As telecommunications and information processing have exploded over the several decades, the need for extremely accurate, high-yield microchip assembly solutions has shifted from a low volume aerospace and defense industry niche to a broad, high-volume commercial market encompassing multiple industries. From palmtops to telecommunication switches, the RF-IC industry is witnessing an insatiable requirement for more and more accurate devices at ever increasing and more cost-effective production rates.
The keys to responding to this challenge are improved hardware and software to enable greater speeds without sacrificing precision, increased automation to eliminate error-prone human handling during processing, and greater integration to create a seamless, integrated assembly platform—complete process solutions coupled with agile automation.
To address these needs, an RF precision assembly machine has been developed to specifically support the RF power amplifier component assembly manufacturers. The Palomar Technologies die attach HotRail™ RFA (radio frequency assembly) cell is a fully automatic, high-accuracy (±10 µm) system that provides heat profile vs. time eutectic reflow on a single, large work area build site.
The die attach machine utilizes a general purpose optical workbench platform with command and I/O-rich programming to accommodate virtually any combination of material presentation devices for assembly automation. These component presentations include waffle pack, gel pack, tape and reel and expanded wafer configurations. Two- and four-inch waffle and gel packs may be utilized. Wafers from three to eight inch can be accommodated, with multiple wafer presentation available (1-up, 2-up, 4-up and 6-up).
Utilizing HotRail RFA technology, operators can load an entire shirt of parts at once while the component assembly system can eject and attach fragile die of materials such as Gallium Arsenide (GaAs). The HotRail high-accuracy attach process provides void-free assembly and programmable steady state phased heat control for high-yield eutectic die attach.
An advanced temperature-profiling device and method eliminates eutectic control inconsistencies common in today's die-attach methods, and provides programmability for increased yield and throughput. RF headers are conveyed through a ramped temperature gradient that gradually brings the packages to the eutectic reflow temperature. After chip placement, the packages are conveyed out of the placement area and gradually returned to ambient temperature. The system supports tightly regulated temperatures of the preheat, eutectic and cool-down zones.
The HotRail RFA enables an RF component manufacturer to achieve precision side-by-side placement of die for subsequent wire bonding of consistent wire loop profiles. Repeatable wire loop profiles are essential for meeting high frequency, RF device impedance specifications. The RF component assembly cell provides precision juxtaposition of die with steady-state heat eutectic processing, resulting in consistent wire loop bonding profiles from bond to bond.
There are many benefits derived from using the HotRail RFA. These advantages include quick and easy vacuum tool changeover for a wide range of parts and die during production. Up to eight eutectic collet or conical tip vacuum bond tools may be mounted and pre-calibrated in the bond head. Tools are changed "on the fly," speeding up assembly of multi-chip devices and eliminating the need for a space-consuming tool dock. This capability helps maximize production speed and yield over time. Careful handling of fragile parts and die is achieved via programmable force (10 to 400 grams in 1 gram increments), programmable approach speed and deceleration, and programmable over-travel (in 0.1 mil increments). This helps to maximize product yield and performance, and minimize loss due to broken or impaired parts.
Transfer and scrub parameters are programmed and the temperature is set to achi
eve optimal placement, adhesion and alloy results. The header is heated and held to a set temperature for the duration of the eutectic assembly process. Preheat mesas or HotRails are available for faster part presentation. Nitrogen cover gas is applied to the reflow area for purification of the bonding area. Each die in the assembly sequence is transferred and scrubbed into place.
The HotRail RFA eutectic die attach system provides high-precision, high-reliability placement of components to meet today's high-volume, low-cost RF assembly requirements.
The HotRail RF component assembly cell is a fully automatic assembly tool for the support of manufacturers of high frequency RF power amplifier integrated circuits. Its versatility and ease of use can lower cost and improve performance of assembling RF-IC devices.
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Jessica Sylvester
Marketing Communications
Palomar Technologies, Inc.