Wire bonding method and device therefor

[Detailed Description of the Invention]

[Field of the Invention] The present invention relates to bonding art, is applied to the wirebonding process especially in the assembly of a semiconductor device, and is made into effective art in between.

[Background of the Invention] The wirebonding method is known as one of the means which attains the electrical link of the electrode of a pellet, and an external terminal. As a junction method by this wirebonding method, the - bonding-by thermo-compression method and the supersonic method are known. Although the former adds load under a heating state about 300 degreeC and junction to the end of a wire and an electrode is performed, since high temperature service is needed, we are anxious about the influence of the products on a pellet etc. On the other hand, although ultrasonic energy is impressed and it joins under the usual temperature conditions, the latter method needs directivity for bonding, and since the quality of the material of a wire will also be limited to things, such as aluminum (A.I. Artificial Intelligence), it cannot perform flexible Ponding. In view of the above-mentioned point, what is called a thermostat Sonic Ponding method that uses together thermo compression bonding and an ultrasonic wave can be considered. At the time of press-fit, with predetermined load, this thermosonic bonding method impresses supersonic vibration continuously, and attains junction to a wire and an electrode. Since heating and load can be low pressed down rather than the bonding-by thermo-compression method, while being able to prevent influence on a product, it has the advantage that flexibility is expectable rather than an supersonic method. However, also in the above-mentioned art, since the high temperature service about 200 degreeC was required as welding temperature conditions, as for fear of heat destruction of a product, in addition, a certain thing was clarified by this artificer. By the way, in the above-mentioned art, although low-temperature-izing temperature conditions further was also considered, in such a case, poor bonding was produced and it was further shown clearly by this artificer that there was a possibility that junction Confidence may fall on the contrary. As an example described in more detail as art of the wirebonding method explained above, they are Kogyo Chosakai Publishing Co., Ltd. and January 15, 1980 issue "rC-ized mounting technology" (Japanese microelectronics association i). There is PLQL~P103.

[Objects of the Invention] The object of the present invention is to provide the wirebonding art in which Confidence is high. The above of the present invention, and the other objects and the new feature will become clear from description and the accompanying drawing of this specification.

[Summary of the Invention] It will be as follows if the outline of a typical thing is briefly explained among the inventions indicated in this application. Namely, the thing for which the load and supersonic vibration for junction are impressed and are performed after impressing the supersonic vibration for sanctifying a bonded surface with load in junction on the Ponding part of at least 1 side, and a wire for a predetermined period, Since a bonded surface can be sanctified by impression of supersonic vibration in advance of impression with the load for junction, and supersonic vibration, junction intensity can be raised under a low-temperature condition, and wirebonding with high junction Chivalrous can be performed. It carries out and is Example]. schematic diagram and Drawing 2 +a+ which shows the wire bonding apparatus whose Drawing 1 is one example of the present invention -- and (bl is an explanatory view explaining the load of this example, and the relation of supersonic vibration.) Wire bonding apparatus 1 of this example is for connecting Vered's 2 pad 3, and inner lead 4a of leadframe 4, for example. It has XY table 6 and bonding stage 7 in which bonding head 5 as drive mechanism was carried. After heat block 9 which can move up and down has installed heater 10 according to cam mechanism 8, it is attached to bonding stage 7, and leadframe 4 held on the surface of heat block 9 is heated by predetermined temperature conditions. Leadframe 4 has structure fixed after having been pinched by lead control 11 attached to the upper part of the above-mentioned heat block 9 and Pounding stage 7. The above-mentioned cam mechanism 8 has structure as for which concave ' Rolling motion carries out for every predetermined Ponding cycle through pulley 33 and belt 34 which were provided in XY table 6 and which moves heat block 9 up and down. On the other hand, up-and-down motion block 21 is attached to the inside of bonding head 5 by guiding shaft 22 provided perpendicularly, enabling free rise and fall. Besides, rotational movement of servo motor 23 fixed to Ponding head 5 is carried out to the side piece of downward moving block 21 in the pole changed into the straight-line motion of the up-and-down direction, and mechanism 24 is established, Up-and-down motion block 21 is moved in the up-and-down direction only in the specified quantity with the operation of servo motor 23. In the lead Ritsuko side, Ponding arm 25 which can rotate freely is attached to up-and-down motion block 21 focusing on axis of rotation 24. The one end side of this bonding arm 25 is energized up by voice coil motor 26 attached to up-and-down motion block 21, and it is constituted so that counterclockwise rotation power may act on Ponding arm 25 by the operation of this voice coil motor 26. Ultrasonic horn 28 connected to ultrasonic oscillation part 27 is attached to the other end side of above-mentioned Ponding arm 25, Capillary 29 as a bonding tool is attached at the tip of this ultrasonic horn 28 almost perpendicularly to ultrasonic horn 28, Wire 31 looped around wire spool 30 is inserted in this capillary 29 where an end is made to project from the tip of capillary 29. The above-mentioned voice coil motor 26 and ultrasonic oscillation part 27 are independently controlled by control part 32 in the operation, respectively. Next, the operation of this example is explained. First, when leadframe 4 in the state where pellet 2 was attached on heat block 9 of Pounding stage 7 is supplied, pulley 33 of XY table 6 rotates, and this torque is transmitted with belt 34 and makes cam mechanism 8 of bonding stage 7 drive. Leadframe 4 is fixed in the state of heat block 9 going up with the drive of this cam mechanism 8, and pinching between lead control 11. Next, the lower end part of capillary 29 is positioned right above predetermined pad 3 of pellet 2 by moving XY table 6 suitably. at this time, from the tip part of capillary 29, the end of wire 31 is in the state where only predetermined length projected and was carried out, it is heated on the electric discharge torch which this end does not illustrate, and a fusion ball is formed. Next, up-and-down motion block 21 is moved below, capillary 29 descends, and it lands on band 3 of pellet 2. While voice coil motor 26 starts an operation by control of control part 32 here and impression of load g of a predetermined value, for example, the load about 60g / a+I, is started at the tip of capillary 29, Ultrasonic oscillation part 27 operates, ultrasonic hoe 728 is transmitted to supersonic vibration omega, and it carries out the oscillating operation of the tip of capillary 29. while in this oscillating operation supersonic vibration omega declines for a predetermined period TI, for example, after being carried out about 5 ms, load g is raised by a predetermined value, for example, 100g / cal grade, -- predetermined time T2 -- for example, m Continuing is carried out about [ 30 m ] five, and it is impressed (2nd [ The ] figure ial, (bl).) Thus, the above-mentioned ball portion is pressed by pad 3 of pellet 2, and the first bonding is completed. Thus, since pad 3 of pellet 2 which is a joined part by impressing supersonic vibration omega between Tl(s) for a predetermined period with impression of load g first can be sanctified, Moreover, the load impression time T2 can attain bonding with high junction intensity with a short time by little [ after that ] load. Control of load g by System ?111 copy 32 and supersonic vibration omega is faced, When it is besides the above, as it is shown in Drawing 2 of Midnight ('b), impression of load g is also started, for example with the value of about 60 g/cn with impression of supersonic vibration omega for purifying a bonded surface, while attenuating supersonic vibration omega after progress of T3 for a predetermined period -- impression of load g -- 60 g/c -- control of maintaining about four may be performed and junction may be ml(ed) between T4 for a predetermined period. In such control, since a bonded surface is sanctified among T3 of the first stage, wirebonding with high junction reliability becomes possible, without junction intensity falling, even if it makes load value g lower than the example shown in Drawing 2 in T4. Thus, according to this example, in the first bonding, impression of the load in low thrust and short-time supersonic vibration perform wirebonding. Therefore, modification of the wire shape by thrust or supersonic vibration power can be suppressed small as much as possible, and wirebonding can be performed by few bonded surface products. As a result, a band can be miniaturized and the miniaturization of a pellet and high integration of a semiconductor device can be promoted. Right above the predetermined region of inner lead 4a which is a Ponding part of leadframe 4, it is moved after the first above-mentioned Ponding, capillary 29 sending out wire 31 from the tip by horizontal movement of XY table 6, while up-and-down motion block 21 goes up. Next, up-and-down motion block 21 is moved below again, and capillary 29 holding wire 31 lands on the predetermined region of inner lead 4a. The same control as the time of the first above-mentioned bonding is performed by the control part here, and the end of another side of wire 31 is joined by the predetermined region of inner lead 4a. At the time of this second bonding, supersonic vibration is continued for a predetermined period by the above-mentioned capillary with impression of load, and also supersonic vibration declines, only impression of load is continued, and junction is performed. Thus, also in the second bonding by the side of a leadframe, the surface of inner lead 4a which is a joined part can be sanctified by impressing supersonic vibration first with impression of load. Therefore, bonding with high junction intensity can be attained by press by subsequent load. When using the wire of a copper system in which an oxide film is especially easy to be formed on the surface of a wire, by impression of the above-mentioned supersonic vibration, an oxide film can be removed and sanctification on the surface of a joined part by the side of a wire can also be attained. Since Ponding can be performed even if it is impression of the load in low thrust, crushing of the cross direction of the wire by thrust can be suppressed small, and wirebonding can be performed in little width area. As a result, an inner lead can be miniaturized and it also becomes possible to promote many pin-ization of a package. In a passage clear from having mentioned above performing wirebonding in the present invention, a wire and a wirebonding side are cleaned according to supersonic vibration power. Therefore, the second process of performing wirebonding is performed after the first process of removing deleterious material which bars an oxide film and wirebonding. Therefore, the supersonic vibration and impression load in the first process should just be sufficient impression power required for cleaning and impression time of a wire and a wirebonding side. The second process performs wirebonding after cleaning of a wire and a Ponding-ed side. Therefore, impression of load required for junction to the wire in the state where it was cleaned, and a wirebonding side, and sufficient, and supersonic vibration is enough. Therefore, in the second process, where supersonic vibration impression is decreased or stopped only by load impression, wirebonding can be performed. What load in the second process is enlarged and promotion of junction mechanisms, such as metal diffusion with the wire of a bonded surface and Ponding-ed material, is aimed at for rather than the load in the first process, Wirebonding is performed where junction shape is made small as much as possible as almost the same as that of the load of the first process and the second process, wirebonding can be performed, where it made load in the second process small and junction shape is made smaller than the first process as much as possible -- so Thermostat compression (TC) Ponding which performs thermo-compression-bonding wirebonding without impressing the conventional supersonic vibration, If it is considered as about load 130g and impression time compares from what was about 5 Qmsec, the impression load in the present invention being load as small as 100g or less and impression time will also turn into about 35m5 ec and a short time. On the other hand, it compares with load 60 Sonic [ to which the load of about g and impression time 60 m5ec is applied / thermostat ] (TS) Ponding which performs wirebonding, impressing the conventional supersonic vibration, The present invention can perform wirebonding by short-time supersonic vibration time and short-time load impression time.

[Effect] After the first process of impressing the supersonic vibration for sanctifying a bonded surface with load in junction on (1), the Ponding part of at least 1 side, and a wire for a predetermined period, It is what performs wirebonding according to the second process of impressing supersonic vibration smaller than impression and the first process of the load for junction, Since ' sanctification of a bonded surface can be done by impression of supersonic vibration in advance of impression of the load for junction, junction intensity can be raised under a low-temperature condition, and wirebonding with high junction Faithfulness can be performed. With (2) and the above (1), since the amount of impression of load can be lessened, the bonded surface product at the time of junction can be made small. With (3) and the above (2), Bud and an internal electrode can be miniaturized and high integration of a semiconductor device can be promoted. With (4) and the above (1), since the amount of impression of load can be lessened, damage to Vered and an internal electrode can be prevented. Although the invention made by this artificer above was concretely explained based on the example, it cannot be overemphasized that it can change variously in the range which the present invention is not limited to the above-mentioned example, and does not deviate from the gist. For example, although the example explained only the case where a bonding member was provided in the state of a leadframe, it may be provided not only in the state of this but in the state of a package board. Although the operation of the example explained only the case where impression of supersonic vibration was attenuated with impression of load, load may be impressed where impression of supersonic vibration is stopped. When the bonding in the part of the both sides of the Vered and internal electrode side was followed, zeta Hold it explanation of supersonic vibration and the independent control of impression of load was given, but it may control by an example either only at the time of the bonding in a side.

[Application of the Invention] Although the above explanation explained the case where it applied to the wire bonding apparatus which performs inter-electrode wire connection of what is called a semiconductor device which is the use field about the invention made by this artificer as a king, It is effective art even if it applies to other wire bonding apparatus instead of what is limited to this.

[Brief Description of the Drawings]

Drawings 1 are a schematic diagram showing the wire bonding apparatus which is one example of the present invention, and Drawing 2 (al (bl and Drawing 3 [a) and [bl are the explanatory views explaining the load of an example, and the relation of supersonic vibration.).