Analysis of the selection parameters of #RO4003C and #RO4350B high frequency laminates with TIKER TCR thin film #resistor layer
For high-frequency #circuit design engineers, there are more choices for line laminates than ever before, each with its own advantages and disadvantages. If you do not carefully compare the various #parameters of the board, it is difficult to choose the most suitable sheet. This article will help circuit design engineers understand the most appropriate method for selecting the most suitable sheet by comparing the main parameters of #Rogers' #microwave sheet RO4003C and RO4350B.
Microwave defination
Microwaves are electromagnetic spectrum allocations by definition it refers to the wavelength range from 1m to 0.1mm electromagnetic waves, the corresponding frequencies from 0.3GHz to 3000GHz. This electromagnetic spectrum includes decimeter (frequency from 0.3GHz to 3GHz) \ centimeter wave (frequency from 3GHz to 30GHz) \ millimeter wave (frequency from 30GHz to 300GHz) and sub-millimeter wave (frequency from 300GHz to 3000GHz, some literature This paragraph does not contain the definition of microwave) four bands (including caps, excluding the lower limit). Like having light resistance, like the sound of nature, penetrating, non-ionizing, informative five characteristics.
So most of microwave field must use high frequency #pcb(＞1GHZ),means microwave pcb must use high frequency printed circuit boards(rogers/#Taconic/#arlon/#isola etc)
Microwave pcb material
#Rogers4003C: thickness(0.254 0.508、0.813、1.524) DK 3.38
#Rogers4350B: thickness(0.254 0.508、0.762、1.524) DK 3.5
#Rogers5880: thickness(0.254 0.508、0.762) DK 2.2
#Rogers3003: thickness(0.127,0.508、0.762、1.524) DK 3
#Rogers3010: thickness(0.635) DK 10.2
#Rogers3206: thickness(0.635) DK 10.2
#Rogers3035: thickness(0.508) DK 3.5
#Rogers6010: thickness(0.635,1.27) DK 10.2
RO4003C and RO4350B are high frequency laminates with #TICORTM TCR? thin film resistor layers. The main parameters are as follows:
Dielectric constant DkWhen the circuit design engineer selects the board, the first cares is whether the working frequency of the board meets the requirements. The main parameter affecting the working frequency of the board is whether the dielectric constant and the variation meet the design requirements within a certain bandwidth. The following figure shows the variation of the dielectric constant of the RO4003C and RO4350B with the frequency. And it is selected by the working frequency and bandwidth of the actual product. In addition, the dielectric constant also affects the line width of the transmission line or the matching line. Smaller the #Dk, wider the transmission line. Using materials with different dielectric constants requires recalculation or simulation of the linewidth.
Dissipation factor Df
Regardless of the influence of other factors, smaller the dissipation factor, smaller the loss of the signal during transmission. Both RO4003C and RO4350B have very low dissipation factors of 0.0027 and 0.0037, respectively. The #transmission line loss of RO4350 is larger than that of RO4003C during transmission. When the system gain design margin is tight, the RO4003 with a smaller dissipation factor can reduce the transmission loss of the dielectric board.
?r thermal stability coefficient
The temperature change causes a change in the dielectric constant. The thermal stability coefficient of RO4003C and RO4350B can be used to estimate the dielectric constant of the two sheets at a certain temperature, then determine whether they are within an acceptable range. The lower absolute value of #?r, the more stable dielectric constant within the operating temperature range.
Thermal expansion coefficient
Temperature changes will inevitably cause changes in the physical dimensions of the board. For the PCB, the copper layer (including the through hole) is pressed against the dielectric material at normal temperature. As the temperature changes, the copper and the medium change with different coefficients of thermal expansion. Due to the inconsistent expansion coefficient, the temperature stress is inevitably caused. When the temperature stress exceeds the bonding ability of the copper layer, the dielectric or the copper layer to the medium, the PCB board will be damaged. Temperature stress in the Z-axis direction may cause metallized through-hole fracture; repeated stress on the X/Y axis may cause tearing of the copper layer or loosening of the bond between the copper layer and the medium. When the sheet is processed, due to etching shrinkage (post-etching), the coefficient of thermal expansion is different, which causes a change in the size of the sheet after processing.
The thermal expansion coefficient of copper is about 19ppm/°C, and both RO4003C and RO4350B have thermal expansion coefficients similar to those of copper. The X/Y/Z axial values are 11/14/46 (#ppm/°C) and 10/12/32, respectively. Ppm/°C). In comparison, RO4003C is closer to the thermal expansion coefficient of copper in the X/Y axis and has better dimensional stability during sheet metal processing. R04350B is closer to the thermal expansion coefficient of #copper in the Z-axis, which can better protect the metalize #through-hole.
Water absorption rate
The water absorption rate indicates the ability of an object to absorb water under normal atmospheric pressure. The higher water absorption rate, the higher proportion of water in the medium. and the greater influence on the characteristics of the #medium. Working in a high humidity environment, it is more appropriate to choose RO4003C sheet with low water absorption.
When selecting the board, in addition to consider the above main indicators, it is also necessary to consider other performance indexes according to the actual application environment, such as copper foil peeling strength, thermal #conductivity, flame retardant grade, lead-free process, and cost etc. When you have a fully understanding of the actual application environment and the meaning of the parameters of the plate, it's better to choose the most suitable plate.