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This guide explains what design engineers need to know about selecting potting and encapsulating materials, a category of products you&#;ll find on Gluespec. These protective liquids and gels are poured over printed circuit boards (PCBs) and their components and then cured. Pottants and encapsulants provide excellent protection against moisture, dust, shock, vibration, heat, electrical discharges, and other hazards that can cause electronics to fail. Specialized materials can provide flame resistance, protection against radiation, or have low levels of outgassing for high vacuum applications.
Potting and encapsulating materials can be used instead of conformal coatings, thin protective films that are applied to PCB assemblies (PCBAs) and conform to the shape of individual components. Although conformal coatings weigh less and take up less space, they offer less robust protection against chemical, thermal, and environmental hazards. Pottants and encapsulants are thicker, heavier, and enclose the entire PCBA. There are some important differences between pottants and encapsulants, however, and this category of products also includes casting materials.
Potting requires the use of a pot, a plastic case or container with an open top. The PCBA is put in the pot and the potting compound is poured over it until the case is full. The pottant is then cured so that it hardens, and the pot becomes part of the brick-like unit. With encapsulation, the PCBA is dipped into a resin that fully encloses or encases the device. In other words, encapsulation also uses a resin but does not use a pot. Casting, a related process, uses a removable mold instead of a permanent pot. The electronic device is put in the mold, resin is poured over and cured, and the mold is then removed.
When selecting potting and encapsulating materials, design engineers need to consider the chemistry and the curing system as well as the substrate materials and performance requirements. Epoxy, polyurethane, and silicone are the leading chemistries. Curing systems include moisture, evaporation, heat, ultraviolet (UV) or visible light, and dual curing mechanisms. Pottants and encapsulants are available as one-part or two-part materials, liquids or gels, and as optically clear or opaque materials. Thermally conductive potting compounds include a heat-conductive filler material.
Gluespec divides potting and encapsulating materials into the following categories and makes it easy to search for them online.
Within each category, you can search for products based on technical specifications for curing, bond strength, material resistance, conductivity, and other properties. The following sections describe each category of potting and encapsulating materials in detail. You&#;ll also find links to technical resources with additional information, either in the Gluespec Knowledge Center or from other trusted resources.
Casting and moldmaking materials are used to fill or create molds into which protective resins are added. Casting materials fill the hollow cavity in the mold, surround the PCBA, and are cured so that the resin hardens. The enclosed device is then removed from the mold, which may be reused. Casting materials are sometimes referred to as pottants, but casting is a different process that uses removable molds instead of permanent pots. Casting is also different from encapsulation because a tool, the mold, is required. Moldmaking materials are related to casting because they used to create the molds.
Applications for casting and moldmaking materials include:
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Here are some of the technical specifications for casting and moldmaking materials like Resinlab EP Black.
Type
Spec
Definition
Cure
Cure Time (min)
The length of time needed for a conformal coating to fully cure, acquiring its end-use properties.
Bond Strength
Tear Strength (piw)
The property of a material that is measured by the force required to tear it
Conductivity
Dielectric Strength (V/mil)
The electrical strength of an insulating material.
Here are some additional resources about casting and moldmaking materials.
Dielectric pottants and encapsulants provide electrical insulation and protect against electrical discharge, the release and transmission of electricity in an applied electric field through a medium such as a gas. Although air is normally an electrical insulator, electricity can pass through it if the distance between components or traces is small and the quantity of a charge is large. The results can include damage to the PCBA or individual components. With the addition of thermally conductive materials, dielectric pottants and encapsulants can conduct heat while providing electrical insulation.
Applications for dielectric pottants and encapsulants include:
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Here are some of the technical specifications for dielectric pottants and encapsulants like Dow Sylgard 184 Silicone Elastomer.
Type
Spec
Definition
Cure
Viscosity (cPs)
A measure of a fluid&#;s resistance to flow
Material Resistance
Ozone Resistance
The ability of a material to resist the deteriorating effects of ozone exposure
Conductivity
Dissipation Factor
A measure of loss-rate of energy (mechanical, electrical or electromechanical) of a mode of oscillation in a dissipative system
Here are some additional resources about dielectric pottants and encapsulants.
Epoxy pottants and encapsulants provide excellent moisture resistance, high-temperature resistance, and chemical resistance. They also have higher rigidity and greater tensile strength than potting and encapsulating materials that use polyurethane or silicone chemistries. With their strong dielectric properties, epoxy products can be used in high-voltage applications. Cured epoxies can be brittle, however, and brittle solids can fail because of shock-induced fracture. Epoxies are also relatively slow to cure, and temperature cycling can affect performance properties.
Applications for epoxy potting and encapsulating materials include:
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Here are some of the technical specifications for epoxy pottants and encapsulants like Devcon (ITW) 2 Ton Epoxy.
Type
Spec
Definition
Cure
Work/Pot Time (min)
Pot life is the length of time in which multiple part coatings or paints can be applied to a surface
Bond Strength
Compressive Strength (Psi)
The maximum compressive stress that, under a gradually applied load, a given solid material can sustain without fracture
Hardness
Elongation %
The process of becoming or making something become longer, and often thinner
Here are some additional resources about epoxy pottants and encapsulants.
Micro-encapsulants include two main types of products: glob top materials and encapsulants, and underfills. Glob tops are used to encapsulate a single chip in chip-on-board (COB) applications. They provide greater protection than conformal coatings and are often used with wire-bonded chips and dies. Underfills are micro-encapsulants for chip scale package (CSP) and ball grid array (BGA), two popular types of integrated circuit (IC) packaging. Underfill materials use capillary action to fill and seal spaces during the secondary mounting of packaged chips to motherboards.
Applications for micro-encapsulants include
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Explore Underfills
Here are some of the technical specifications for micro-encapsulants like Hernon® Tuffbond 326.
Type
Spec
Definition
Cure
Cure Temperature (°F)
The temperature at which the material cures
Bond Strength
Shear Strength (psi)
The ability of a material to resist forces that cause the material&#;s internal structure to slide against itself
Hardness
Durability
The ability of a physical product to remain functional, without requiring excessive maintenance or repair, when faced with the challenges of normal operation over its design lifetime.
Here are some additional resources about micro-encapsulants.
Polyurethane pottants and encapsulants have a flexible, rubbery consistency after curing that makes them a good choice for protecting delicate components. They can be formulated to have a wide range of physical properties and generally have greater resistance to shock and cracking than epoxies. Compared to silicones, polyurethanes have moderately greater tensile strength and significantly greater abrasion resistance. Because polyurethanes can adhere to a wide variety of electronic substrates, including plastics and composites, they form strong bonds to pots and PCBAs.
Applications for polyurethane pottants and encapsulants include:
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Here are some of the technical specifications for polyurethane pottants and encapsulants like Henkel Loctite UK U-05FL.
Type
Spec
Definition
Bond Strength
Peel Strength (piw)
A measure of the adhesive strength of two or more materials that have been bonded together.
Hardness
Flexibility
The ability to bend easily or without breaking.
Other Properties
Flash Point (°F)
The lowest temperature at which vapors above a volatile combustible substance ignite in air when exposed to flame.
Here are some additional resources about polyurethane pottants and encapsulants.
Silicone pottants and encapsuling materials are soft, flexible, and maintain their performance properties over a wide range of temperatures. Compared to epoxies, silicones can withstand higher temperatures and greater shock. They also provide better resistance to thermal cycling. Silicones can&#;t match epoxies in terms of strength, however, and silicones lack the abrasion resistance of polyurethanes. Often, silicone pottants and encapsulants are used in environments with high heat and high humidity. Products that contain thermally conductive fillers help move heat away from sensitive electronics.
Applications for silicone pottants and encapsulants include:
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Here are some of the technical specifications for silicone pottants and encapsulants like Resin Designs ThermoSink 35-1.
Type
Spec
Definition
Cure
Set Time (min)
The time it takes to form an acceptable bond when two or more substrates are combined with an adhesive
Conductivity
Volume Resistivity (O)
Ratio of electrical resistance through a cross-section divided by length through which current flows.
Other Properties
Specific Gravity
The ratio of the density of a substance to the density of some substance (such as pure water) taken as a standard when both densities are obtained by weighing in air.
Here are some additional resources about silicone pottants and encapsulants.
UV/visible light pottants and encapsulants cure with ultraviolet (UV) light or visible light. Irradiation at a specific wavelength and energy intensity is required. To reach shadowed areas where UV light or visible light cannot penetrate, or light-based curing is otherwise incomplete, a secondary moisture cure may be required. UV/visible light pottants that fluoresce facilitate the inspection of bond lines. When exposed to low intensity blacklight, the fluorescing color provides significant contrast and high visibility against the substrates
Applications for UV/visible pottants and encapsulants include:
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Here are some of the technical specifications for UV/visible light cure pottants and encapsulants like Dymax Multi-Cure 9-.
Type
Spec
Definition
Goto HumenChem to know more.
Bond Strength
General Bond Strength (psi)
The amount of adhesion between the bonded substrates
Conductivity
Surface Resistivity (O)
The resistance experienced by the leakage of current along the surface of the coat/insulating material
Other Properties
%Solids
The percentage by weight of the nonvolatile matter in an adhesive
Here are some additional resources about UV/visible light cure pottants and encapsulants.
Masking materials are applied to functional areas of a PCBA that should not be coated with a pottant or encapsulant. They include reusable masking shields and disposable tapes. PCB masking tapes include low-ESD materials that resist electrostatic discharge (ESD) and are therefore less likely to damage PCB components. Polyimide masking tapes are generally less expensive than low-ESD tapes and can be die cut into specific shapes. Crepe masking tapes are constructed with a heavy, thick, crepe paper backing and, like polyimide tapes, can resist elevated temperatures.
Applications for masking materials include:
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Here are some of the technical specifications for masking materials like 3M Scotch Performance Masking Tape 233+.
Type
Spec
Definition
Cure Specs
Application Temperature (°F)
The temperature at the point that the adhesive/tape is applied
Bond Strength
General Bond Strength (psi)
The amount of adhesion between the bonded substrates usually measured in pounds per square inch
Hardness
Elongation%
The process of becoming or making something become longer, and often thinner
Here are some additional resources about masking materials.
Optically clear pottants and encapsulants have optical properties that include optical transparency, high transmittance, low haze, and minimal yellowing. Unlike opaque pottants and encapsulants, which can hide the contents of a PCBA from visual inspection, optically clear materials keep the electronic device in view. Optically clear pottants and encapsulants are available in various chemistries, but silicones are popular choice because of their thermal stability and high-temperature performance, properties that make them suitable for lighting and other applications.
Applications for optically clear pottants and encapsulants include:
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Here are some of the technical specifications for optically clear pottants and encapsulants like Permabond 200.
Type
Spec
Definition
Cure Specs
Thixotropic
A thixotropic fluid is one that takes a fixed time to return to its equilibrium viscosity when subjected to abrupt changes in shear state
Bond Strength
Impact Strength (psi)
The impact strength of a material is defined as its capability to resist a sudden applied load or force.
Other Properties
Specific Gravity
The ratio of the density of a substance to the density of some substance (such as pure water) taken as a standard when both densities are obtained by weighing in air.
Here are some additional resources about masking materials.
Gel pottants and encapsulants cure in-place to form soft, resilient materials that provide cushioning against shock and vibration. Cured gels retain much of the stress relief provided by liquids while providing the dimensional stability of solid elastomers. To protect circuits and interconnects from mechanical and thermal stresses, gels are applied in thick layers. Products with excellent thermal stability and an extremely low modulus are used in systems that operate over wide temperature ranges and where stress-sensitive components are used. Some UV cured products fluoresce to support bond line inspection.
Applications for gel pottants and encapsulants include:
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Here are some of the technical specifications for gel pottants and encapsulants like HumiSeal UV20GEL.
Type
Spec
Definition
Cure Specs
Fluorescent
A fluorescent surface, substance, or color has a very bright appearance when light is directed onto it, as if it is actually shining itself.
Bond Strength
Shear Strength (psi)
The shear strength of a material is defined as its ability to resist forces that cause the material&#;s internal structure to slide against itself.
Hardness
Shore A Hardness
The Shore A Hardness Scale is a method used to characterize how resistant materials are to localized deformation or indentation.
Here are some additional resources about gel pottants and encapsulants.
Primerless pottants and encapsulants eliminate the priming step that is typically required for proper adhesion. These products require clean surfaces but can help reduce operational costs by simplifying assembly and improving cycle times. Often, primerless pottants and encapsulants are designed for auto-dispensing and high-speed production. They are available in a variety of chemistries and, like other potting and encapsulating materials, absorb shock and vibration while resisting moisture and adhering to a variety of substrates.
Applications for primerless pottants and encapsulants include:
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Here are some of the technical specifications for primerless pottants and encapsulants like Wacker Elastosil 288.
Type
Spec
Definition
Cure Specs
Tack Free Time
Tack free time is when the surface of the adhesive ceases to be sticky, preventing the pickup of dirt or debris that could cause discoloration.
Material Resistance
High Temperature Resistance (°F)
The adhesive&#;s ability to withstand prolonged exposure to high temperatures.
Other Properties
Density (g/cm3)
Density is the mass of an object divide by its volume.
Here are some additional resources about primerless pottants and encapsulants.
Shallow potting compounds are poured into pots to a reduced depth and have a shallower depth of cure than other potting and encapsulating materials. Because of their faster curing times, these materials support faster processing for great throughputs and lower processing costs. Shallow potting compounds are available in a variety of curing systems and chemistries, and some products can adhere to a wide variety of substrates. Shallow potting compounds that are formulated to cure primarily with UV/visible light may still require a secondary curing mechanism.
Applications for shallow potting compounds include:
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Here are some of the technical specifications for get pottants and encapsulants like Hernon Ultrabond 758.
Type
Spec
Definition
Cure Specs
Fluorescent
A fluorescent surface, substance, or color has a very bright appearance when light is directed onto it, as if it is actually shining itself.
Bond Strength
Shear Strength (psi)
The shear strength of a material is defined as its ability to resist forces that cause the material&#;s internal structure to slide against itself.
Hardness
Shore A Hardness
The Shore A Hardness Scale is a method used to characterize how resistant materials are to localized deformation or indentation.
Here are some additional resources about gel pottants and encapsulants.
UL pottants and encapsulants meet requirements from Underwriters Laboratories (UL), which develops safety standards for materials used with PCBs. There are many UL standards, but two are especially important for potting and encapsulating materials. UL-746E comprises a series of tests for dielectric strength and flame retardance. UL 94 is used to measure the burn rate of a horizontal or vertical specimen of a specific thickness. There are five different UL 94 flame ratings that apply to pottants and encapsulants: HB, V-2, V-1, V-0, and 5-V.
Applications for UL conformal coatings include:
Explore Products
Here are some of the technical specifications for get pottants and encapsulants like Resin Designs ThermoSink 35-1.
Type
Spec
Definition
Cure Specs
Set Time
Set time is the time it takes to form an acceptable bond when two or more substrates are combined with an adhesive.
Conductivity
Dielectric Constant
Dielectric constant is the ratio of an insulator&#;s capacitance to that of dry air. A dielectric constant of 10 means the insulator will absorb 10x more electrical energy than air.
Thermal Conductivity (W/m°K)
The ability of a material to conduct or transfer heat.
Here are some additional resources about UL pottants and encapsulants.
Gluespec&#;s comprehensive and quality-tested database of 28,000 adhesive materials includes the pottants and encapsulants that design engineers need. The materials and manufacturers in our database are not limited to specific suppliers, and data is quality-checked and updated as needed whenever new data sheets or product specifications are released.
If you need deep data on pottants and encapsulants or other materials, you&#;ll find what you&#;re looking for in our proprietary adhesives database. Along with technical data and key specifications, you&#;ll find best practices and comparable materials. Design engineers can also view test method information on dozens of material properties and data points.
Finally, Gluespec&#;s Advanced Search provides the tools you need to conduct deep filtering among all material properties. The result is a customized grid that contains materials and data points that are specific to your project. Save custom grids for quick access and share them, along with this Potting and Encapsulating Materials Guide, with your colleagues.
LEDs come in a huge variety of styles. We'll take a look at the most common features:
Mounting Types
There are three common way in which LEDs can be mounted:
THT components might be what you are most familiar with: Their pins go through holes in a PCB and are soldered on the other side.
SMD parts are soldered directly to the surface of a PCB. With this method they can be made much smaller than THT parts and are perfect for tiny projects, such as wearables. On the flipside they are more difficult to solder.
Some LEDs, especially power LEDs are mounted on an aluminum or ceramic substrate to improve the cooling. They are meant to be mounted with either screws or a thermal adhesive.
Optics
The LED chip itself produces a wide beam of light (about 120°). To make it suitable for spotlights a clear dome is placed right above the chip to act as a lens. Some LEDs, so called diffused LEDs, don't have any beam at all, they evenly scatter the light in all directions. This is very useful for indication LEDs as the light is visible from any direction.
Multi-Color/ RGB LEDs
You may have seen LEDs with multiple chips for different colors into one case. With such LEDs you can not only select the color you want, but also mix the light to get any color in between! We'll come back to this in "Chapter 3: Switching & Dimming".
Often it is not possible to have two dedicated pins for each LED chip, in such case either the anodes or cathodes are connected internally to only one common pin.
LED Matrix
Similar to Multi-Color LEDs these contain multiple LEDs in one package, but usually all the same color. They are also available as both, common anode and common cathode configurations. They can be used to display text or numbers and are readable from quite afar. However the high LED count usually requires a micro-controller and multiplexing. In "Chapter 4: Matrix & Multiplexing" we'll dig deeper into this.
7 Segment Display
While numbers can be displayed with a simple LED matrix, a seven segment display provides a much more elegant solution with way less LEDs you need to control. Alphanumeric displays are based on the same idea, but with a total of 14 or 16 segments they can show in addition all uppercase English letters. Electrically this kind of display is identical to the common LED matrix.
Integrated circuit
No matter the light effect you want, with some effort everything is possible. For the most common effects, such as blinking or color cycling, you don't even need to invest that much time. Some LEDs come equipped with a tiny circuit to do just that.
A very special LED is the WS/ WSB, sold as "Neopixel" by Adafruit. The chip inside takes serial data from a micro-controller (such as an arduino) and controls the RGB LED to match that!
No matter which LED you decide to get, check the datasheet briefly, so you don't miss anything important.
Contact us to discuss your requirements of Led Encapsulation Materials. Our experienced sales team can help you identify the options that best suit your needs.