Unlocking The Mystery of Aperture Architecture for Fine Line Printing
This paper covers issues of printing for challenging area ratio components and their associated aspect ratio will be investigated.
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Authored By:
Clive Ashmore
ASM Assembly Systems
Summary
The art of screen printing solder paste for the surface mount community has been discussed and presented for several decades. However, the impending introduction of passive Metric 0201 devices has reopened the need to re-evaluate the printing process and the influence of stencil architecture.
The impact of introducing apertures with architectural dimensions' sub 150um whilst accommodating the requirements of the standard suite of surface mount connectors, passives and integrated circuits will require a greater knowledge of the solder paste printing process.
The dilemma of including the next generation of surface mount devices into this new heterogeneous environment will create area ratio challenges that fall below today's 0.5 threshold. Within this paper the issues of printing challenging area ratio and their associated aspect ratio will be investigated. The findings will be considered against the next generation of surface mount devices.
Conclusions
The findings from this investigation have discovered the following:
The smallest area ratio which can be printed is 0.4.
The aspect ratio has an impact on the Cp value of the print deposition.
An aspect ratio value of 1.6-1.8 produces the most repeatable solder paste deposit.
The findings have recognised that an interaction between both the horizontal/vertical wall surface area and the aperture opening area exists.
M03015 solution with 80um stencil thickness = 180um x 100um (Area Ratio 0.4 and Aspect Ratio 1.8) - Tested
M0201 solution with 60um stencil thickness = 135um x 75um (Area Ratio 0.4 and Aspect Ratio 1.8) - Theoretical
Initially Published in the IPC Proceedings
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