6.1 PC Board Bake
It is recommended to bake the PCB for approximately 24 hours at 125°C prior to rework in order to drive off residual moisture that could cause other component failures during the rework reflow process.

6.2 PC Board Preheat
Once the PCB has finished the baking process, the PCB under rework is then placed in the rework holder and preheated to a temperature of 125°C. Localized heating of the area under rework is recommended. (Use 4°C/second maximum ramp rate)

6.3 Reflow/Removal of the Component from the PCB
Specialized vacuum collets come in contact with the rework component. These collets incorporate a hot gas shroud that heats up the part to a temperature required for
reflowing the solder interconnects. Once the solder reflows, the vacuum collet lifts the unit from the PCB. The collet size and hot gas flow should be optimized to keep the heat flow
localized to the component being removed, while uniformly heating the component.

6.4 Cleaning and Prep of the PCB Land
The PCB can be cleaned and prepared using conventional tools and processes currently used for gullwing packages. Removal of excess solder using a hot iron, a small scraping
tool and solder wick is typical. Place the solder wick under the scraping mechanism to remove the solder from the land area.

6.5 Screen Printing of Solder Paste
Based on some of the tight geometries used on today’s PCBs, it is difficult to screen print a PCB that is nearly 100% populated with components. Hence the approach of manual screen-printing the solder paste directly onto the new component has been adopted. It is recommended to use a type 3 or 4 printing no-clean solder paste. The solder stencil design should follow the guidelines outlined in this application note.

6.6 Placement and Reflow of Component
The placement of the new μModule component should be done with a split field vision system. The image of the screen-printed component and the PCB land pattern are
superimposed during the placement operation, thus making the placement easier to align with the terminal footprint. The reflow of the new component should be done with a localized gas shroud similar to that used during the component removal operation. The profile used for the reflow should have ramp rates and peak temperatures that follow the guidelines specified in this outline.

6.7 Inspection of Reworked Solder Joints
Inspection techniques for the μModule closely resemble those techniques used for Ball Grid. Array components. Visual inspection of solder joints from overhead (z-plane) is not possible for these packages. Thus, the use of z-plane X-ray or a high precision camera system capable of viewing parallel to the x-y plane is necessary.

6.8 Rework Equipment for μModule
Rework systems for the μModule are based on wellestablished rework systems created for Ball Grid Array packages.

7.0 MATERIALS DECLARATION
Materials declarations can be obtained through Linear Technology. Please contact your local representative.