Thermoforming in pharma packaging: how the cavity gets shaped

Thermoforming is the production technique that shapes plastic film into the cavities of a blister pack. The process is straightforward: heat the plastic until it's pliable, press it into a mold, cool it back to solid form. The cavity holds the tablet. The plastic chosen and the geometry of the mold determine almost everything else about the pack performance.

How thermoforming works in a pharma line

A roll of plastic film feeds into the thermoformer. A heating station softens the film. A mold presses the softened plastic into cavity shape, sometimes with vacuum assist to pull the film tight against the mold surface. The film cools, the cavity is locked into shape, and the formed strip moves to the filling station.

The whole cycle takes seconds. A modern thermoformer can run 200-400 cavities per minute, which is what makes blister packaging economically viable.

Materials commonly thermoformed

PVC is the most common. Easy to thermoform, prints well, basic moisture barrier. The default for stable solid orals.

PVDC-coated PVC adds a moisture barrier layer. The thermoforming step is similar to PVC, but the coating chemistry is more sensitive to overheating.

ACLAR is harder to thermoform. The temperature window is tight and the material can crack if cooled too fast. Reserved for products that need its high moisture barrier.

Cold-formed Alu-Alu doesn't thermoform at all. The aluminum laminate is shaped by pressure alone, no heat. Different process, different equipment, different cost structure. Read more about the difference.

Where thermoforming gets tricky

A few common issues:

Cavity geometry. Deep cavities for capsules need careful tooling. Shallow cavities for thin tablets are easier. Square cavities for medical devices need different tooling than round cavities.

Material temperature window. Each plastic has a narrow heating range. Below it, the film won't form cleanly. Above it, the film burns or cracks.

Cooling rate. Too fast and the cavity warps. Too slow and the line throughput drops.

All of this is engineering work the equipment supplier and the contract packer figure out together.

When to use thermoforming vs cold forming

Thermoforming wins on cost and throughput. Cold forming wins on barrier protection. The decision is dictated by the API stability data:

Stable formulation, basic moisture protection? Thermoformed PVC.

Moderate moisture sensitivity? Thermoformed PVDC-coated PVC.

Light-sensitive plus moisture-sensitive? Thermoformed ACLAR.

Hygroscopic, light-sensitive, or oxygen-sensitive? Cold-formed Alu-Alu.

If you're scoping a thermoformed blister

We run thermoforming on standard pharma blister formats and on specialty formats for medical devices. Send us the API stability data and the cavity geometry and we'll come back with a thermoforming spec or recommend cold forming if the stability data demands it.