Cuming Microwave C-STOCK AK and AK-500 Low Loss Plastic Stock With Adjusted Dielectric Constant

The C-STOCK AK is a series of plastic stock materials with an adjusted dielectric constant and low loss tangent, intended for a variety of RF and microwave applications. The available dielectric constants range from 3 to 25.

C-STOCK AK is a ceramic filled cross-linked plastic and unlike sintered ceramics, is readily machined with carbide tools. It has many applications as a dielectric spacer or circuit substrate, tapered permittivity transition, radome, RF lens, or other uses where a machined part of a specific dielectric constant is needed.

C-STOCK AK-500 is a similar product, having essentially the same electrical and mechanical properties as C-STOCK AK, except that it is made from a high temperature plastic which allows continuous use to 200o C (390o F), and short term exposure to 260o C (500o F).

DIELECTRIC CONSTANT C-STOCK

AK and AK-500 are available in standard dielectric constants of 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, and 20. Other custom dielectric constants between these values and as high as 25 are also possible. The material is homogeneous and isotropic to within +/- 5% at all points within the material (+/- 10% for dielectric constant values above 15). Cuming Microwave can also quote the material to tighter tolerances on the dielectric constant when required.

MACHINING AND USE

C-STOCK AK and AK-500 are ceramic filled plastics, and can be machined using carbide or diamond tools. Relatively slow speeds should be used. C-STOCK AK can be difficult to bond to other materials with adhesives. In most applications, mechanical attachment is used. C-STOCK AK can be bonded to itself using a silicone adhesive. It can also be bonded to other materials if those materials have first been primed with a silicone adhesive primer. Prepreg film adhesives can be used to adhere a copper film to the material for circuit applications. Epoxy or cyanate ester adhesives can be used for bonding AK-500. Consult a sales engineer for more information.

AVAILABILITY

All grades of C-STOCK AK and AK-500 are available in standard sheet sizes 12 in x 12 in (305 x 305 mm), in thicknesses of 1/4in, 3/8in, 1/2in, 1in, 2in, and 3in (6.4, 9.5, 12.7, 25.4, 50.8, and 76.2 mm). Unless tolerances are specified, the sheets are normally supplied “as cast”, with skins and approx. 0.05 to 0.10 inches over the nominal thickness, and in a size larger than 12 inches.

All grades are also available in 12 in (305 mm) rods in standard diameters of .375 in, .50 in, and 1.00 in (9.5, 12.7, and 25.4 mm), as well as in other custom diameters. Rods are also supplied “as cast” unless machined dimensions are specified.

Cuming Microwave can also supply sheets precision ground to a specified thickness, and can machine parts to customer drawings. Custom shaped castings are also possible. Contact a Cuming Microwave sales engineer for more details.

Specify the material as C-STOCK AK (or AK500) K=nn, a x b x c, where nn is the dielectric constant, and a, b, c are the dimensions, for example:

C-STOCK AK K=10.0, 12 x 12 x 0.5 inch or C-STOCK AK-500 K=5.0, 12in by 1.0in diameter