Wiring is a very important part of PCB design, which will directly affect the performance of PCB. During PCB design, different layout engineers have their own understanding of PCB layout, but all layout engineers are in agreement on how to improve wiring efficiency, which not only saves the client project development cycle, but also maximizes guaranteed quality and cost. The following describes the PCB design process and steps to improve wiring efficiency.

1、PCBの層数を決定します

Board dimensions and wiring layers need to be determined early in the design process. 設計で高密度ボールグリッドアレイ（BGA）コンポーネントを使用する必要がある場合は、これらのコンポーネントを配線するために必要な配線層の最小数を考慮する必要があります。 The number of wiring layers and the layering method directly affect the wiring and impedance of printed wiring. The size of the board helps determine the stack and line width to achieve the desired design.

2. Design rules and limitations

The automatic routing tool itself doesn’t know what to do. ルーティングタスクを実行するには、ルーティングツールが適切なルールと制約の範囲内で機能する必要があります。 Different signal lines have different wiring requirements, and all special requirements of signal lines are classified, and different design classifications are different. Each signal class should have priority. The higher the priority is, the stricter the rule is. Rules concerning trace width, maximum number of through-holes, parallelism, interaction between signal lines, and layer limits have a great impact on the performance of routing tools. Careful consideration of design requirements is an important step in successful wiring.

3.コンポーネントのレイアウト

Optimize assembly processes and design manufacturability (DFM) rules to impose constraints on component layouts. If the assembly department allows components to move, the circuit can be optimized to automate wiring more easily. 定義されたルールと制約は、レイアウト設計に影響します。

4. Fan out design

ファンアウトの設計段階では、コンポーネントピンを接続する自動ルーティングツールの場合、追加の接続が必要なときにボードが内層を実行できるように、表面実装デバイスの各ピンに少なくともXNUMXつのスルーホールが必要です。 接続性、インラインテスト（ICT）および回路の再処理。

For the automatic routing tool to be most effective, the largest possible through-hole size and printed line must be used, with an interval of 50 mils preferred. Use a VIA type that maximizes the number of routing paths. When performing fan out designs, consider on-line testing of the circuit. Test fixtures can be expensive and are usually ordered when they are ready for full production. It’s too late to consider adding nodes to achieve 100% testability.

5、手動配線とキー信号処理

この記事では自動ルーティングに焦点を当てていますが、手動ルーティングは現在および将来のPCB設計における重要なプロセスです。 Manual routing helps automatic routing tools complete routing work. Regardless of the number of critical signals, these signals can be routed first, manually, or used in combination with automatic routing tools. Critical signals must often be carefully designed to achieve the desired performance. It is relatively easy for engineering personnel to check signal wiring after wiring is completed. This process is relatively easy. After the inspection, the wire is fixed, and other signals are automatically routed.

6, automatic wiring

Wiring of critical signals requires consideration of controlling some electrical parameters during wiring, such as reducing distributed inductance and EMC, and wiring for other signals is similar. すべてのEDAベンダーは、これらのパラメーターを制御する方法を提供しています。 The quality of automatic wiring can be guaranteed to a certain extent after knowing the input parameters of automatic wiring tool and their influence on wiring.

7, the appearance of the board

Previous designs often focused on the visual effects of the board, but now it’s different. The circuit board designed automatically is not more beautiful than manual design, but it meets the requirements of electronic characteristics and ensures the integrity of the design.

レイアウトエンジニアにとって、貧弱な技術は層の数と速度だけで判断されるべきではありません。 Only when the number of components is equal to the signal speed and other conditions, the smaller the area, the fewer layers, the lower the cost. PCB board is well designed to ensure good performance and beauty. これがマスターです。