August, 2018
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Aerosol Jet Printing: Dispensing Solution Continued from previous page
surrounded by a collimated sheath of nitrogen, the printer is relatively clog-free, robust and material-friend- ly. A divert function within the depo- sition head temporarily shutters material into a recyclable filter. The Aerosol Jet printing process
deposits inks with viscosities up to 1,000 cP that may include entrained solid particles up to 500 nm in diam-
tain types of component and die attach applications. Jet dispense is used for applica-
tions ranging from die bonding and underfill to LED assemblies. The technology typically has a
minimum printed feature size of greater than 10 mil (250 µm), although there have been some recent developments pushing feature sizes closer to 8 mil (200 µm). These dispense technologies support a wide array of materials that provide the highest level of manufacturing flexi- bility. Fluid dispensing is widely used for coating applications — RFI/EMI shielding in particular. Aerosol Jet printing has been
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deployed in mass production and the custom printing of sensors, anten- nas, and functional circuits onto non- planar substrates. It is being used to augment wirebond applications where pad-to-pad spacing and multi- ple stacked dice cause cross-talk. Due to its precise selective coat-
ing capability on all five sides of a package, without depositing material on critical circuitry, Aerosol Jet printing is a viable alternative to PVD and spray-coating solutions. Military and aerospace electronic manufacturing companies use Aerosol Jet for dispensing conductive epoxies. They also use it for small component and die attach and as a
method for printing underfill materi- als where component-to-component spacing is less than 4 mil (100 µm).
Specialized Applications In the case of printed sensors,
antenna and functional circuits, cus- tomers have seen significant produc- tion savings through the elimination of specialized plastic and expensive- to-maintain plating baths and facili- ties.
Direct-write antenna printing
has enabled manufactures to print batches of phone antennas, stock them on their shelves, and then print custom circuitry for specific geo- graphic markets. For stacked dice, 2 mil (50 µm) pad spacings and less
Continued on page 56
Interior of the Aerosol Jet printer.
eter. Typical formulations include nanoparticle metal inks, functional organic materials, dielectrics, poly- mers, adhesives, conductive epoxies, graphene, and carbon nanotube materials.
Printed features are created by
translating the deposition head with respect to the substrate in x, y, z, and theta (optional) using a tool path generated from a CAD design file. A distinct difference between the Aerosol Jet printing approach and other direct-write printing processes is that the Aerosol Jet process is non- contact and relies on its aerodynamic jetting to propel droplets to the sub- strate. This enables a relatively large standoff distance of approximately 0.04 to 0.2 in. (1 to 5 mm) between the deposition head and the sub- strate, allowing the deposition head to print in varying orientations on 2D and 3D substrates.
Filling the Production Gap Not all products require such
precise deposition capabilities. Like all production tools, the Aerosol Jet printer should be viewed as another capability in an arsenal of dispensing solutions used by electronic packaging and assembly manufacturers. The usefulness of screen printing, time- pressure and jet dispensing, along with other methods has been proven in high-volume manufacturing. For ultra-fine mesh and 0.8 mil
(20 µm) feature sizes, screen printing continues to be a viable electronics tool solution for electronic printing tasks that range from solder bump- ing to photomask printing. Time- pressure dispensing is excellent for depositing small features (approxi- mately 3 mil [75 µm]), with high aspect ratios, greater than 0.8 mil (20 µm), and is widely used for cer-
See at NEPCON South China, Booth 1L45
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