|Ask the Experts|
July 10, 2017
BGA re-balling process
Can you recommend a process or semi-automatic machine for re-balling BGA's? Is there a process or system available to repair these components after rework and repair?
|Expert Panel Responses|
VJ Electronix has not typically recommended re-balling BGA packages due to the stress induced to the package through multiple thermal cycles. When one factors in the original ball attach, reflow of the component to the board, removal from the board, residual solder removal, re-ball attach, and re-attach to the board, the package is subjected to a minimum of seven thermal cycles. In most cases, for reliability, it is far more prudent to scrap removed components. However there are many cases where scrapping components is not practical. Cases include high value components and components with limited availability (i.e., prototypes). There is also a relatively new requirement stemming from Lead Free packages. Many components are no longer available with tin-lead solder balls. Since there are still a number of applications, such as Mil-Aero, where tin-lead solder is required, these packages can be prepared and re-balled with tin-lead spheres. Removing residual solder from the BGA after removal for rework, or removing entire solder balls for tin-lead re-balling, requires precise control to avoid damage to the component. We recommend use of a non-contact solder scavenging tool. For small quantities using of hand tools should suffice. For high quantities the component can be fixtured face up on the table of an automated rework system. There are a number of automated systems for re-balling BGA components. The cost of these systems must be justified by the volume of re-balling. When justified, these systems provide the ability to accurately and quickly re-ball a wide variety of components. For low to mid volume we have also had very good success with solder ball preforms (www.solderquik.com). The preform is an array of solder balls suspended in a removable backing material. The preform is aligned and placed using the rework system pick and place mechanism, and reflowed using the rework nozzle. After the solder balls are reflowed onto the component the backing material is removed. Another nice benefit of the preform for standard rework is the ability to re-ball the board. The same process is applied except that the array of solder balls is placed directly onto the pads at the rework site and reflowed to the board using the rework nozzle. The process is completed by placing the prepared (bare) BGA component onto the solder balls on the board and reflowing using the same profile used for standard rework process. The benefit of this process is one fewer thermal cycle for the component.
VJ Technologies, Inc.
Much will depend upon how many spheres need to be placed or replaced. Assuming that the component (for example BGA, CSP, etc.) comes from the manufacturer with minimal defects, replacement of one or a small number of spheres can be achieved using the FINEPLACER Pico Rework System. In this case, the defective sphere(s) is removed by a "touchless" vacuum solder removal process, fresh flux is applied, and the new solder sphere is placed in position and reflowed using Finetech's COMISS hot gas module. Obviously, if a large number need to be replaced, it would be preferable to remove all spheres from the component, and, using a template, replace and reflow all spheres at the same time. Our Ball Array Placement Module can handle simultaneous, high precision placement of up to 200 solder balls directly onto a substrate or wafer.
Photo Stencil offers a Universal BGA repair tool. The tool holds the BGA package in place with a ball drop stencil registered to the holding tool. The entire tool, with balls in place, is sent through the reflow oven. See our website for more information.
Vice President Technology
A great source for solder spheres for re-balling is East Spheres.
Production Solutions, Inc.
Winslow automation have an excellent process for reballing.
Regional Sales Manager
OK International Inc.
We sell a fixture for reballing BGA's one at a time. You apply liquid flux to the bottom of the part, Place the part in the fixture. Pour the spheres into the fixture and reflow the part. You would need a fixture for each part number you want to reball. The kit contains the fixture, 25K spheres and the liquid flux. The kit sells for $295.00 ea.
SMT Sales Associates Inc
There are several reballing techniques that are quite effective at reballing or even initially placing spheres for prototype components. STI has a reballer kit that has been used for as many years as BGA packages have been in common use for our products. Each kit is specific for the component package footprint and is reusable.
FSO/Director Training Resources
STI Electronics Inc.
BGA reballing has been quite common for several years. We utilize a few different pieces of equipment to support the requirement. Both will require proper prep of the component prior to reflowing the new solder spheres in-place. The use of a fixture to hold the component and overlay solder spheres in position along with either a full convection reflow system, or small benchtop oven can be utilized. We use MARTIN’s Mini-Oven for Reballing and Solder Bumping.
Circuit Technology Center
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