JP6850854B2 - Bonding head and mounting device - Google Patents

Description

The present invention relates to a bonding head used when heat-bonding an electronic component such as a semiconductor chip to a wiring board or the like, and a mounting device provided with the bonding head.

The flip chip method is known as a method of mounting an electronic component such as a semiconductor chip on a substrate such as a wiring board. In the flip-chip method, the mounting device 1 as shown in FIG. 5 is used to thermocompression-bond the electrodes of the electronic component and the electrodes of the substrate.

In the mounting device 1 of FIG. 5, first, the electronic component C is arranged at the tip of the bonding head 2 by an electronic component delivery mechanism (not shown), and is held by the bonding head 2. After that, the image recognition means 5 recognizes the alignment mark provided on the substrate B held on the substrate stage 4 and the alignment mark provided on the electronic component C, and performs alignment. The alignment is performed by moving at least one of the bonding head 2 and the substrate stage 4 in the in-plane direction (XY direction and θ direction) parallel to the substrate B. After the alignment, the bonding head 2 is lowered by the bonding unit 3, and the electronic component C is heated and pressure-bonded to the substrate B to bond the electrode of the electronic component C and the electrode of the substrate B. When the bonding is completed, the bonding head 2 releases the holding of the electronic component C, is raised by the bonding unit 3, holds the electronic component C to be mounted next at the tip portion, and performs the above-mentioned series of operations.

Here, the bonding head 2 has a configuration as shown in FIG. That is, the bonding head 2 includes an attachment tool 20 that attracts and holds the electronic component C on the lower surface, a heater 21 that is arranged above the attachment tool 20, and a heat insulating block 22 that is arranged above the heater 21. The electronic component C is heated by heating the heater 21 having a function of raising the temperature of the attachment tool 20, but in order to efficiently supply the heat of the heater 21 to the electronic component C, heat is transferred upward to the heater 21. The heat insulating block 22 is arranged in order to suppress the above. Further, the heat insulating block 22 is connected to the head body 24 via the holder 23.

In the flip-chip method, solder bumps are often used as electrodes of electronic components, and the electronic components heat-bonded to the substrate need to be cooled until the solder reaches a solid phase state. Further, in recent years, a method of providing a thermosetting adhesive layer in advance on the surface of an electronic component on the electrode side and curing the thermosetting adhesive layer at the time of thermocompression bonding has been adopted. In the construction method, the temperature of the attachment tool must be lower than the curing start temperature of the thermosetting adhesive layer at the stage of holding the electronic parts. Therefore, in a series of takt times, the ratio of the time for cooling the heated attachment tool (and heater) is increasing, and an effective cooling means is required from the viewpoint of shortening the takt time.

For example, Patent Document 1 introduces a method of air cooling using an attachment tool and a cooling blow nozzle provided around the heater. However, in this method, a temperature difference is generated between the air-cooled surface and the inside, and a large reduction in the cooling time to the inside cannot be expected.

Therefore, a method has been proposed in which a plurality of grooves are provided in the heater and cooling air is flowed from the inside of the heater through a flow path formed by superimposing the heater and the heat insulating block to cool the heater (for example, Patent Document 2).

An example thereof is shown in FIG. FIG. 7 shows a portion of the heater 21 and the heat insulating block 22 in the bonding head 2 shown in FIG. Also. 8 and 9 are three views showing the shapes of the heater 21 and the heat insulating block 22 constituting the portion shown in FIG. 7. As shown in FIG. 8, a plurality of grooves 21U are provided on the upper surface of the heater 21, and a plurality of tubular flow paths 21P are formed by superimposing the heat insulating block 22 and the heater 21 shown in FIG. On the other hand, the heat insulating block 22 is formed with a recess 22D in a range straddling all the grooves 21U of the heater 21, and is provided with a ventilation hole 22V connected to the recess 22D.

Therefore, by sending the cooling air into the ventilation hole 22V, the cooling air flows from the vicinity of the center of the heater 21 to both side surfaces (front direction and rear direction in FIG. 7), and the heater 21 is cooled from the inside. In addition, in FIGS. 7 and 8, the groove 21U and the tubular flow path 21P are drawn larger for the sake of explanation, but in reality, a large number of grooves 21U (tubular flow paths 21P) in which each piece is less than 1 mm are formed.

In this way, in the method of forming the groove 21U on the upper surface of the heater 21 and forming the flow path by overlapping with the lower surface 22S of the heat insulating block 22, the heater 21 can be cooled from the inside, so that the method is compared with the case where the cooling air is blown from the outside. This is an advantageous cooling method.

Japanese Unexamined Patent Publication No. 10-340915 Japanese Unexamined Patent Publication No. 2014-22629

In this method, in FIG. 7, the upper portion 21T of the wall 21W forming the groove 21U is in close contact with the lower surface 22S of the heat insulating block 22. As a result, heat transfer from the upper portion 21T of the wall 21W to the outside is hindered, and there is a difficulty in heat dissipation characteristics on the uppermost surface of the heater 21. On the other hand, when the temperature of the heater 21 is raised, the heat transfer from the heater 21 to the heat insulating block 22 is present even if it is small, so that the temperature of the heat insulating block 22 having low thermal conductivity and low heat dissipation rises. As a result, at the stage of cooling the heater 21, heat is transferred from the heat insulating block 22 (which is in close contact with the heater 21) to the heater 21, which is also an adverse effect when cooling the heater 21.

Further, since the upper portion 21T of the wall 21W is in close contact with the lower surface 22S of the heat insulating block 22, the tubular flow path 21P formed by the groove 21U of the heater 21 and the lower surface 22S of the heat insulating block 22 leaks air between each other. It is in a non-existent state. Therefore, if the shape of the tubular flow path 21P varies (due to variations in processing accuracy when the groove 21U is formed, etc.), the cooling effect differs between the individual tubular flow paths 21P, and cooling unevenness occurs in the heater surface. ..

On the other hand, in this method, since the heater 21 and the heat insulating block 22 are fixed in the vertical direction by fastening parts near the center, the heater 21 and the heat insulating block 21 are thermally expanded in the lateral direction on the contact surface other than the center. Can shrink. For this reason, in the form in which the heater 21 in which a large number of minute grooves 21U are formed on the upper surface and the heat insulating block 22 are superposed, adverse effects may occur due to repeated temperature raising and cooling.

This adverse effect is caused by the fact that the materials of the heater 21 and the heat insulating block 22 are different, and when the temperature is raised or cooled, a temperature difference is formed at the interface between the heater and the heat insulating member due to the difference in thermal conductivity. It is related to the generated stress. For example, when the heater 21 is made of aluminum nitride and the heat insulating block 22 is a combination of Adcerum (registered trademark), the coefficient of thermal expansion is ^{about 5 × 10-6} / K, which is the same, but the thermal conductivity is 100 times higher. Because of the above differences, a large temperature difference is created at the interface between the two materials, and a difference in elongation due to thermal expansion occurs. That is, since a large number of narrow grooves 21U are formed on the upper surface of the heater 21, the thin wall 21W (which forms the grooves 21U) is easily affected by stress, and the upper portion 21T of the wall 21W is deformed or causes friction. .. Even if such deformation and friction are extremely slight, as shown in FIG. 10, the upper portion 21T of the wall 21W is scraped as the heater 21 is repeatedly heated and cooled (AB in FIG. 10). , It may be damaged (BR in FIG. 10), or the lower surface 22S of the heat insulating block 22 may be scraped. In particular, in the case of ceramic, since it is a hard and brittle material, there is a drawback that stress is concentrated on the corners of the upper portion 21 of the wall 21W and the material is easily chipped.

When the wall 21W forming the groove 21U of the heater 21 and the lower surface 22S of the heat insulating block 22 are scraped or damaged, the wear debris PW and the debris BP enter the groove 21U, and a part of them is produced to the outside together with the cooling air. Remains in the groove 21U and closes the tubular flow path 21P. Here, the abrasion powder PW and the debris BP discharged to the outside become foreign substances in the mounting atmosphere and adversely affect the mounting quality of the electronic component C. Further, the wear remaining in the groove 21U obstructs the flow of cooling air by blocking the tubular flow path 21P, which causes uneven cooling.

The present invention has been made in view of the above problems, and provides a bonding head having excellent cooling performance and which does not adversely affect the mounting quality even if the temperature is raised and cooled repeatedly, and a mounting device using the same. Is.

In order to solve the above problems, the invention according to claim 1 is
A bonding head used for heat crimping of electronic components.
An attachment tool that holds electronic components on the underside,
A heater located on top of the attachment tool,
It is provided with a heat insulating block arranged on the upper part of the heater.
A plurality of plate-shaped walls are formed by providing a plurality of parallel grooves on the upper surface side of the heater.
Further, the bonding head is provided with a gap between the lower surface of the heat insulating block and the upper portion of the plate-shaped wall by lowering the upper portion of the plate-shaped wall with respect to the upper surface of the heater.

The invention according to claim 2 is the bonding head according to claim 1.
The bonding head is characterized in that the gap between the gaps is 0.3% or more and 40% or less of the height of the plate-shaped wall.

The invention of claim 3 is a mounting apparatus characterized by comprising a bonding head according to claim 1 or claim 2.

With the bonding head of the present invention and the mounting device using the same, it is possible to mount an electronic component which is excellent in cooling performance and does not adversely affect the mounting quality even if the temperature is raised and cooled repeatedly.

It is a figure which shows the heater and the heat insulation block of the bonding head which concerns on one Embodiment of this invention. It is a three-view view which shows the structure of the heat insulation block of the bonding head which concerns on one Embodiment of this invention. It is a figure which shows the heater and the heat insulation block of the bonding head which concerns on another embodiment of this invention. It is a three-view view which shows the structure of the heater of the bonding head which concerns on another embodiment of this invention. It is a figure which shows the structure of the mounting apparatus. It is a figure which shows the structure of a bonding head. It is a figure which shows the heater and the heat insulation block of the bonding head of a known technique. It is a three-sided view which shows the structure of the heater of the bonding head of a known technique. It is a three-view drawing which shows the structure of the heat insulation block of the bonding head of a known technique. It is a figure explaining one of the problems of a known technique.

Embodiments of the present invention will be described with reference to the drawings.
The mounting device and the bonding head according to the embodiment of the present invention have the same configurations as the mounting device 1 shown in FIG. 5 and the bonding head 2 shown in FIG. 6, and the heater 21 and the heat insulating block 22 in the bonding head 2 are provided. FIG. 1 is an enlarged view of. Further, FIG. 2 shows a three-view view of the heat insulating block 22 shown in FIG.

In FIG. 1, the material of the heater 21 is ceramics, and a heat generating resistor is embedded therein. As the ceramics, those having high thermal conductivity (50 W / m · K or more) and excellent electrical insulation are desirable, and aluminum nitride or the like is preferable. On the other hand, although ceramics are used as the material of the heat insulating block 22, the thermal conductivity is preferably 5 W / m · K or less, preferably 1.5 W / m · K or less.

The heater 21 of FIG. 1 has the same shape as that shown in the three views of FIG. 8, and a plurality of grooves 21U having a width of WU and a depth of HU are formed from one side surface of the upper surface toward the opposite side surface. is there. By forming a plurality of grooves 21U, a plurality of comb-shaped walls 21W are formed. In the heater 21 shown in FIG. 8, the upper portion 21T of the wall 21W has the same height as the upper surface 21S of the heater 21, and the height of the wall 21W is HU. The width of the wall 21W is WT, but the width WT is determined by the width WU of the groove 21U and the formation pitch.

On the other hand, the heat insulating block 22 of FIG. 1 has the shape of the three views shown in FIG. The heat insulating block 22 shown in FIG. 2 has a second lower surface 22C, unlike the one shown in FIG. The second lower surface 22C is a flat surface parallel to the lower surface 22S, but has a step of height HG with respect to the lower surface 22S, and when the lower surface 22S is installed on a flat surface, the gap 22G has a tunnel shape. When the heat insulating block 22 is superposed on the heater 21, the second lower surface 22C has a width in which the longitudinal direction of the tunnel shape is parallel to the groove 21U and a gap 22G is formed in a range including all the grooves 21U. There is.

In the bonding head 2 provided with the heater 21 and the heat insulating block 22 shown in FIG. 1, when cooling, cooling air is sent to the ventilation hole 22V by a ventilation system (not shown), and the sent cooling air passes through the recess 22D and passes through the groove 21U. By passing through, the heater 21 is cooled from the inside. Further, the cooling air also passes through the gap 22G, but at that time, it also comes into contact with the upper surface 21T of the wall 21W, so that there is an effect of cooling the heater 21 from the upper surface. This is an effect not found in the prior art, in which the upper surface 21T of the wall 21W is in close contact with the lower surface 22S of the heat insulating block 22 and the upper surface 21T is difficult to cool.

On the other hand, due to the low thermal conductivity of air, the gap 22G of the heat insulating material makes it difficult for heat to be transferred from the upper portion 21T of the wall 21W to the second lower surface 22C. Therefore, the temperature rise of the heat insulating block 22 when the temperature of the heater 21 is raised is suppressed. Further, the amount of heat taken away when the heater 21 generates heat is also reduced, and the heat can be effectively transferred to the attachment tool 20 side, which is attracted and held on the lower surface of the heater 21 at the time of heat crimping, and to the electronic component C. There is also the effect of saying.

Even if the shape of the grooves 21U varies, the upper part of each groove 21U is connected to the gap 22G, and the heat of the groove 21U having a low cooling effect propagates to the surroundings, so that the cooling effect varies between the grooves 21U. Will be improved.

By the way, the distance HG of the gap formed by the step between the lower surface 22S of the heat insulating block 22 and the second lower surface 22C is determined as follows. That is, the lower limit is a value at which the upper portion 21T of the wall 21W does not come into contact with the second lower surface of the heat insulating block 22 even if the heater 21 and the heat insulating block 22 are deformed due to the temperature rise and cooling of the heater 21. The upper limit value is determined by the ratio of the cross-sectional area of the gap 22G to the cross-sectional area of the groove 21U from the viewpoint of cooling efficiency and the like.

That is, as a lower limit value, the interval HG satisfies the following equation (1) so that the upper portion 21T does not come into contact with the second lower surface 22C of the heat insulating block 22 even if the wall 21W expands to the maximum extent. Here, α is the coefficient of thermal expansion of the material constituting the heater 21, and ΔT is the temperature difference between the temperature rise and the cooling of the heater 21.

HG> α × ΔT × HU ・ ・ ・ ・ ・ (1)
On the other hand, as the upper limit value, if the cooling area / flow path volume from the viewpoint of cooling efficiency is to be higher than the method in which the gap 22G is not provided, the following equation (2) must be satisfied. 3) is desirable.

(2HU + WU) / (HU × WU) ≦ WT / (HG × (WU + WT)) ・ ・ (2)
HG ≤ WT x HU x WU / ((WU + WT) x (2HU + WU)) ... (3)
However, the viewpoint of heat insulating property between the heater 21 and the heat insulating block 22 and the effect of reducing cooling unevenness can be obtained even if the equation (3) is not satisfied. Therefore, as a condition for effectively sending the cooling air into the groove 21U, there is no problem as long as the cross-sectional area formed by the gap 22G is equal to the cross-sectional area formed by the groove 21U. That is, the equation (5) may be satisfied as the condition of the interval HG from the equation (4).

HG x (WU + WT) ≤ HU x WU ... (4)
HG ≤ HU x WU / (WU + WT) ... (5)
The conditions for satisfying such conditions differ depending on the shape and arrangement of the groove 21U, but as a specific numerical value, a range of 0.3% to 40% of the depth HU of the groove 21U is preferable.

By the way, since the cooling effect can be expected as the number of grooves 21U in the heater 21 increases, it is desirable to form as many grooves as possible according to the processing accuracy. Further, since the cooling effect can be expected as the depth HU of the groove 21U becomes larger, it is desirable to make the groove 21U deep as long as it does not hinder the embedding of the heat generating resistor. Here, increasing the number of grooves 21U and increasing the depth HU reduces the mechanical strength of the wall 21W, but as described above, the upper portion 21T of the wall 21W does not come into contact with the heat insulating block 22. Therefore, it is not stressed. Therefore, as compared with the prior art, more grooves 21U can be formed deeper, which is effective in improving the cooling effect.

As described above, by using the bonding head 2 described in the present embodiment, the cooling efficiency of the heater 21 can be improved, and the wall 21W of the heater 21 can be prevented from being scraped or damaged. Therefore, in the mounting device 1 using the bonding head 2 of the present embodiment, the tact time for mounting electronic components can be shortened without adversely affecting the mounting quality.

The example in which the heat insulating block 22 is provided with the gap 22G has been described above with reference to FIG. 1, but the present invention is not particular about this if the upper portion 21T of the wall 21W does not come into contact with the heat insulating block 22. That is, as in another embodiment shown in FIG. 3, a gap 21G may be provided so as to lower the upper portion 21T of the wall 21W with respect to the upper surface 22S of the heater 21. That is, even if the heater 21 shown in the three views shown in FIG. 4 is used in combination with the heat insulating block 22 shown in FIG. 9, the same effect as that of the configuration of FIG. 1 can be obtained. Here, it is preferable that the gap 21G of the heater 21 is also in the same range as the gap HG formed by the step between the lower surface 22S of the heat insulating block 22 and the second lower surface 22C shown in FIG.

Further, the present invention may be used not only for the bonding head 2 but also for the substrate stage 4 that holds and heats the substrate B side, or may be used for both the bonding head 2 and the substrate stage 4 to heat and cool from both sides. good. When the electronic component C is minute and the volume is larger on the substrate B side and the amount of heat from the head side is not sufficiently transferred, it is effective to heat the electronic component C from the substrate B side with a heater, and both the electronic component C and the substrate B are minute. If this is the case, it is effective to heat with heaters from both sides.

1 Mounting device 2 Bonding head 3 Bonding unit 4 Board stage 5 Image recognition means 20 Attachment tool 21 Heater 21G Gap 21P Tubular flow path 21S Upper surface of heater 21T Upper part of wall 21U Groove 21W Groove forming wall 22 Insulation block 22C Insulation block 2nd lower surface 22D dent 22G gap 22S lower surface of heat insulating block 22V vent hole 23 holder 24 head body B board C electronic component AB wall scraped part BP debris BR wall damaged part HG gap spacing HU groove depth PW abrasion powder WT Wall width (thickness)
WU groove width

Claims (3)

A bonding head used for heat crimping of electronic components.
An attachment tool that holds electronic components on the underside,
A heater located on top of the attachment tool,
It is provided with a heat insulating block arranged above the heater.
A plurality of plate-shaped walls are formed by providing a plurality of parallel grooves on the upper surface side of the heater.
Furthermore by lowering the upper portion of the plate-shaped wall to the heater upper face, a bonding head provided with a gap at the top of the lower surface and the plate-like wall of the insulation block. The bonding head according to claim 1.
A bonding head characterized in that the gap between the gaps is 0.3% or more and 40% or less of the height of the plate-shaped wall. Mounting apparatus characterized by comprising a bonding head according to claim 1 or claim 2.

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