TIM (Thermal Interface Materials) are a key component in today's high speed processes. These processes generate significant amounts of heat for their form factor. TIM is the interface to transfer the heat from the unit to the heat sink. The application of applying the heat sink is called Heat Dissipator Placement and assemblage of a single heat sink can consist of dispensing up to two different fluids and placing up to two components.
Heat Dissipator Methods
The two different methods of heat dissipator attach on FCBGA are single piece and two piece:
Single piece heat dissipator attach consists of a single, formed heat dissipater that interfaces with the top of the flip chip via thermal grease and the FR4 base substrate via an adhesive. Thermal grease and the adhesive need to be dispensed in specific, customer-defined patterns designed for the best interface for heat dissipation. Repeatable TIM dispensing is required for uniform material coverage after the heat dissipator is placed. Non-uniform material coverage will result in varying thermal dissipation and could lead to product failure.
Dispensing the adhesive that actually secures the heat dissipator in place is also key to avoiding excess fluid outside of the package which, although it does not affect package performance, is a cosmetic flaw. Too little fluid may result in a faulty package where separation could occur.
Two piece heat dissipator attach is a similar to the single piece heat dissipator process except for the addition of a stiffener to the main heat spreader or lid. The entire process adds an additional step of dispensing adhesive for only the stiffener. Once the adhesive has been dispensed, the stiffener has been placed, and the adhesive has been cured, the entire package is returned to the reconfigured production line where two fluids are dispensed as is done to the single piece heat dissipater.
Highly efficient TIM (Thermal Interface Materials) have a high viscosity with fillers that transmit heat and are highly abrasive. Correct pump selection is essential for an effective, quick, dispense process. The HyFlo pump is a large diameter, very aggressive, double helix auger machined from carbide and connected to a high-torque, high-RPM motor. Due to the abrasiveness of the fluid, auger diameter is customized to accommodate the fillers in the fluid. If the fillers are not taken into account, an excessive amount of grinding will lead to eventual damage to and excessive wear of the auger.
Nozzle selection is an important component of high dispense rates. Our precision nozzles have been designed with a large ID to funnel fluid to the dispense surface. Additionally, the nozzle is positively attached to the cartridge so it withstands the high pressures generated between the auger and nozzle.
Auto Weight Calibration of the Pattern
To aid in program setup, use our innovative Weight Calibrated Shapes software routine. This feature allows the operator to program a complex dispense pattern - consisting of lines, arc, dots, etc. - with as many features as required.
During pattern setup, a base pump speed is defined and the desired weight for the dispensed pattern is entered. The program is run and the system records pump starts, pump stops, and even the movement time between segments. These starts, stops, and delays are then duplicated at the weight scale. The system adjusts pump speed to attain the desired weight.
Each dispense pattern used in a program can be calibrated to a specific weight or just to a specific pattern. This feature greatly reduces the setup time and allows engineers to (1) make adjustments to the dispense pattern while maintaining the desired weight or (2) adjust the weight with the same pattern. The operator does not need to perform trial and error program adjustments to reach the desired weight.
Each of the GPD Global dispense systems can be used for the lid attach process:
Use for R&D environments where repeatability of a dispense pattern is required. Configured with a single HyFlo dispense pump to dispense one fluid at a time. (Our "Weight Calibrated Shapes" software routine is not available for the Island Series.)
The most popular platform for high volume lid attach. Each MAX Series system can be configured with two HyFlo dispense pumps and can interchange between pumps during the program. Our "Weight Calibrated Shapes" software routine allows for the quickest program setup time. Depending on process set up, an additional MAX Series system can also be used to place heat dissipators.
A great system for R&D environments - an all-in-one platform that's great for process development. This system may be configured with two HyFlo dispense pumps and a P&P head to place heat dissipators. Our "Weight Calibrated Shapes" software routine is available for quick process set up.