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Applying Gel or Encapsulant

Manual Mixing and Dispense

 Manual dispense units have separate chambers for each component which connect to a common static mixer tube. Applying pressure to the plungers on the chambers pushes the material through the static mixer. This can be done manually by squeezing a hand trigger or can be gas powered. Static mixers are typically disposable one-time use units and may need to replaced or cleaned when not being used for long periods to avoid having the encapsulant cure in the mix tube. These units can be supplied pre-filled and ready to use or can be loaded with mixed and de-aired material immediately before use.

Automated Meter-Mix

Automated meter-mix equipment is typically used for higher volume production processes. These systems consist of a separate feed reservoir and pump for each component. The systems are set to achieve the desired ratio of the two components. The materials are then fed through a dispense head attached to a static mixer which is used to achieve a uniform mix. The dispense head is used to control the amount of material that is dispensed into the part. Static mixer tubes may need to replaced or cleaned when the process is shut down for long periods to avoid having the encapsulant cure in the mix tube. If air entrapment in the cured material is a problem, it may be necessary to deair the material in the feed reservoirs or in extreme cases, deair the material in the parts. Mixing in the reservoirs may also be needed to keep the filler distributed uniformly in some products. 

Applying Gel or Encapsulant

When filling a cavity, carefully pour or dispense the liquid encapsulant into the low point of a container so that it will rise slowly around components and entrap a minimum amount of air. Some work may be necessary in determining the correct dispense spot. When potting a module in which the circuit board is very close to the housing, the potential exists for air to become trapped under the board. This may be avoided through the proper selection of a potting point from which the gel or encapsulant can push the air out. It is often necessary to apply a vacuum after filling to ensure a void-free finished unit.

For applications looking for void free filling it may be necessary to isolate the material from air pressure prior to dispense.  Material held under air pressure can become supersaturated with air relative to atmospheric pressure.  Upon dispense this air leaves the material and can create fine bubbles or voids.  Isolation can be accomplished by either using a platten press type pump to introduce the material in the MMD system or by using a bladder pack type package.  The bladder package installs in a standard pressure pot but provides a barrier between the air and the material.  The material is contained in a bag that is connected via a tube to the outlet of the pressure pot.  Air pressure on the outside of the bag forces the material up the tube and out of the pot.    


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  1. Gel and Encapsulant Processing - General

  2. Gel and Encapsulant Processing - General

  3. Substrate Preparation

  4. Material Preparation

  5. Applying Gel or Encapsulant

  6. Curing

  7. Cure Inhibition

  8. Where Does Inhibition Occur

  9. Repairing Gels or Encapsulants

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