predictability and efficient initial backplane pcb fabrication: working designs depend on understanding signal integrity, materials and plating.

by:Rocket PCB     2020-03-27
High-
Speed backplane system consisting of printed circuit boards (PCB)
The interconnect that maximizes signal integrity is the transmission path that provides financial services, military intelligence, commercial communications, and digital video links.
The successful introduction of such a system requires technical expertise in PCB manufacturing, with low
Understand the design of signal integration and understand the selection and application of connectors.
The connector affects the PCB design of the back panel.
Some are above level 6.
Between 25 and 25 Mb/s, differential pairs are used.
The choice of DPimpedance usually includes 85 [OMEGA]and 100[OMEGA].
The impedance selection depends on the semiconductor operating system.
Table 1 describes the 100 difference pair attributes compared to 850 [OMEGA]
Differential pairs. During high-
The speed signal travels, and the signal travels mainly along the surface of the conductor.
Rough surface of conductor leads to signal degradation.
The total signal loss is a combination of the loss of the conductor and the dielectric laminate.
Since the laminate or dielectric loss increases with the frequency, the conductor loss is proportional to the square of the frequency, so the contribution of the trajectory surface texture and width to the signal degradation is very small. An 85[OMEGA]
Designed with reduced trace width and laminate thickness, good electrical
Trodepositionin the plated inner-
The potential to use small diameter, acceptable production yield and lower circuit board manufacturing complexity provides imaginable cost savings and improved manufacturing predictability. High-
The speed connector has generally completed the nominal diameter from 0 to 0. 46 to 0.
60mm, according to RoHS, in addition to SnPb, there will also be a depth finish.
These finishes may include dip tin or chemical NiAu and require more stringent tp tolerances than SnPb finishes.
Successful plating in these depth holes depends on the manufacturer\'s technical expertise and is controlled by the ratio of the nominal thickness of the multi-layer to the diameter of the finished product depth.
The reduction of PCB thickness helps to minimize this ratio and promotes uniform metalization of the depth wall and a strong connection to the internal layer trace.
Figure 1 depicts a uniform geometry and an internal connection. [
Figure 1 slightly]
Inherent properties of laminated materials, loss factors or losses, Df and dielectric constants, Dk, PCB process stability and transmission definition end
Product performance and forecast performance meet the requirements.
Backplane suppliers with technical capabilities are related to PCB suppliers that characterize signal integrity variables (including effective dielectric constant Dkeff.
Dkeff considers the combination core and B-
Cascade lamination during impedance and signal propagation.
There should be a proven process capability to support composite structures, sequential lamination, back
ROHScompliance and long-
Term reliability
After selecting a prototype and production supplier with the technical capabilities of foregone, comprehensive process predictability, compliance and consistency must be demonstrated through effective monitoring and statistical process control.
This includes manufacturing process, assembly process, selection of finished products and mechanical properties.
These process and final product attributes are listed in tables 2 and 3. [
Figure 2:
Many of the process functions shown in Table 2 and May 3 are verified through continuous monitoring and predictability of SPC applications, in particular, a control chart describing upper and lower limits that meet the physical and electrical requirements of unmanned and unmanned backplates.
In addition to the control chart, the process capability index should also be known.
Some companies have developed automated finished production monitoring equipment for unmanned and inhabited backboards.
Features include the definition of impedance, propagation delay, effective dielectric constant, measurement of S parameters, and verification of contact seats that meet the requirements.
When selecting a backplane manufacturing source, whether it is a prototype manufacturing source or a production manufacturing source, the following criteria summarize the material and technical functions, and backplane verification facilitates an efficient transition from design to viable hardware: it includes incoming material, manufacturing and electrical testing, continuity and impedance.
* Qualified process control by adopting a controlled assembly operation.
* The Chart reflects the insert parameters that meet the requirements, x-
Rayverification and electrical testing for assembly.
* Fill the back panel electrical test in addition to the continuity including impedance and parameters.
AQL can be applied to impedance and parameter verification. High-
When selecting a connector system through PCB manufacturing knowledge and a thorough understanding of the required performance attributes and their applicability to system performance, speed backplane manufacturing and assembly that meets technical, price and delivery requirements is very
Strict and comprehensive quality control procedures improve cost efficiency
Delivery time and consistent performance solutions. CARL HORNIG, P. E.
A consulting engineer who worked as technical director for backpanel manufacturing, signal integrity, and assembly at sanmina (sanmina. com);
_ Hornig @ comcastnet.
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