?
Parylene, also know as Polyparaxylelene, is a very good Conformal Coating that applies by a vapor deposition process. However Parylene is also a very expensive coating. Not only is the material itself expensive, the equipment required to apply Parylene is also expensive. Parylene is vacuum deposited onto the assembly and one application cycle can require many hours to complete. Due to its cost and application issues, Parylene does not readily lend itself to large volume application and subsequently HumiSeal has chosen not to include it in our range of product offerings. If you have an application where you feel that Parylene may be required, there is a strong possibility that another Coating may suffice at far less expense. Please contact HumiSeal directly and allow us to assist you with a potential offset recommendation. Tuesday, 19th December 2006
▶ Q1: We are in the design phase of a new project and were wondering if you could provide us with the estimated cost of conformal coating a PCB assembly?
The cost of actually applying the conformal coating to the assembly will vary greatly by application method and projected volumes. The material costs for the Conformal Coating itself are very low and will normally be less than $0.001 per square inch of board surface for a 1mil dry film thickness. This may vary slightly dependent upon the Conformal Coating used and can be further reduced dependent upon your purchasing volumes. Overall, the application of a quality Conformal Coating is the cheapest way to insure the long term reliability of your printed Circuit assemblies. Please contact HumiSeal directly for further assistance in determining your actual Conformal Coating costs at our Contact Us page. Monday, 8th March 2010
Yes. Samples of our products are readily available. Please contact HumiSeal directly so that we may recommend the product which best fits your particular requirement. Monday, 11th August 2008