ginngi engineering

The PCB layout phase of a board design is among the most critical, if not the most critical, of a typical board design. For high speed boards the correct layout of its PCB can spell the difference between a working, reliable board or not. A single PCB error can bring down part or all of a board. Ginngi takes pride in laying out PCB boards that work the first time. Our many satisfied customers leverage Ginngi's vast experience in PCB layout to ensure that their designs will work the first time, are reliable, are manufacturable, and are as cost-effective as can be (minimal stackup). We start with a minimal technology approach using standard vias and a minimal stackup. Only after it is clear that this may not be enough do we apply more creative technology. At Ginngi we are not afraid of a high stack count, microvias, buried/blind vias or 2 mil traces. We will work closely with the PCB designer to ensure that your board will go beyond the requirements isolating you, the customer, from the details and responsibility.

For many of our PCB layouts a Signal Integrity Analysis is also performed using specialized simulation tools to ensure that high speed signals will maintain their integrity along the physical traces on the board and will not be affected by or affect other traces that are nearby. For a detailed description of these services refer to: www.ginngi.com/services/highspeed

Parts Placement

After the board's physical dimensions have been closed the design parts are placed on the board starting with the external mechanical components, such as connectors, and proceeding with the electrical devices. Careful attention is made for separation of specific signal groups while maintaining signal flow. For example, analog signaling and conditioning circuits are typically placed in an isolated area so that PCB space can be specially allocated for it to eliminate cross-talk effects from digital circuitry. Special attention is made to following manufacturing recommendations for critical components.

Stackup Design

There are many factors that contribute to a board's stackup definition. Ginngi determines a board stack-up by carefully analyzing the net list, critical net definitions, power distribution and decoupling requirements, impedance matching requirements, EMC requirements and possible manufacturing limitation factors.

Clock Routing

Clocks are the most critical nets on a board and typically require careful, manual routing. This is done in the first phase of the routing before any other signal, when the entire stackup is potentially available. Strict signal integrity rules are applied to minimize impedance jumps along the clock trace. Often, a clock trace will only be routed on a single layer.

Critical Net Routing

After clock nets the routing of the critical nets takes place. Critical nets are high speed signal that need special attention. A typical case is a DDR design where the data traces of each group must be routed as short as possible and each must have the same length. Such a group would be manually routed with proper shielding and/or spacing applied to eliminate cross-talk effects.

Impedance Matching

Most high-speed signals require a specific impedance for proper operations. To implement impedance matching Ginngi applies high-speed rules to compute the necessary width and spacing of a net relative to the ground plane(s) that are next to it and works with the PCB manufacturer to ensure that it is manufacturable (by taking into account the dielectric materials that are to be used).

Autorouting

For larger designs with many buses and/or lower speed signals an auto-router can greatly reduce the routing time and effort. Today's auto-routers use a special language to instruct the auto-router in its work. Ginngi works closely with the PCB designer to ensure auto-router success.

Signal Integrity

Following design rules are often not enough to ensure the integrity of a clock or other critical net. To ensure signal integrity Ginngi optionally can perform simulations using specialized tools. Two types of simulations are typically performed: pre-layout and post-layout simulation. In pre-layout simulation the layout tool's database is used for the board's layout definition and traces are stimulated and measured under real conditions in simulation. In post-layout simulation the final Gerber file is used instead. Information used during this phase is fed back to the PCB designer to correct for any anomalies that are discovered.

Emissions Minimization

A high-speed board can typically produce significant RF emissions from its switching operations, which often must be specifically dealt with. Ginngi can use specialized shielding techniques to keep such emissions on the inside layers of the board.

Power Decoupling

The power decoupling strategy employed in a layout is another critical factor to a board's proper functionality. Although the device manufacturer usually provides detailed decoupling information it is often the case that additional considerations must be applied. In some cases it is possible to significantly reduce the amount of decoupling capacitors by utilizing special layout techniques that Ginngi has successfully employed in customer designs.

Manufacturability

Ginngi works closely with both the PCB Designer and assembly manufacturers to ensure that the PCB layout not works but is also manufacturable. In general the more exotic the technology used in the PCB the harder it is to manufacture. Hence, the use of such means is only adopted if there is no other way to overcome a layout obstacle.