PCB wiring methods continue to improve, and flexible wiring techniques can reduce wire length and free up more PCB space. Conventional PCB wiring is limited by fixed wire coordinates and the lack of arbitrarily angled wires. Removing these limitations can significantly improve the quality of wiring.

Let’s start with some terminology. Definiamo il cablaggio ad angolo arbitrario come cablaggio a filo utilizzando segmenti angolari e radianti arbitrari. È una sorta di cablaggio, ma non è limitato all’utilizzo di soli segmenti di linea ad angolo di 90 gradi e 45 gradi. Topological wiring is wire wiring that does not adhere to grids and coordinates and does not use regular or irregular grids like shape-based wiring. Definiamo il termine cablaggio flessibile come cablaggio senza forma fissa che consente il ricalcolo della forma del filo in tempo reale per ottenere le seguenti possibilità di trasformazione. Per formare la forma della linea vengono utilizzati solo gli archi degli ostacoli e le loro tangenti comuni. (Obstacles include pins, copper foil, forbidden areas, holes and other objects) part of the circuit of two PCB models. I fili verde e rosso corrono su diversi strati del modello PCB. The blue circles are the perforations. The red element is highlighted. There are also some red round pins. Use only line segments and models with an Angle of 90 degrees between them. La Figura 1B è un modello di PCB che utilizza archi e angoli arbitrari. Wiring at any Angle may seem strange, but it does have many advantages. The way it is wired is very similar to how engineers wired it by hand half a century ago. Mostra un vero PCB sviluppato nel 1972 da un’azienda americana chiamata Digibarn per il cablaggio manuale completo. This is a PCB board based on Intel8008 computer. Il cablaggio dell’angolo arbitrario mostrato nella Figura 2 è in realtà simile. Why would they use arbitrary Angle wiring? Perché questo tipo di cablaggio ha molti vantaggi. Arbitrary Angle wiring has many advantages. First, not using the angles between line segments saves PCB space (polygons always take up more space than tangents). Traditional automatic cablers can place only three wires between adjacent components (see left and center in Figure 3). Tuttavia, quando si esegue il cablaggio in qualsiasi angolazione, c’è spazio sufficiente per posare 4 fili sullo stesso percorso senza violare il controllo delle regole di progettazione (DRC). Supponiamo di avere un chip in modalità positiva e di voler collegare i pin del chip ad altri due pin. Using only 90 degrees takes up a lot of space. L’utilizzo di un cablaggio ad angolo arbitrario può ridurre la distanza tra il chip e gli altri pin, riducendo al contempo l’ingombro. In this case, the area was reduced from 30 square centimeters to 23 square centimeters. Rotating the chip at any Angle can also provide better results. In this case, the area was reduced from 23 square centimeters to 10 square centimeters. It shows a real PCB. Arbitrary Angle wiring with rotating chip function is the only wiring method for this circuit board. Questa non è solo una teoria, ma anche una soluzione pratica (a volte l’unica soluzione possibile). Shows an example of a simple PCB. Topology cabler results, while automatic cabler results based on optimal shape are photos of the actual PCB. An automatic cabler based on optimal shape cannot do this because the components are rotated at arbitrary angles. Hai bisogno di più area e se non ruoti i componenti, il dispositivo deve essere ingrandito. Layout performance would be greatly improved without parallel segments, which are often a source of crosstalk. The level of crosstalk increases linearly as the length of parallel wires increases. As the spacing between parallel wires increases, crosstalk decreases quadratic. Let’s set the level of crosstalk produced by two parallel 1mm wires spaced d to e. Se c’è un angolo tra i segmenti di filo, all’aumentare di questo angolo, il livello di diafonia diminuirà. The crosstalk does not depend on the length of the wire, but only on the Angle value: where α represents the Angle between the wire segments. Consider the following three wiring methods. On the left side of Figure 8 (90 degree layout), there is the maximum wire length and the maximum emi value due to parallel line segments. In the middle of Figure 8 (45 degree layout), the wire length and emi values are reduced. On the right-hand side (at any Angle), the wire length is shortest and there are no parallel wire segments, so the interference value is negligible. So arbitrary Angle wiring helps to reduce the total wire length and significantly reduce electromagnetic interference. You also remember the effect on signal delay (conductors should not be parallel and should not be perpendicular to the PCB fiberglass). Advantages of flexible wiring Manual and automatic movement of components does not destroy the wiring in flexible wiring. The cabler automatically calculates the optimal shape of the wire (taking into account the necessary safety clearance). Flexible cabling can therefore greatly reduce the time required to edit the topology, nicely supporting multiple recabling to meet constraints. Questo mostra un design PCB che si muove attraverso fori e punti di diramazione. During automatic movement, wire branch points and through-holes are adjusted to the optimal position. In most computer-aided design (CAD) systems, the wiring interconnection problem is reduced to the problem of sequentially finding paths between pairs of points in a maze of pads, forbidden areas, and laid wires. Quando viene trovato un percorso, viene fissato e diventa parte del labirinto. The disadvantage of sequential wiring is that the wiring result may depend on the wiring order. Quando la qualità topologica è ancora lontana dall’essere perfetta, il problema del “bloccarsi” si presenta in aree localmente piccole. But no matter which wire you rewire, it’s not going to improve the quality of the wiring. This is a serious problem in all CAD systems using sequential optimization. This is where the bending elimination process is useful. La piegatura del filo si riferisce al fenomeno per cui un filo in una rete deve camminare attorno a un oggetto su un’altra rete per accedere a un oggetto. Rewiring a wire will not correct this. Viene mostrato un esempio di piegatura. A lit red wire travels around a pin in the other network, and an unlit red wire connects to this pin. Vengono visualizzati i risultati dell’elaborazione automatica. In the second case (on another layer), a lighted green wire is automatically rewired by changing the wiring layer (from green to red). Eliminate wire bending by automatically optimizing wire shape (approximate arcs with line segments just to show any Angle examples without arcs). (top) original design, (bottom) after eliminating bending design. Red bent wires are highlighted. In a Steiner tree, all lines must be connected as segments to vertices (endpoints and additions). Nella parte superiore di ogni nuovo vertice, tre segmenti devono convergere e non devono terminare più di tre segmenti. The Angle between the line segments that converge to the vertex shall not be less than 120 degrees. It is not very difficult to construct a Steiner with these sufficient conditional properties, but it is not necessarily minimal. Gray Steiner trees are not optimal, but black Steiner trees are. Nella progettazione pratica della comunicazione, devono essere considerati diversi tipi di ostacoli. Limitano la capacità di costruire alberi di copertura minimi utilizzando sia algoritmi che alberi di Steiner utilizzando metodi geometrici. The obstacles are shown in gray and we recommend starting at any end vertex. If there is more than one adjacent terminating vertex, you should choose one that allows you to continue using the second vertex. It depends on the Angle. Il meccanismo principale qui è un algoritmo basato sulla forza che calcola le forze che agiscono sui nuovi vertici e le sposta ripetutamente in un punto di equilibrio (l’entità e la direzione delle forze dipendono dai fili nei punti di diramazione adiacenti). Se l’angolo tra una coppia di segmenti di linea collegati a un vertice (terminale o addizione) è inferiore a 120 gradi, è possibile aggiungere un punto di diramazione e quindi utilizzare un algoritmo meccanico per ottimizzare la posizione del vertice. It’s worth noting that simply sorting all angles in descending order and adding new vertices in that order doesn’t work, and the result is worse. After adding a new node, you should check the minimum of a subnet consisting of four pins:

1. If a vertex is added to the vicinity of another newly added vertex, check for the smallest four-pin network.

2. If the four-pin network is not minimal, select a pair of “diagonal” (belonging to the quadrilateral diagonal) endpoints or virtual terminal nodes (virtual terminal nodes – wire bends).

3. The line segment that connects the endpoint (virtual endpoint) to the nearest new vertex is replaced by the line segment that connects the endpoint (virtual endpoint) to the distant new vertex.

4. Use mechanical algorithms to optimize vertex positions.

This method does not guarantee to build the smallest network, but compared with other methods, it can achieve the smallest network length without grazing. It also allows for areas where endpoint connections are prohibited, and the number of endpoint nodes can be arbitrary.

Flexible wiring at any Angle has some other interesting advantages. For example, if you can automatically move many objects with the help of automatic real-time wire shape recalculation, you can create parallel serpentine lines. This cabling method makes better use of space, minimizes the number of iterations, and allows for flexible use of tolerances. If there are two serpentine lines interlaced with each other, the automatic cabler will reduce the length of one or both, depending on rule priority.

Consider the wiring of BGA components. In the traditional peripheral-to-center approach, the number of channels to the periphery is reduced by 8 with each successive layer (due to a reduction in perimeter). For example, a 28x28mm component with 784 pins requires 10 layers. Some of the layers in the diagram have escaped wiring. La Figura 16 mostra un quarto di BGA. At the same time, when using the “center to periphery” wiring method, the number of channels required to exit to the periphery does not change from layer to layer. This will greatly reduce the number of layers. For a component size of 28x28mm, 7 layers are sufficient. For larger components, it’s a win-win. Figure 17 shows a quarter of the BGA. An example of BGA wiring is shown. When using the “center to periphery” cabling approach, we can complete the cabling of all networks. Arbitrary Angle topological automatic cabler can do this. Traditional automatic cablers cannot route this example. Shows an example of a real PCB where the engineer reduced the number of signal layers from 6 to 4 (compared to the specification). In addition, it took engineers only half a day to complete the wiring of the PCB.