While we specialize in paperboard, we understand that many of our clients also use or compare blister packaging. Let me briefly explain the typical process of blister packaging, which is commonly used for pharmaceuticals, electronics, toys, and food trays.
What is Blister Packaging?
Blister packaging uses a plastic sheet (such as PVC, PET, or PETG) that is heated and formed over a mold to create a cavity or "blister." This blister holds a product and is then sealed to a backing material, which can be paperboard, aluminum foil, or plastic film.
The Step-by-Step Process
Step 1: Material Preparation
A roll of plastic film is loaded into the thermoforming machine. The film thickness typically ranges from 150 to 500 microns, depending on the product weight and required rigidity. For food contact, materials like RPET or biodegradable PLA are often used.
Step 2: Heating
The plastic film passes through an infrared heater, which softens it to a specific temperature. The material becomes pliable but not melted. Accurate temperature control is critical – too hot and the film will thin out or burn; too cold and it will not form properly.
Step 3: Forming
The heated, softened plastic is drawn over or into a mold. There are three common methods. The first is vacuum forming, where a vacuum sucks the plastic tightly against the mold. The second is pressure forming, where compressed air pushes the plastic onto the mold for sharper detail. The third is mechanical forming, where a plug assists in shaping the material. For most standard blisters, vacuum forming is sufficient and most economical.
Step 4: Cooling
The formed plastic is cooled, either by fans or by contact with a chilled mold. This sets the shape permanently. Cooling must be even to prevent warping or shrinkage.
Step 5: Trimming
The formed sheet moves to a trimming station, where a steel rule die or a punch press cuts each blister cavity from the surrounding web. Waste plastic material is typically ground and recycled.
Step 6: Product Loading
Products are placed manually or automatically into each formed blister cavity. For high-speed lines, robotic pick-and-place systems are common.
Step 7: Sealing
A backing material – often our food-grade paperboard coated with a heat-seal layer – is placed over the filled blisters. Heat and pressure are applied, bonding the paperboard to the plastic flange around each blister. The seal must be strong enough to protect the product but easy for the end user to open.
Step 8: Cutting and Packaging
The sealed sheet passes through a final cutting station, separating individual blister cards. These are then stacked, counted, and packed into shipping cartons.
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