Rod Resistors Revisited

I met with a gentleman last week who has been an engineer in the RF/microwave industry for a number of years. His knowledge base is very broad in this field.

Anyway, he explained something to me that I knew, but perhaps did not fully understand. He told me that Res-net Microwave, a subsidiary of Electro Technik Industries, was one of the few companies that manufactured rod resistors, and one of even a smaller set them made them AlN. He further explained that Res-net should probably promoting this product line specifically with advertisements and the like, and he was right.

Res-net Microwave does manufacture a complete line of rod resistors for the RF/microwave markets. Below is a Hubpage that was created after our meeting.

Rod Resistors

Rod resistors are a cylindrical type resistor that are used in both RF and microwave applications. They are thin film in nature and can be made of alumina, beryllium oxide, or aluminum nitride.

Because of their thin film construction they can achieve very high frequencies. These frequencies can be as high as 26.5 GHz or even higher in certain applications. Res-net Microwave Inc. is one of the few companies that offer rod resistors in alumina, beryllium oxide, and aluminum nitride materials.

The resistance range for rod resistors is generally from 10 ohms to 500 ohms and the resistive tolerances can be 1%, 2%, or 5%, The temperature range is -65 Degrees Celsius to +175 Degrees Celsius. The resistors are covered with a protective coating of high temperature epoxy to insulate them from these temperature extremes.

In addition to these classic thin film rod resistors, they can also be supplied using pyrolytic carbon. These carbon rod resistors also perform very well at microwave frequencies and have the added advantage of being able to work to the temperature of +200 Degrees Celsius. The sizes of the carbon resistors mimic those for the other thin film types. These carbon rod resistors will have a negative temperature coefficient as compared to the other resistors which will have either a plus or minus 100 ppm TC.

The power ratings can go from 0.050 watts all the way up to 75 watts, depending upon the material used. They are used extensively in the RF/microwave industries especially in the manufacture of other components such as, SMA terminations.

New Advertisements

After acquiring Arizona Capacitors, a manufacturer of wound film capacitors, on the first of this year we have developed our first advertisement for the new Electro Technik subsidiary. It is a little smaller than some of our previous ads we have run for our various companies, but we also went a little more specific when it came to the technical capabilities.

To the right is a sneak preview. It will be running in US Tech magazine and a few other trade publications over the next year or so. We will be revamping all our ads as time permits. A survey was conducted on some of our existing advertisements and we are taking into account these readers' suggestions as we create these new versions.

Passive Components

Passive electronic components are used in all types of electronic circuitry, but are often overlooked in their importance to the operation of the circuit. The passive electronic component stands ready to perform in a circuit when provided an external voltage or current stimulus. The active component, on the other hand, is often part of the power supply providing the stimulus for the passive circuit. Semiconductors are probably the most commonly used active electronic component.

Passive components, like resistors and transformers, are often constructed using resistance wire for resistors and magnet wire for transformers. Various metal foils are often used in wound film capacitor construction.

Another construction method used for metal film resistors and tantalum capacitors is to deposit either metal or dielectric film using vacuum thin film sputtering techniques. Vacuum sputtering is a precise and accurate means of construction. No wire or foil windings are necessary with this type of resistor or capacitor construction.

When ceramic substrates are used and RF or microwave frequency performance is desired, thick film construction of the metal conductors becomes a cost effective method for products like attenuators and terminations.

Thin film construction, while more costly, provides the best performance for RF/microwave resistors since the thin film morphology can be made very homogenous. The created homogenous resistor surface then distributes the applied power very uniformly eliminating hot spots that often lead to poor MTBF’s and early product failures. Since thin film resistors are created using optical masking techniques, very small and accurate resistors can be constructed.