Design Guide for PET Clamshell Blister Packaging in electronics and electrical: Draft, Radii and Draw Ratio

Thermoforming rewards designs that respect how a heated sheet stretches. These rules prevent most tooling rework and most thickness complaints.

Use it as a working checklist when you write your next enquiry.

Product Overview

This category covers a family of products rather than a single item. In practice a buyer defines clamshell blister packaging by three things: the base resin, the format or dimension, and the performance or certification level it has to meet. Typical options in this category include hinged single piece designs; snap lock, button lock and RF seal closures; gauge 0.30 to 0.80 mm. Materials most often specified are Polypropylene, Polyvinyl Chloride, Polystyrene, Polyethylene Terephthalate, and the choice between them changes stiffness, temperature resistance, chemical behaviour and price.

In the electronics and electrical sector the decision is usually driven by ESD protection and dimensional accuracy, with cleanliness as a secondary requirement. Typical end uses include accessory blisters, device inserts, component trays.

Key Material Properties

The table below summarises the values that usually decide the material choice.

Polyethylene Terephthalate is frequently the default selection here: High IV PET resin is the reason a 1.5 L bottle can be light yet hold carbonation pressure.

Design Rules for Thermoformed Parts

Thermoforming rewards designs that respect how the sheet stretches. These rules prevent most tooling rework.

• Keep the draw ratio moderate: deep cavities thin the sheet and force you to start with a thicker gauge.
• Design uniform wall thickness by avoiding abrupt depth changes in the same cavity.
• Make corner radii at least equal to the sheet thickness; sharp corners are where holes start.
• Leave a flat sealing flange of at least 6 mm when the pack has to be heat sealed or lidded.
• Add ribs, steps or kiss-offs instead of increasing overall gauge to gain stiffness.
• Avoid undercuts unless the tool has moving sections, which adds cost to every cycle.

Send these rules to your designer together with the sheet gauge and the target cycle time; most tooling modifications come from ignoring draft and corner radii.

Common Grades and Variants

• Polystyrene based: rigid and glossy
• Polyvinyl Chloride based: inherently flame retardant
• Polypropylene based: lowest density among commodity plastics
• Polyethylene Terephthalate based: excellent barrier to CO2 and moisture

Beyond the base resin, most suppliers offer UV stabilised, food contact, flame retardant, anti-static and recycled content versions of the same product. Ask which additive package is included, because it is often the difference between a part that lasts three years and one that lasts ten.

Processing and Finishing Options

Each step below has its own control points, and skipping one of them is where most defects start.

• Vacuum forming
• Pressure forming
• Twin sheet forming
• Die cutting

Secondary operations such as printing, welding, machining and assembly are often cheaper to do in the same factory, and they reduce the risk of mismatch between components.

How to Specify Clamshell blister packaging Correctly

Use this checklist when comparing two or three supplier quotations.

1. avoid sharp internal corners at the hinge
2. specify the closure type and tamper evidence level
3. check the pack passes the retail drop test
4. test the hinge for at least 20 open-close cycles
5. confirm the trim method to avoid sharp edges

Send this list to your supplier with the drawing and you will receive comparable quotations from every factory you contact.

Frequently Asked Questions

How do you control colour consistency?

Colour is controlled with a masterbatch reference approved by the customer, and every production lot is checked against the approved sample under standard lighting before shipment.

What is the minimum order quantity for clamshell blister packaging?

For standard sizes and colours the minimum is usually one pallet or one production run; for custom tooling the economic minimum depends on the tooling cost amortised over the expected volume. Send us your annual volume and we will calculate the break even point.

How long does tooling and sampling take?

A new tool typically takes 25 to 45 days depending on cavity count and complexity, followed by T1 samples within one week. Existing tools can usually start production within 10 to 15 days of order confirmation.

Do you offer samples?

Yes. Standard samples are normally free of charge and shipped within three working days; custom samples are charged at cost and credited against the first production order.

What tolerance can be achieved?

Standard production tolerance follows the relevant ISO or DIN tolerance class for the process; tighter tolerances are possible after machining or grinding, but they add cost. Define the tolerance only on the functional dimensions.

Conclusion

Our team supplies clamshell blister packaging to electronics and electrical customers worldwide, with samples, material certificates and full inspection reports available before mass production.