JP2010045160A - Die bonder and bonding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a die bonder and a bonding method can prevent the occurrence of a void to provide an accurate bonding by removing the impurity causing the occurrence of the void. <P>SOLUTION: The die bonder picks up a chip 22 by a collet at the pickup position to bond the chip 22 held by the collet to a substrate 23 at the bonding position. The chip is passed through an impurity removal atmosphere when transferred from the pickup position to the bonding position. After the removal of the impurity S attached to the chip 22 to cause the occurrence of the void, the bonding is conducted with the state of the impurity S removed by an impurity removal means 35 maintained. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a die bonder and a bonding method.

  The die bonder picks up a chip (semiconductor chip) with a collet at a pickup position and bonds the chip to a substrate heated at a bonding position.

  In general, a semiconductor chip is formed by forming a large number of semiconductor elements on a silicon wafer or the like, and then sticking the wafer on which the large number of semiconductor elements are formed to an adhesive sheet, and cutting and separating the semiconductor elements by dicing, A large number of semiconductor chips are manufactured. Then, with the adhesive sheet extended in the radial direction to widen the space between the semiconductor chips, the peripheral portion of the adhesive sheet is fixed to a metal ring, and the semiconductor chip is picked up from the adhesive sheet by adsorbing it with an adsorption nozzle. Then, it is transferred to a substrate position such as a lead frame and bonded to the substrate.

  When bonding a chip having an adhesive layer on the back surface of silicon, it is necessary to heat a substrate such as a lead frame. And the chip | tip currently hold | maintained at the collet was pressed by applying a predetermined load for a predetermined time, and required joining strength was obtained.

  That is, when the operation is started, the collet 1 (see FIG. 6) moves to the pip-up position and receives the chip 2 as shown in FIG. Thereafter, the chip 2 transferred to the bonding position on the substrate 3 is bonded at this bonding position. The substrate 3 is heated by a heating means such as a heater rail 4, and the chip 2 is mounted on the heated substrate 3.

  By the way, as shown in FIG. 7A, the solder 5 is applied to the island 3a for bonding the chip 2 of the lead frame 3, and the solder 5 is heated by the heater rail 4 or the like. If the collet 1 is brought closer to the solder 5 in this state, the back surface of the chip 2 is heated.

  Thus, when the back surface of the chip 2 is heated, the impurities S adhering to the back surface and the like of the chip 2 are vaporized by the heat of the solder 5, and as shown in FIG. Void 6 occurs between the two. That is, when the adsorbed gas, moisture and impurities on the back surface of the chip come into contact with the melt-formed solder, the adsorbed gas expands due to the heat of the solder, starts to melt, vaporizes, and is trapped between the chip 2 and the solder 5.

  Further, after bringing the solder 5 and the chip 2 into contact, as shown in FIG. 7C, the lowering of the collet 1 is temporarily stopped, and a scrubbing operation (operations such as vertical, horizontal, and oblique methods on a plane) is performed. To do. As a result, solder is applied to the back surface of the chip 2. However, even if the scrubbing operation is performed, the generated void 6 is not removed. After the scrubbing operation is completed, the collet 1 is lowered to a predetermined height as shown by the arrow in FIG. Thereafter, the collet 1 is raised as shown in FIG.

  As described above, when the void 6 is formed, there is a problem that the adhesiveness is inferior, the thermal resistance, the electrical resistance, etc. are increased, and the bonding quality is deteriorated. Therefore, there has conventionally been a technique for avoiding such a problem due to the occurrence of the void 6 (Patent Document 1 and Patent Document 2).

  In the thing of patent document 1, when a void generate | occur | produces between die | dye center parts and a board | substrate, the mutual contact part of a die | dye (semiconductor chip) and a board | substrate moves to the edge of a die | dye (semiconductor chip) in order. Follow and drive out. The device described in Patent Document 2 also excludes the air interposed between the semiconductor chip and the substrate in the outward direction.

Furthermore, there is a conventional technique that removes a solder oxide film generated on a solder surface (Patent Document 3). That is, in the device described in Patent Document 3, the solder oxide film breaking brush is vibrated in contact with the solder layer to break the solder oxide film formed on the surface of the solder layer in advance, and then the semiconductor chip is formed on the solder layer. On the other hand, it is soldered.
JP 2006-165188 A JP 2006-303151 A Japanese Patent Laid-Open No. 5-109790

  However, those described in Patent Document 1 and Patent Document 2 are intended to eliminate the void when the void is generated. That is, it does not prevent the generation of voids. For this reason, there is a possibility that the generated void cannot be completely eliminated.

  In the device described in Patent Document 3, soldering can be performed with good adhesion by destroying the solder oxide film. For this reason, the generation of voids itself is not prevented.

  In view of the above problems, the present invention provides a die bonder and a bonding method capable of preventing the generation of voids and removing high quality bonding by removing impurities that cause voids.

  The die bonder of the present invention picks up a chip with a collet at the pick-up position, conveys the collet to the bonding position, and attaches the chip adsorbed to the collet to the substrate at the bonding position. Then, an impurity removing unit that removes impurities that cause voids during transportation from the pickup position to the bonding position is provided, and bonding is performed with the impurities removed by the impurity removing unit.

  According to the die bonder of the present invention, the impurities that cause voids can be removed by the impurity removing means during conveyance from the pickup position to the bonding position. Moreover, bonding is performed in a state where impurities are removed by the impurity removing means. By the way, when impurities are attached to the chip, the impurities are vaporized by the heat of the solder and are generated as bubbles (voids) between the solder and the chip. For this reason, voids are eliminated or reduced by removing impurities that cause voids as in the present invention. Here, the impurities are moisture, organic matter, and the like.

  The impurity removing means may be high-temperature gas blowing for blowing a high-temperature gas to the chip, high-temperature heating for heating the chip, high-temperature gas blowing for blowing high-temperature gas to the chip, and high-temperature heating for heating the chip. May be.

  In the case of high-temperature gas blow, impurities can be blown off from the chip by blowing high-temperature gas. In the case of high-temperature heating, impurities are vaporized by heating. In this manner, the chip is heated regardless of high-temperature gas blowing or high-temperature heating, and the wetting of the chip with respect to solder can be improved.

  The impurity removing means may be plasma cleaning that irradiates the chip with plasma gas. In the plasma cleaning, for example, an inert gas such as argon gas is used as a plasma discharge gas. In such plasma cleaning, a part of argon gas is ionized, and argon gas molecules, ionized Ar + and negative electrons move intensely at high speed. For this reason, an argon gas molecule etc. collide with a chip | tip and an impurity can be removed.

  Impurity removing means can be provided on the heater rail constituting the substrate heating means and transport means. Thus, by providing the heater rail with the impurity removal means, the impurity removal by the impurity removal means can be performed in the vicinity of the bonding position, and the impurity removal state can be stably maintained during bonding.

  The bonding method of the present invention is a bonding method in which a chip is picked up by a collet at a pickup position, and a chip held by the collet is bonded to a substrate at the bonding position. During the chip conveyance from the pickup position to the bonding position. Then, after passing through an impurity removal atmosphere to remove impurities that adhere to the chip and cause voids, bonding is performed while maintaining the state where the impurities are removed.

  According to the bonding method of the present invention, it is possible to pass through the impurity removal atmosphere during chip conveyance from the pickup position to the bonding position. Thereby, impurities adhering to the chip can be removed. Further, in the case of bonding, the bonding can be performed with impurities removed.

  In the present invention, impurities that cause voids can be removed, and voids are eliminated or reduced. For this reason, it is possible to prevent the occurrence of defects such as a decrease in bonding force due to voids and chipping of chips, and high-quality bonding can be performed.

  Impurities can be stably removed regardless of whether the impurity removal means is high-temperature gas blow or high-temperature heating, and in particular, the combined use of high-temperature gas blow and high-temperature heating can provide a more stable impurity removal function. . In addition, the chip can be warmed, the chip can be improved with respect to solder, the generation of voids can be suppressed, and the voids can be released to the outside even if the voids are generated. In addition, since the chip is in a heated state, the bonding property with the solder is excellent. Further, when the impurity removing means is plasma cleaning, it is possible to further improve the wetting of the chip, and to improve the reliability of the void generation preventing function.

  By providing the impurity removal means on the heater rail, the impurity removal state maintenance at the time of bonding is stabilized, and the void generation preventing function is stabilized.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. The die bonder according to the present invention pips up a chip 22 cut out from a wafer and transfers (mounts) it onto an island 23a of a substrate 23 such as a lead frame. The wafer is adhered onto a wafer sheet stretched on a metal ring (wafer ring), and is divided (divided) into a large number of chips 22 by a dicing process. A solder 45 is applied on the island 23a.

  The board | substrate 23 is arrange | positioned and conveyed on the heater rail 24 provided with the heating means. That is, the heater rail constitutes a heating unit and a conveying unit for the substrate 23. The heater rail 24 includes a placement surface 30 on which the substrate 23 is placed, and guide walls 31 and 32 disposed on both sides of the placement surface 30.

  Impurity removing means 35 is disposed on one guide wall 31 side of the mounting surface 30. As shown in FIG. 2A, the impurity removing unit 35 is configured by high temperature gas blowing that blows high temperature gas onto the chip 22. That is, an impurity removing portion 36 is provided on one guide wall 31 side of the mounting surface 30 of the heater rail 24, and a high-temperature gas passage 38 having a gas ejection port 37 opening in the impurity removing portion 36 is provided in the heater rail 24. ing. The high temperature gas G is an inert gas such as nitrogen gas or a reducing gas obtained by adding hydrogen to the inert gas. A gas supply source (not shown) is connected to the hot gas passage 38. Here, the impurities are moisture, organic matter, and the like.

  This die bonder includes a collet (adsorption collet) 21 (see FIG. 3). As shown in FIG. 1, the collet 21 is moved upward in the direction of the arrow A1 on the pickup position P, and obliquely upward in the direction of the arrow B1 in the state of being raised in the direction of the arrow A1, as shown in FIG. Ascending, horizontally moving in the direction of the arrow C1 in the state of rising in the direction of the arrow B1, in the state of moving horizontally in the direction of the arrow C1, descending obliquely downward in the direction of the arrow D1, and in the state of falling in the direction of the arrow D1 Lowering in the direction of arrow E1 is possible. Conversely, the arrow E2 rises in the direction of the arrow E1, the arrow D2 rises obliquely upward in the state of the arrow E2, and the arrow C2 rises in the direction of the arrow D2. The horizontal movement of the direction, the downward movement of the arrow B2 in the state of horizontal movement in the direction of the arrow C2, and the downward movement of the arrow A2 in the state of movement in the direction of the arrow B2 are possible.

  That is, it is possible to carry the collet 21 from the pickup position P to the impurity removal unit 36 and to carry the collet 21 from the impurity removal unit 36 to the pickup position P.

  Further, as shown in FIG. 2A, the collet 21 is moved upward and downward in the direction of the arrow F1 on the impurity removing portion 36, and the arrow between the impurity removing portion 36 and the bonding position Q. The reciprocation in the G1 and G2 directions, the lowering in the arrow H1 direction and the rising in the arrow H2 direction at the bonding position Q are possible. That is, the collet 21 can be transported from the impurity removing unit 36 to the bonding position Q and the collet 21 can be transported from the bonding position Q to the impurity removing unit 36.

  In the moving mechanism, movement in the direction of each arrow is controlled by a control unit configured by, for example, a microcomputer. In addition, as a moving mechanism, it can comprise with various mechanisms, such as a cylinder mechanism, a ball screw mechanism, and a motor linear mechanism.

  The suction collet 21 includes a head having a suction hole opened on the lower surface thereof, and the chip 22 is vacuum-sucked through the suction hole, and the chip 22 is suctioned to the lower end surface (tip surface) of the head. When this vacuum suction (evacuation) is released, the chip 22 is detached from the head.

  Next, a bonding method using the die bonder configured as described above will be described. First, a wafer divided (divided) into a large number of chips 22 is placed on, for example, an XYθ table, and push-up means having push-up pins are placed on the XYθ table. That is, the chip 22 to be picked up is pushed up from below by the pushing-up means, and is easily peeled off from the adhesive sheet. In this state, the chip 22 is adsorbed to the adsorbing collet 21 that has been lowered.

  The collet 21 that has adsorbed the chip 22 moves as indicated by an arrow A1, an arrow B1, an arrow C1, an arrow D1, and an arrow E1. As a result, the chip 22 can be disposed on the impurity removal portion 36 as shown in FIG.

Here, as shown to Fig.3 (a), the hot gas which has the gas outlet 37 of the channel | path 38 for hot gas is ejected. Thereby, impurities can be blown off from the chip 22. That is, when the high temperature gas is ejected from the gas ejection port 37, as shown in FIG. 3B, the impurity S is vaporized and can be blown off from the chip 22 (particularly the back surface of the chip) as indicated by an arrow X.

  After that, the chip 22 arranged on the impurity removing unit 36 transports the collet 21 as indicated by arrows F1 and G1 in FIG. 2A and positions it on the bonding position Q, and then moves the collet 21 to the arrow. Lower in the H1 direction. That is, as shown in FIGS. 3C, 3 </ b> D, and 3 </ b> E, the chip 22 is lowered and placed on the solder 45 of the substrate 23. Thereafter, the solder is lowered to a predetermined position, and the bonding operation is finished or a scrubbing operation is performed so that the solder 45 is applied to the back surface of the chip. After the scrubbing operation, as shown in FIG. 3 (f), the collet 21 is lowered to a predetermined position, thereby completing the bonding operation. This bonding operation is performed with the impurities removed by the impurity removing means 35. Thereafter, as shown in FIG. 7 (e), the collet 1 is raised to a collet standby state. The collet standby state is a state where the next chip 22 can be transported from the pickup position to the bonding position.

  In the present invention, the impurities that cause voids can be removed by the impurity removing means 35 during the conveyance from the pickup position P to the bonding position Q, and voids are eliminated or reduced. For this reason, it is possible to prevent the occurrence of problems such as a decrease in bonding quality due to an increase in thermal resistance, electrical resistance, etc., and high-quality bonding can be performed.

  Since the impurity removal means 35 is high-temperature gas blow, impurities can be removed stably and stable bonding can be performed. By providing the impurity removal means 35 on the heater rail 24, the impurity removal by the impurity removal means 35 can be performed in the vicinity of the bonding position. During the bonding, the impurity removal state is stably maintained and the void generation preventing function is stable. .

  The impurity removing means 35 may be high-temperature heating that heats the chip 22 as shown in FIG. In this case, a heating means such as the heater 40 may be embedded in the impurity removal unit 36. That is, instead of the steps shown in FIGS. 3A and 3B, the steps shown in FIGS. 4A and 4B are performed. The collet 21 is lowered on the impurity removing portion 36 and the chip 22 is moved to the heater 40. Are brought into contact with or close to each other. Thereby, the impurities S adhering to the back surface of the chip 22 are vaporized by heating the chip 22 of the heater 40. For this reason, impurities are removed from the back surface of the chip 22, and then the steps of FIGS. 3C, 3D, 3E, and 3F are performed.

  As described above, even when the heating is performed at a high temperature, as shown in FIG. 4B, the impurities S are vaporized by the heating, and the impurities S can be removed. Thereby, stable bonding can be performed.

  Further, the impurity removing means 35 may be a high temperature gas blow for blowing a high temperature gas to the chip 22 and a high temperature heating for heating the chip 22. That is, a combination of high temperature gas blowing and high temperature heating may be used. In this case, for example, the heater 40 shown in FIG. 2B is provided with a high-temperature gas passage 38 (connected to a gas supply source) having a gas outlet 37 as shown in FIG. That's fine.

  In this case, first, when arranged on the impurity removing unit 36, as shown in FIG. 2A, high-temperature gas blowing is performed to inject a high-temperature gas to vaporize impurities and blow off the vaporized substance. As shown in 2 (b), the heater 40 is brought into contact with or close to the heater 40. As a result, the impurities S that have not been blown away by the high-temperature gas blow can be vaporized and removed. Further, after removing impurities by this high temperature heating, high temperature gas blowing may be performed when separating from the impurity removing portion 36.

  Thus, if a high temperature gas blow and high temperature heating are used together, a more stable impurity removal function can be exhibited. The chip 22 can be warmed only by high temperature gas blowing, only high temperature heating, or a combination of high temperature gas blowing and high temperature heating. For this reason, it is possible to improve the wetting of the chip 22 with respect to the solder, to suppress the generation of voids, and to release the voids to the outside even if the voids are generated. Moreover, since the chip 22 is in a heated state, the bonding property with the solder is excellent.

  The impurity removing means 35 may be plasma cleaning that irradiates the chip 22 with plasma gas. In the plasma cleaning, for example, an inert gas such as argon gas is used as a plasma discharge gas. In such plasma cleaning, a part of argon gas is ionized, and argon gas molecules, ionized Ar + and negative electrons move intensely at high speed. For this reason, argon gas molecules or the like collide with the chip to remove the impurities, and further improve the wetting of the chip 22 with respect to the solder. For this reason, the reliability of the void generation preventing function can be improved.

  As described above, the embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and various modifications can be made. The means and the means for transporting from the impurity removing unit 36 to the bonding position are configured by the same means, but these means may be different.

  The temperature of the gas at the time of high temperature gas blowing and the heating temperature at the time of high temperature heating can be arbitrarily set within a range in which the impurities are vaporized according to the impurity S adhering to the chip 22 or the like. The speed can be variously set within a range in which the vaporized impurity S can be blown off from the chip 22.

  By the way, the board | substrate in this invention shall include a lead frame and a printed circuit board. Here, the lead frame is a thin metal plate used as an internal wiring of a semiconductor package and serves as a bridge with external wiring. The printed circuit board is a plate-like or film-like component that constitutes an electronic circuit by fixing a large number of electronic components such as integrated circuits, resistors, capacitors, etc. on the surface and connecting the components by wiring. . The printed circuit board includes a rigid board (using an inflexible insulator base), a flexible board (a flexible wiring board using a thin and flexible material for the insulator base), and There is a rigid flexible substrate (a composite of a hard material and a flexible material).

It is a simplified diagram of a die bonder showing an embodiment of the present invention. The main part of the die bonder is shown, (a) is a cross-sectional view when performing high-temperature gas blowing, and (b) is a cross-sectional view when performing high-temperature heating. It is process drawing which shows the bonding method in the case of performing high temperature gas blow. It is a principal part process drawing of the bonding method in the case of performing high temperature heating. It is a simplified diagram showing a bonding method using a conventional die bonder. It is an enlarged view of an adsorption collet. It is process drawing which shows the conventional bonding method.

Explanation of symbols

21 Adsorption collet 22 Chip 23 Substrate 24 Heater rail 35 Impurity removing means S Impurity

Claims (7)

In a die bonder that picks up a chip with a collet at a pickup position, transports the collet to a bonding position, and bonds the chip adsorbed to the collet to the substrate at the bonding position.
A die bonder comprising an impurity removing means for removing impurities that adhere to a chip and cause voids during conveyance from a pickup position to a bonding position, and bonding is performed with the impurities removed by the impurity removing means. .   2. The die bonder according to claim 1, wherein the impurity removing means is a high temperature gas blow for blowing a high temperature gas to the chip.   2. The die bonder according to claim 1, wherein the impurity removing means is high-temperature heating for heating the chip.   2. The die bonder according to claim 1, wherein the impurity removing means is high-temperature gas blowing for blowing a high-temperature gas to the chip and high-temperature heating for heating the chip.   2. The die bonder according to claim 1, wherein the impurity removing means is a plasma cleaning that irradiates a chip with a plasma gas.   The die bonder according to any one of claims 1 to 5, wherein the impurity removing means is provided on a heater rail that constitutes a substrate heating means and a conveying means. In the bonding method of picking up a chip with a collet at the pickup position and bonding the chip held by the collet to the substrate at the bonding position,
While carrying the chip from the pick-up position to the bonding position, pass through the impurity removal atmosphere, remove the impurities that adhere to the chip and cause voids, and then bond while maintaining the state where the impurities are removed A bonding method characterized by the above.

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