Component Courtyard And Clearance Design Rules
The land pattern defines where the solder joints are; the courtyard defines the space the part needs around them. It is the outline of the body plus the room the placement nozzle, the rework tool and the inspection equipment need to reach the part without touching anything else. Ignoring it produces a layout that passes every electrical check and then cannot be assembled at the density the designer imagined.
This article explains what the courtyard contains, where its dimensions come from, how it differs from a keepout and a mask opening, and how a layout is checked against it.
What The Courtyard Contains
The courtyard is a closed outline on a mechanical layer, drawn around the land pattern at a distance that depends on the part. For a chip resistor it might be 0.25 millimetres beyond the pads; for a fine pitch package it may be 0.5 millimetres; for a connector it follows the body and the latch. It represents the space that must be free of other components, of vias and often of tall traces, so that the part can be placed and later serviced.
The courtyard is not a manufacturing tolerance and it is not the same as the body outline. It is a working space, and it is defined so that two neighbouring parts can be placed next to each other and both can still be handled. Manufacturers publish a recommended courtyard with the land pattern, and those recommendations are the most reliable starting point, because they are derived from the nozzle and the feeder geometry that the parts are actually used with.
Why The Clearance Matters
The placement nozzle arrives from above and needs a clear approach. If a tall part sits inside the courtyard of its neighbour, the nozzle can strike it on the way down, and the collision is detected only when the machine faults or, worse, when the part is displaced. The risk is highest for a small part beside a tall one, which is exactly the arrangement produced by a dense layout with mixed package heights.
Rework needs more room than placement. A hot air nozzle or a soldering iron has to reach the joint from the side, and a part that is surrounded by taller neighbours cannot be removed without disturbing them. Inspection adds a third requirement, because a camera looking at an angle, an X-ray system with a rotating source and a microscope all need to see the joint, and a joint that is hidden under a neighbouring body cannot be verified.
Where The Dimensions Come From
Three inputs set the number. The first is the manufacturer recommendation, which is published with the land pattern and is the default. The second is the capability of the assembly house, since a machine with a small nozzle and a good vision system can work closer than one with a large nozzle and mechanical centring. The third is the rework policy, because a board that will never be reworked does not need the tool access that one in a low volume product does.
The result is that the courtyard is not a constant. A high volume consumer board may use a tighter courtyard and accept that rework is impractical, while an industrial board with a long service life and a repair route uses a wider one. The value should be stated in the design rules for the project rather than being taken from a default library without thought.
Courtyard, Keepout And Mask Opening
Three outlines are often confused. The mask opening defines where the solder mask is removed and is slightly larger than the pad. The keepout defines where copper or vias may not be placed and is an electrical and manufacturing rule. The courtyard defines where components may not be placed and is a mechanical and assembly rule. A via inside a courtyard is usually acceptable, while a via inside a pad is not; a component inside a keepout may be acceptable electrically while a component inside a courtyard is never acceptable for assembly.
Treating the three as one outline is a common cause of unnecessary density loss. A designer who inflates the courtyard to cover the keepout will push parts apart for no reason, and one who treats the courtyard as advisory will produce a board that the assembly line has to reject. Keeping the three separate in the library and in the design rule check is what makes the checking useful.
Density, Panelization And Placement Order
The courtyard sets the density that can be achieved, and the density sets the panel size and the cost. A layout with generous courtyards uses more area and produces a larger board, while one with courtyards that are too tight produces a board that cannot be built. The balance is a design decision that belongs with the rest of the placement planning, which is described under placement order and pad positioning.
The land pattern itself is the other half of the same question, and its dimensions are covered under PCB pad design standards. The way the two interact with fabrication and with the cost of the finished board is discussed under layout decisions that affect production.
Checking A Layout Against The Rules
The check is mechanical rather than electrical, and it is done with a design rule that compares the courtyard outlines of neighbouring components. Many tools ship with such a rule and with courtyards in the library, and the rule is only useful if the courtyards are present and correct. A library where half the parts have no courtyard will pass the check silently and produce a false sense of security.
The second check is on the assembly side. A placement program can report the nozzle that will be used for each part and the approach angle, and a part whose courtyard is violated by a tall neighbour will appear there rather than in the layout tool. Running that check before the first build is the cheapest way to find the problem, because afterwards it means a layout revision, a new stencil and a new set of panels.
Mixed Heights And Fine Pitch Packages
The hardest cases combine a fine pitch package with tall neighbours. A quad flat no lead body sits almost flat on the board, so a nozzle that is positioned for its neighbour may pass over it without touching, while a large electrolytic capacitor beside the same body needs a wide approach and a wide courtyard. The practical rule is to group parts by height and by package family rather than by function, so that the tall parts sit together at the edge of the board and the fine pitch devices occupy their own quiet area.
The second rule is to keep the courtyard wide enough for the rework route that the product will actually use. A board that is repaired at a depot with a hot air station needs more room around every large package than one that is replaced as a unit, and the difference is a few millimetres per package and therefore a few millimetres on the board. Deciding that at the start of the layout costs nothing; deciding it after the first build costs a revision, a new stencil and a new set of panels.
FAQ
Can courtyards overlap if the parts are short? They should not, because the rule exists mainly for handling and rework rather than for the height of the bodies. An overlap that happens to work on one build will fail when a supplier ships a taller body.
Is a via allowed inside a courtyard? Yes, provided it is not under the body in a way that traps flux, and provided the via is tented or filled so that the nozzle is not disturbed by a raised ring.
Who defines the courtyard? The part manufacturer publishes a recommendation, the assembly house may add its own allowance, and the project design rules decide which of the two applies. The important point is that the value is stated rather than assumed.
