A weak seal on a blister pack isn’t just a minor flaw—it can lead to product damage, contamination, or lost sales. Whether you’re dealing with custom blister trays for electronics or clamshell packaging for small tools, sealing issues like gaps, peeling, or inconsistent bonds need targeted solutions. Let’s break down the root causes and how to fix them.​

One of the most common culprits is material mismatch. Blister packs rely on the compatibility between the thermoformed plastic (like PET, PVC, or PP) and the sealing layer, often a cardboard backing or heat-seal film. For example, using a low-temperature seal film with a high-melt PET blister will result in poor adhesion, while pairing PVC with an incompatible adhesive can cause the seal to break down over time. The fix? Work with your supplier to confirm material pairings—reputable manufacturers of custom blister packaging can recommend tested combinations for your specific product.​

Equipment calibration is another critical factor. Heat-sealing machines that run too hot can warp the blister plastic, creating thin, weak spots, while insufficient heat leaves gaps where moisture or dirt can seep in. Uneven pressure across the sealing plate, often caused by worn parts or misalignment, also leads to patchy seals. Regular maintenance checks—adjusting temperature settings (typically 160–200°C for most thermoplastics) and ensuring pressure plates are clean and level—can resolve these issues. For high-volume runs, investing in digital controls for precise heat and pressure management reduces errors.​

Finally, don’t overlook tooling quality. Dull or damaged sealing dies can create uneven contact between the blister and backing, while poorly designed molds may cause the plastic to sit unevenly during sealing. Inspecting dies for wear and tear, and replacing them when edges become rounded, ensures a consistent seal. Post-production testing—like pull tests or vacuum checks—also helps catch issues early, before faulty blister packs reach retailers.​

By addressing material compatibility, equipment calibration, and tooling maintenance, you can eliminate sealing problems and ensure your blister packaging delivers the protection and professionalism your products deserve.