Editing Printed circuit board (section)

== Types ==
{{Further|Monoboard}}

=== Breakout boards ===
[[File:Breakout board.jpg|thumb|A breakout board can allow interconnection between two incompatible connectors.]]
[[File:SD Card Breakout Board.jpg|thumb|This breakout board allows an [[SD card]]'s pins to be accessed easily while still allowing the card to be hot-swapped.]]

A minimal PCB for a single component, used for [[Prototype#Electronics prototyping|prototyping]], is called a '''breakout board'''. The purpose of a breakout board is to "break out" the leads of a component on separate terminals so that manual connections to them can be made easily. Breakout boards are especially used for surface-mount components or any components with fine lead pitch.

Advanced PCBs may contain components embedded in the substrate, such as capacitors and integrated circuits, to reduce the amount of space taken up by components on the surface of the PCB while improving electrical characteristics.<ref>{{Cite web|url=https://www.electronicdesign.com/technologies/embedded-revolution/article/21799095/use-embedded-components-to-improve-pcb-performance-and-reduce-size|title = StackPath| date=February 11, 2014 }}</ref>

=== Multiwire boards ===
Multiwire is a patented technique of interconnection which uses machine-routed insulated wires embedded in a non-conducting matrix (often plastic resin).<ref>{{Cite patent |country=US |number=4175816 |pubdate=1979-11-27 |title=Multi-wire electrical interconnecting member having a multi-wire matrix of insulated wires mechanically terminated thereon |assign1=Kollmorgen Technologies Corp. |inventor1-last=Burr |inventor1-first=Robert P. |inventor2-last=Morino |inventor2-first=Ronald |inventor3-last=Keogh |inventor3-first=Raymond J. }}</ref> It was used during the 1980s and 1990s. {{As of|2010|post=,}} Multiwire is still available through Hitachi.

Since it was quite easy to stack interconnections (wires) inside the embedding matrix, the approach allowed designers to forget completely about the routing of wires (usually a time-consuming operation of PCB design): Anywhere the designer needs a connection, the machine will draw a wire in a straight line from one location/pin to another. This led to very short design times (no complex algorithms to use even for high density designs) as well as reduced [[crosstalk]] (which is worse when wires run parallel to each other&mdash;which almost never happens in Multiwire), though the cost is too high to compete with cheaper PCB technologies when large quantities are needed.

Corrections can be made to a Multiwire board layout more easily than to a PCB layout.<ref>{{cite web |last=Weisberg |first=David E. |date=2008 |title=14: Intergraph |pages=14–8 |url=https://www.vgamuseum.info/images/doc/intergraph/intergraph_history.pdf}}</ref>

===Cordwood construction===
{{More citations needed section|date=December 2016}}
[[File:Cordwoodcircuit.agr.jpg|thumb|upright=1.5|A cordwood module]]
[[File:MK53 fuze.jpg|thumb|Cordwood construction was used in [[proximity fuze]]s.]]

Cordwood construction can save significant space and was often used with [[Through-hole technology|wire-ended components]] in applications where space was at a premium (such as [[fuze]]s, missile guidance, and telemetry systems) and in high-speed [[computer]]s, where short traces were important. In cordwood construction, axial-leaded components were mounted between two parallel planes. The name comes from the way axial-lead components (capacitors, resistors, coils, and diodes) are stacked in parallel rows and columns, like a stack of firewood. The components were either soldered together with jumper wire or they were connected to other components by thin nickel ribbon welded at right angles onto the component leads.<ref>{{cite journal |last=Wagner |first=G. Donald |title=History of Electronic Packaging at APL: From the VT Fuze to the NEAR Spacecraft |journal=Johns Hopkins APL Technical Digest |volume=20 |issue=1 |date=1999 |url=http://www.jhuapl.edu/techdigest/TD/td2001/Wagner.pdf |archive-url=https://web.archive.org/web/20170510111809/http://www.jhuapl.edu/techdigest/TD/td2001/Wagner.pdf |archive-date=May 10, 2017 }}</ref> To avoid shorting together different interconnection layers, thin insulating cards were placed between them. Perforations or holes in the cards allowed component leads to project through to the next interconnection layer. One disadvantage of this system was that special [[nickel]]-leaded components had to be used to allow reliable interconnecting welds to be made. Differential thermal expansion of the component could put pressure on the leads of the components and the PCB traces and cause mechanical damage (as was seen in several modules on the Apollo program). Additionally, components located in the interior are difficult to replace. Some versions of cordwood construction used soldered single-sided PCBs as the interconnection method (as pictured), allowing the use of normal-leaded components at the cost of being difficult to remove the boards or replace any component that is not at the edge.

Before the advent of [[integrated circuit]]s, this method allowed the highest possible component packing density; because of this, it was used by a number of computer vendors including [[Control Data Corporation]].