Package on Package (PoP) is an IC-packaging technology with vertical combined logic and memory components where two or more BGAs (Ball Grid Arrays) are stacked. Normally the discrete logic is located in the bottom with a memory device on top of it. Because of the high package density, these components are very important for the communication technology (handset makers etc.).
Beside an intelligent combination of bottom and top heating providing precise thermal management, a special nozzle design is required to pick up those components during rework.
What are the Challenges?
The PoP rework process is similar to standard BGA rework, but because of the vertical assembly, a special clamping solution is necessary. PoP packaging involves the following specific challenges:
- High-count fine ball pitch (<0,65 mm)
- Reflow simultaneously on the PCB
- Applying a sufficient clamping force to lift the component out of liquid solder without lateral movement
- Reworking different component heights
- Avoid disturbing neighboring components on densely populated boards
- Amount of warpage for each package must be limited
- Precise force control during stacking to avoid shifting of already placed package levels
The Finetech Solution
Remove, Clean, Replace
- Preheating the PCB
- Desoldering the PoP component without affecting neighbored components by using software controlled heating units and qualified tooling
- Pick up the component with Finetech’s special vacuum activated tweezers
- Removing residual solder material contactless to avoid any stress to the solder pads
- Pick up, flux-dip and precise alignment of each package
- In a final step, simultaneous reflow of all interconnections; packages and PCB
Controlled Mixed Soldering System
Finetech’s unique thermal management concept uses “cold” air or gas (typically nitrogen) introduced into the hot-gas stream in a mixing chamber. The chamber location is just before the air passes through the nozzle onto the component. This gas mixture results in a highly responsive system - reducing over and under-shoot to barely perceptible levels. Tracking of the pre-set temperature is optimized and when combined with mass-flow-control of gas volumes (up to 70L/min), produces an effective heat delivery system. Heater lifetime is also increased and system-to-system reproducibility is greatly enhanced (±2ºC).
Special Nozzle Design for Quick and Safe Rework
- Specific nozzle with vacuum controlled tweezers for de-soldering and soldering
- Nozzle can be adapted easily to different component heights by turning one screw
- Thin and specially shaped tweezers to clamp the component on every stack level
- Tweezers distance easily adjustable for rework on densely populated PCBs even in clearance of 0.3 mm to adjacent components
- Synchronic tweezers actuation is freely software programmable to avoid any stress to non-molten solder joints
Integrated Process Management (IPM)
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
- Process-integrated camera and light control
- 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
FINEPLACER® Rework Systems
Amongst other factors, the recommended system mainly depends on size and pitch of your component and the required process flexiblity.
Browse our product range or get in contact with your sales contact to figure out the best equipment solution for your needs.