This application is a national stage filing under 35 U.S.C. § 371 of international application number PCT/CN2020/115357, filed Sep. 15, 2020, which claims priority to Chinese patent application No. 201910872663.5 filed Sep. 16, 2019. The contents of these applications are incorporated herein by reference in their entirety.
Embodiments of the disclosure relate to but are not limited to the technical field of electronic power, and in particular, relate to but are not limited to a circuit board.
Currently, high-speed product rates have reached more than 25 Gbps, and this poses a great challenge to the signal integrity of high-speed interconnection channels. To meet this challenge, deep optimization design needs to be performed on passive components that form a high-speed interconnection channel. The performance of a via, as a key passive component of the high-speed interconnection channel, directly affects the performance of the signal integrity of the entire high-speed channel. For the via, a main factor affecting signal integrity is that the impedance of the via is lower than that of a transmission wire, resulting in discontinuous impedance. Factors affecting the impedance of the via include aperture, diameter of pad, diameter of anti-pad, dielectric constant, and the like. The sheet material and the aperture generally cannot be changed, optimization of the anti-pad is limited, and a via pad generally needs to be 10 mils larger than the aperture due to drilling alignment and cannot be reduced. As a result, the capacitivity of the via pad is relatively high, which leads to decrease of impedance. Consequently, the impedance of the entire via is relatively low, which affects the signal integrity.
Embodiments of the disclosure provides a circuit board to address the problems at least to some extent that impedance of a via on a current circuit board is lower than impedance of a signal wire, resulting in discontinuous impedance and affecting signal integrity, and serpentine wiring is used for a differential via on the circuit board, affecting improvement of wiring density.
In view of this, an embodiment of the disclosure provides a circuit board, including a circuit board body and at least one via apparatus provided on the circuit board body, where the via apparatus includes a via formed on the circuit board body, a via pad surrounding the via and separately provided from the via, and an electrical conductor electrically connecting the via pad with the via.
Other features and corresponding beneficial effects of the disclosure are described later in the specification, and it should be understood that at least some of the beneficial effects are apparent from the description of the disclosure.
To make objectives, technical schemes and advantages of the disclosure clearer, the following further describes embodiments of the disclosure in detail by using specific implementations with reference to the accompanying drawings. It should be understood that specific embodiments described herein are merely intended to explain the disclosure, but are not intended to limit the disclosure.
To increase impedance of a via on a circuit board and improve the signal integrity of the via and a system channel, an embodiment of the disclosure provides a circuit board.
The circuit board in this embodiment of the disclosure includes a circuit board body and at least one via apparatus formed on the circuit board body. As shown in
It can be understood that, in some embodiments, all the via apparatuses on a circuit board may be of the structure of the via apparatus in the disclosure. Alternatively, a part of the via apparatuses on a circuit board are of the structure of the via apparatus in the disclosure, and the other part of the via apparatuses on the circuit board are of a structure of another via apparatus.
A parasitic capacitance of a via is calculated as shown in a formula (1):
where εr is a PCB dielectric constant, D1 is a diameter of a via pad, and D2 is a diameter of a via anti-pad.
It can be learned from the formula 1 that a larger diameter D1 of the via pad indicates a larger parasitic capacitance of the via.
In addition, according to an impedance formula (2), when the parasitic inductance is constant, a larger parasitic capacitance indicates a lower impedance of the via.
The structure of the via apparatus according to this embodiment of the disclosure is shown in
In some embodiments of the disclosure, the via pad is a non-closed circular pad, as shown in
In some embodiments of the disclosure, the electrical conductor between the via and the via pad has a sector shape, as shown in
In some embodiments of the disclosure, the via pad is an irregularly-shaped circular pad, as shown in
In some embodiments of the disclosure, the via is an irregularly-shaped via, as shown in
Beneficial Effects
The circuit board provided in the embodiment of the disclosure includes a circuit board body and at least one via apparatus provided on the circuit board body, where the via apparatus includes a via formed on the circuit board body, a via pad surrounding the via and separately provided from the via, and an electrical conductor electrically connecting the via pad with the via. The capacitivity of the pad is greatly reduced by using a ring-shaped pad. Some implementations include, but not limited to, increasing the impedance of the via, so that the impedance of the via better matches the impedance of a transmission wire, thereby improving the signal integrity of the via and a system channel.
To increase impedance of a via on a circuit board and improve the signal integrity of the via and a system channel, an embodiment of the disclosure provides a circuit board.
The circuit board in this embodiment of the disclosure has a structure of BGA (Ball Grid Array) chip differential vias with an interval of 1.0 mm and a hole depth of 3 mm. The circuit board includes a circuit board body, a differential via apparatus at an inner layer of the circuit board, and a differential via apparatus at a surface layer of the circuit board. The differential via apparatus at the inner layer of the circuit board is shown in
Because the pads 201 to 204 in this embodiment of the disclosure are no longer circular as a whole in the existing technology but have a ring-shaped structure, an conductor area is greatly reduced. Consequently, the capacitivities of the pad at the surface layer and the pad at the inner layer are reduced. In addition, the ring width of the pad and the width of a connection structure of the electrical conductor are only 2 mils. Therefore, compared with the increase of inductance of the circular pad, it can be learned from the formula (2) that the inductance L increases, the capacitance C decreases, and the impedance increases, so as to increase impedance of the entire via, and improve the signal integrity of the via and a system channel.
Emulation results of impedance and insertion losses of a BGA differential via that exists before and after the disclosure is adopted are shown in
In some embodiments of the disclosure, high-speed crimping connectors with an interval of 1.2 mm are provided on the circuit board, and the hole depth is 2 mm. Because the crimping connector is assembled in a form of crimping, there is no signal wire on the surface layer, but the pad at the surface layer and the pad at the inner layer still exist. Moreover, the impedance of a crimping via is mainly affected by the pad at the inner layer. Similarly, the ring-shapged pad provided in the disclosure may be used, to increase the impedance of the via pad, thereby increasing the impedance of the entire via, and improving the signal integrity of the via and a system channel.
Beneficial Effect
The circuit board provided in the embodiment of the disclosure includes a circuit board body and a differential via apparatus provided on the circuit board body, where the differential via apparatus includes a via formed on the circuit board body, a via pad surrounding the via and separately provided from the via, and an electrical conductor electrically connecting the via pad with the via. The capacitivity of the pad is greatly reduced by using a ring-shaped pad. Some implementations include, but not limited to, increasing impedance of the via, so that the impedance of the via better matches impedance of a transmission wire, thereby improving the signal integrity of the via and a system channel, and relieving the problem of a large insertion loss of the differential via.
To increase impedance of a via of a circuit board, improve the signal integrity of the via and a system channel, and improve the wiring density of a signal wire, an embodiment of the disclosure provides a circuit board.
This embodiment of the disclosure provides a circuit board. A structure including BGA chip fan-out differential vias with an interval of 1.0 mm is provided on the circuit board. A differential via apparatus at a surface layer of the circuit board is shown in
In this embodiment of the disclosure, a ring-shaped pad is used as the via pad, and a path through which a current flows is changed by changing a location of an electrical conductor.
Beneficial Effect
The circuit board provided in the embodiment of the disclosure includes a circuit board body and a differential via apparatus provided on the circuit board body, where the differential via apparatus includes a via formed on the circuit board body, a via pad surrounding the via and separately provided from the via, and an electrical conductor electrically connecting the via pad with the via. The capacitivity of the pad is greatly reduced by using a ring-shaped pad, and a length difference between signal wires is compensated by changing a location of the electrical conductor. Some implementations include, but not limited to, increasing impedance of the via, so that the impedance of the via better matches impedance of a transmission wire, thereby improving the signal integrity of the via and a system channel, and relieving the problem of a large insertion loss of the differential via. In addition, serpentine wiring is not required, and this can reduce space occupied for wiring and finally improve product competitiveness.
The foregoing content is further detailed description of the embodiments of the disclosure with reference to specific implementations, and cannot be considered that the specific implementation of the disclosure is limited to these descriptions. For a person having ordinary skills in the art to which the disclosure belongs, simple deductions or substitutions may be made without departing from the concept of the disclosure, which shall fall within the protection scope of the disclosure.
Number | Date | Country | Kind |
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201910872663.5 | Sep 2019 | CN | national |
Filing Document | Filing Date | Country | Kind |
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PCT/CN2020/115357 | 9/15/2020 | WO |