Product category:
PCB Assembly Equipment and Tools
News Release from: AccuPlace | Subject: HAF placement solutions
Edited by the Electronicstalk Editorial
Team on 21 March 2006
Hot designs need a stronger bond
Heat-activated film answers many of the bonding challenges posed by design miniaturisation, but its efficient placement is a further challenge in itself.
The success of today's consumer electronics stands and falls with its design and functionality Handheld devices increasingly include more features such as hard drives, radios, and digital cameras, with fancier designs incorporating mirrors, aluminium bezels, or steel name plates on the plastic housings
This article was originally published on Electronicstalk on 11 Jul 2005 at 8.00am (UK)
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And still, size is everything: the device is getting smaller and smaller, while it should become more rugged.
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Fastening, for example, is traditionally accomplished using mechanical means such rivets, welding, screws, clips etc, as well as liquid, hot-melt, and pressure-sensitive adhesives.
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Adhesives and mechanical fasteners, however, often do not offer the characteristics needed to solve today's fastening challenges such as simplicity of application, reduced preparation time and fewer process steps.
Smaller package sizes require high bonding strength where space restrictions and thickness are an issue.
Heat-activated film (HAF) answers these and other challenges, offering high bonding strength, the ability to bond different materials together (such as metal to plastic), and high temperature stability.
HAFs offer numerous benefits and advantages over other fastening methods.
They eliminate drying time and solvent issues normally related to liquid glues, epoxies, cyanoacrylates etc They replace screws, bolts and pressure-sensitive double-sided tapes often used for joining and assembly.
The films eliminate drilling, punching, crimping or clipping typically required for mechanical fastening.
HAF offers precise dimensioning - no metering errors as typically found with liquids - together with flexural strength and high bond integrity when bonding metal to plastic.
The films can replace traditional welding, soldering and riveting as fastening techniques.
In addition, the technique: renders completely clean processing - no residue or disposal problems; reduces flow or oozing compared with other thermoplastic systems; is easily die-cut into customised shapes and configurations; features excellent cold shock performance despite thin calliper; has excellent heat resistance after full cure; and is available in varying thicknesses.
Using HAF, however, presents another set of challenges: it is a rather elastic material, has no tack when cold, and needs temperatures of up to 220C for a certain time to bond.
This requires a placement mechanism that can handle fragile, nontacky materials, while offering the ability to program time, temperature, and pressure to control the bonding process.
There are two ways to meet the unique combination of requirements for this application: a fully automatic and a semi-automatic solution.
The fully automatic solution incorporates its fully automatic assembly platform APAC.
The APAC is an innovative, fast pick-and-place cell that blends a high-performance robot with adhesive component feeders for up to four components.
The programmable system can be loaded/unloaded with drawers and requires only minimal human involvement.
Multiple process stations - which heat up the target part before the HAF is placed - allow programmable dwell time for the adhesive to react.
Short cycle times are met by multiple process stations working simultaneously.
The target part is then automatically returned to its tray to cool down - this is a very safe procedure for the operator as, he/she is not forced to handle hot target parts.
Equipped with an optional vision system, the APAC fulfils the required placement accuracy for the HAF assembly of up to +/-0.013mm.
The semi-automatic solution relies on the model 3065 with bench-top configuration.
One recent application involves the placement of an HAF assembly into a MultiMediaCard (MMC) lid.
In addition to the well-established standard platform, this model uses a customised nest with heating device and a linear feeder enabling manually fed automatic operation.
The linear feeder, with integrated heater, feeds and pre-heats target parts before they enter the heated nest.
Once in the nest, the lid is automatically centred, and the HAF is placed.
The temperature of nest and pre-heater, the placement force, and the placement dwell time are all adjustable parameters, allowing complete process control.
Using the bench-top platform for stand-alone operation allows for a simple yet automated operation.
Operator responsibilities are limited to manually loading the lids and replacing rolls of heat activated film.
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