Reworking BGA High Value Test interface PCB’S + Burn in PCB

Overview Test Interface (TIU PCB‘s) are extremely expensive. BGA chipsets are developed on these thick PCB circuits, these designs test for speed and functionality of the Firmware Time to market during development of BGA Chipset is critical to product Marketing needs. Unusual components used in development and difficult to rework. PCB up to 44 layers 6mm thick. Low volume PCB made as cost is extremely high of PCB also difficult to assemble.

Examples of development BGA Pcbs Cost of these TIU PCB can easily start at $30,000

Challenges of TIU Rework Massive size and thermal mass of PCB substrate Mountains Thermal power required to rework 3-6mm thick PCB’S. Surface mount relays need solder paste printed to replace. Plastic inductors and part on underside will melt easily if heating from below is to high. Heating to much from top will burn top of PCB so a important balance is required. Dual heating zones from preheater make this rework possible not possible without this technology from OK/Metcal.

Rework process Probe Card Relay Rework process Heat PCB up to approximately 100c from bottom Preheaters (with inner and outer heaters explained later),on simultaneously but at different temperatures this stops damage to underside components. A custom metal conduction tip is used with Metcal technology to add additional heat to solder connections without heating adjacent components in 8-10 secs. The relay is discarded when this conduction process is used. If the component needs to be analyzed for any internal faults then convection technology is used as in next slide. The component pcb pads are then printed with solder paste with mini custom stencils. The New part replacement is done on APR-5000XLS with camera to align and place component. Reflow is done with convection profile in APR-5000XLS

TIU Probe Card (conduction tool)

Movie shows conduction removal with PCB at 100°c Probe Card Movie shows conduction removal with PCB at 100°c

APR-5000 Description Heater Head Vacuum tube Inspection camera Dual Preheater zone Board Holders Thermo-couples Main power switch Manual heater head controls

Relay removed with conduction

Probe Card (Mini stencil)

Examples of TIU PCB’s on Metcal APR 5000XLS hot air rework station

Removing GRF303 Relays Once you mount the TIU on the APR5000, you need to prepare the following equipment: Metcal MX5000 with Customized conduction tip cartridge PN: SMTC-8RND86.

Probe Card (For Close packaging a machined nozzle is used)

Reflow profile for hot air replacement

Conclusion Removal done with hot air and custom conduction tools to remove parts fast while pcb is preheated to 100°c PCB old solder is cleaned with solder tools and wick on preheated PCB so not to damage pads. Solder paste is printed onto PCB cold with mini stencils made for each part. Component is placed under vision on rework machine onto pasted PCB pad. Rework machine can now reflow part back onto pcb without damage. Removal time 400 secs preheat and 10 secs per device with conduction tool. Placement is 400sec preheat and total time of 10-12 mins.

Contact details OK International Ltd. Eagle Close, Chandlers Ford SO53 4NF, Hampshire, U.K. Tel: +44 (0)2380 489 100 European Contact Andy Cotton – acotton@okinternational.com North America Contact Paul Wood – pwood@okinternational.com www.okinternational.com www.metcal.com

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