Polyimide Tape (the generic version of Dupont© Kapton Tape), typically comes in various polyimide thicknesses. These thicknesses are generally labelled as 1-mil, 2-mil, 3-mil or even 5-mil thick polyimide tape. Each of these variations serves different purposes and is therefore used for different applications. Of course, the thicker the polyimide film used, the more expensive the tape too.
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:
- The polyimide (kapton) film layer
- 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.
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What is the thickness of a 65µm Kapton tape under heavy compression (pressure 30kg/cm²) ?!
Polyimide tape (Kapton) is a very rigid material and can support a great deal of compression. Even a heavy compression like the one mentioned above will do little to reduce the thickness of a polyimide tape. This is particularly true of thinner (ie. 1 mil or 25um) Polyimide Tape backing.
This being said, the adhesive will see some displacement, and will make up most of the thickness reduction.
As with most bonding applications under pressure, even high pressure will not completely displace the adhesive, and we would expect the bondline (ie the adhesive layer) to maintain at least 20µm of thickness.
Therefore, to answer your question: a 65µm Kapton tape under heavy compression should still have a total thickness of 40µm.
what’s the thickness of kapton with (?r = 3.5)?
It’s available in thicknesses from 0.5mil to 5mil. Please see our complete polyimide tape and film product offering.