Ball grid array
This article needs additional citations for verification. (September 2010) |
A ball grid array (BGA) is a type of
BGAs were introduced in the 1990s and became popular by 2001.[1]
Soldering of BGA devices requires precise control and is usually done by automated processes such as in computer-controlled automatic reflow ovens.
Description
The BGA is descended from the
In more advanced technologies, solder balls may be used on both the PCB and the package. Also, in stacked
Advantages
High density
The BGA is a solution to the problem of producing a miniature package for an integrated circuit with many hundreds of pins. Pin grid arrays and dual-in-line surface mount (
Heat conduction
A further advantage of BGA packages over packages with discrete leads (i.e. packages with legs) is the lower
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. BGAs, with their very short distance between the package and the PCB, have low lead inductances, giving them superior electrical performance to pinned devices.
Disadvantages
Lack of compliance
A disadvantage of BGAs is that the solder balls cannot flex in the way that longer leads can, so they are not mechanically compliant. As with all surface mount devices, bending due to a difference in coefficient of thermal expansion between PCB substrate and BGA (thermal stress) or flexing and vibration (mechanical stress) can cause the solder joints to fracture.
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
Mechanical stress issues can be overcome by bonding the devices to the board through a process called "underfilling",[5] which injects an epoxy mixture under the device after it is soldered to the PCB, effectively gluing the BGA device to the PCB. There are several types of underfill materials in use with differing properties relative to workability and thermal transfer. An additional advantage of underfill is that it limits tin whisker growth.
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. This technique has become standard for packaging DRAMs in BGA packages.
Other techniques for increasing the board-level reliability of packages include use of low-expansion PCBs for ceramic BGA (CBGA) packages, interposers between the package and PCB, and re-packaging a device.[5]
Difficulty of inspection
Once the package is soldered into place, it is difficult to find soldering faults.
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.
A cheaper and easier inspection method, albeit destructive, is becoming increasingly popular because it does not require special equipment. Commonly referred to as
Difficulties during circuit development
During development it is not practical to solder BGAs into place, and sockets are used instead, but tend to be unreliable. There are two common types of socket: the more reliable type has spring pins that push up under the balls, although it does not allow using BGAs with the balls removed as the spring pins may be too short.
The less reliable type is a
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.
Variants
- CABGA: chip array ball grid array
- CBGA and PBGA denote the ceramic or plastic substrate material to which the array is attached.
- CTBGA: thin chip array ball grid array
- CVBGA: very thin chip array ball grid array
- DSBGA: die-size ball grid array
- FBGA: fine ball grid array based on ball grid array technology. It has thinner contacts and is mainly used in
- FCmBGA: flip chip molded ball grid array
- LBGA: low-profile ball grid array
- LFBGA: low-profile fine-pitch ball grid array
- MBGA: micro ball grid array
- MCM-PBGA: multi-chip module plastic ball grid array
- nFBGA: New Fine Ball Grid Array
- PBGA: plastic ball grid array
- SuperBGA (SBGA): super ball grid array
- TABGA: tape array BGA
- TBGA: thin BGA
- TEPBGA: thermally enhanced plastic ball grid array
- TFBGA or thin and fine ball grid array
- UFBGA and UBGA and ultra fine ball grid array based on pitch ball grid array.
- VFBGA: very fine pitch ball grid array
- WFBGA: very very thin profile fine pitch ball grid array
Effectively also the flip chip methods for mounting chip dies to a carrier is sort of a BGA design derivate with the functional equivalent of the balls there being called bumps or micro bumps. This is realized at an already microscopic size level.
To make it easier to use ball grid array devices, most BGA packages only have balls in the outer rings of the package, leaving the innermost square empty.
Intel used a package designated BGA1 for their Pentium II and early Celeron mobile processors. BGA2 is Intel's package for their Pentium III and some later Celeron mobile processors. BGA2 is also known as FCBGA-479. It replaced its predecessor, BGA1.
For example, the "micro-FCBGA" (flip chip ball grid array) is Intel's current[when?] BGA mounting method for mobile processors that use a flip chip binding technology. It was introduced with the Coppermine Mobile Celeron.[citation needed] 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
Procurement
Primary end-users of BGAs are original equipment manufacturers (OEMs). There is also a market among electronic hobbyists do it yourself (DIY) such as the increasingly popular maker movement.[14] While OEMs generally source their components from the manufacturer, or the manufacturer's distributor, the hobbyist will typically obtain BGAs on the aftermarket through electronic component brokers or distributors.
See also
- Dual in-line package (DIP)
- Pin grid array (PGA)
- Land grid array (LGA)
- Thin quad flat pack(TQFP)
- Small-outline integrated circuit(SOIC)
- Chip carrier: chip packaging and package types list
- Embedded wafer level ball grid array
References
- ^ "Ball Grid Array (BGA) - Engineering Technical - PCBway".
- ^ "Soldering 101 - A Basic Overview". Archived from the original on 2012-03-03. Retrieved 2010-12-29.
- ^ Alpha (2010-03-15) [September 2009]. "Reducing Head in Pillow Defects - Head in pillow defects: causes and potential solutions". 3. Archived from the original on 2013-12-03. Retrieved 2018-06-18.
- ^ "TEERM - TEERM Active Project - NASA-DOD Lead-Free Electronics (Project 2)". Teerm.nasa.gov. Archived from the original on 2014-10-08. Retrieved 2014-03-21.
- ^ a b Solid State Technology: BGA underfills - Increasing board-level solder joint reliability, 12/01/2001
- ^ "CT Services - Overview." Jesse Garant & Associates. August 17, 2010. "Industrial Computed Tomography Scanning Services – JG&A". Archived from the original on 2010-09-23. Retrieved 2010-11-24.
- ^ "Dye and Pry of BGA Solder Joints" (PDF). cascade-eng.com. 2013-11-22. Archived from the original (PDF) on 2011-10-16. Retrieved 2014-03-22.
- ^ Das, Santosh (2019-08-22). "BGA Soldering & Repairing / How to Solder Ball Grid Array". Electronics and You. Retrieved 2021-09-07.
- ^ Sparkfun tutorials: Reflow skillet, July 2006
- ^ Design Requirements - Fine Pitch Ball Grid Array Package (FBGA) DR-4.27D, jedec.org, MAR 2017
- ^ Ryan J. Leng. "The Secrets of PC Memory: Part 2". 2007.
- ^ Intel. "Mobile Intel Celeron Processor (0.13 μ) in Micro-FCBGA and Micro-FCPGA Packages". Datasheet Archived 2014-03-18 at the Wayback Machine. 2002.
- ^ "FCBGA-479 (Micro-FCBGA)". Archived from the original on 2021-02-28. Retrieved 2011-12-20.
- ^ "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". The Economist. Dec 3, 2011.
External links
- PBGA Package Information from Amkor Technology
- PBGA Package Information Archived 2019-01-02 at the Wayback Machine from J-Devices Corporation