Parallel plate light path diagram scanning system, the parallel plate instead of four optical wedge module of optical wedge in the translation, the parallel plate according to the tilt Angle of a fixed place to produce a translation of the light beam, its biggest advantage is lower cost and using life is longer, the disadvantage is that different machining taper cone hole, the need to adjust the Angle of the parallel flat, parallel plate must be reinstalled, but due to the existence of a shock when processing, the precision of the lateral displacement is not easy to guarantee.
With the rapid development of industrial technology, micro-pores with high accuracy are applied in various industries. Their development trend is small pore size, large depth, high accuracy and wide application of materials (such as metals, ceramics, glass, polymer materials, crystals and other substances with high strength, high hardness, high toughness and high melting point). Traditional microhole processing technology mainly includes machining, electric spark, chemical corrosion, ultrasonic drilling and other technologies. These technologies have their own characteristics, but they can no longer meet the higher demand of microhole processing. FIG. 3 is the optical path diagram of the four-optical wedge scanning device. In the figure, the two large Angle optical wedges on the left can realize the translation of the incident beam, and the taper of the machining hole can be adjusted by changing the distance between them. The combination of two small Angle optical wedges on the right realizes the Angle deflection of the human beam and causes the focused spot to deviate from the optical axis of the focusing mirror. When working, the four optical wedges rely on servo motor to rotate synchronously, so that the focal spot can be scanned around the optical axis of the focusing mirror to remove the material on the circumference, and at the same time, trace feed is provided along the optical axis, finally realizing circular hole machining with different apertures, taper and depth. In order to realize the synchronous rotation of the four optical wedges and the spacing adjustment of the left two optical wedges, the device generally adopts a complex squirrel-cage structure. Edm can only process metal materials. Laser drilling has the advantages of high efficiency, small limit aperture, high accuracy, low cost and almost no material selectivity, etc. It has become one of the mainstream technologies in microhole processing.
Laser rotary cutting drilling technique
Currently the most commonly used laser drilling processing way of the galvanometer scanning, can ring cut step by step a scan or spiral scan, but the deficiency of the galvanometer scanning is inevitable taper, as shown in figure 1, in the process of making hole, because of the focused laser beam divergence and multiple reflection phenomenon, as material ablation rate which is dropped sharply with the increase of the depth of the hole. Therefore, it is difficult to prepare micropores with large depth-diameter ratio on thicker materials.
Thus, get the depth to diameter ratio (≧ 10:1), high processing quality, zero even inverted cone cone microporous is challenging, for this kind of demand, the most suitable processing method is to use rotary cutting head module, the rotary cutting head can not only make the beam around the axis rapid rotation, still can change the relative material on the surface of the light beam Angle beta, change the beta can realize from the change of the cone to zero or even inverted cone cone. Currently commonly used rotary cutting head modules are concentrated in the four-optical wedge scanning head, Dway prism scanning head and parallel plate scanning head. Their optical principles are much the same. The beam entering the focusing mirror is properly translated and tilted by optical devices, and the beam is rotated around the optical axis by relying on the rotation of high-speed motor, as shown in Figure 2.
The light path diagram of The Daoway prism scanning system. The Daoway prism is installed on a high-speed rotating hollow torque motor. The prism can rotate once to make the laser rotate twice. After collimating, the laser passes through the Angle deflection and lateral translation of the front end and then enters the Dowell prism and the adjusting optical wedge. Finally, the laser is focused to the working plane through the focusing mirror to realize the ring-cut scanning drilling. Three optical wedge through the deflection and rotating compensation dove prism of processing and assembling error, this device can realize flare 2 times the speed of rotation, avoid the effect of light quality on the quality of the hole, but the machining accuracy of the dove prism and assembly accuracy requirement is high, in subsequent campaigns compensation adjustment wedge structure is relatively complex, for mass production of the engineering application has certain limitations.
Application of rotary drilling technology in semiconductor industry
Probe card is the interface between the chip under test and the testing machine in wafer testing. It is mainly used for preliminary measurement of the electrical performance of the chip before the chip is sliced and packaged, and then for subsequent packaging engineering after the defective chips are screened out. It is very important for the development of early test and the yield assurance of late mass production test, and it is an important manufacturing process that has great influence on the manufacturing cost in wafer manufacturing process.
With the design of the chip getting smaller and densier, more and more pins are required, the spacing between adjacent tips is developed from millimeter to tens of microns, the aperture and hole spacing of the guide plate must also be correspondingly smaller and smaller, and the rectangular and irregular shape holes are also a trend. At present, the most widely used probe card in China is the cantilever beam type epoxy probe card, and the imported vertical probe card is still used for the chip test of high-end devices.
The upper cover (UD) and the lower cover (LD) of the vertical probe card guide plate. The microhole parameters of the probe guide plate are determined by the test points set by the chip design and the diameter of the probe used. Generally speaking, the processing aperture is 20-200 m, the hole spacing is 40-200 m, the thickness is 0.1-1mm, the hole wall of the hole type is required to be vertical, and the position accuracy is high. Most of the guide plates are made of ceramics and Silicon nitride (Si3N4). Silicon nitride has been more and more used in the new generation of probe CARDS. However, due to its extremely high hardness, it cannot be mechanically processed like traditional machinable ceramics, and conventional laser drilling method cannot meet the requirements.
The laser rotary cutting drilling technology solves the above problems well. It is not limited by materials, but also can process non-taper holes with high depth-diameter ratio. A large number of researches and experiments have been conducted on the processing of microholes with probe by Using the self-developed laser rotary drilling technology. At present, the processing capacity with minimum pore diameter of 25 m, depth diameter ratio ≥ 10:1, and maximum thickness up to 1mm can be achieved. Figure 7 and Figure 8 are the microphotographs of the microholes drilled by The Ino laser in Si3N4 material. In addition to round holes, square holes can be machined for some probe CARDS, the minimum size up to 35×35 m, R Angle ≦6 m, and no taper. FIG. 9 shows a 50×50 m square hole with an R Angle of about 6 m.
There is a process of Wire bonding in the semiconductor packaging industry. The technology of connecting the chip and lead frame with metal wires with a diameter of 15-50 m enables the tiny chip to communicate with the outside circuit without adding too much area. And joint way is divided into wedge-shaped joint and spherical joint, made the needle is mainly used for wedge joint, can let the wire through the among them, like the needle sewing machine, wire rod through the on line the machine needle mouth, wear a needle mouth in the wires on the chip end after down to complete the first solder, wire rod will be the base board connections on the chip, robotic arms line will lead to rising needle mouth, then wire to the solder joints, cutting down while wire, complete a cycle, and then continue to the next cycle of joint offense, as shown in figure 10.