AD250C High Frequency PCB

Introduction
Welcome back to our channel. My name is Jane, the regional sales manager for Bicheng PCB. Today, we’re going to talk about a type of commercial microwave and RF laminate material which is designed with low and tight controlled dielectric constant --- AD250C.

The AD250C laminates are glass-reinforced, PTFE based materials that provide controlled dielectric constant, low loss performance, and very good PIM performance (passive intermodulation). The woven glass reinforcement affords good circuit processability and enables high yield circuit board fabrication.

Now let’s look at the data sheet to get more properties of AD250C.

AD250C Typical Properties
This table consists of Electrical Properties, Thermal Properties, Mechanical Properties and Physical Properties.

The first column is PIM. Typical PIM values using reverse treated ED copper foil are -159 dBc at 30 mil thickness and -163 dBc at 60 mil thickness. These are typical values obtained using the extensive PIM testing capability at Rogers at 1900 MHz using a two tone, reflected method on a 50Ω microstrip test vehicle.

Dielectric constant of process value is 2.52 at 10GHz, design Dk values at 2.5. This particular value is specifically because more and more antenna applications target that dielectric constant number.

The dissipation factor at 10GHz is 0.0013, this is considered very low loss.

And then TCDk......Thermal Coefficient of Dielectric Constant describes how much the dielectric constant will change with changes in temperature. TCDk at 50 ppm/ºC or less, at absolute value anyway, is considered very good. And this case of AD250C material has -117ppm/ºC TCDk, this can be considered a medium level number.

Volume resistivity of 4.8 x 108?Mohm/cm and surface resistivity of 4.1 x 107 Mohm are very good.

Electrical strength is 979 V/mil accordance with IPC TM-650 2.5.6.2;

Dielectric breakdown is greater than 40 kV.

Now let’s look at the thermal properties.

Decomposition temperature(Td) exceeds 500ºC measured under the condition of baking 2 hours at 105ºC, 5% weight loss in accordance with IPC TM-650 2.3.40.

While the X and Y axes show a median level of thermal expansion coefficient, Z direction seems a little bit poor with 196 ppm/ºC.

With 0.33 W/m/K, thermal conductivity is likewise showing a general level.

T288 is a good number and lasts longer than 60 minutes.

Okay, let’s go on with mechanical characteristics.

According to IPC TM-650, the peel strength of 1oz of copper foil after thermal stress is 2.6 N/mm.

Flexural strength is 8.8 MPa in machine direction and 6.4 MPa in cross machine direction.

Tensile strength is 6.0 MPa in MD and 5.6 MPa in CMD.

In MD, the flex modulus is 885 MPa, while in CMD, it is 778 MPa.

In the machine direction and cross direction, dimensional stability is 0.02 mils/inch and 0.06 mils/inch, respectively.

For mechanical qualities, these data are quite good.

Finally, let’s see the physical characteristics.

Flammability complies with the 94V0 standard.

The amount of moisture absorbed is only 0.04%.

Its specific heat capacity is 0.813 J/g K, and its density is 2.28 g/cm3

PCB Capability (AD250C)
For AD250C PCBs, we can provide you with single-sided boards, double-sided boards, multi-layer boards and hybrid types.
The standard thicknesses for AD250C PCBs are 20 mils, 30 mils, and 60 mils.

Finished copper on track lines can be 1oz and 2oz.

Our maximum PCB size on AD250C materials is 400mm by 500mm, it can be a single board in the sheet and also can be different designs in this panel.

Solder mask of green, black, blue, red and yellow etc is available in house.

There are several plating possibilities for pads, such as immersion gold, HASL, immersion silver, immersion tin, OSP, pure gold, ENEPIG and bare copper etc.

A Piece of AD250C PCB
Now on the screen is a type of 60mil AD250C high frequency PCB with black solder mask.

The typical applications of AD250C PCBs are cellular infrastructure base station antenna, automotive telematics antenna systems and commercial satellite radio antenna etc.

Conclusion
Passive Intermodulation (PIM) has been a concern in wireless transmission systems since the 1970s. PIM affects systems that use a single antenna for both transmitting and receiving signals on multiple carrier frequencies.

In order to minimize PIM generation on the laminates, Rogers determined that high conductor purity and low conductor profile, dielectric formulation and physical qualities, as well as proper control of the conductor-dielectric interface are all properly managed.

Antenna designers can be assured of having an opportunity to create an antenna design with the lowest PIM possible. Just like AD250C, it features low values of PIM, better than -157 dBc.

OK. This concludes today's episode. Thank you for reading. See you next time.