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Understanding Flexible Packaging for Clean Rooms and ESD

In industries such as electronics, aerospace, medical device, pharmaceutical and automotive, manufacturers place significant emphasis on the cleanliness of their products. The shrinking geometries of devices combined with the need for higher product yields have increased the demand for clean packaging materials over the last several decades.

Large investments are being made today to standardize cleanliness throughout today’s manufacturing processes. Unless the cleanliness can be maintained up to the end user, the benefits of clean manufacturing are lost because of the choice of the wrong packaging.

For example, if a specification calls for an ultra clean valve and the packaging material adds to its particulate level or fails to prevent corrosion the valve can fail. A particle on the valve seat could cause the valve not to seal. Corrosion from moisture or oxidation could cause the valve to seize and not function properly. Choosing the right packaging material, with the right properties to protect the product from failure is critical.

Cleanliness is a relative term…

Cleanliness is a relative term based on the industry the product is intended for being used. Medical device end users may accept submicron particles if they have been gamma irradiated. Semiconductor end users may allow bacteria on the product if it doesn’t change conductive properties. Identify the enemy, is it particles, is it moisture, is it oxidation, is it ESD from a static charge, is it all of the above or a mix?

Anti-static materials are great for reducing particle attraction and ESD events, but can sometimes cause a thermogenic response in medical applications.

ESD:  Acronym for Electrostatic Discharge. The discharge of static energy that emits heat, light, and sound.

Thermogenic: Tending to produce heat.

Nylon is incredibly tough, highly resistant to sloughing of particles and also an excellent gas barrier, but it is hygroscopic and will absorb moisture and let it pass right through to the bag’s contents.

Outgassing: The transfer of gaseous material onto a product inside the bag.

Sloughing: Material shed onto a product inside the bag when the film is flexed.

Knowledge of flexible packaging materials strengths and weaknesses is crucial for selecting the right packaging.

Packaging Materials

Polyethylene is used in cleanrooms all around the world for every application imaginable.  The primary reason for its universal usage is low cost.

Several forms of polyethylene include Low Density (LDPE), Medium Density (MDPE), High Density (HDPE), and Anti-Static Low Density (SDLDPE). Chemical and physically pure polyethylene film is created purely from using a specialized clean resin that contains no regrind, slip or anti-block agent.  Polyethylene has a low melting point and is easily heat sealed, making it a common choice as the inner layer of most laminated structures.

The problems encountered with its use are sloughing of particulate and transfer contamination of film processing additives like slip agents and anti-block. Sometimes the addition of a small amount of slip or blocking agents is acceptable when the ease of bag opening outweighs the contamination risk.

Featured Products: 7000 Series, 7100 Anti Static Series

Clean Polyethylene sheeting, tubing, and bags are available in various widths, colors, and thicknesses from 2 mils to 8 mils. All are available with or without anti-static properties.

Nylon is a blown film extrusion.  The advantages of Nylon film are: toughness, vacuum sealability, and a suitable gas barrier.  A disadvantage of Nylon is that it is hygroscopic. This makes it a poor moisture barrier, and it has a high melting point, which can cause heat-sealing difficulties.  Clean Nylon sheeting, tubing, and bags are available in various widths.

Featured Product: 7200 Series 

Coextruded Nylon / Polyethylene is a visually clear, moisture and gas barrier material that is reasonably tough, puncture resistant, and vacuum sealable.  Coextrusion is a process where these two materials are simultaneously pressed through the same die forming a single sheet.

Featured Product: BB450 Series

The resulting product has characteristics of both materials: visual clarity, gas barrier, toughness, and moisture barrier properties.  It is used when a moisture and gas barrier is required, but the product needs to remain visible inside the bag. These films typically have been manufactured with a small amount of slip agent and generally are not available in anti-static versions. Coextruded Nylon / Polyethylene bags and sheeting are available in various sizes.

Metalized Polyester / Anti-Static Polyethylene Laminate provides a small amount of moisture and gas barrier protection while protecting the contents from ESD damage.  

Featured Product: 8100 Series

Polyester with a thin layer of aluminum sputtered onto its surface is laminated to anti-static polyethylene. The resulting structure can be used to make a bag that forms a Faraday cage around ESD sensitive electronics and is heat sealable.  The material is translucent allowing the contents of the packaging, including barcodes, to be read through the bag.

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