материал для МПП Опции

[Serg1976]

Добрый день!
собираемся отдать на изготовление МПП из 14 слоев с лазерными микро-via и скрытыми переходными отверстиями. Сигналы в плате 100-140МГц (DDR, MAC-уровень) и 1.25 ГГц (SERDES). Какой материал для платы выбрать? Производитель предлагает RF408 или RO4003. Какой материал посоветуете использовать?

[PCBtech]

Добрый день!
собираемся отдать на изготовление МПП из 14 слоев с лазерными микро-via и скрытыми переходными отверстиями. Сигналы в плате 100-140МГц (DDR, MAC-уровень) и 1.25 ГГц (SERDES). Какой материал для платы выбрать? Производитель предлагает RF408 или RO4003. Какой материал посоветуете использовать?

There are a variety of applications that use GbE SERDES for its cost saving benefits.
However, designers must carefully select components that provide the required
performance. The GbE controllers were designed to be compliant with the PICMG 3.1
specifications and thus minimize risk of an improper backplane design. As a general
rule, backplane designs should be kept as short as possible due to signal degradation in
long traces, especially when using FR4 fabric for the PCB.
Other less “lossy” PCB materials, such as “Rogers”, are available but these can be more
costly than FR4. When making design trade-offs to save costs, designers need to
understand the impact on the performance and overall back plane design. This means
careful attention to layout to maintain the 100 Ω differential impedance and testing
thoroughly both on the prototype and the final production boards. Should the
backplane exceed 30 inches there is much more likelihood that signal degradation may
be too great to compensate, even with amplitude adjustment--especially on FR4 PCB
material.

**Designing SERDES Applications--
82545/82546, 82571/82572 &
631xESB/632xESB
Application Note--AN498
August 2006

FR408 is a high-performance FR-4 epoxy laminate & prepreg systems designed for advanced circuitry applications. Its low dielectric constant and low dissipation factor make it an ideal candidate for broadband circuit designs requiring faster signal speeds or improved signal integrity.
Improved Dielectric Properties
DK less than 3.8 (50MHz - 1GHz) - Supports increased signal speeds
DF less than 0.010 (50MHz - 1GHz) - Provides better signal integrity

RO4003®, RO4350® High Frequency Laminates
Woven Glass Reinforced Ceramic Filled Thermoset Materials
Dielectric Constant @10 GHz 3.38 ± 0.05 3.48 ± 0.05 –
Thermal Coefficient of εr
@ 0 to 100°C +40 +50 ppm/°C
Dissipation Factor @10 GHz 0.0027 0.0040 –

Вывод:
Если трассы короткие, до 10 см. то пойдет и FR408.
Да и обычный FR4 не сильно бы картину испортил.
А если хотя бы сантиметров 15 - тут уже все зависит от того, куда идет сигнал дальше, какие там потери на разъемах. кабелях и других платах или бэкплейнах.