Investigation into Printing Miniaturized Devices

Clive Ashmore
Mark Whitmore

The electronics market is divided into many segments each having its own challenges; but one theme that connects the electronics community together is a need for higher yield with lower costs. Or simply the manufacturing process needs to become ever efficient.

Within the consumer sector miniaturisation is the watch-word and all eyes are on the 0.3mm CSP and metric 03015 components. Both of these devices will pose serious heterogeneous questions for High Volume Manufactures, especially if the current stencil thickness of 100 microns is required for standard technology.

The Automotive and Industrial electronics sector which are not normally brushed with the challenges of miniaturisation have started to become connected to this demanding world. The reason for this is not through the consumer driver of increased functionality, but one of pure supply and demand economics. The demands for large foot print devices are decreasing therefore the unit price and scarcity is increasing; whereas smaller foot print devices are increasing in demand and availability and as a consequence the unit price and scarcity is reducing. For this reason Automotive and Industrial electronic manufacturers are now faced with implementing fine pitch devices due to availability and cost.

The Automotive and Industrial electronics sector have several large obstructions when engaging with miniaturised devices: - the addition of large devices on the same product, harsh environmental concerns and safety/reliability demands. All of these issues require a highly capable heterogeneous solder paste printing process.

This paper investigates a solution the Automotive and Industrial electronics community can implement to ensure a high yield print process in which fine pitch footprint devices can be printed alongside traditional larger footprint devices.

The purpose of this paper was to answer the question, Can 0.4mm CSP devices be printed within an Automotive and Industrial assembly environment? As considered throughout this paper, the issues of printing 0.4mm CSP compatible apertures through the established 127um stencil foil thickness leads to an infringement of industry recognized Area Ratio rules. Therefore this investigation focused around the possibility of breaking these established Area Ratios with no detrimental effect on standard depositions.

The findings from this investigation are listed below:

* The results from this investigation demonstrated the ultrasonic squeegees ability to extend the print process window to include Area Ratios ≥ 0.45. This allows 225um apertures to be printed using 127um stencil foils.

* The analysis has demonstrated the 200um diameter apertures were outside the ultrasonic squeegees capability. Therefore the ability to print Area Ratio's below 0.4 is still an unknown.

* The ability to print 225um diameter apertures using 127um foil thicknesses gives the Automotive and Industrial sector the possibility of printing solder paste deposits for the 0.4mm CSP.

* The inclusion of an ultrasonic squeegee does not adversely affect the paste deposition of larger footprint devices
Therefore the ability to print 0.4mm CSP compatible apertures using incumbent material sets is possible when ultrasonic squeegee technology is employed.