Each layer has a thickness and the sum of these thicknesses makes up the total tape thickness.

What is often misunderstood by customers is what exactly “1-mil thick” polyimide tape implies. Customers are not sure whether “1-mil” (25µm) thick polyimide tape refers to the polyimide film thickness or the total thickness, since ultimately polyimide tape is made up of both the polyimide film layer plus the silicone adhesive layer (read more about why we believe in silicone-based tapes here).

As can be seen in the photo (click to enlarge), polyimide tape is madeup of two distinct layers:

1. The polyimide (kapton) film layer
2. The adhesive (silicone) layer

Each layer has a thickness and the sum of these thicknesses makes up the total tape thickness.

The Polyimide (Kapton) Film Layer

This is the layer that is specified in the product description. For example, 1-mil tape (referred to as LINQTAPE PIT1 by CAPLINQ) has a polyimide film layer of 1 mil (25µm). Similarly, 2-mil tape has a polyimide film layer of 2 mil (50µm), 3-mil tape has a polyimide film layer of 3 mil (75µm) and so on. This is in fact the layer that determines the thickness used in the description.

The Adhesive (Silicone) Layer

This is the layer of silicone adhesive applied to the backside of the polyimide (kapton) film. Though this layer thickness can vary, the standard average thickness is 1.6 mil (40um). Of course, there is some variation in this adhesive thickness and the thickness can actually range between 35µm – 45µm (1.4 – 1.8 mil) though historical data suggests that the actual range is betweeen 40µm – 45µm (1.6 – 1.8 mil). For all intents and purposes, 1.6 mil (40µm) can be used as the silicone adhesive layer thickness.

Of course, this assumes single sided polyimide (Kapton) tape. Since CAPLINQ also supplies double-sided Polyimide (Kapton) Tape (referred to as LINQTAPE PITD2 by CAPLINQ) this tape would have adhesive layers on both sides of the polyimide film layer in fact doubling the adhesive thickness of the double-side polyimide tape from 1.6 mil (40µm) to 3.2 mil (80µm).

The total thickness is then the sum of these two layers. For example, as can be inferred by the name, LINQTAPE PITD1 is 1-mil double-sided polyimide (kapton) tape that has a polyimide film layer of 1 mil (25µm) and two adhesive layers of 1.6 mil (40µm) each for a total thickness of 4.1 mil (25µm + 40µm + 40µm = 105µm) . Likewise, 1-mil (LINQTAPE PIT1) tape has a total thickness of 2.6 mil (65µm), 2-mil (LINQTAPE PIT2) tape has a total thickness of 3.5 mil (90µm), and so on.

Contact us or visit us at www.caplinq.com today for more information on these or other products.

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Polyimide Tape is made up of two separate steps. First is the manufacture of the polyimide film itself and the second is the application of the adhesive backing.

The Polyimide Film Manufacturing Process

Polyimide film, the generic name of of DuPont’s tradename Kapton®, is synthesized by polymerizing PMDA and ODA in strong polar solvents through the process of forming film and imine treatment at high temperature. This synthesis creates excellent physical, chemical, and electrical properties, as well as atomic radiation resistance, solvent resistance and low & high temperature resistance. It performs well in a wide range of temperatures as low as -452°F (-269°C) and as high as +500°F(+260°). Because of these characteristics, it is uniquely suitable for specific for many high temperature applications.

Manufacturing Polyimide Silicone PSA Tapes

Polyimide Silicone Adhesive Tape is made by first taking polyimide film and coating it with a heat-resistant silicone adhesive. Due to its stable pressure-sensitive macromolecule adhesive layer at high temperature, the tape offers excellent properties of heat resistance, electrical insulation, solvent resistance and radiation protection. Being silicone, it offers better elongation at break, and is used for electrical insulation of electrical equipment and high temperature insulation. It offers the highest heat resistance among film adhesive tapes, so it can also be applied for insulation in high-end electronic equipment, motors, and Lithium (Li) batteries. Other applications include the protection of the gold fingers on Printed Circuit Boards (PCBs) during wave soldering, as lead-free solders often require reflow temperatures up to 260°C – an operating temperature for which polyimide tape is uniquely suited – leaving no adhesive film once the tape is removed. Finally (though the true list of applications is nearly endless), it can be used for shielding in high temperature applications.

Manufacturing Polyimide Acrylic PSA Tapes

Polyimide Acrylic Tape is made using the same process as the silicone process described above, but though the acrylic is typically a heat-resistant acrylic, it still cannot withstand the high temperature range of the silicone PSA described above. Also, acrylics tend to be more brittle, so the lower temperature range is also somewhat more limited as the adhesive can crack at extremely low temperatures. However, since the polyimide acrylic tape still uses a base of polyimide, the film itself is still able to withstand a wide temperature range and can still be used in many of the same high-temperature applications; it is just that the adhesion properties of the film become more limited with an acrylic adhesive. Acrylic chemistries are typically cheaper materials also, so the final selling price of acrylic-based polyimide tapes are generally lower.  Though CAPLINQ offers both acrylic-based and silicone-based tapes; given the marginal price difference and the wider range of applications, the most popular tapes remain the silicone-based polyimide tapes.

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