Manhattan-Style routing being the use of expressly east-west planes and north-south planes, using a via and changing planes when a signal changes direction. Comparing to freestyle routing, which lets define as routing signals in any direction on a given layer, would manhattan routing generally result in increased density, signal integrity, and more or less layers?

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Manhattan routing is a PCB routing strategy. You use one dedicated layer for horizontal tracks and another layer for vertical tracks. No horizontal tracks are allowed on the vertical layer, and no vertical traces are used on the horizontal layer. This means that most connections will go through a via, but this strategy can provide surprisingly dense boards with little routing effort.

In this passage, we will focus on the Manhattan routing during the PCB manufacturing. If you are curious about the Manhattan routing during the PCB manufacturing, please check and read the content below for more.

What are the techniques of Manhattan routing in PCB?

One really neat method of building circuits without making a PCB is called Manhattan style, so called because the components look like buildings in Manhattan. I really like it because it’s simple, quick, and if you do it right, can be good enough for RF frequencies. I also like the way it looks. The method I’ve been using is to get free samples of Rogers material, most of which can be cut with just scissors. It’s a little easier than scoring and breaking FR4, but the trade off is that the copper clad board can bend slightly, which can crack some of your joints. You use the main copper surface as a ground plane, and superglue small squares of copper to use as nodes. Here are a couple of the circuits I’ve built using this style:

With a set of advanced PCB layout tools, you can set up a number of different design constraints to control the direction of your trace routing, plus much more. You will also have features in the tools that will assist you in your routing by reporting trace lengths and other useful data. In the picture above you can see how these tools have reported the direct distance, the Manhattan distance, and the actual etch distance of the selected trace routing. In this case, the actual trace routing is slightly less than the Manhattan distance due to its more direct routing pattern.

What are the advantages of Manhattan routing in PCB?

Manhattan-Style routing being the use of expressly east-west planes and north-south planes, using a via and changing planes when a signal changes direction. Comparing to freestyle routing, which lets define as routing signals in any direction on a given layer, would manhattan routing generally result in increased density, signal integrity, and more or less layers?

The primary advantage of a Manhattan route is that it can always be completed. You just need to have enough board area to accommodate all of the traces — but otherwise, you'll never find yourself unable to complete a route. This can be important if you need to get a layout done on a fixed schedule — the amount of work is roughly proportional to the number of pins, and you won't spend days or weeks trying to complete the task because of blockages.

Constraints and rules are used in PCB design for a number of reasons. They will help you to organize your design and communicate important information between the schematic and the layout. Primarily, though, they are used to prevent manufacturing problems and to ensure the electrical performance of the circuit board. Here are some issues that constraints are designed to address:

Manufacturing Problems:

Components that are placed too close to each other or oriented incorrectly may be difficult to assemble or solder correctly. Additionally, auto-insertion machinery may not be able to place the parts as needed, and technicians doing manual assembly may not be able to fit their tools and solder materials into the tight areas.

Metal on the circuit board that is too close to other metal objects may also cause problems during the manufacturing process. Solder slivers can form, causing intermittent shorts, which are difficult to find and correct. Solder can also bridge between traces or pads causing direct shorts.

Electrical Performance:

Traces used to conduct power that aren’t wide enough may be inadequate for the amount of current that they are carrying. Some traces also must have exact widths to control their impedance. Other traces need to be routed to a specific length or to match the length of similar nets. Differential pairs must be perfectly routed side-by-side.

It used to be that you could take a PCB design, throw it into the auto-router, and end up with a completely routed board that worked perfectly. That is no longer the case. Without the proper care in trace routing widths, spacing, lengths, and topologies, you may end up with a plethora of signal integrity problems.

What are the causes of Manhattan routing in PCB?

As we mentioned already, the term “Manhattan routing” is based on the regularly spaced roads in New York city that crisscross horizontally and vertically on a grid. Although we use the term to describe PCB routing, “Manhattan” is also associated with distance or length, and wiring as well.

Manhattan Distance or Length

The Manhattan distance is the shortest path that a wire can have when it is restricted to being routed orthogonally, or in the X and Y axis only. Manhattan distance becomes important when the two points being measured are not aligned in the same axis with each other. While the direct measurement of a diagonal path will be the shortest distance between the two points, the orthogonal path of following a grid pattern will be longer. Measuring Manhattan length is relatively easy by adding the X distance(s) to the Y distance(s) between the two points.

Manhattan Wiring

This is a method of laying out circuitry for an integrated circuit. The interconnects are aligned with a grid, and the connection points are perpendicularly creating a Manhattan pattern. This method of representing circuitry can be done either physically in the chip, in the documentation, or in both. There are also other terms for Manhattan wiring such as right-angle wiring, and they are all based on what is known as the taxicab geometry. This description again goes back to the idea of traveling in gridded orthogonal movements in order to get from one point to another in a city like Manhattan.