JP4692101B2 - Part joining method - Google Patents

Description

  The present invention relates to a component bonding method suitable for use in, for example, a process of mounting a semiconductor device on a wiring board, and a component bonding jig used in this method.

  The bonding (mounting) form of a semiconductor device to a wiring board or the like has been shifted from a pin insertion type to a surface mounting type in response to the demand for light and thin electronic devices. The BGA (Ball Grid Array) type in which bumps are arranged in an array on the back surface of the semiconductor device is more advantageous than the surface mount type in which the connection leads protrude from the side surface of the semiconductor device. ing.

  As a method for bonding a BGA type semiconductor device, for example, a method shown in FIG. 6 is known (see Patent Document 1 below). As shown in FIG. 6A, bumps 82 of high-temperature solder are formed on the semiconductor device 81, and low-temperature solder 86 is applied on the conductor portion (land) 85 of the substrate 84. On the substrate 84, a flux 83 is applied to remove the oxide film and improve the bonding property.

  As shown in FIG. 6B, the semiconductor device 81 is heated while being pressed against the substrate 84, the low-temperature solder 86 is melted, and the bumps 82 are electrically joined to the conductor portions 85. After joining, as shown in FIG. 6C, the flux 83 is removed by washing. Then, as shown in FIG. 6D, an underfill material 87 made of a thermosetting resin is supplied to the gap between the semiconductor device 81 and the substrate 84 and is cured by heating to protect the joint.

  In this method, after the semiconductor device 81 and the substrate 84 are bonded, a step of removing the flux 83 remaining in the bonded portion is required. However, the flux cannot be sufficiently cleaned due to the finer bump pitch. At the same time, organic solvents with detergency have a high environmental impact, so there is a high demand for use restrictions.

  On the other hand, recently, as shown in FIG. 7A, a resin material 94 having a flux function is applied in advance onto the substrate 95, and as shown in FIG. 7B, the tip end portions 92a of the bumps 92 of the semiconductor device 91 and the substrate 95 are applied. A method has also been proposed in which an underfill is formed by heat-curing the resin material 94 at the same time as bonding to the conductor portion 96 (see Patent Document 2 below).

  In the uncured state, the resin material 94 used for this removes the joining surface and the oxide of the solder material to improve the joining property, and further hardens at the time of joining (during reflow) to reinforce the joined part. Unlike the general flux material, the resin material 94 does not require cleaning and removal after bonding.

  Incidentally, the above-described conventional bonding method of the semiconductor device 91 is performed using a mounting machine called a flip chip mounter. As schematically illustrated in FIG. 8, the mounting machine 101 has a configuration in which the suction tool 102 that sucks and holds the semiconductor device 91 can be moved along the guide shaft 103. The mounting machine 91 has a built-in mechanism for heating and cooling the semiconductor device 91 held by the suction nozzle 102.

  The substrate 95 to be bonded to the semiconductor device 91 is held on the substrate holding surface 104 on the work table 103 and is opposed to the semiconductor device 91 sucked by the suction nozzle 102. At the time of bonding, the suction nozzle 102 moves in the direction of arrow A, and the semiconductor device 91 is heated to the reflow temperature and soldered while pressing the semiconductor device 91 against the substrate 95 with a predetermined pressure. Thereafter, through the cooling process of the semiconductor device 91, the suction operation of the semiconductor device 91 by the suction nozzle 102 is released, and the joining is completed.

JP 2005-51128 A JP 2003-158153 A

  In the conventional component bonding method using the mounting machine 101 shown in FIG. 8, the bump 92 is bonded to the conductor portion 96 of the substrate 95 while mechanically pressing the semiconductor device 91 with the mounting machine 101 as described above. ing. The pressing force applied to the semiconductor device 91 is limited to a preset pressure.

  However, for example, the heat generated during reflow heating causes the mechanical portion of the mounting machine 101 to thermally expand, which may cause an overload to the semiconductor device 91 and cause damage to the bumps, the semiconductor device 91, or the substrate 95. is there. Further, the bump may be crushed due to overload, and a bridge may be generated due to contact with an adjacent bump.

  Furthermore, since the conventional component bonding method is a method of bonding the semiconductor devices 91 to the substrate 95 one by one using the mounting machine 101, there is a problem that productivity cannot be improved. Although it is possible to increase the productivity by using a plurality of mounting machines 101, the work space and the apparatus cost increase, which is not realistic.

  The present invention has been made in view of the above-described problems, and provides a component bonding method that can prevent overload of components during bonding and can improve productivity, and a component bonding jig used therefor. Let it be an issue.

  In solving the above problems, the component joining method of the present invention joins a first joined component having a protruding electrode and a second joined component having a terminal portion joined to the protruding electrode. A solder bonding layer is formed on the protruding electrode or the terminal portion, and a step of forming an adhesive resin layer on the terminal forming surface of the second bonded component, and a protrusion on the adhesive resin layer A process of making a temporary fixing body of the first and second parts to be joined by biting in the electrodes, and melting the solder layer while joining the temporary fixing body with fluid pressure to join the protruding electrode and the terminal portion. Process.

  In the present invention, the first and second parts to be joined are temporarily fixed via the adhesive resin layer, and then heated while applying a certain fluid pressure to the temporarily fixed body, and the solder layer Are reflowed to bond the protruding electrode and the terminal portion to each other. By applying a constant fluid pressure to the parts, the parts are prevented from being overloaded during reflow heating, and damage to the joints and occurrence of bridges are avoided.

  On the other hand, the component joining jig of the present invention includes a jig body, a pressure chamber formed in the jig body and into which fluid pressure is introduced, and formed in the jig body. The component storage chamber for storing the temporarily fixed body of the component to be joined, the elastic sheet body for partitioning between the pressure chamber and the component storage chamber, and the valve is opened when the fluid pressure introduced into the pressure chamber exceeds a predetermined pressure. And a relief valve.

  The component joining jig according to the present invention is configured to be loaded in a heating device such as a reflow furnace as it is. In the reflow furnace, the temporarily fixed bodies of the parts to be joined housed in the parts housing chamber of the jig main body are joined by receiving a pressurizing action by fluid pressure through the elastic sheet material. As the fluid pressure, a gas pressure such as air and a fluid pressure such as oil can be applied, but air pressure is advantageous in handling.

  Since the air pressure expanded by heating is released from the pressure chamber via the relief valve, the pressing force against the temporarily fixed body can always be kept constant. In addition, by accommodating a plurality of temporarily fixed bodies in the processing chamber, a plurality of joining processes can be performed at the same time, so that productivity can be improved.

  Therefore, according to the present invention, it is possible to prevent overloading of components at the time of joining, so that it is possible to avoid breakage of the joint and occurrence of a bridge. In addition, since a plurality of joining processes can be performed at the same time, productivity can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  1 and 2 are cross-sectional process diagrams for explaining a component joining method according to an embodiment of the present invention. FIG. 1A shows a semiconductor chip 11 and a wiring substrate 21 bonded to the semiconductor chip 11. In the present embodiment, the semiconductor chip 11 corresponds to the “second bonded component” of the present invention, and the wiring board 21 corresponds to the “first bonded component” of the present invention.

  A plurality of electrode pads 14 are arranged in a grid on the active surface of the semiconductor chip 11 with a passivation film 13 interposed therebetween. On the electrode pad 14, a conductive film 15 is formed by heat-curing a paste film in which, for example, Ag (silver) fine particles are dispersed. A convex bonding pad 18 having a multilayer structure of Cu (copper), Ni (nickel), and Au (gold) is formed on the conductive film 15. The bonding pad 18 corresponds to the “terminal portion” of the present invention.

  The specific size of the semiconductor chip 11 is a vertical and horizontal dimension of 10 mm, a thickness of 250 μm, and an array pitch of the bonding pads 18 of 200 μm. The thicknesses of the Cu film, Ni film, and Au film constituting the bonding pad 18 are 22 μm, 3 μm, and 0.05 μm, respectively.

  In the semiconductor chip 11 configured as described above, the active resin layer 19 is formed on the formation surface (terminal formation surface) of the bonding pad 18 as described later prior to mounting on the wiring substrate 21. The active resin layer 19 is formed by applying a thermosetting resin having adhesiveness and a flux function in an uncured state to the terminal forming surface of the semiconductor chip 11. This active resin layer corresponds to the “adhesive resin layer” of the present invention.

  This type of thermosetting resin is, for example, a liquid bisphenol-based epoxy resin to which dihydroxybenzoic acid having an action of a curing agent and an action of flux, phenolphthaline, and a curing accelerator are added (Japanese Patent Laid-Open No. 2003-1999). -105054 gazette), but is not limited thereto. A filler such as silica fine particles may be added to the active resin layer 19 to adjust the elastic modulus or thermal expansion coefficient after complete curing.

  On the other hand, the wiring substrate 21 may be a mother substrate or an interposer substrate. The wiring board 21 is provided with bumps 28 corresponding to the arrangement intervals of the bonding pads 18 of the semiconductor chip 11. The bumps 28 correspond to “projection electrodes” of the present invention.

  The bump 28 includes a copper core 26 formed on the outer insulating resin film 23 on the wiring substrate 21 and connected to the wiring layer 24 through a via, and a solder 27 formed around the copper core 26. Yes. The copper core 26 is not limited to copper as long as it has a function of ensuring a gap between the bonded semiconductor chip 11 and the wiring substrate 21 and does not melt during reflow. The copper core 26 is subjected to, for example, Ni / Au plating in order to improve the adhesion with the solder 27.

  The solder 27 corresponds to the “solder layer” of the present invention, melts during reflow, and spreads wet on the bonding pads 18 of the semiconductor chip 11. As the solder 27, SnAgCu series, in particular, Sn3Ag0.5Cu solder is used. In addition, other Sn-based solders such as Sn-based, SnAg-based, SnBi-based, SnCu-based, SnAgBi-based, and SnAgBiCu-based may be used.

  The semiconductor chip 11 configured as described above and the wiring substrate 21 are joined as follows.

  First, the active resin layer 19 is formed on the terminal formation surface of the semiconductor chip 11 (FIG. 1A).

  Examples of the method for forming the active resin layer 19 include coating by a printing method, spin coating method, and the like, and a dry film laminating process. The thickness of the active resin layer 19 is, for example, 30 μm. The active resin layer 19 may be formed during the manufacturing process of the semiconductor chip 11 or may be performed immediately before mounting on the wiring substrate 21.

  Next, the semiconductor chip 11 is temporarily fixed on the wiring board 21, and the temporarily fixed body 10A of the semiconductor chip 11 and the wiring board 21 is manufactured (FIG. 1B).

  The semiconductor chip 11 is aligned so that the bonding pad 18 is located immediately above the bump 28 of the wiring board 21, and then heated to about 140 ° C. and lightly pressed against the wiring board 21. The amount of pressing of the semiconductor chip 11 against the wiring substrate 21 is set to such a size that the tip of the bump 28 bites into the active resin layer 19. The alignment of the semiconductor chip 11 with respect to the wiring board 21 is performed using a device having an alignment function such as a chip mounter.

  Subsequently, the semiconductor chip 11 is reflow mounted on the wiring board 21 (FIG. 2C).

  In this reflow mounting process, the semiconductor chip 11 is heated to the reflow temperature (250 ° C. in this example) while being pressurized by receiving a constant air pressure on the upper surface thereof. As a result, the active resin layer 19 is melted and the bumps 28 come into contact with the bonding pads 18. Then, the solder 27 is melted and spreads on the bonding pad 18. The active resin layer 19 surrounds the molten solder 27 and removes the oxide with a flux function. Thereafter, the process proceeds to a cooling step and the solder 27 is solidified. Thereby, the component mounting body 10 </ b> B in which the bonding portion 30 is formed between the bonding pad 18 and the copper core 26 is manufactured.

  The reflow mounting process is performed using a component joining jig 35 shown in FIG. Details of the configuration of the component joining jig 35 and the reflow mounting process will be described later. Further, the active resin layer 19 is not cleaned and removed after bonding.

  Finally, a process of sealing the joint portion 30 of the manufactured mounting body 10B with the underfill 31 is performed (FIG. 2D). Thereby, the semiconductor device 10C is manufactured.

  The constituent resin of the underfill 31 is determined by the relationship with the physical properties of the active resin layer 19. In the present embodiment, the material design is such that the underfill 31 has a lower elastic modulus and a higher thermal expansion coefficient than the active resin layer 19. Thereby, it is possible to effectively protect the joint 18 from stress (thermal stress) acting on the joint 31.

  Next, the configuration of the component joining jig 35 according to the present invention will be described with reference to FIG.

  FIG. 3 is a cross-sectional view showing a schematic configuration of the component joining jig 35 of the present embodiment. An elastic sheet body 39 that divides the pressure chamber 37 and the component storage chamber 38 in the upper and lower directions is provided inside a jig body 36 made of metal such as stainless steel or aluminum alloy. The jig main body 36 has a two-part structure of an upper main body portion 36A and a lower main body portion 36B. The elastic sheet 39 is fixed to the lower surface side of the upper main body portion 36A, and the upper and lower main body portions are combined with the lower main body 36B. A peripheral part and an intermediate part are clamped between 36A and 36B.

  The pressure chamber 37 communicates with a pressure supply port 40 connected to a pressure source (an air tank or an air compressor) (not shown). The pressure supply port 40 is provided with a check valve 41 that allows air to flow into the pressure chamber 37 from the pressure source and prohibits the reverse flow. As a result, the air pressure of a predetermined pressure introduced into the pressure chamber 37 is prevented from flowing out, and the jig alone that is disconnected from the pressure source can be handled.

  The upper body portion 36A is provided with a relief valve 42 that releases the excess pressure to the outside when the introduced air pressure exceeds a predetermined pressure. That is, the relief valve 42 functions to release the increased pressure of the air expanded by heating when it is loaded into the reflow furnace to maintain the inside of the pressure chamber 37 at a constant pressure.

  The component accommodating chamber 38 accommodates the semiconductor chip 11 and the temporarily fixed body 10A of the wiring board 21 described with reference to FIG. 1B. The component storage chamber 38 can be formed to a size that can simultaneously store a plurality of temporarily fixed bodies 10A. A through hole 43 is formed at the bottom of the component storage chamber 38 on which the temporarily fixed body 10A is placed, and air can be moved inside and outside the component storage chamber 38.

  The plurality of temporarily fixed bodies 10A accommodated in the component accommodating chamber 38 may be in the form of individual pieces as shown in FIG. 1B, but in this embodiment, as shown in FIG. A composite temporarily fixed body 10 in which a plurality of semiconductor chips 11 are temporarily solidified on the wiring board 21A is formed. The composite temporarily fixed body 10 may be a so-called multi-chip package, or may be individually separated after joining.

  The jig main body 36 is configured to have a plurality of component housing chambers 38 within a range that can be loaded into the reflow furnace. The component storage chamber 38 and the component storage chamber 38 are separated by a partition wall 36C (FIG. 3). Each component storage chamber 38 has a common pressure chamber 37.

  The elastic sheet 39 is not particularly limited as long as it is a material having heat resistance that can withstand the reflow temperature, and fluorine rubber, silicone rubber, or the like is used. When a predetermined air pressure is introduced into the pressure chamber 38, the elastic sheet body 39 is elastically deformed toward the component storage chamber 38 as shown in FIG. 5, and the temporary solid body 10 stored in each component storage chamber 38. The elastic modulus is such that the upper surface side can be evenly pressed.

  The component joining jig 35 of the present embodiment configured as described above is shown in FIG. 4 in each component storage chamber 38 opened by separating the upper main body portion 36A and the lower main body portion 36B. The semiconductor chip 11 having the configuration and the temporarily fixed body 10 of the wiring board 21A are accommodated. Thereafter, the upper main body portion and the lower main body portion 36B are integrated, and the elastic sheet 39 partitions the pressure chamber 37 and the component storage chamber 38 in an airtight manner.

  Here, since the semiconductor chip 11 and the wiring board 21A constituting the temporarily fixed body 10 are positioned via the active resin layer 19 (FIG. 1B) having tackiness (adhesiveness), there is a misalignment between them. It can be accommodated in the component accommodating chamber 38 without being raised. Further, misalignment in the transfer process of the reflow furnace is also prevented.

  Next, a pressure source (not shown) is connected to the pressure supply port 40, and compressed air having a predetermined pressure (in this example, 0.1 atmospheric pressure or less) is introduced into the pressure chamber 37. As a result, the elastic sheet 39 is elastically deformed toward the component housing chamber 38, and as shown in FIG. 5, the upper surface of each semiconductor chip 11 constituting the temporarily fixed body 10 in each component housing chamber 38 is equalized. Pressurize.

  Thereafter, the component joining jig 35 is loaded into a reflow furnace (not shown). In the reflow furnace, the component joining jig 35 is heated to the reflow temperature. Then, the semiconductor chip 11 and the wiring board 21A constituting the temporarily fixed body 10 are soldered to each other as shown in FIG. 2C while receiving a pressurizing action from the pressure chamber 37, so that the component mounting body 10B. Is manufactured.

  According to the present embodiment, in the reflow furnace, the compressed air in the pressure chamber 37 is expanded by the heating action, but the increased pressure is released to the outside through the relief valve 42. Therefore, since the inside of the pressure chamber 37 is always maintained at a constant pressure before and after heating, the pressure applied to the semiconductor chip 11 is also constant. Thereby, breakage of the solder joint due to overload and occurrence of a bridge can be reliably avoided, and highly reliable component joining can be realized.

  In particular, since a desired bonding pressure can be applied when the semiconductor chip 11 is bonded, an optimum bonding pressure can be set according to the weight of the semiconductor chip 11, the viscosity of the active resin layer 19, the tip shape of the bump 28, and the like. Moreover, it becomes possible to easily change the product type and set the conditions. Furthermore, the degree of freedom in the amount of filler mixed into the active resin layer 19 was increased, and the thermal expansion coefficient could be reduced to, for example, 60 ppm or less (40 ppm).

  Further, according to the component joining jig 35 of the present embodiment, a plurality of component mounting bodies 10B (FIG. 2C) can be manufactured simultaneously with this single unit, so that a mounting process using a conventional chip mounter can be achieved. In comparison, productivity can be improved. In fact, it has been confirmed that the processing time can be reduced by half compared to the case of using a chip mounter.

  Furthermore, according to the component joining jig 35 of the present embodiment, the check valve 41 for preventing the backflow of air is provided at the pressure supply port 40 connected to the pressure source. There is no need to always connect to the pressure source, and it is possible to handle the jig alone.

  The embodiment of the present invention has been described above. Of course, the present invention is not limited to this, and various modifications can be made based on the technical idea of the present invention.

  For example, in the above embodiment, the active resin layer 19 is provided on the semiconductor chip 11 side, but instead, the active resin layer 19 may be provided on the wiring board 21 (21A) side. Further, the protruding electrode may be formed on the semiconductor chip 11 side, and the terminal portion may be formed on the wiring board 21 side. Furthermore, the solder 27 is not limited to being formed on the bump 28, and may be provided on the bonding pad 18.

  The component bonding method according to the present invention is not limited to bonding between the semiconductor chip 11 and the wiring substrate 21 (21A), but can be applied to bonding between semiconductor chips. The semiconductor chip 11 is not limited to a bare chip, and may be a package component obtained by molding a semiconductor chip with a resin.

  In the above embodiment, the active resin layer 19 is used as the adhesive resin layer. However, the present invention is not limited to this, and for example, a resin having a certain adhesive property in an uncured state such as an anisotropic conductive film (ACF). Layers may be used.

  Further, in the above embodiment, the component bonding jig 35 is loaded into the reflow furnace to bond the semiconductor chip 11 and the wiring board 21A. The component bonding jig includes a heater or the like. It is also possible to incorporate the heat source and to join the components with a jig alone without using a reflow furnace.

  In addition, a valve mechanism such as a check valve may be provided for the component joining jig 35 described in the above embodiment so that the underpressure can be replenished from the outside when the air pressure falls below the set pressure. Good. Thereby, in a reflow furnace, the pressure shortage in a cooling process can be relieved, and it becomes possible to apply a fixed pressure to the semiconductor chip 11 from beginning to end.

It is process sectional drawing explaining the component joining method by embodiment of this invention. It is process sectional drawing explaining the component joining method by embodiment of this invention. It is sectional drawing which shows schematic structure of the jig | tool 35 for component joining by embodiment of this invention. It is a figure which shows the composite temporarily fixed body 10 by which several semiconductor chip 11 was temporarily fixed to the wiring board 21A. It is sectional drawing explaining one effect | action of the components for actual 35. It is process sectional drawing explaining the conventional component joining method. It is process sectional drawing explaining the other conventional component joining method. It is a schematic block diagram of a chip mounter.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10,10A ... Temporary solid body, 10B ... Component mounting body, 10C ... Semiconductor device, 11 ... Semiconductor chip, 18 ... Bonding pad (terminal part), 19 ... Active resin layer (adhesive resin layer), 21 ... Wiring board, DESCRIPTION OF SYMBOLS 27 ... Solder, 28 ... Bump (projection electrode), 30 ... Joint part, 31 ... Underfill, 35 ... Jig for component joining, 36 ... Jig main body, 37 ... Pressure chamber, 38 ... Component accommodation chamber, 39 ... Elasticity Sheet body, 40 ... pressure supply port, 41 ... check valve, 42 ... relief valve.

Claims (5)

A component bonding method for bonding a first bonded component having a protruding electrode and a second bonded component having a terminal portion bonded to the protruding electrode to each other,
A solder layer is formed on the protruding electrode or the terminal portion,
Forming an adhesive resin layer on the terminal forming surface of the second bonded part;
Producing the temporarily fixed body of the first and second bonded parts by biting the protruding electrode into the adhesive resin layer;
Component bonding method and a step of joining the said protruding electrode temporarily fixed member by melting the solder layer while applying a constant pressure in the fluid pressure and the terminal portion. The component bonding method according to claim 1, wherein an active resin having a flux function is used as the adhesive resin layer. The component joining method according to claim 1, wherein one of the first and second parts to be joined is a wiring board and the other is a semiconductor element. The component joining method according to claim 1, wherein the first and second parts to be joined are both semiconductor elements. The component joining method according to claim 1, wherein in the reflow process of the temporarily fixed body, a plurality of temporarily fixed bodies are collectively processed simultaneously.

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