ULTRASONIC ‘FLIP’ CHIP BONDER

Claiming to be the only one of its kind in Europe manufac- tured on a commercial basis, an ultrasonic ‘flip’ chip and beam lead bonder is now available from Micromatic of Dorset .

The bonder manufactured by this recently established com- pany is designed specifically for bonding microcircuit chips on to a substrate thus providing the external connections to the circuits within the chip. Until now, such machines have only been available from the USA.

Operating with standard, pulsed ultrasonic welding techniques, the bonder will accept substrates upto 5 x loin and chips containing as many pads (or, conducting areas for external connections) as desired (the maximum number of pads avail- able on a chip is at present about 30). With an optional Sweeping Frequency or Self Tuner frequency control device, the ‘flip’ chip bonder welds at 6OkHz (the Sweep Frequency option sweeps through 500Hz either side of the resonant frequency). Pulse duration is variable from lms75s and welding pressures, though related to the pulse duration, are variable between lOO-Zkg.

Normal chip bonding practice involves 2 bonds per pad and with commercial microcircuit chips containing some 30 pads this produces 60 bonds, each with the possibility of failure. With the Micromatic bonder, however, a 30 pad chip can be bonded in one operation, thus saving time, labour, and increasing the reliability. Micromatic claim that even if the chip is found to be faulty it can be removed, leaving the aluminium pads intact whereupon a replacement chip can be bonded on immediately. The yield strength of the bonds is said to approach that of the aluminium used.

Constructed of high stability alloy casting the ‘flip’ chip bonder has a semi-automatic operation and is fitted with a Bausch and Lomb Stereo Zoom microscope. The bonder is illustrated in Fig 2.

Micromatic, Stone Lane Industrial Estate, Wimbourne, Dorset, England

Fig 2 The ‘flip’ chip bonder shown prior to recent modifications in the optical system

ULTRASONIC VAPOUR DEGREASERS

The established range of Radyne ultrasonic aqueous cleaning equipments has been supplemented recently by a series of units employing hydrocarbon solvents (see Fig 3).

Fig 3 One of a new series of ultrasonic vapour degreasers

Fig 4 Schematic representation of the %-stage operation of the vapour degreaser

The cleaning procedure is based on a S-stage operation (see Fig 3). Items to be cleaned are suspended initially in solvent vapour where condensation rinsing occurs and the contami- nant is dissolved.off. Gn transferring to a cooled solvent sump fitted with ultrasonic transducers, cavitation scrubbing removes particular matter. Withdrawing the cleaned articles from the ultrasonic bath involves a second pass through the solvent vapour where excess liquid solvent is flash vapourized off, so drying the suspended items.

The solvent is continuously re-distilled by condensing coils and clean solvent replenishes the ultrasonic sump. The con- densing coils prevent the solvent vapour from escaping and thus reduce solvent loss to a minimum.

Manufactured from stainless steel, the new series of degrea- sers (series UVD2) covers a range of sump capacities of 4.5,6.5 and 20gal. Operating at a nominal frequency of 2OkHz, the ultrasonic generators provide 300,600 and 1OOOW respectively.

I&dyne Ltd, Wokingham, Berkshire, England

ULTRASONICS April 1969 91