Single Ball Reballing

It takes only one defective ball to render an arrayed component unusable. The ability to replace just a single sphere enables a package to be repaired – one that may be expensive, may otherwise be unavailable, or where reworking is more expediant than waiting for a replacement.

Faulty grid array with solder ball bridge and missing balls
Repaired grid array
Missing solder ball
Replaced solder ball
Soldering a single ball
Result: Placement of solder balls with diameter of 200 µm

What are the Challenges?

Remove ‘only’ the defective ball
Prevent surface contamination during removal
Apply flux to the ball
Align, place and reflow

The Finetech Solution

Adapted Nozzle Design

Single solder ball at tool tip
Pick-up of single solder ball from tray
Soldering a single ball
Soldering a single ball

The key to a successful solder removal process is to leave the surrounding area undisturbed. The Finetech solution uses two nozzles - the first, a solder removal nozzle, uses hot air to liquefy the solder and has vacuum port designed to draw the solder into a container for proper disposal. The second nozzle, which is used to place the ball, is similar to a solder removal nozzle but without the vacuum port.

The nozzle is developed to not only produce enough vacuum to hold the small ball, but also to precisely channel air/nitrogen to the site being repaired without damaging or disturbing the neighboring attached balls.

Flux Dipping

Flux Transfer Module
Pick-up of single ball from tray before flux dipping
Flux dipping
Flux dipping

The use of a tacky flux to hold the ball in place during reflow provides a good surface tension between the interposer and the ball, which helps keep the ball aligned to the pad that it will be soldered to. It provides a good thermal transfer mechanism between the solder on the board and that which makes up the ball. Compare the flux to the grease used to cook an egg. Using a thermal transfer material always makes the job much easier.

Integrated Process Management (IPM)

Integrated Process Management (IPM)
Principle of process gas integration
Operating software for rework

The Integrated Process Management (IPM) is the center piece of a FINEPLACER^® system¹ - the place where it all comes together. IPM is more than just thermal management. It synchronizes the control of all process modules and their related parameters:

Controlled and precisely balanced interaction of top and bottom (pre-)heating and cooling
Control of temperature, time, force, power, energy, flow
Controlled process gas integration for reduced solder contamination, minimized surface tension effects and smooth spherical solder residues

IPM is very complex, yet easy to access. Via the GUI of the operating software, the user has perfect control of all required adjustments. Just drag 'n drop to define temperature ramps or activate process modules. All settings are represented in only one profile, making for a very intuitive work flow.

The operating software provides an ever-growing library of profiles for all kinds of processes. It also offers comprehensive data logging functions essential for statistical process control.

In combination with the system-to-system process transfer capability this is as easy as process development can get.

¹ _{FINEPLACER^® core offers co-ordinated top and bottom heating but does not support IPM}