JP6135891B2 - Electronic component mounting method and electronic component mounting line - Google Patents

Description

  The present invention relates to a mounting method and a mounting line for mounting an electronic component having a plurality of bumps on a substrate.

  Various electronic components are incorporated in the electronic device, and these electronic components are incorporated in the device as a mounting structure in a state of being bonded to a predetermined position of a substrate having a plurality of electrodes. As electronic devices have been downsized in recent years, electronic components incorporated in the devices have been downsized, and electronic components such as flip chips and chip size packages (CSP) are often mounted on a substrate. ing.

  Electronic components such as flip chip and CSP have a main surface on which a plurality of terminals are regularly arranged, and solder bumps (electrodes) are formed on each terminal. In order to mount such an electronic component on a substrate, the bump is made to land on a substrate electrode (connection terminal) called a land, heated, melted (reflowed), and then allowed to cool, whereby the electronic component and Interconnection with the substrate is made. Thereby, each terminal of the electronic component is electrically connected to the electrode of the substrate, and the electronic component is held on the substrate by the solder joint portion.

  When thermal stress or external force due to heat cycle is applied to the mounting structure consisting of the board and electronic parts obtained by the mounting process as described above, the electronic parts that are joined to the board by bumps are The strength may be insufficient. In view of this, it has been practiced to reinforce the solder joint by adhering the electronic component to the substrate with a reinforcing resin.

  As a method of reinforcing the solder joint portion with the reinforcing resin, before mounting the electronic component on the substrate, a thermosetting resin is used as the reinforcing resin on at least a part of the mounting region of the substrate on which the electronic component is previously mounted. Supply is done. According to such a method, at the time of reflow, it is possible to cure the thermosetting resin simultaneously with the solder joining, and there is an advantage that the mounting process can be simplified.

  However, since the reinforcing resin is applied to the substrate before the electronic component is mounted, the lands provided in the mounting area are covered with the reinforcing resin. When bumps of electronic parts are landed on the land covered with the reinforcing resin, the reinforcing resin is interposed between the bumps and the land, so that the bumps (solder) melted during the reflow are sufficiently wetted and spread on the land. Therefore, the strength of the solder joint tends to be weak. Such a problem can be reduced by mixing the flux with the reinforcing resin, but the viscosity of the reinforcing resin containing the flux increases. Therefore, it is necessary to store the reinforcing resin in a frozen state, and it must be used up within a few hours after thawing, and temperature management is difficult.

  On the other hand, flux is applied in advance to the bumps of the electronic component, the reinforcing resin is penetrated by the bumps to which the flux is applied, and the flux is interposed between the bumps and the lands. In addition, it is proposed that when flaky metal powder is mixed with the flux and the flux is applied to the bump, the metal powder is inserted into the surface of the bump, and then the electronic component is mounted on the substrate. . In this case, since the bump melted at the time of reflow can be spread on the land through the surface of the metal powder, it is easy to ensure the strength of the solder joint (see Patent Document 1).

JP 2006-73976 A

  As described above, when flux is applied to the bumps of the electronic component in advance and then the electronic component is mounted on the substrate, it is not necessary to mix the flux with the reinforcing resin more than necessary, and the viscosity change of the reinforcing resin It is possible to prevent this. However, the viscosity of the flux is usually much lower than that of the reinforcing resin. Therefore, as shown in FIG. 17A, when the bump 204 coated with the flux 206 is landed on the land 102 covered with the reinforcing resin 105 on the substrate 101, the flux 206 is applied to the reinforcing resin 105. In some cases, most of them are pulled and wiped off from the bumps 204 as shown in FIG. Therefore, it may be difficult to interpose a sufficient amount of flux 206 between the bump 204 and the land 102.

  Further, as in Patent Document 1, when the metal powder is included in the flux, the viscosity change of the flux is increased by the catalytic action of the metal powder, and the pot life is likely to be shortened. Moreover, since the metal composition of the solder changes due to the mixing of the metal powder, the solder joint becomes fragile, and the connection reliability may be lowered.

  An object of the present invention is to provide an electronic component mounting method and a mounting line that can improve the storage stability of a flux and a reinforcing resin and ensure the reliability of a solder joint.

One aspect of the present invention is an electronic component mounting method for mounting an electronic component having a plurality of solder bumps on a main surface of a package on a substrate having a mounting area provided with a plurality of lands corresponding to the plurality of solder bumps. And a step of applying a first thermosetting resin having a first viscosity C1 to at least a part of the mounting region, and a plurality of solder bumps having a second viscosity C2 satisfying 1.5 × C1 ≦ C2. A step of applying a flux; a step of mounting the electronic component on the substrate such that a plurality of solder bumps to which the flux is applied land on the corresponding lands; and the substrate on which the electronic component is mounted The electronic component is bonded to the substrate by melting the bump, curing the first thermosetting resin, and allowing to cool. And the flux includes a solid component that is particulate and melts when heated, and the solid component is at least one selected from the group consisting of an activator and a second thermosetting resin. Further, the present invention relates to an electronic component mounting method, wherein the activator is at least one selected from the group consisting of organic acids, amines, and halides thereof.

Another aspect of the present invention is an electronic component mounting in which an electronic component having a plurality of solder bumps on a main surface of a package is mounted on a substrate having a mounting area provided with a plurality of lands corresponding to the plurality of solder bumps. In the line, 1.5 × C1 ≦ C2 is applied to at least a part of the mounting region of the substrate, a resin coating apparatus that applies a first thermosetting resin having a first viscosity C1, and the plurality of solder bumps. An electronic component mounting apparatus for mounting the electronic component on the substrate so that the plurality of solder bumps land on the corresponding lands, after applying a flux having a second viscosity C2 that satisfies, and the electronic component The mounted substrate is heated to melt the bumps, and the first thermosetting resin is cured and allowed to cool, whereby the electronic component is brought into contact with the substrate. A reflow device that combines, wherein the flux is particulate and includes a solid component that melts upon heating, the solid component selected from the group consisting of an activator and a second thermosetting resin It is related with the electronic component mounting line which is at least 1 sort (s), and the said activator is at least 1 sort (s) selected from the group which consists of organic acid, amines, and these halides.

  According to the present invention, since the viscosity of the flux is set higher than the viscosity of the reinforcing resin, the bump 204 coated with the flux 206 is applied to the substrate 101 as shown in FIG. When landing on the land 102 via the reinforcing resin 105, the flux 206 is less likely to be pulled by the reinforcing resin 105. Therefore, as shown in FIG. 1B, a sufficient amount of flux 206 can be interposed between the bump 204 and the land 102. Therefore, at the time of reflow, the oxide on the surface of the bump can be removed, and the melted bump can be sufficiently wetted and spread on the land of the substrate. As a result, high reliability of the solder joint can be ensured. It becomes possible.

  And according to this invention, since it is not necessary to mix a flux with reinforcing resin or to mix metal powder with a flux, the viscosity change of reinforcing resin and a flux is suppressed, and preservability improves. Therefore, the temperature management of the reinforcing resin and the flux is facilitated.

It is a figure which shows a mode that the bump | vamp with which the flux which concerns on one Embodiment of this invention was apply | coated is landed on a land via reinforcement resin. It is a front view of an example of the BGA type electronic component which has a plurality of bumps. It is a bottom view of the electronic component. It is a longitudinal cross-sectional view of an example of the board | substrate before an electronic component is mounted. It is a perspective view of an example of a chip type electronic component. It is a flowchart which shows the procedure which mounts a BGA type electronic component on a board | substrate. It is explanatory drawing which shows the process of the first half of the electronic component mounting method which concerns on one Embodiment of this invention. It is explanatory drawing which shows the process of the second half of the electronic component mounting method which concerns on one Embodiment of this invention. It is explanatory drawing which shows the latter half process of the electronic component mounting method in the case of apply | coating a thin thermosetting resin to a board | substrate. It is the schematic diagram which looked at the transfer unit which forms the coating film of a flux from upper direction. It is sectional drawing which shows typically the operation | movement in which the transfer unit forms the coating film of a flux. It is sectional drawing which shows typically the operation | movement which makes a solder bump of a BGA type electronic component contact the coating film of the flux which the same transfer unit formed, and transfers a flux. It is a flowchart which shows the procedure which transfers a flux to the solder bump of a BGA type | mold electronic component. It is explanatory drawing which shows the whole structure of the electronic component mounting line which concerns on one Embodiment of this invention. It is the block diagram which looked at the structure which connected the resin coating apparatus and BGA type | mold electronic component mounting apparatus which are a part of the electronic component mounting line which concerns on the same embodiment from the upper direction. It is explanatory drawing which shows the whole structure of the electronic component mounting line which concerns on other embodiment of this invention. It is the block diagram which looked at the structure of the unit apparatus which integrated the resin coating device, the BGA type | mold electronic component mounting apparatus, and another electronic component mounting apparatus which are a part of the electronic component mounting line which concerns on the same embodiment from the upper direction. It is a figure which shows a mode that the bump by which the conventional flux was apply | coated is landed on a land through resin for reinforcement.

First, the structure of an electronic component having a plurality of solder bumps on the main surface of the package and a substrate on which the electronic component is mounted will be described.
FIG. 2 is a front view of an example of an electronic component 200 having a plurality of solder bumps on the main surface of the package. The electronic component 200 has a ball grid array (BGA) type package connected to the electrodes (lands) of the substrate 101 by a plurality of bumps 204. FIG. 3 is a bottom view of the electronic component 200. The BGA type electronic component 200 includes a thin component inner substrate 201 constituting a package, a semiconductor element 202 mounted on the upper surface thereof, and a sealing resin 203 covering the semiconductor element 202. The lower surface of the component inner substrate 201 constitutes a main surface 201s of the electronic component 200, and a plurality of terminals are regularly arranged in a matrix on the main surface 201s. Each terminal is provided with a bump 204.

  The structure shown in FIGS. 2 and 3 is only an example of the structure of the BGA type electronic component, and various forms of flip chips other than the above are included in the electronic component having a plurality of solder bumps on the main surface of the package. And CSP.

  As shown in FIG. 4, the substrate 101 has a first mounting region in which first electrodes 102 a (lands) connected to the plurality of bumps 204 of the BGA type electronic component 200 are provided. A thermosetting resin is applied as a reinforcing resin to at least a part of the first mounting region. Further, the substrate 101 may have a region for mounting a component other than the BGA type electronic component 200.

  FIG. 5 is a perspective view of an example of a small electronic component 210 that may be mounted on the substrate 101 together with the BGA type electronic component 200. The small electronic component is, for example, a chip type electronic component having at least one connection terminal 211. Examples of the chip-type electronic component include a chip resistor, a chip LED, and a chip capacitor. As shown in FIG. 4, the substrate on which the chip type electronic component 210 is mounted is provided with a second mounting region having a plurality of second electrodes 102 b connected to the connection terminals 211 of the chip type component 210. . Such an electronic component 210 is mounted on the substrate 101 by applying cream solder to the second electrode 102b by screen printing and landing the connection terminal 211 on the second electrode 102b via the cream solder.

Next, the electronic component mounting method of the present invention will be described.
The electronic component mounting method of the present invention includes a step of preparing an electronic component having a plurality of solder bumps on the main surface of the package (hereinafter referred to as a first electronic component), and a plurality of lands corresponding to the plurality of solder bumps. A step of preparing a substrate having a first electronic component mounting region (hereinafter referred to as a first mounting region), and a step of applying a thermosetting resin having a first viscosity C1 to at least a part of the first mounting region. And applying a flux having a second viscosity C2 that satisfies C1 ≦ C2 to the plurality of solder bumps, and the plurality of solder bumps coated with the flux landing on the corresponding lands, respectively. Mounting the first electronic component on the substrate; heating the substrate on which the first electronic component is mounted to melt the bump; and curing the thermosetting resin. By cooling, including a step (reflow step) of bonding the electronic part to the substrate.

  The electronic component mounting method of the present invention further prepares an electronic component 210 (hereinafter referred to as a second electronic component) having a connection terminal 211 such as a chip-type electronic component, and connects the connection terminal 211 provided on the substrate 101 to the connection terminal 211. It may include a step of applying the cream solder to the corresponding second electrode by screen printing and mounting the second electronic component 210 on the substrate 101 so that the connection terminal 211 is landed on the second electrode via the cream solder. Good. This step is performed before the reflow step.

  Hereinafter, with reference to the flowchart of FIG. 6 and the explanatory diagrams of FIGS. 7A and 7B, the case where the first electronic component 200 and the second electronic component 210 are mounted on the substrate 101 will be described as an example. A method will be described.

  As shown in FIG. 7A (a), the substrate 101 is provided with a first electrode 102a connected to the bump 204 of the first electronic component 200 and a second electrode 102b connected to the terminal 211 of the second electronic component 210. It has been.

  First, as shown in FIG. 7A (b), the cream solder 103 is applied to the second electrode 102b by a technique such as screen printing by shielding the first electrode 102a with a mask (SP11). However, when the cream solder 103 has a flux function, the cream solder may be applied to both the first electrode 102a and the second electrode 102b by screen printing.

  Next, as shown in FIG. 7A (c), a thermosetting resin 105 having a first viscosity C1 is applied as a reinforcing resin to at least a part of the first mounting region of the substrate (SP12). At this time, at least a part of the plurality of first electrodes 102 a is covered with the thermosetting resin 105, and in one aspect, all of the plurality of first electrodes 102 a are covered with the thermosetting resin 105. From the viewpoint of enhancing the reinforcing effect on the solder joint portion, the thermosetting resin 105 is made 80% or more, preferably 100% (entire surface) of the area of the mounting region (the projected area of the first electronic component 200 on the substrate 101). It is preferable to apply so that it spreads wet.

  As a method for applying the thermosetting resin 105, it is preferable to perform the dispensing method using an application head that is installed in a predetermined resin application apparatus and is movable in various directions. The coating head includes a coating nozzle 323 d that discharges the thermosetting resin 105. However, the application method is not particularly limited, and if possible, the thermosetting resin may be applied to the first mounting region by a screen printing apparatus.

  The first viscosity C1 of the thermosetting resin is relatively determined in relation to the viscosity C2 of the flux applied to the solder bump of the first electronic component 200, and the value is not particularly limited. However, from the viewpoint of promoting wetting and spreading to the first region and suppressing excessive wetting and spreading due to dripping, a cone plate type E-type viscometer (a cone angle of 3 ° and a diameter of 28 mm is used at 25 ° C.) ), The viscosity when measured at a rotational speed of 5 rpm is preferably, for example, 20 to 70 Pa · s.

  Next, as shown in FIG. 7B (d), a flux 206 having a second viscosity C2 is applied to the plurality of bumps 204 of the first electronic component 200 (SP13). A method of applying the flux 206 to the plurality of bumps 204 is not particularly limited, but a method of transferring a coating film of the flux 206 formed on a flat surface using a squeegee to the bumps 204 is preferable. The thickness of the coating film of the flux may be appropriately adjusted in consideration of the size of the bump 204 and the coating amount per bump. For example, a coating film of the flux 206 is formed on a predetermined transfer table, the bump 204 of the first electronic component 200 is brought into contact with the coating film, and the flux 206 is attached (transferred) to the bump 204. Thereby, the flux 206 is evenly applied to the bumps 204 of the first electronic component 200.

  The operation of transferring the flux as described above can be performed by using a mounting head that is movable in various directions installed in a predetermined electronic component mounting apparatus. The mounting head includes, for example, a suction nozzle 324d that picks up an electronic component by suction.

  The flux viscosity C2 is relatively determined in relation to the viscosity C1 of the thermosetting resin applied to the first mounting region, and the value is not particularly limited. However, from the viewpoint of facilitating transfer to the solder bumps, when measured at 25 ° C. using a cone plate type E viscometer (using a spindle with a cone angle of 3 ° and a diameter of 28 mm) at a rotational speed of 5 rpm. The viscosity of is preferably 20 to 100 Pa · s, for example.

  Next, as shown in FIG. 7B (e), the first electronic component 200 is mounted on the first mounting region of the substrate 101 (SP14). At this time, the lower surface (main surface) of the first electronic component 200 is in contact with the thermosetting resin 105 applied to the reinforcing position 104. Here, since the viscosity C2 of the flux 206 is set to be higher than the viscosity C1 of the thermosetting resin 105, when the bump 204 coated with the flux 206 enters the thermosetting resin 105, the flux 206 is The amount pulled and wiped off by the thermosetting resin 105 can be kept small. Therefore, the plurality of bumps 204 can all land on the corresponding first electrode 102a via the flux 206, and a sufficient amount of flux can be interposed between the bump and the land. Thereby, at the time of reflow, all the bumps 204 and the first electrode 102a are sufficiently wetted by the flux 206.

  Next, as necessary, as shown in FIG. 7B (f), the second electronic component 210 is mounted on the substrate 101 (SP15). However, the second electronic component 210 may be mounted either before or after the first electronic component 200 is mounted. For example, after the flux 206 and the thermosetting resin 105 are in contact with each other, the second electronic component 210 is mounted before the first electronic component 200 is mounted from the viewpoint of shortening the time during which both components diffuse. May be.

  Thereafter, the substrate 101 on which the first electronic component 200 and the second electronic component 210 are mounted is heated by a reflow apparatus (SP16). As shown in FIG. 7B (g), since all the bumps 204 and the first electrode 102a are sufficiently wetted by the flux 206 during reflow, the effect of removing oxide on the surface of the bump 204 is enhanced. The melted bump can be sufficiently wet and spread on the land 102b of the substrate. Therefore, conduction at the solder joint and sufficient joint strength are ensured. At the time of reflow, the solder component in the cream solder 103 is also melted and spreads wet on the second electrode 102b. When the reflow process is completed, the solder is cooled and solidified, and the terminals of the first electronic component 200 and the second electronic component 210 are joined to the corresponding electrodes of the substrate 101. The thermosetting resin 105 is cured to form a resin reinforcing portion 105a. Further, when the flux 206 is a thermosetting flux, a cured product 206a of the flux is formed.

  In FIG. 7A (c), the thermosetting resin 105 is applied so as to be in contact with the main surface 201s of the first electronic component to be mounted. Therefore, the effect of reinforcing the solder joint is extremely enhanced. However, the thickness of the applied thermosetting resin 105 is not particularly limited.

  FIG. 8A and FIG. 8B show a case where a thinner thermosetting resin 105 is applied to at least a part of the first mounting region of the substrate. For example, the thermosetting resin 105 may be thinly applied so that only 90% or less of the height of the solder bump 204 before melting, or even 80% or less, is in contact with the thermosetting resin 105. Even in such a case, as shown in FIG. 8C, the thermosetting resin 105 can reach the main surface of the first electronic component 200 through the solder bump 204 by the action of surface tension. It is. Therefore, the effect of reinforcing the solder joint can be sufficiently obtained.

  When only the portion of 90% or less of the height of the solder bump 204 before melting is brought into contact with the thermosetting resin 105, the thermosetting resin is placed in most of the space between the electronic component and the substrate like underfill. It will not be filled. Therefore, since a gap can be formed between the bumps, there is an advantage that solder flash hardly occurs. It is also advantageous in that the flux attached to the solder bumps can easily penetrate the thermosetting resin. Furthermore, since the amount of the thermosetting resin interposed between the electronic component and the substrate can be reduced, the work is facilitated even when the electronic component is removed from the substrate and repaired.

  Next, an example of a method for transferring the flux to the solder bumps of the first electronic component using the flux coating film will be described. Here, the case where the transfer unit which supplies the coating film of a flux is used is demonstrated.

  As shown in FIG. 9, the transfer unit 320 includes a base table 320 a provided below, a transfer table 321 provided on the upper surface of the base table 320 a, and a squeegee unit 322 disposed above the transfer table 321. It has. The squeegee unit 322 includes a first squeegee member 322a and a second squeegee member 322b having a length substantially equal to the width of the transfer table, and these are arranged in parallel with a predetermined interval therebetween. Each squeegee member can be moved up and down by an elevating mechanism built in the squeegee unit 322, that is, can advance and retreat with respect to the coating film formed on the transfer table 321.

  As shown in FIG. 10, by moving the squeegee unit 322 relative to the transfer table 321 in the direction of the arrow, the flux 206 in the transfer table 321 is thinly stretched by each squeegee member. A coating film is formed.

After that, as shown in FIG. 11, the solder bump 204 of the first electronic component 200 is brought into contact with the coating film of the flux 206, and the flux 206 is transferred to the solder bump 204.
FIG. 12 is a flowchart when the flux 206 is transferred to the solder bump 204. After the first electronic component 200 is picked up (SP21), the mounting head 324 moves above the transfer unit 320 (SP22), and as shown in FIG. 11, the suction nozzle 324d is moved up and down to move the first electronic component 200. The solder bump 204 is brought into contact with the coating film of the flux 206, and the flux 206 is transferred to the solder bump 204 (SP23). At this time, the viscosity C2 of the flux is adjusted to an appropriate height so that the first electronic component 200 does not fall off from the suction nozzle 324d with the first electronic component 200 still attached to the coating film of the flux 206. Thereafter, the mounting head 324 moves to the first mounting area of the substrate 101 (SP24), and the first electronic component 200 is placed on the substrate 101 so that the plurality of solder bumps 204 are landed on the corresponding first electrodes 102a. Install (SP25). Such movement of the mounting head 324 is controlled by a command from a predetermined control unit.

Next, the relationship between the thermosetting resin viscosity C1 and the flux viscosity C2 will be described in more detail.
The viscosity C1 of the thermosetting resin and the viscosity C2 of the flux only need to satisfy C1 ≦ C2. However, as C2 increases with respect to C1, the thermosetting resin is used when the first electronic component is mounted in the first region. The effect of suppressing the amount of the flux that is pulled and wiped down is increased. As a method for increasing C2 with respect to C1, it is conceivable to decrease the viscosity C1 of the thermosetting resin or increase the viscosity C2 of the flux. However, if the viscosity C1 of the thermosetting resin is too low, the thermosetting resin may excessively spread due to dripping, and may protrude from the first mounting region. On the other hand, if the flux viscosity C2 is too high, it may be difficult to transfer the flux to the solder bumps. From the above, C1 and C2 satisfy 2 × C1 ≦ C2 from the viewpoint of suppressing the amount of flux to be wiped down, suppressing excessive spread of the thermosetting resin, and facilitating transfer of the flux. Is preferable, 1.7 × C1 ≦ C2 is more preferable, and 1.5 × C1 ≦ C2 is more preferable.

Next, a thermosetting resin (first thermosetting resin) serving as a reinforcing resin will be described.
Although it does not specifically limit to a thermosetting resin, An epoxy resin, a phenol resin, a melamine resin, a urethane resin etc. can be used. The thermosetting resin may contain a curing agent, a curing accelerator, and the like. As the curing agent, an acid anhydride, an aliphatic or aromatic amine, imidazole or a derivative thereof is preferably used, and examples of the curing accelerator include dicyandiamide. The thermosetting resin may further contain a filler such as a thixotropic agent, a pigment, a coupling agent, a reactive diluent (viscosity modifier), carbon black, and inorganic ceramic particles. The viscosity of the thermosetting resin can be controlled, for example, by changing the content of the reactive diluent or inorganic ceramic particles.

  Components such as an activator included in the flux may be included in the thermosetting resin. Thereby, even when the thermosetting resin penetrates between the land and the solder bump, the wettability between the melted bump and the land is more reliably ensured. However, when the flux component is mixed with the thermosetting resin, the viscosity change of the thermosetting resin increases, and the pot life of the thermosetting resin tends to be shortened. Good. In the present invention, since the flux is previously applied to the solder bumps of the BGA type electronic component, even if the flux component is included in the thermosetting resin, a small amount is sufficient. Therefore, the temperature control of the thermosetting resin is easy.

Next, the flux will be described.
The flux may be any material that has an action of removing oxides and the like existing on the surface of the land and the surface of the solder bump and reducing the surface tension of the solder during solder joining. By these actions (hereinafter referred to as “active action”), the wettability between the solder and the lands is increased, and good solder bonding with high reliability becomes possible.

  The composition of the flux is not particularly limited, and includes, for example, a base agent such as rosin, an activator, a solvent, a thixotropic agent, and the like. A thermosetting flux may be used as the flux. When the thermosetting flux is used, even when the flux and the thermosetting resin are in contact with each other, normal curing of the thermosetting resin is hardly inhibited. This is considered because the movement of the active component of the flux to the thermosetting resin is suppressed. The thermosetting flux can be obtained by including a thermosetting resin component in the flux. As the thermosetting resin component contained in the flux, for example, an epoxy resin is suitable from the viewpoint of excellent heat resistance. Moreover, as long as the pot life of the thermosetting flux is not impaired, a thermosetting resin component curing agent or the like may be included in the thermosetting flux. Such a thermosetting flux also functions as a bonding material.

  As described above, as a method of increasing the viscosity C2 of the flux with respect to the viscosity C1 of the thermosetting resin, it is conceivable to increase the viscosity C2 of the flux. Here, an example of a method for increasing the viscosity C2 of the flux will be described.

  The viscosity C2 of the flux can be increased, for example, by including a particulate solid component in the flux. The solid component not only increases the viscosity of the flux, but also easily penetrates the thermosetting resin and contacts the land when the solder bump is landed on the land of the substrate. Therefore, it becomes easier to achieve a state in which the solder bump and the land are sufficiently wet during reflow.

  The solid component may be a solid at 50 ° C. or less, for example, in a state dispersed in the flux. This is because the operation of mounting the electronic component on the substrate is usually performed at room temperature. That is, it is preferable that the solid component has a melting point of more than 50 ° C., more preferably 100 ° C. or more.

  Although content of the solid component disperse | distributed to a flux is not specifically limited, For example, 5 mass% or more is enough. However, if the content of the solid component is too large, the viscosity of the flux may be too high. Therefore, the content of the solid component is preferably 30% by mass or less, for example.

  The average particle size of the solid component is not particularly limited, but if the solid component of the flux is too large for the solder bump, it is difficult to sufficiently adhere the solid component to the solder bump when transferring the flux to the solder bump. It may become. Therefore, it is preferable that the average particle diameter of the solid component is, for example, 1/10 or less of the height of the solder bump. The size of the solder bump varies, but is usually about 700 μm, and even a small one is about 100 μm. Therefore, the average particle diameter of the solid component may be 50 μm, for example, and is preferably 30 μm or less. If the average particle size of the solid component is too small, it may take a long time to disperse the solid component in the flux, or the viscosity may increase more than necessary. Therefore, the average particle diameter of the solid component is, for example, preferably 0.1 μm or more, and more preferably 1 μm or more. However, the upper limit and the lower limit of these average particle diameters can be arbitrarily combined. In addition, the average particle diameter of a solid component is a numerical value calculated | required by microscope observation. For example, an average value of the maximum diameters of any ten solid component particles observed with an electron microscope may be obtained.

As the solid component, a component that melts during reflow and does not hinder solder joints is suitable. For example, it is preferable to use at least one selected from the group consisting of an activator and a thermosetting resin (second thermosetting resin) . This is because they are easily melted during reflow and are suitable as a modifying component for flux and thermosetting flux. Among them, it is preferable to use an activator having an average particle size of 0.1 μm to 50 μm.

As the thermosetting resin that can be used as the solid component, for example, at least one selected from the group consisting of epoxy resins, phenol resins, melamine resins, and these curing agents (including curing accelerators) can be used. Moreover, as an activator, at least 1 sort (s) selected from the group which consists of organic acid, amines, and these halides can be used, for example. These materials may be used individually by 1 type, and may be used in combination of multiple types. Examples of the halogen contained in the halide include bromine and chlorine. Boron based activators can also be used.

  The epoxy resin is not particularly limited, but is bisphenol A type epoxy resin, bisphenol F type epoxy resin, various polyfunctional epoxy resins, flexible epoxy resin, glycidyl ester type epoxy resin, polymer type epoxy resin, biphenyl type epoxy. Resin etc. can be illustrated. Although it does not specifically limit as a phenol resin, A novolak type phenol resin, a resol type phenol resin, etc. are mentioned. Although it does not specifically limit as a melamine resin, A methylated melamine resin, a butylated melamine resin, etc. are mentioned. These may be used alone or in combination of two or more.

  As a curing agent for these resins, an acid anhydride, an aliphatic amine, an aromatic amine, an imidazole, an imidazole derivative, dicyandiamide, and the like can be used as in the case of the curing agent for the thermosetting resin. These may be used alone or in combination of two or more.

  Suitable organic acids that can be used as a solid component include aliphatic carboxylic acids and aromatic carboxylic acids. For example, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, oxalic acid, and malon are suitable. Acid, succinic acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, tartaric acid, citric acid, benzoic acid, phthalic acid, salicylic acid, anisic acid, phenylacetic acid, diphenylacetic acid, cinnamine An acid etc. are mentioned. Examples of amines include monoethanolamine, diethanolamine, triethanolamine, hexamethylenediamine, tetramethylenediamine, morpholine, hexylamine, octylamine, butylamine, propylamine, alanine, and toluidine. A salt of an amine and an organic acid (amine organic acid salt) may be used. Examples of the halide of the activator include salts of the above amines and hydrogen halides (for example, hydrochlorides and odorates). These may be used alone or in combination of two or more.

Next, an example of the device configuration of the electronic component mounting line will be described with reference to FIG.
The electronic component mounting line 300 is formed by connecting a plurality of devices with a substrate transport conveyor, and performs solder paste printing, electronic component mounting, reflow, etc. on the substrate while moving the substrate from upstream to downstream by the connected substrate transport conveyor. It is performed sequentially.

The electronic component mounting line 300 is
(I) a substrate supply device 301 for supplying a substrate 101 having a first mounting area for mounting the first electronic component 200 and a second mounting area for mounting the second electronic component 210;
(Ii) a screen printing device 302 that applies cream solder to the second electrode 102b in the second mounting region of the substrate 101 supplied from the substrate supply device 301 by screen printing;
(Iii) a resin application device 303 for applying the thermosetting resin 105 to at least a part of the first mounting region of the substrate 101;
(Iv) a first electronic component mounting device 304 for mounting the BGA type first electronic component 200 on the first mounting region of the substrate 101 conveyed from the resin coating device 303;
(V) a second electronic component mounting device 305 for mounting the second electronic component 210 on the second electrode 102b coated with cream solder;
(Vi) a reflow device 306 for soldering the first electronic component 200 and the second electronic component 210 to the substrate 101 by heating the substrate 101 on which the first electronic component and the second electronic component are mounted to melt the solder;
(Vii) a substrate recovery device 307.

  Here, the resin coating device 303 includes a coating head that supplies thermosetting resin to the first mounting region, and the first electronic component mounting device includes a component supply unit that supplies the BGA type first electronic component, A substrate holding unit that holds and positions the substrate, a transfer unit that supplies a coating film of flux, and a mounting head that moves the first electronic component are provided. The mounting head can pick up and hold the first electronic component by the suction nozzle, release it by releasing the suction, and can move above the component supply unit, the substrate holding unit, and the transfer unit. .

FIG. 14 is a configuration diagram of a configuration in which a resin coating device 303 and a first electronic component mounting device 304, which are a part of the electronic component mounting line 300, are connected, as viewed from above.
The resin coating device 303 and the first electronic component mounting device 304 are connected to the substrate transport conveyors 309a and 309b provided on the base forming the stage of each device, so that the substrate transported from the screen printing device 302 is obtained. The line for conveying 101 is comprised. The substrate transport conveyors 309a and 309b function as a substrate holding unit for transporting and positioning the substrate to a working position for mounting electronic components and applying resin in each apparatus.
In addition, the arrow in FIG. 14 shows the advancing direction from the upstream of the electronic component mounting line 300 to the downstream.

  The resin coating device 303 includes a substrate transport conveyor 309 a disposed in the center and a coating head 323 having a coating nozzle 323 d that discharges the thermosetting resin 105. The resin coating device 303 applies the thermosetting resin 105 to at least a part of the first mounting region of the substrate 101 positioned on the substrate holding unit 310a. The coating head 323 is supported by an XYZ moving mechanism (not shown), and moves in the horizontal and vertical directions in the upper space of the substrate transport conveyor 309a under the control of the XYZ moving mechanism by a predetermined control unit. Operations such as movement of the coating head 323 and ejection of the thermosetting resin 105 from the coating nozzle 323d are controlled by commands from the control unit.

  The first electronic component mounting device 304 forms a substrate film conveyor 309b, a first component supply unit 314, a mounting head 324, and a flux coating film as shown in FIGS. A transfer unit 320. The first electronic component mounting device 304 mounts the first electronic component 200 on the first mounting region of the substrate 101 which is transported from the resin coating device 303 and positioned on the substrate holding portion 310b. The first electronic component mounting device 304 is disposed in a state where the substrate transport conveyor 309 b is connected to the substrate transport conveyor 309 a of the resin coating device 303, that is, adjacent to the downstream of the resin coating device 303. For this reason, the board | substrate which finished application | coating of the thermosetting resin with the resin coating device 303 is immediately conveyed to the 1st electronic component mounting apparatus, and a 1st electronic component is mounted. The first component supply unit 314 is a tray feeder, and a tray in which a plurality of first electronic components 200 are stored is disposed. The mounting head 324 is supported by an XY movement mechanism (not shown), and moves from the first component supply unit 314 to the upper space of the substrate transport conveyor 309b under the control of the XY movement mechanism by a predetermined control unit.

  The mounting head 324 includes a suction nozzle 324d that moves up and down by a built-in lifting mechanism, and picks up the first electronic component 200 from the first component supply unit 314 by the lifting and lowering operation and suction of the suction nozzle 324d, and transfers it. After the flux is transferred to the solder bumps by the unit 320, the first electronic component 200 is mounted on the substrate 101 by lifting and lowering from above the first mounting region of the substrate 101 and suction release (vacuum break).

  The transfer unit 320 has a mechanism capable of supplying a flux coating film having a thickness suitable for transferring to the bumps 204 of the first electronic component 200.

  Note that the arrangement of each of the above devices is merely an example, and a line having various other arrangements may be configured, or a composite device having a plurality of device functions may be used. For example, the second electronic component mounting device 305 may be disposed between the screen printing device 302 and the resin coating device 303. Further, the resin coating device 303 and the first electronic component mounting device 304 may be an integrated unit device. In such a unit device, the coating head and the mounting head are integrated so as to move in a common space, and more efficient mounting is possible. Moreover, the unit apparatus with which the 1st electronic component mounting apparatus 304 and the 2nd electronic component mounting apparatus 305 were integrated may be sufficient. Furthermore, a unit device in which the resin coating device 303, the first electronic component mounting device 304, and the second electronic component mounting device 305 are integrated may be used. In such a unit device, the coating head and the mounting head are not only integrated so as to move in a common space, but the first electronic component and the second electronic component are transferred to the substrate by one mounting head. Can be installed.

  Here, the common space in which the coating head and the mounting head are movable is the space above the base having a single stage on which one or more component supply units and one or more substrate holding units are installed. is there. The movement path of the coating head and the movement path of the mounting head may or may not overlap each other.

Next, a unit device in which the resin coating device, the first electronic component mounting device, and the second electronic component mounting device are integrated will be described with reference to FIGS. 15 and 16. In FIG. 16, elements having the same functions as those in FIG.
FIG. 15 is an example of a device configuration of the electronic component mounting line 300X including the unit device, and FIG. 16 is a configuration diagram of the unit device 304X as viewed from above.

  The unit device 304X includes a substrate transfer conveyor 309 disposed in the center of the base, and holds an upstream substrate holding the substrate 101 that is a work target of the coating head 324 in the middle of the path of the substrate transfer conveyor 309. A portion 310c and a downstream substrate holding portion 310d that holds the substrate 101 that is the work target of the mounting head 325 are provided.

  The coating head 323 moves in the horizontal direction and the vertical direction in the upper space of the upstream substrate holding part 310c by the control of the XYZ moving mechanism by a predetermined control part. On the other hand, the mounting head 324 moves from the first component supply unit 314 and the second component supply unit 315 to the upper space of the downstream substrate holding unit 310d under the control of the XY movement mechanism by a predetermined control unit. That is, the coating head 323 and the mounting head 324 share the upper space of the substrate transport conveyor 309 in the same unit apparatus, the coating head 323 can move in the upstream space, and the mounting head 324 moves in the downstream space. It is configured to be movable.

  In the upstream substrate holding part 310 c, the reinforcing resin 105 is applied to the reinforcing position 104 of the substrate 101 by the application head 323. When the work in the upstream side substrate holding unit 310c is completed, the substrate 101 is then transferred by the substrate transfer conveyor 309 to the downstream side substrate holding unit 310d provided in the same unit device 304X. Then, the first electronic component 200 and the second electronic component 210 are mounted by the mounting head 324 on the first mounting region and the second mounting region of the substrate 101 held by the downstream substrate holding unit 310d.

  In the unit device 304X, while the reinforcing resin 105 is applied to the reinforcing position 104 of the substrate 101 held by the upstream substrate holding unit 310c, the first of the other substrate 101 held by the downstream substrate holding unit 310d is applied. Since the first electronic component 200 and the second electronic component 210 can be mounted in the mounting area and the second mounting area, the work efficiency when manufacturing the mounting board is improved.

In the above description, the unit device X including the upstream substrate holding unit 310c and the downstream substrate holding unit 310d has been described. However, the number of substrate holding units may be one, or three or more. When there is only one substrate holding unit, the movement path of the coating head and the movement path of the mounting head overlap each other. By controlling the order of operation of the coating head and the mounting head by a predetermined control unit, Efficient mounting work can be realized. The second component supply unit 315 may be installed in the unit device as necessary, and the unit device X may be a device that only mounts the first electronic component 200.
Next, the present invention will be described based on examples, but the present invention is not limited to the following examples.

Example 1
First, lands having a predetermined pattern were formed as first electrodes at predetermined locations on the FR4 substrate. Next, the following thermosetting resin was applied as a reinforcing resin so that all the lands were completely covered.
On the other hand, a coating film of the following flux A is formed using a squeegee on a transfer table, and the coating film is composed of a Sn-Ag-Cu solder of a flip chip BGA type electronic component (1005 chip) as the first electronic component. Transferred to the bumps (melting point: about 220 ° C.). Thereafter, BGA type electronic components were mounted on the substrate so that the bumps landed on the corresponding lands. At that time, the application amount of the thermosetting resin was adjusted so that the reinforcing resin was in contact with the entire lower surface of the BGA type electronic component. Then, the board | substrate which mounted the BGA type | mold electronic component was heated by 240 degreeC-250 degreeC with the reflow apparatus, and the solder joint was performed.

  Next, when the BGA type electronic component that had been soldered was peeled off from the substrate and it was observed whether or not the bumps were sufficiently attached to the lands, the bump residues were sufficiently attached to all of the lands.

<Thermosetting resin>
Resin composition mainly composed of epoxy resin Viscosity at 25 ° C .: 40 Pa · s

<Flux A>
Thermosetting flux containing a solid component of 26% by mass (of which 10% by mass is an activator X having an average particle diameter of 9 μm and a melting point of 223 ° C.) Viscosity at 25 ° C .: 60 Pa · s

Example 2
When the BGA type electronic component is mounted on the substrate, the amount of the thermosetting resin applied is adjusted so that the reinforcing resin does not contact the lower surface of the BGA type electronic component so that the thickness is 75% of the bump height. The same operation as Example 1 was performed except having adjusted. Then, the board | substrate which mounted the BGA type | mold electronic component was heated by 240 degreeC-250 degreeC with the reflow apparatus, and the solder joint was performed.

  Next, when the BGA type electronic component that had been soldered was peeled off from the substrate and it was observed whether or not the bumps were sufficiently attached to the lands, the bump residues were sufficiently attached to all of the lands. In addition, since the hardened | cured material of the thermosetting resin which scooped up through the bump had adhered to the board | substrate sufficiently, the peeling strength at the time of peeling a BGA type electronic component from a board | substrate does not reach Example 1. The strength was sufficient.

Example 3
The same operation as in Example 1 was performed except that the following flux B was used. Then, the board | substrate which mounted the BGA type | mold electronic component was heated by 240 degreeC-250 degreeC with the reflow apparatus, and the solder joint was performed.

  Next, when the BGA type electronic component that had been soldered was peeled off from the substrate and it was observed whether or not the bumps were sufficiently attached to the lands, the bump residues were sufficiently attached to all of the lands.

<Flux B>
Thermosetting flux containing a solid component of 23% by mass (of which 10% by mass is an activator X having an average particle size of 9 μm and a melting point of 223 ° C.) Viscosity at 25 ° C .: 40 Pa · s

<< Comparative Example 1 >>
The same operation as in Example 1 was performed except that the following flux C was used. Then, the board | substrate which mounted the BGA type | mold electronic component was heated by 240 degreeC-250 degreeC with the reflow apparatus, and the solder joint was performed.

  Next, the BGA type electronic component that has been soldered is peeled off from the substrate, and it is observed whether or not the bumps are sufficiently attached to the lands. However, the reinforcing resin entered between the bump and the land.

<Flux C>
Thermosetting flux containing 13% by mass of a solid component in which an activator Y having a melting point of −70 ° C. was dissolved instead of an activator having an average particle diameter of 9 μm and a melting point of 223 ° C. Viscosity at 25 ° C .: 23 Pa · s

  Next, 48 samples made of the same substrate and BGA type electronic component as described above were prepared, and the total connection resistance value when the electronic component, the solder joint, and the substrate electrode were connected (daisy chain) was measured. A product having a value in the normal range was judged as a non-defective product, and a non-defective product rate (%) was determined.

  In addition, a drop test was performed on a non-defective BGA type electronic component, and the number of drops until the resistance value of the solder joint decreased by 20% or more from the initial value was measured.

  Table 1 shows the compositions of the thermosetting resin and the flux used in the above examples and comparative examples. In Table 1, the indication of solid or liquid indicates the properties of the component at room temperature. The unit of the numerical values in the column is mass%.

  Table 2 summarizes the evaluation items and the evaluation results. ◎ means excellent, ○ means pass, × means fail.

  From the results of Examples 1 to 3 and Comparative Example 1 described above, according to the present invention, when the solder bumps coated with the flux are mounted on the substrate coated with the thermosetting resin, the thermosetting resin is used. It can be understood that the flux can be suppressed from being wiped off. This indicates that the bumps melted at the time of reflow can easily wet the land of the substrate and ensure the reliability of the solder joint.

  In the electronic component mounting method and the electronic component mounting line of the present invention, when an electronic component having a plurality of bumps on the main surface of the package is bonded to the substrate, a flux or a reinforcing resin excellent in storage stability can be used. In addition, reliable electrical continuity and sufficient bonding strength can be ensured. Therefore, the present invention is extremely useful in the field of surface mounting of BGA type electronic components.

  DESCRIPTION OF SYMBOLS 101 ... Board | substrate, 102a ... 1st electrode, 102b ... 2nd electrode, 103 ... Cream solder, 104 ... Reinforcement position, 105 ... Thermosetting resin (resin for reinforcement), 105a: Resin reinforcement (cured product of thermosetting resin), 200: First electronic component (BGA type electronic component), 201: In-component substrate, 201s: Main surface, 202. -Semiconductor element 203 ... Sealing resin, 204 ... Bump, 206 ... Flux, 206a ... Hardened product of flux, 210 ... Second electronic component, 211 ... Terminal for connection, 300, 300X ... electronic component mounting system, 301 ... substrate supply device, 302 ... screen printing device, 303 ... resin coating device, 304 ... first electronic component mounting device, 304X ... Unit device, 305 ..Second electronic component mounting device, 306... Reflow device, 307 .. substrate recovery device, 309, 309a, 309b .. substrate transfer conveyor, 310a-d. First component supply unit, 315, second component supply unit, 320, transfer unit, 320a, base table, 321, transfer table, 322, squeegee unit, 322a, first Squeegee member, 322b ... second squeegee member, 323 ... coating head, 323d ... coating nozzle, 324 ... mounting head, 324d ... suction nozzle

Claims (9)

In an electronic component mounting method for mounting an electronic component having a plurality of solder bumps on a main surface of a package on a substrate having a mounting region provided with a plurality of lands corresponding to the plurality of solder bumps,
Applying a first thermosetting resin having a first viscosity C1 to at least a part of the mounting region;
Applying a flux having a second viscosity C2 that satisfies 1.5 × C1 ≦ C2 to the plurality of solder bumps;
Mounting the electronic component on the substrate such that a plurality of solder bumps coated with the flux land on the corresponding lands, respectively.
Heating the substrate on which the electronic component is mounted, melting the bump, curing the first thermosetting resin, and allowing to cool, thereby bonding the electronic component to the substrate; Including
The flux includes a solid component that is particulate and melts upon heating;
The solid component is at least one selected from the group consisting of an activator and a second thermosetting resin;
The electronic component mounting method, wherein the activator is at least one selected from the group consisting of organic acids, amines, and halides thereof.   The electronic component mounting method according to claim 1, wherein an average particle diameter of the solid component is 0.1 to 50 μm.   The electronic component mounting method according to claim 1, wherein the first thermosetting resin is applied so as to spread over 80% or more of the mounting region.   The first thermosetting resin is applied to a thickness such that a portion of 90% or less of the height before melting of the plurality of solder bumps is in contact with the first thermosetting resin. Electronic component mounting method.   5. The electronic component according to claim 1, wherein the second thermosetting resin is at least one selected from the group consisting of an epoxy resin, a phenol resin, a melamine resin, and a curing agent thereof. Implementation method.   The electronic component mounting method according to claim 1, wherein a content of the solid component in the flux is 5% by mass or more and 30% by mass or less. In an electronic component mounting line for mounting an electronic component having a plurality of solder bumps on a main surface of a package on a substrate having a mounting region provided with a plurality of lands corresponding to the plurality of solder bumps,
A resin coating device that applies a first thermosetting resin having a first viscosity C1 to at least a part of the mounting region of the substrate;
After the flux having the second viscosity C2 satisfying 1.5 × C1 ≦ C2 is applied to the plurality of solder bumps, the electronic component is mounted so that the plurality of solder bumps land on the corresponding lands, respectively. An electronic component mounting apparatus mounted on the substrate;
A reflow device that heats the substrate on which the electronic component is mounted, melts the bump, cures the first thermosetting resin, and cools, thereby bonding the electronic component to the substrate; With
The flux includes a solid component that is particulate and melts upon heating;
The solid component is at least one selected from the group consisting of an activator and a second thermosetting resin;
The electronic component mounting line, wherein the activator is at least one selected from the group consisting of organic acids, amines, and halides thereof. The resin coating device is
An application head for supplying the first thermosetting resin to the mounting region;
The electronic component mounting device is
A component supply unit for supplying the electronic component;
A substrate holding unit for holding and positioning the substrate;
A transfer unit for supplying the coating film of the flux;
A mounting head capable of holding and releasing the electronic component and movable above the component supply unit, the substrate holding unit, and the transfer unit;
The electronic component mounting line according to claim 7 , wherein the resin coating device and the electronic component mounting device are integrated so that the coating head and the mounting head can move in a common space.   The electronic component mounting line according to claim 7 or 8, wherein a content of the solid component in the flux is 5% by mass or more and 30% by mass or less.

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