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Process Optimization for Fine Feature Solder Paste Dispensing
Process Optimization for Fine Feature Solder Paste Dispensing
In this paper the authors evaluate variables in the solder paste dispensing process, and review the impact on dispense quality of the solder paste.
Production Floor

Authored By:
Maria Durham, Greg Wade, and Brandon Judd
Indium Corporation

ohn Boggiatto
ITW EAE - Speedline Technologies
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Summary
With the rapid trend towards miniaturization in surface mount and MEMs lid-attach technology, it is becoming increasingly challenging to dispense solder paste in ultra-fine dot applications such as those involving chip capacitors or BGA packages, as well as dispensing ultra-fine lines in MEMs lid-attach applications. In order to achieve ultra-fine dots and fine line widths while dispensing solder paste, both the solder material and dispensing equipment need to be optimized. Optimizing the equipment can be very challenging, as there are many input variables that can affect the dispense quality of the solder paste. In this paper we will evaluate the many equipment variables involved in the solder paste dispensing process, and the impact these variables have on the dispense quality of the solder paste.
Conclusions
While the changes exhibited in the graphs show a definite trend, the changes are relatively small in many cases. In this testing, we intentionally changed only one parameter at a time. Had multiple settings been changed, the effect on line width and dot size would have potentially been greater. In this test, only one board of each parameter was tested. More extensive testing would involve significantly more samples to be produced to ensure the process is repeatable and consistent.

The RPM parameter did not have a significant change on the final measured line width or dot diameter when all other variables are kept constant. This parameter would have had a more significant impact if line width/dot size was changed in conjunction with it. The supplied pressure also did not have a significant impact on the final measured line width or dot diameter when all other variables are kept constant. If the pressure was increased further, a clog would have occurred as too much paste would be forced into the auger and through the fine gauge needle. This had been seen in other testing.

Dispense height had more of an effect on the fine measured line or dot diameter. As the dispense height increased, the dot quality/repeatability or line quality decreased because the further away from the surface of the board the needle is, the harder it is for the paste to create a repeatable dot or line. The dot size or line width input parameter had the greatest impact on the final measured line width or dot diameter, but if too small a number or too large a number is used without changing any other parameters, there will not be a consistent dot or line.

The other aspect of this paper shows that with hardware technology, the optimal settings for one type of mechanism are not necessarily the same for another. The results for this testing show that having the correct combination of parameters such as the hardware technology, the RPM, the supplied pressure, the dispense height, and the line width or dot size is critical in producing an ultra-fine and consistent line or dot in applications such as those involving chip capacitors or BGA packages, or MEMs lid-attach applications.
Initially Published in the IPC Proceedings
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