Editing Printed circuit board (section)

== History ==

=== Predecessors ===
Before the development of printed circuit boards, electrical and electronic circuits were [[Point-to-point construction|wired point-to-point]] on a chassis. Typically, the chassis was a sheet metal frame or pan, sometimes with a wooden bottom. Components were attached to the chassis, usually by insulators when the connecting point on the chassis was metal, and then their leads were connected directly or with [[Jump wire|jumper wires]] by [[soldering]], or sometimes using [[Crimp (electrical)|crimp]] connectors, wire connector lugs on screw terminals, or other methods. Circuits were large, bulky, heavy, and relatively fragile (even discounting the breakable glass envelopes of the vacuum tubes that were often included in the circuits), and production was labor-intensive, so the products were expensive.

Development of the methods used in modern printed circuit boards started early in the 20th century. In 1903, a German inventor, Albert Hanson, described flat foil conductors laminated to an insulating board, in multiple layers. [[Thomas Edison]] experimented with chemical methods of plating conductors onto linen paper in 1904. Arthur Berry in 1913 patented a print-and-[[Etching|etch]] method in the UK, and in the United States [[Max Schoop]] obtained a patent<ref>{{Cite patent |country=US |number=1256599 |pubdate=1918-02-19 |title=Process and mechanism for the production of electric heaters |inventor1-last=Schoop |inventor1-first=Max Ulrich }}</ref> to flame-spray metal onto a board through a patterned mask. Charles Ducas in 1925 patented a method of electroplating circuit patterns.<ref name="Harper03">{{cite book |last=Harper |first=Charles A. |date=2003 |title=Electronic materials and processes handbook |publisher=McGraw-Hill |isbn=0071402144 |pages=7.3, 7.4 }}</ref>

Predating the printed circuit invention, and similar in spirit, was [[John Sargrove]]'s 1936–1947 Electronic Circuit Making Equipment (ECME) that sprayed metal onto a [[Bakelite]] plastic board. The ECME could produce three radio boards per minute.

=== Early PCBs ===
[[File:Mark-53-proximity-fuze-1943.jpg|thumb|upright=1.1|Proximity fuze Mark 53 production line 1944]]

The Austrian engineer [[Paul Eisler]] invented the printed circuit as part of a radio set while working in the UK around 1936. In 1941 a multi-layer printed circuit was used in German [[Naval mine#Influence mines|magnetic influence naval mines]].

Around 1943 the United States began to use the technology on a large scale to make [[proximity fuze]]s for use in World War II.<ref name="Harper03" /> Such fuzes required an electronic circuit that could withstand being fired from a gun, and could be produced in quantity. The Centralab Division of Globe Union submitted a proposal which met the requirements: a ceramic plate would be [[Screenprinting|screenprinted]] with metallic paint for conductors and carbon material for [[resistor]]s, with ceramic disc capacitors and subminiature vacuum tubes soldered in place.<ref>{{Cite book |last=Brunetti |first=Cledo |date=November 22, 1948 |title=New Advances in Printed Circuits |publisher=National Bureau of Standards |location=Washington, DC |url=https://archive.org/details/newadvancesinpri192brun }}</ref> The technique proved viable, and the resulting patent on the process, which was classified by the U.S. Army, was assigned to Globe Union. It was not until 1984 that the [[Institute of Electrical and Electronics Engineers]] (IEEE) awarded Harry W. Rubinstein its [[IEEE Cledo Brunetti Award|Cledo Brunetti Award]] for early key contributions to the development of printed components and conductors on a common insulating substrate. Rubinstein was honored in 1984 by his alma mater, the [[University of Wisconsin–Madison|University of Wisconsin-Madison]], for his innovations in the technology of printed electronic circuits and the fabrication of capacitors.<ref>Engineers' Day, [https://www.engr.wisc.edu/engage/alumni-relations/our-distinguished-alumni/ 1984 Award Recipients], College of Engineering, [[University of Wisconsin–Madison|University of Wisconsin-Madison]]</ref><ref>{{cite web |title=IEEE Cledo Brunetti Award Recipients |url=https://www.ieee.org/content/dam/ieee-org/ieee/web/org/about/awards/recipients/brunetti_rl.pdf |archive-url=https://web.archive.org/web/20180804200901/https://www.ieee.org/content/dam/ieee-org/ieee/web/org/about/awards/recipients/brunetti_rl.pdf |archive-date=August 4, 2018 |publisher=[[IEEE]] }}</ref> This invention also represents a step in the development of [[integrated circuit]] technology, as not only wiring but also passive components were fabricated on the ceramic substrate.

=== Post-war developments ===
In 1948, the US released the invention for commercial use. Printed circuits did not become commonplace in consumer electronics until the mid-1950s, after the ''Auto-Sembly'' process was developed by the United States Army. At around the same time in the UK work along similar lines was carried out by [[Geoffrey Dummer]], then at the [[Royal Radar Establishment|RRDE]].

Motorola was an early leader in bringing the process into consumer electronics, announcing in August 1952 the adoption of "plated circuits" in home radios after six years of research and a $1M investment.<ref>{{cite news |title=New Process Perfected for Radio Wiring |newspaper=[[Chicago Tribune]] |date=August 1, 1952 }}</ref> Motorola soon began using its trademarked term for the process, PLAcir, in its consumer radio advertisements.<ref>{{cite magazine |title='Travel and Play with Motorola' advertisement |magazine=[[Life (magazine)|Life]] |date=May 24, 1954 |page=14 }}</ref> Hallicrafters released its first "foto-etch" printed circuit product, a clock-radio, on November 1, 1952.<ref>"Topics & Trends of TV Trade." Television Digest 8:44 (November 1, 1952), 10.</ref>

Even as circuit boards became available, the point-to-point chassis construction method remained in common use in industry (such as TV and hi-fi sets) into at least the late 1960s. Printed circuit boards were introduced to reduce the size, weight, and cost of parts of the circuitry. In 1960, a small consumer radio receiver might be built with all its circuitry on one circuit board, but a TV set would probably contain  one or more circuit boards.

Originally, every electronic component had wire [[Lead (electronics)|leads]], and a PCB had holes drilled for each wire of each component. The component leads were then inserted through the holes and [[solder]]ed to the copper PCB traces. This method of assembly is called [[Through-hole technology|''through-hole'' construction]]. In 1949, Moe Abramson and Stanislaus F. Danko of the United States Army Signal Corps developed the ''Auto-Sembly'' process in which component leads were inserted into a copper foil interconnection pattern and [[Dip soldering|dip soldered]]. The patent they obtained in 1956 was assigned to the U.S. Army.<ref>{{Cite patent |country=US |number=2756485 |pubdate=1956-07-31 |title=Process of Assembling Electrical Circuits |assign1=[[Secretary of the United States Army]] |inventor1-last=Abramson |inventor1-first=Moe |inventor2-last=Danko |inventor2-first=Stanislaus F. }}</ref> With the development of board [[lamination]] and [[etching]] techniques, this concept evolved into the standard printed circuit board fabrication process in use today. Soldering could be done automatically by passing the board over a ripple, or wave, of molten solder in a [[Wave soldering|wave-soldering]] machine. However, the wires and holes are inefficient since drilling holes is expensive and consumes drill bits and the protruding wires are cut off and discarded.

Since the 1980s, surface mount parts have increasingly replaced through-hole components, enabling smaller boards and lower production costs, but making repairs more challenging.

In the 1990s the use of multilayer surface boards became more frequent. As a result, size was further minimized and both flexible and rigid PCBs were incorporated in different devices. In 1995 PCB manufacturers began using [[microvia]] technology to produce High-Density Interconnect (HDI) PCBs.<ref>{{US patent reference |number=5434751 |issue-date=July 18, 1995 |inventor1-first=Herbert S. |inventor1-last=Cole, Jr. |inventor2-first=Theresa A. |inventor2-last=Sitnik-Nieters |inventor3-first=Robert J. |inventor3-last=Wojnarowski |inventor4-first=John H. |inventor4-last=Lupinski |title=Reworkable high density interconnect structure incorporating a release layer }}</ref>

=== Recent advances ===
Recent advances in [[3D printing]] have meant that there are several new techniques in PCB creation. 3D printed electronics (PEs) can be utilized to print items layer by layer and subsequently the item can be printed with a liquid ink that contains electronic functionalities.

HDI (High Density Interconnect) technology allows for a denser design on the PCB and thus potentially smaller PCBs with more traces and components in a given area. As a result, the paths between components can be shorter. HDIs use blind/buried vias, or a combination that includes microvias. With multi-layer HDI PCBs the interconnection of several vias stacked on top of each other (stacked vías, instead of one deep buried via) can be made stronger, thus enhancing reliability in all conditions. The most common applications for HDI technology are computer and mobile phone components as well as medical equipment and military communication equipment. A 4-layer HDI microvia PCB is equivalent in quality to an 8-layer through-hole PCB, so HDI technology can reduce costs. HDI PCBs are often made using build-up film such as ajinomoto build-up film, which is also used in the production of [[flip chip]] packages.<ref>{{cite book |chapter-url=https://ieeexplore.ieee.org/document/8546431 |title=2018 7th Electronic System-Integration Technology Conference (ESTC) |doi=10.1109/ESTC.2018.8546431 |s2cid=54214952 |chapter=High Density Interconnect Processes for Panel Level Packaging |date=2018 |last1=Ostmann |first1=Andreas |last2=Schein |first2=Friedrich-Leonhard |last3=Dietterle |first3=Michael |last4=Kunz |first4=Marc |last5=Lang |first5=Klaus-Dieter |pages=1–5 |isbn=978-1-5386-6814-6 }}</ref><ref>{{cite book |url=https://books.google.com/books?id=4DmIDQAAQBAJ&dq=build+up+film+substrate&pg=PA319 |isbn=978-3-319-45098-8 |title=Materials for Advanced Packaging |date=November 18, 2016 |publisher=Springer }}</ref> Some PCBs have optical waveguides, similar to optical fibers built on the PCB.<ref>{{cite web |url=https://www.laserfocusworld.com/optics/article/14040276/making-optical-printed-circuit-boards-on-an-industrial-scale |title=Advances in Optical Communications: Making optical printed circuit boards on an industrial scale |date=October 2019 }}</ref>