PCB設計時のインフローを防ぐには？

Inflows are a problem in pcb design and must be avoided. There are several ways to do this, including Solid ground planes, keepouts, Shift-left verification, and component keepouts. These practices will help engineers avoid inflows, and will make a PCB layout easier to manufacture.

Component keepouts

Keepouts are a great way to control the placement of objects on a PCB design. They can be overlaid or assigned to any signal layer, and they can reject specific objects. They’re particularly useful for tightening control of things like Polygon Pours and Via Stitching.

Keepouts are zones of the board where a small part or mechanical shape is too close to a track or trace. These areas should be noted on the schematic. Keepouts can be used to prevent overlapping of vias, power planes, or other noise-prone areas.

Identifying component keepouts is easy if you understand the basics of component placement. Look for identifiers on each pin, and make sure they match with the component. You can also check the dimensions of the pads and pad pitches to identify whether they’re the correct component.

A PCB design software allows you to set keepout zones for components. This can be accomplished with the use of templates or manually. Typically, keepout zones are drawn over the board surface to ensure that they aren’t obstructed.

Solid ground plane

A solid ground plane is an important feature when designing a printed circuit board. Adding a ground plane to your board is a relatively simple and inexpensive process that can significantly improve your PCB design. This important piece of circuitry is used to provide a solid foundation for all of the materials that will be installed on the board. Without a ground plane, your board is prone to electrical noise and problems.

Another benefit of a ground plane is that it can help prevent electromagnetic interference (EMI) from infiltrating your design. This electromagnetic interference can be generated by your device or from nearby electronics. By choosing a ground plane that is located near the signal layer, you can minimize EMI in the final design.

Solid ground planes are particularly important for circuit boards that have multiple layers. Because of the complexities of a PCB design, the ground plane must be properly designed to prevent errors and ensure a reliable connection between multiple layers. Moreover, the ground plane should be large enough to accommodate the components that will be used on it.

Shift-left verification

Shift-left verification during PCB designs is an efficient design process that eliminates the need for extensive full-board verification and lets designers focus on critical second-order issues. Unlike traditional design flow, where the PCB specialist is a last resort, shift-left verification can be performed by design authors. This way, designers can make design improvements before the specialists even see the boards.

Shift-left verification can help designers identify potential issues that can lead to costly revisions. For example, improper diode orientation, missing pull-up resistors, and capacitor voltage derating can be discovered during verification. These issues may not be detectable until physical testing, which often results in re-spins and tooling changes. Using automated verification during the layout phase can dramatically increase the likelihood of a successful first pass.

PCBには、手作業によるピアレビューで専門家が気付かないような微妙なエラーが含まれていることがよくあります。最新の自動検証アプローチは、回路図レベルでこれらのエラーを検出することができます。つまり、設計エンジニアはコストのかかる修正や再設計を減らしながら、より高度な問題に集中することができます。その結果、これらのツールは設計エンジニアとエンジニアリング・プロジェクト・マネージャの双方にとって大きなメリットをもたらします。

標準慣行

すべての設計者が遵守すべきPCB設計の基本原則があります。例えば、シグナル・インテグリティとパワー・インテグリティを提供するためにコンポーネントを十分に離して配置し、適切な配線チャネルを提供するために十分に近づけることが不可欠です。さらに、インピーダンス制御トレース、差動ペア、高感度信号など、特定の配線には特定の間隔要件があります。コンポーネントを配置する際には、DFM（Design for Manufacturing）要件を考慮することも重要です。

PCBを設計する際には、製造コストを考慮することが重要です。埋設ビアやブラインドビアを使用すると、製造コストが増加する可能性があります。したがって、PCB設計者は、前もって設計とビアの使用方法を計画する必要があります。さらに、製造コストを最小限に抑えるために、部品のサイズも考慮する必要があります。

PCB開発のもう一つの重要な要素はデザインレビューです。ピアレビューは、設計者が一般的な設計ミスを回避するのに役立ちます。定期的なレビューは、PCBレイアウト、回路、機能が正確であることを保証します。ピアレビューはまた、設計者が見落としているかもしれないミスを特定します。