A via (Latin, 'path' or 'way') is an electrical connection between two or more metal layers, and are commonly used in printed circuit boards (PCB). Essentially a via is a small drilled hole that goes through two or more adjacent layers; the hole is plated with metal (often copper) that forms an electrical connection through the insulating layers.
Vias are an important concern in PCB manufacturing.[1] This is because the vias are drilled with certain tolerances and may be fabricated off their designated locations, so some allowance for errors in drill position must be made prior to manufacturing or else the manufacturing yield can decrease due to non-conforming boards (according to some reference standard) or even due to failing boards. In addition, regular through-hole vias are considered fragile structures as they are long and narrow; the manufacturer must ensure that the vias are plated properly throughout the barrel and this in turn causes several processing steps.
Different types of vias: (1) Through hole. (2) Blind via. (3) Buried via. The gray and green layers are nonconducting, while the thin orange layers and red vias are conductive.PCB via current capacity chart showing 1 mil plating via current capacity & resistance versus diameter on a 1.6 mm PCB.
In printed circuit board (PCB) design, a via consists of two pads in corresponding positions on different copper layers of the board, that are electrically connected by a hole through the board.[citation needed] The hole is made conductive by electroplating, or is lined with a tube or a rivet.[citation needed] High-density multilayer PCBs may have microvias: blind vias are exposed only on one side of the board, while buried vias connect internal layers without being exposed on either surface. Thermal vias carry heat away from power devices and are typically used in arrays of about a dozen.[2][3]
A via consists of:
Barrel — conductive tube filling the drilled hole
Pad — connects each end of the barrel to the component, plane, or trace
Antipad — clearance hole between barrel and metal layer to which it is not connected
A via, sometimes called PTV or plated-through-via, should not be confused with a plated through hole (PTH). A via is used as an interconnection between copper layers on a PCB while the PTH is generally made larger than vias and is used as a plated hole for acceptance of component leads - such as non-SMT resistors, capacitors, and DIP package IC. PTH can also be used as holes for mechanical connection while vias may not. Another usage of PTH is known as a castellated hole where the PTH is aligned at the edge of the board so that it is cut in half when the board is milled out of the panel - the main usage is for allowing one PCB to be soldered to another in a stack - thus acting both as a fastener and also as a connector.[4]
Three major kinds of vias are shown in right figure. The basic steps of making a PCB are: making the substrate material and stacking it in layers; through-drilling of plating the vias; and copper trace patterning using photolithography and etching. With this standard procedure, possible via configurations are limited to through-holes.[a] Depth-controlled drilling techniques such as using lasers can allow for more varied via types. (Laser drills can also be used for smaller and more precisely positioned holes than mechanical drills produce.) PCB manufacturing typically starts with a so-called core, a basic double-sided PCB. Layers beyond the first two are stacked from this basic building block. If two more layers are consecutively stacked from bottom of core, you can have a 1-2 via, a 1-3 via and a through hole. Each type of via is made by drilling at each stacking stage. If one layer is stacked on top of the core and other is stacked from the bottom, the possible via configurations are 1-3, 2-3 and through hole. The user must gather information about the PCB manufacturer's allowed methods of stacking and possible vias. For cheaper boards, only through holes are made and antipad (or clearance) is placed on layers which are supposed not to be contacted to vias.
IPC 4761edit
IPC 4761 defines the following via types:
Type I: Tented via
Type II: Tented & covered via
Type III-a: Plugged via, sealed with non-conductive material on one side
Type III-b: Plugged via, sealed with non-conductive material on both sides
Type IV-a: Plugged & covered via, sealed with non-conductive material and covered with wet solder mask on one side
Type IV-b: Plugged & covered via, sealed with non-conductive material and covered with wet solder mask on both sides
Type V: Filled via, filled with non-conductive paste
Type VI-a: Filled & covered via, covered with dry film or wet solder mask on one side
Type VI-b: Filled & covered via, covered with dry film or wet solder mask on both sides
Type VII: Filled & capped via, filled with non-conductive paste and overplated on both sides
Failure behavioredit
If well made, PCB vias will primarily fail due to differential expansion and contraction between the copper plating and the PCB in the out of plane direction (Z). This differential expansion and contraction will induce cyclic fatigue in the copper plating, eventually resulting in crack propagation and an electrical open circuit. Various design, material, and environmental parameters will influence the rate of this degradation.[5][6] To ensure via robustness, IPC sponsored a round-robin exercise that developed a time to failure calculator.[7]
In integrated circuit (IC) design, a via is a small opening in an insulating oxide layer that allows a conductive connection between different layers. A via on an integrated circuit that passes completely through a silicon wafer or die is called a through-chip via or through-silicon via (TSV). Through-glass vias (TGV) have been studied by Corning Glass for semiconductor packaging, due to the reduced electrical loss of glass versus silicon packaging.[8] A via connecting the lowest layer of metal to diffusion or poly is typically called a "contact".
Galleryedit
Plated-through holes, in this section there are eight on a multilayer board (magnified)
Double layered plating in CAD. Vias makes EDA placement possible. Bottom layer – Red Top layer – Blue
Plating of plated-through holes: Above – Top layer Down – Bottom layer
^Through-holes per core. It is possible, though more expensive, to create blind or buried vias by using additional cores and lamination steps. It is also possible to backdrill and remove the plating from one side through to the desired layer, which leaves the physical hole as a through-hole, but creates the electrical equivalent of a blind via. If a PCB needs enough layers to justify blind and buried vias, it is probably also using small enough traces packed tightly enough to require (laser-drilled) microvias.
Referencesedit
^"PCB Vias: An In-Depth Guide". ePiccolo Engineering.
^"PCB design: A close look at facts and myths about thermal vias".
^Gautam, Deepak; Wager, Dave; Musavi, Fariborz; Edington, Murray; Eberle, Wilson; Dunford, Willa G. (2013-03-17). A review of thermal management in power converters with thermal vias. 2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC). Long Beach, California, U.S.A: IEEE. doi:10.1109/APEC.2013.6520276.
^. Hi-Tech Corp. 2011. Archived from the original on 2016-05-26. Retrieved 2013-01-02.
"Via Tenting - Overview of the variations". WE Online. Würth Elektronik GmbH & Co. KG. 2014. Printed Circuit Boards > Layout > Design Tip > Tenting. from the original on 2017-12-18. Retrieved 2017-12-18.
"Via Plugging - Overview of the variations". WE Online. Würth Elektronik GmbH & Co. KG. 2014. Printed Circuit Boards > Layout > Design Tip > Plugging. from the original on 2017-12-18. Retrieved 2017-12-18.
"Via Filling - Overview of the variations". WE Online. Würth Elektronik GmbH & Co. KG. 2013. Printed Circuit Boards > Layout > Design Tip > Filling. from the original on 2017-12-18. Retrieved 2017-12-18.
"Microvia Filling". WE Online. Würth Elektronik GmbH & Co. KG. 2015. Printed Circuit Boards > Layout > Design Tip > Microvia Filling. from the original on 2017-12-18. Retrieved 2017-12-18.
Dingler, Klaus; Musewski, Markus (2009-03-18). "Pluggen / Plugging". FED-Wiki (in German). Berlin, Germany: Fachverband Elektronik-Design e.V. (FED). from the original on 2017-12-18. Retrieved 2017-12-18.
"Via Optimization Techniques for High-Speed Channel Designs" (PDF) (Application note). 1.0. Altera Corporation. May 2008. AN-529-1.0. (PDF) from the original on 2017-12-18. Retrieved 2017-12-18.
Chu, Jun (2017-04-11). "Controlled Depth Drilling, or Back Drilling". Online Documentation for Altium Products. Altium. Archived from the original on 2017-12-18. Retrieved 2017-12-18.
Loughhead, Phil (2017-05-30). "Removing Unused Pads and Adding Teardrops". Online Documentation for Altium Products. Altium. Archived from the original on 2017-12-18. Retrieved 2017-12-18.
Brooks, Douglas G.; Adam, Johannes (2017-02-09). PCB Trace and Via Temperatures: The Complete Analysis (2nd ed.). CreateSpace Independent Publishing Platform. ISBN978-1541213524.
External linksedit
The Wikibook Practical Electronics has a page on the topic of: PCB Layout#Holes
Online Via Calculator (Ampacity, Capacitance, Impedance, Power Dissipation Calculation).
April 25, 2024
electronics, this, article, includes, list, general, references, lacks, sufficient, corresponding, inline, citations, please, help, improve, this, article, introducing, more, precise, citations, december, 2017, learn, when, remove, this, template, message, lat. This article includes a list of general references but it lacks sufficient corresponding inline citations Please help to improve this article by introducing more precise citations December 2017 Learn how and when to remove this template message A via Latin path or way is an electrical connection between two or more metal layers and are commonly used in printed circuit boards PCB Essentially a via is a small drilled hole that goes through two or more adjacent layers the hole is plated with metal often copper that forms an electrical connection through the insulating layers Vias are an important concern in PCB manufacturing 1 This is because the vias are drilled with certain tolerances and may be fabricated off their designated locations so some allowance for errors in drill position must be made prior to manufacturing or else the manufacturing yield can decrease due to non conforming boards according to some reference standard or even due to failing boards In addition regular through hole vias are considered fragile structures as they are long and narrow the manufacturer must ensure that the vias are plated properly throughout the barrel and this in turn causes several processing steps Contents 1 In printed circuit boards 2 IPC 4761 3 Failure behavior 4 Vias in integrated circuits 5 Gallery 6 See also 7 Notes 8 References 9 Further reading 10 External linksIn printed circuit boards edit nbsp Different types of vias 1 Through hole 2 Blind via 3 Buried via The gray and green layers are nonconducting while the thin orange layers and red vias are conductive nbsp PCB via current capacity chart showing 1 mil plating via current capacity amp resistance versus diameter on a 1 6 mm PCB In printed circuit board PCB design a via consists of two pads in corresponding positions on different copper layers of the board that are electrically connected by a hole through the board citation needed The hole is made conductive by electroplating or is lined with a tube or a rivet citation needed High density multilayer PCBs may have microvias blind vias are exposed only on one side of the board while buried vias connect internal layers without being exposed on either surface Thermal vias carry heat away from power devices and are typically used in arrays of about a dozen 2 3 A via consists of Barrel conductive tube filling the drilled hole Pad connects each end of the barrel to the component plane or trace Antipad clearance hole between barrel and metal layer to which it is not connected A via sometimes called PTV or plated through via should not be confused with a plated through hole PTH A via is used as an interconnection between copper layers on a PCB while the PTH is generally made larger than vias and is used as a plated hole for acceptance of component leads such as non SMT resistors capacitors and DIP package IC PTH can also be used as holes for mechanical connection while vias may not Another usage of PTH is known as a castellated hole where the PTH is aligned at the edge of the board so that it is cut in half when the board is milled out of the panel the main usage is for allowing one PCB to be soldered to another in a stack thus acting both as a fastener and also as a connector 4 Three major kinds of vias are shown in right figure The basic steps of making a PCB are making the substrate material and stacking it in layers through drilling of plating the vias and copper trace patterning using photolithography and etching With this standard procedure possible via configurations are limited to through holes a Depth controlled drilling techniques such as using lasers can allow for more varied via types Laser drills can also be used for smaller and more precisely positioned holes than mechanical drills produce PCB manufacturing typically starts with a so called core a basic double sided PCB Layers beyond the first two are stacked from this basic building block If two more layers are consecutively stacked from bottom of core you can have a 1 2 via a 1 3 via and a through hole Each type of via is made by drilling at each stacking stage If one layer is stacked on top of the core and other is stacked from the bottom the possible via configurations are 1 3 2 3 and through hole The user must gather information about the PCB manufacturer s allowed methods of stacking and possible vias For cheaper boards only through holes are made and antipad or clearance is placed on layers which are supposed not to be contacted to vias IPC 4761 editIPC 4761 defines the following via types Type I Tented via Type II Tented amp covered via Type III a Plugged via sealed with non conductive material on one side Type III b Plugged via sealed with non conductive material on both sides Type IV a Plugged amp covered via sealed with non conductive material and covered with wet solder mask on one side Type IV b Plugged amp covered via sealed with non conductive material and covered with wet solder mask on both sides Type V Filled via filled with non conductive paste Type VI a Filled amp covered via covered with dry film or wet solder mask on one side Type VI b Filled amp covered via covered with dry film or wet solder mask on both sides Type VII Filled amp capped via filled with non conductive paste and overplated on both sidesFailure behavior editIf well made PCB vias will primarily fail due to differential expansion and contraction between the copper plating and the PCB in the out of plane direction Z This differential expansion and contraction will induce cyclic fatigue in the copper plating eventually resulting in crack propagation and an electrical open circuit Various design material and environmental parameters will influence the rate of this degradation 5 6 To ensure via robustness IPC sponsored a round robin exercise that developed a time to failure calculator 7 Vias in integrated circuits editMain article Through silicon via In integrated circuit IC design a via is a small opening in an insulating oxide layer that allows a conductive connection between different layers A via on an integrated circuit that passes completely through a silicon wafer or die is called a through chip via or through silicon via TSV Through glass vias TGV have been studied by Corning Glass for semiconductor packaging due to the reduced electrical loss of glass versus silicon packaging 8 A via connecting the lowest layer of metal to diffusion or poly is typically called a contact Gallery edit nbsp Plated through holes in this section there are eight on a multilayer board magnified nbsp Double layered plating in CAD Vias makes EDA placement possible Bottom layer Red Top layer Blue nbsp Plating of plated through holes Above Top layerDown Bottom layer nbsp Cross cut section of a multilayer via nbsp The small metallic circles are vias nbsp Filled vias with no visible holeSee also editThrough hole technology THT Surface mount technology SMT Through silicon via TSV Via fence FeedthroughNotes edit Through holes per core It is possible though more expensive to create blind or buried vias by using additional cores and lamination steps It is also possible to backdrill and remove the plating from one side through to the desired layer which leaves the physical hole as a through hole but creates the electrical equivalent of a blind via If a PCB needs enough layers to justify blind and buried vias it is probably also using small enough traces packed tightly enough to require laser drilled microvias References edit PCB Vias An In Depth Guide ePiccolo Engineering PCB design A close look at facts and myths about thermal vias Gautam Deepak Wager Dave Musavi Fariborz Edington Murray Eberle Wilson Dunford Willa G 2013 03 17 A review of thermal management in power converters with thermal vias 2013 Twenty Eighth Annual IEEE Applied Power Electronics Conference and Exposition APEC Long Beach California U S A IEEE doi 10 1109 APEC 2013 6520276 Castellated Holes Edge Plating PCB Castellations Hi Tech Corp 2011 Archived from the original on 2016 05 26 Retrieved 2013 01 02 C Hillman Understanding plated through via failures Global SMT amp Packaging November 2013 pp 26 28 https www dfrsolutions com hubfs Resources services Understanding Plated Through Via Failures pdf t 1514473946162 C Hillman Reliable Plated Through Via Design and Fabrication http resources dfrsolutions com White Papers Reliability Reliable Plated Through Via Design and Fabrication1 pdf Plated Through Hole PTH Fatigue calculator DfR Solutions Retrieved 2017 12 17 Progress and Application of Through Glass Via TGV Technology PDF corning com Retrieved 2019 08 08 Further reading edit Tips for PCB Vias Design PDF Technical note Quick teck 2014 EN 00417 Retrieved 2017 12 18 Via Tenting Overview of the variations WE Online Wurth Elektronik GmbH amp Co KG 2014 Printed Circuit Boards gt Layout gt Design Tip gt Tenting Archived from the original on 2017 12 18 Retrieved 2017 12 18 Via Plugging Overview of the variations WE Online Wurth Elektronik GmbH amp Co KG 2014 Printed Circuit Boards gt Layout gt Design Tip gt Plugging Archived from the original on 2017 12 18 Retrieved 2017 12 18 Via Filling Overview of the variations WE Online Wurth Elektronik GmbH amp Co KG 2013 Printed Circuit Boards gt Layout gt Design Tip gt Filling Archived from the original on 2017 12 18 Retrieved 2017 12 18 Microvia Filling WE Online Wurth Elektronik GmbH amp Co KG 2015 Printed Circuit Boards gt Layout gt Design Tip gt Microvia Filling Archived from the original on 2017 12 18 Retrieved 2017 12 18 Dingler Klaus Musewski Markus 2009 03 18 Pluggen Plugging FED Wiki in German Berlin Germany Fachverband Elektronik Design e V FED Archived from the original on 2017 12 18 Retrieved 2017 12 18 Via Optimization Techniques for High Speed Channel Designs PDF Application note 1 0 Altera Corporation May 2008 AN 529 1 0 Archived PDF from the original on 2017 12 18 Retrieved 2017 12 18 Chu Jun 2017 04 11 Controlled Depth Drilling or Back Drilling Online Documentation for Altium Products Altium Archived from the original on 2017 12 18 Retrieved 2017 12 18 Loughhead Phil 2017 05 30 Removing Unused Pads and Adding Teardrops Online Documentation for Altium Products Altium Archived from the original on 2017 12 18 Retrieved 2017 12 18 Brooks Douglas G Adam Johannes 2017 02 09 PCB Trace and Via Temperatures The Complete Analysis 2nd ed CreateSpace Independent Publishing Platform ISBN 978 1541213524 External links edit nbsp The Wikibook Practical Electronics has a page on the topic of PCB Layout Holes Online Via Calculator Ampacity Capacitance Impedance Power Dissipation Calculation Retrieved from https en wikipedia org w index php title Via electronics amp oldid 1216368576, wikipedia, wiki, book, books, library,
