LED ENCAPSULATION BASICS

ENCAPSULATION PROCESS

LED’s are widely used throughout the lighting industry. Their use is becoming extremely diversified, and the design requirements and technical challenges have found successful answers using an encapsulation process. Encapsulation was originally introduced to protect the LED and the related electronics creating high-quality LED lighting and making them suitable for the most demanding outdoor applications. However, with the wide spread growth the use of encapsulation has also become an aesthetically significant and functional answer to new market demands and special design requirements. Flexible LED strips are a good example of this development.

CHEMISTRY AND RAW MATERIALS

Several encapsulation chemistries are available on the market today such as epoxy and silicon resins. Polyurethane resins (PU) provide the most versatile choice. PUs have a vast and easily modifiable range of properties and are therefore one of the most frequently used two-component (2K) materials in industry. PU is the result of the additive reaction of polyisocyanates (the hardeners) with polyvalent alcohols known as polyols (the resins). Using suitable ingredients and additives, the properties of polyurethanes can be varied much more than any other class of materials, depending on the requirement and application. It is possible to create “custom materials”, which have properties ranging from hard and brittle to pliable and soft, from highly fluid to highly paste-like. Properly filled they can provide enhanced flame resistance and improved thermal conduction. PUs are available in colours and with various degrees of opacity permitting you to get outdoor durable aesthetical effects. ENCAPLED PU resins and hardeners are a custom developed group of ingredients which can be used to satisfy a large variety of encapsulation polymers. Their combined use is an industry best in the production of high quality flexible LED strips.

EQUIPMENT

COLOR-DEC LED dispensing units, and automated robotic units, are designed to be modular and upgradable. PU-based casting resins always have to be protected from moisture during processing, since the curing components react with water. To produce high quality polymers, the use of a dispensing machine equipped with proper raw material degassing and storage system is highly recommended. Additionally in the LED encapsulation process there is a large variety of possibilities and the use of a programmable gear-pump automatic mixing and dosing machine is the best industrial solution. The ENCAPLED 400GP4 equipment is an example of an LED encapsulation dispensing machine. The 400GP4 can be used as a standalone metering and dispensing unit or used in combination with XYZ Cartesian robotic units. The 400GP4 can be configured to use up to six ingredients, which permits a wide variety of encapsulation possibilities. Ingredients combinations are based on adjustable and preset ratios each one of them can be easily saved and recalled on demand.

FLEXIBLE LED STRIP PRODUCTION

Producing flexible LED strips is similar to encapsulating an LED strip in an aluminium housing. A substantial amount of the basics described above remain the same. The main difference is that the rigid, and easily moveable aluminium housing is replaced by a flexible housing. The handling of the flex introduces some complexity, but they can be easily managed.

Encapsulated LED strips can be produced according to two different manufacturing processes.

  • Encapsulation process via extruded thermoplastic housing
  • Encapsulation process via in house cast thermoset housing

Each production method has its advantages, but also disadvantages, so evaluate them carefully, in relation to you own organization and production targets.

THE HOLDING JIGS

In the production of flexible strips the holding jigs are an important part of the process. Regardless of the production method the use of a jig to house the strips is necessary. The jig must house the strip and keep it in the proper shape throughout the production of the strip from the casting processes until the casted PU is cured enough to maintain the proper shape. The size of the jig must match the size of the final strips so consequently the jigs must always be considered in the setup cost.

ENCAPSULATION PROCESS: EXTRUDED THERMOPLASTIC PROFILE

The thermoplastic profile is available as a flat tape or as C-profile. They are available in thermoplastic PVC or PU and supplied in rolls. According to their dimensions the profiles can be used for the production of top view and side view profiles. When producing the side view the LED strip will be mounted on the side of the flexible housing and not on the bottom.

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