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{{short description|Surface-mount packaging that uses an array of solder balls}}
{{More citations needed|date=September 2010}}
[[Image:Solder_ball_grid.jpg|thumb|300px|A grid array of solder balls on a printed circuit board after removal of an integrated circuit chip.]]
[[File:Bga und via IMGP4531 wp.jpg|thumb|300x300px|Cross-cut section of BGA mounted circuit]]
A '''ball grid array''' ('''BGA''') is a type of [[surface-mount]] packaging (a [[chip carrier]]) used for [[integrated circuit]]s. BGA packages are used to permanently mount devices such as [[microprocessor]]s. A BGA can provide more interconnection pins than can be put on a [[Dual in-line package|dual in-line]] or [[Quad Flat Package|flat package]]. The whole bottom surface of the device can be used, instead of just the perimeter. The traces connecting the package's leads to the wires or balls which connect the die to package are also on average shorter than with a perimeter-only type, leading to better performance at high speeds.{{cn|date=January 2020}}
Soldering of BGA devices requires precise control and is usually done by automated processes such as in computer-controlled automatic [[reflow oven]]s.
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== Description ==
[[Image:BGA RAM.jpg|thumb|300px|BGA [[Integrated circuit|ICs]] assembled on a [[Random access memory|Memory module]]]]
The BGA is descended from the [[pin grid array]] (PGA), which is a package with one face covered (or partly covered) with pins in a [[grid pattern]] which, in operation, conduct electrical signals between the integrated circuit and the [[printed circuit board]] (PCB) on which it is placed.
In more advanced technologies, solder balls may be used on both the PCB and the package. Also, in stacked [[multi-chip module]]s,
== Advantages ==
=== High density ===
The BGA
=== Heat conduction ===
A further advantage of BGA packages over packages with discrete leads (i.e. packages with legs) is the lower [[thermal resistance]] between the package and the PCB.
=== Low-inductance leads ===
The shorter an electrical conductor, the lower its unwanted [[inductance]], a property which causes unwanted distortion of signals in high-speed electronic circuits.
== Disadvantages ==
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Thermal expansion issues can be overcome by matching the mechanical and thermal characteristics of the PCB to those of the package. Typically, plastic BGA devices more closely match PCB thermal characteristics than ceramic devices.
The predominant use of [[RoHS compliant]] lead-free solder alloy assemblies has presented some further challenges to BGAs including "[[Head in pillow (metallurgy)|head in pillow]]"<ref>{{cite web |title=Reducing Head in Pillow Defects - Head in pillow defects: causes and potential solutions |author=Alpha |date=2010-03-15 |orig-year=September 2009 |version=3 |url=http://www.slideshare.net/Alpha1Cookson/head-on-pillow-v3-sept-09 |access-date=2018-06-18 |url-status = live|archive-url=https://web.archive.org/web/20131203002809/http://www.slideshare.net/Alpha1Cookson/head-on-pillow-v3-sept-09 |archive-date=2013-12-03}}</ref> soldering phenomenon, "[[pad cratering]]" problems as well as their decreased reliability versus lead-based solder BGAs in extreme operating conditions such as high temperature, high thermal shock and high gravitational force environments, in part due to lower [[ductility]] of RoHS-compliant solders.<ref>{{cite web |url=http://teerm.nasa.gov/NASA_DODLeadFreeElectronics_Proj2.htm |title=TEERM - TEERM Active Project - NASA-DOD Lead-Free Electronics (Project 2) |publisher=Teerm.nasa.gov |access-date=2014-03-21 |archive-url=https://web.archive.org/web/20141008003914/http://teerm.nasa.gov/nasa_dodleadfreeelectronics_proj2.htm |archive-date=2014-10-08 |url-status = dead}}</ref>
Mechanical stress issues can be overcome by bonding the devices to the board through a process called "underfilling",<ref name=underfill>[https://archive.today/20130719180947/http://www.electroiq.com/articles/ap/print/volume-10/issue-12/features/bga-underfills.html Solid State Technology: BGA underfills - Increasing board-level solder joint reliability, 12/01/2001]</ref> which injects an epoxy mixture under the device after it is soldered to the PCB, effectively gluing the BGA device to the PCB.
Another solution to non-compliant connections is to put a "compliant layer" in the package that allows the balls to physically move in relation to the package.
Other techniques for increasing the board-level reliability of packages include use of low-expansion PCBs for ceramic BGA (CBGA) packages, [[interposer]]s between the package and PCB, and re-packaging a device.<ref name=underfill/>
===Difficulty of inspection===
Once the package is soldered into place, it is difficult to find soldering faults. [[X-ray]] machines, [[industrial CT scanning]] machines,<ref>"CT Services - Overview." Jesse Garant & Associates. August 17, 2010. {{cite web|url=http://www.jgarantmc.com/ct-services.html |title=Industrial Computed Tomography Scanning Services – JG&A |access-date=2010-11-24 |url-status = dead|archive-url=https://web.archive.org/web/20100923150138/http://www.jgarantmc.com/ct-services.html |archive-date=2010-09-23 }}</ref> special microscopes, and endoscopes to look underneath the soldered package have been developed to overcome this problem.
Due to the cost of visual X-ray BGA inspection, electrical testing is very often used instead. Very common is [[boundary scan]] testing using an IEEE 1149.1 [[JTAG]] port.
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=== Cost of equipment ===
Expensive equipment is required to reliably solder BGA packages; hand-soldering BGA packages is very difficult and unreliable, usable only for the smallest packages in the smallest quantities.<ref>{{cite news |last=Das |first=Santosh |url=http://www.electronicsandyou.com/blog/bga-ball-grid-array-repairing-and-soldering-bga.html |title=BGA Soldering & Repairing / How to Solder Ball Grid Array |work=Electronics and You |date=2019-08-22 |accessdate=2021-09-07 }}</ref> However, as more ICs have become available only in leadless (e.g. [[quad-flat no-leads package]]) or BGA packages, various DIY [[Rework (electronics)#Reflowing and reballing|reflow]] methods have been developed using inexpensive heat sources such as [[heat gun]]s, and domestic [[Toaster#Toaster oven|toaster ovens]] and [[Frying pan#Electric|electric skillets]].<ref>[https://www.sparkfun.com/tutorials/59 Sparkfun tutorials: Reflow skillet, July 2006]</ref>
== Variants ==
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leaving the innermost square empty.
Intel used a package designated BGA1 for their [[Pentium II]] and early [[Celeron]] mobile processors.
For example, the "micro-FCBGA" (flip chip ball grid array) is Intel's current{{When|date=May 2011}} BGA mounting method for mobile processors that use a [[flip chip]] binding technology. It was introduced with the ''Coppermine'' Mobile Celeron.{{Citation needed|date=April 2016}} Micro-FCBGA has 479 balls that are 0.78 mm in diameter. The processor is affixed to the motherboard by soldering the balls to the motherboard. This is thinner than a pin grid array socket arrangement, but is not removable.
The 479 balls of the Micro-FCBGA package (a package almost identical to the 478-pin socketable [[micro-FCPGA]] package) are arranged as the 6 outer rings of a 1.27 mm pitch (20 balls per inch pitch) 26x26 square grid, with the inner 14x14 region empty.<ref>Intel.
"Mobile Intel Celeron Processor (0.13 μ) in Micro-FCBGA and Micro-FCPGA Packages".
[http://pdf.seekdatasheet.com/2008715/200807151345533917.pdf Datasheet] {{Webarchive|url=https://web.archive.org/web/20140318091556/http://pdf.seekdatasheet.com/2008715/200807151345533917.pdf |date=2014-03-18 }}.
2002.</ref><ref>{{Cite web |url=http://www.x86-guide.com/en/articles/packages/FCBGA-479%20(Micro-FCBGA)-no56.html |title=FCBGA-479 (Micro-FCBGA) |access-date=2011-12-20 |archive-date=2021-02-28 |archive-url=https://web.archive.org/web/20210228145820/http://www.x86-guide.com/en/articles/packages/FCBGA-479%20(Micro-FCBGA)-no56.html |url-status=dead }}</ref>
== Procurement ==
Primary end-users of BGAs are [[original equipment manufacturer]]s (OEMs). There is also a market among electronic hobbyists [[Do it yourself|do it yourself (DIY)]] such as the increasingly popular [[maker culture|maker movement]].<ref>{{cite news|title=More than just digital quilting: The "maker" movement could change how science is taught and boost innovation. It may even herald a new industrial revolution|url=
== See also ==
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}}
* [https://amkor.com/packaging/laminate/pbga/ PBGA Package Information] from [[Amkor Technology]]
* [https://c44f5d406df450f4a66b-1b94a87d576253d9446df0a9ca62e142.ssl.cf2.rackcdn.com/2015/03/PBGA-J-Devices-DSJD401.pdf PBGA Package Information] {{Webarchive|url=https://web.archive.org/web/20190102095019/https://c44f5d406df450f4a66b-1b94a87d576253d9446df0a9ca62e142.ssl.cf2.rackcdn.com/2015/03/PBGA-J-Devices-DSJD401.pdf |date=2019-01-02 }} from J-Devices Corporation
{{Semiconductor packages}}
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