The surface mount technology available at Corintech also includes the placement of ball grid arrays.
A ball grid array, BGA for short, is a commonly used surface mount packaging for integrated circuits such as microprocessors. Unlike conventional surface mount integrated circuits, where leads from the side of the package are used to connect to the printed circuit board, a BGA uses an array of solder balls underneath the package to make the connections.
To mount a ball grid array, the package is placed on the PCB and then heated until the solder takes a semi-liquid state. Surface tension maintains the correct alignment of the BGA on the circuit board until the solder cools and solidifies.
The temperature applied to the array when mounting the BGA is of vital importance. Too much and the solder balls may melt enough for them to bridge with the adjoining ball. Too little heat may result in a weak or non-existing connection with the PCB causing immediate or future failure of the device.
As the connections are beneath the package on a ball grid array, visual inspection is not an option. The assembly must be inspected by x-ray to ensure correct placement and to confirm all connections are strong and made without bridging.
There are many advantages to designing ball grid arrays into your circuit. By using the underside of the chip to connect with the surface of the PCB, BGA’s are able to have a much higher density of connections than a conventional surface mount package of the same size. This means a more efficient circuit design can be achieved.
Due to the added surface area available for the connections, wider spacing between the solder balls is possible. This can improve upon manufacturing yield as the potential for bridged joints occurring is reduced.
As BGA’s are mounted closer to the surface of the printed circuit board there is a lower lead inductance making for lower levels of distortion and superior electrical performance.
A size advantage also comes with selecting a ball grid array. BGA’s are much thinner than a traditional IC meaning the final package can also be thinner. This is becoming increasingly important as mobile technology continues to get smaller. The thermal properties of a BGA allow for heat to be conducted onto the PCB faster and more efficiently – this means less need for alternative cooling methods and an even further reduction in circuit and product size.