WO2017065073A1 - Bonding head and mounting device - Google Patents

Abstract

Provided are a bonding head which offers excellent cooling performance even after repeated heating and cooling, and which does not adversely affect mounting quality, and a mounting device using the same. Specifically, there are provided a bonding head and a mounting device using the same, the bonding head being provided with: an attachment tool which holds an electronic component on a lower surface thereof; a heater disposed on an upper portion of the attachment tool; and a heat-insulating block disposed on an upper portion of the heater, wherein the heater has a plurality of grooves formed in an upper surface thereof, and, in an interface between the upper surface of the heater and a lower surface of the heat-insulating block, a gap is provided in an area including the region in which the grooves are provided.

Description

Bonding head and mounting device

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

As a method for mounting an electronic component such as a semiconductor chip on a substrate such as a wiring substrate, a flip chip method is known. In the flip-chip method, an electronic component electrode and a substrate electrode are bonded by thermocompression bonding using a mounting apparatus 1 as shown in FIG.

In the mounting apparatus 1 in 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. Thereafter, the alignment mark provided on the substrate B held on the substrate stage 4 and the alignment mark provided on the electronic component C are recognized by the image recognition means 5 to perform alignment. The alignment is performed by moving at least one of the bonding head 2 and the substrate stage 4 in an 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 pressure-bonded to the substrate B while heating and heating, and the electrode of the electronic component C and the electrode of the substrate B are joined. When the bonding is completed, the bonding head 2 releases the holding of the electronic component C, moves up by the bonding unit 3, holds the electronic component C to be mounted next at the tip portion, and the above-described series of operations is performed.

Here, the bonding head 2 is configured as shown in FIG. That is, the bonding head 2 includes an attachment tool 20 that sucks and holds the electronic component C on the lower surface, a heater 21 that is disposed above the attachment tool 20, and a heat insulating block 22 that is disposed 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. However, in order to efficiently supply the heat of the heater 21 to the electronic component C, heat transfer to the upper side of the heater 21 is performed. Insulation block 22 is arranged to suppress this. Further, the heat insulating block 22 is connected to the head main body 24 via the holder 23.

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

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

Therefore, a method of cooling a heater by providing a plurality of grooves in the heater and flowing cooling air from the inside of the heater through a flow path formed by overlapping the heater and the heat insulating block has been proposed (for example, Patent Document 2).

An example is shown in FIG. FIG. 7 shows 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 that constitute the portion shown in FIG. 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 overlapping the heat insulating block 22 and the heater 21 shown in FIG. On the other hand, the heat insulation block 22 is formed with a recess 22D in a range extending over all the grooves 21U of the heater 21, and is provided with a vent hole 22V connected to the recess 22D.

For this reason, by sending the cooling air to the ventilation hole 22V, the cooling air flows from the vicinity of the center of the heater 21 to both side surfaces (forward and backward in FIG. 7), and the heater 21 is cooled from the inside. 7 and 8, the groove 21U and the tubular flow path 21P are drawn larger for the sake of explanation, but in practice, a large number of grooves 21U (tubular flow paths 21P) each having a piece of less than 1 mm are formed.

Thus, the method of forming the flow path by forming the groove 21U on the upper surface of the heater 21 and overlapping the lower surface 22S of the heat insulating block 22 allows the heater 21 to be cooled from the inside, and therefore, compared with the case of blowing cooling air from the outside. This is an advantageous cooling method.

Japanese Patent Laid-Open No. 10-340915 JP 2014-22629 A

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 in FIG. As a result, heat transfer from the upper portion 21 </ b> T of the wall 21 </ b> W to the outside is hindered, resulting in 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 increased, heat transfer from the heater 21 to the heat insulation block 22 is present even slightly, so that the temperature of the heat insulation block 22 with low thermal conductivity and low heat dissipation rises. As a result, when the heater 21 is cooled, heat transfer from the heat insulating block 22 (which is in close contact with the heater 21) to the heater 21 occurs, which is also an adverse effect when the heater 21 is cooled.

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 is free from air leakage between each other. There is no state. For this reason, if there is a variation in the shape of the tubular flow path 21P (due to variations in processing accuracy when forming the groove 21U, etc.), the cooling effect differs between the individual tubular flow paths 21P, resulting in uneven cooling within the heater surface. .

On the other hand, in this method, since the heater 21 and the heat insulation block 22 are fixed in the vertical direction by fastening parts near the center, the heater 21 and the heat insulation block 21 in the contact surface other than the vicinity of the center are thermally expanded and laterally expanded. Can shrink. For this reason, in the form in which the heater 21 and the heat insulating block 22 in which a large number of minute grooves 21U are formed on the upper surface are overlapped, there may be a negative effect due to repeated heating and cooling.

This adverse effect is caused by the difference in the material of the heater 21 and the heat insulation block 22, and a temperature difference due to the difference in thermal conductivity can be produced at the interface between the heater and the heat insulation member during temperature rise / cooling. It relates to the generated stress. For example, when the heater 21 is a combination of aluminum nitride and the heat insulating block 22 is ADCERAM (registered trademark), the thermal expansion coefficient is about 5 × 10 ⁻⁶ / K, but the thermal conductivity is 100 times higher. Because of these differences, a large temperature difference is created at the interface between the two materials, resulting in a difference in elongation due to thermal expansion. That is, since a large number of narrow grooves 21U are formed on the upper surface of the heater 21, the thin wall 21W (forming the groove 21U) is easily affected by stress, and the upper portion 21T of the wall 21W is deformed or generates friction. . Even if such deformation and friction are negligible, the upper portion 21T of the wall 21W is scraped as shown in FIG. 10 while the temperature of the heater 21 is repeatedly raised and cooled (AB in FIG. 10). In some cases, the bottom surface 22S of the heat insulating block 22 may be scraped or damaged (BR in FIG. 10). In particular, in the case of ceramic, since it is a hard and brittle material, the corner portion of the upper portion 21 of the wall 21 </ b> W has a drawback that stress concentrates and is easily chipped.

When the wall 21W forming the groove 21U of the heater 21 or the lower surface 22S of the heat insulating block 22 is scraped or damaged, the wear powder PW and debris BP enter the groove 21U, and a part is produced outside together with the cooling air. Remains in the groove 21U and closes the tubular channel 21P. Here, the wear powder PW and debris BP discharged to the outside become foreign matters 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 the cooling air by closing the tubular flow path 21P and causes uneven cooling.

The present invention has been made in view of the above problems, and provides a bonding head that is excellent in cooling performance and does not adversely affect mounting quality even if heating and cooling are repeated, and a mounting apparatus using the same. It is.

In order to solve the above problems, the invention described in claim 1
A bonding head used for thermocompression bonding of electronic components,
An attachment tool for holding electronic components on the bottom surface;
A heater disposed on top of the attachment tool;
A heat insulation block disposed on top of the heater;
A plurality of grooves are formed on the upper surface of the heater,
In the bonding head, a gap is provided in a range including the region in which the groove is provided at an interface between the upper surface of the heater and the lower surface of the heat insulating block.

The invention according to claim 2 is the bonding head according to claim 1,
The bonding head is characterized in that an interval of the gap is not less than 0.3% and not more than 40% of the depth of the groove.

Invention of Claim 3 is the bonding head of Claim light 1 or Claim 2, Comprising:
The bonding head is characterized in that the gap is formed by providing a recess on a lower surface of the heat insulating block.

The invention according to claim 4 is a mounting apparatus comprising the bonding head according to any one of claims 1 to 3.

The bonding head of the present invention and the mounting apparatus using the same can mount electronic components that have excellent cooling performance and do not adversely affect mounting quality even if heating and cooling are repeated.

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

Embodiments of the present invention will be described with reference to the drawings.
A mounting apparatus and a bonding head according to an embodiment of the present invention are configured like the mounting apparatus 1 shown in FIG. 5 and the bonding head 2 shown in FIG. FIG. 1 is an enlarged view of FIG. FIG. 2 shows a three-sided view of the heat insulation block 22 shown in FIG.

In FIG. 1, the material of the heater 21 is ceramics, and a heating resistor is embedded inside. As 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, ceramic is also used as the material of the heat insulating block 22, but the thermal conductivity is preferably 5 W / m · K or less, preferably 1.5 W / m · K or less.

The heater 21 in FIG. 1 has the same shape as that shown in the three-view diagram in FIG. 8, and a plurality of grooves 21U having a width WU and a depth HU are formed from one side surface of the upper surface to the opposite side surface. is there. A plurality of comb-like walls 21W are formed by forming a plurality of grooves 21U. In the heater 21 shown in FIG. 8, the upper portion 21T of the wall 21W is the same height as the upper surface 21S of the heater 21, and the height of the wall 21W is HU. The wall 21W has a width 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 insulation block 22 of FIG. 1 has the shape of the three views shown in FIG. Unlike the one shown in FIG. 9, the heat insulating block 22 shown in FIG. 2 has a second lower surface 22C. The second lower surface 22C is flat and parallel to the lower surface 22S, but has a step height HG with respect to the lower surface 22S. When the lower surface 22S is placed on a flat surface, the gap 22G has a tunnel shape. The second lower surface 22C has a width that forms a gap 22G in a range including all the grooves 21U, with the longitudinal direction of the tunnel shape being parallel to the grooves 21U when the heat insulating block 22 is superimposed on the heater 21. Yes.

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

On the other hand, due to the low thermal conductivity of the air, heat from the upper portion 21T of the wall 21W to the second lower surface 22C is hardly transmitted by the gap 22G of the heat insulating material. For this reason, the temperature rise of the heat insulation block 22 when the heater 21 is heated is suppressed. In addition, the amount of heat taken away when the heater 21 generates heat is reduced, and heat can be effectively transferred to the attachment tool 20 side that is attracted and held on the lower surface of the heater 21 during heating and pressure bonding, and to the electronic component C. There is also an effect.

Even if the shape of the groove 21U varies, the upper portion 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. Is improved.

By the way, the gap HG of the gap formed by the step between the lower surface 22S of the heat insulation block 22 and the second lower surface 22C is determined as follows. That is, the lower limit value is a value at which the upper portion 21T of the wall 21W does not contact the second lower surface of the heat insulation block 22 even when the heater 21 and the heat insulation block 22 are deformed as the heater 21 is heated and cooled. The upper limit 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 the lower limit, the interval HG satisfies the following formula (1) so that the upper portion 21T does not contact the second lower surface 22C of the heat insulating block 22 even if the wall 21W is thermally expanded to the maximum. Here, α is a coefficient of thermal expansion of the material constituting the heater 21, and ΔT is a temperature difference between when the heater 21 is heated and when it is cooled.

HG> α × ΔT × HU (1)
On the other hand, as the upper limit value, if the cooling area / flow path volume in terms of cooling efficiency is to be higher than the method without providing the gap 22G, the following equation (2) must be satisfied: 3) is desirable.

(2HU + WU) / (HU × WU) ≦ WT / (HG × (WU + WT)) (2)
HG ≦ WT × HU × WU / ((WU + WT) × (2HU + WU)) (3)
However, the viewpoint of the heat insulation between the heater 21 and the heat insulation block 22 and the effect of reducing the cooling unevenness can be obtained without satisfying the expression (3). For this reason, there is no problem if the cross-sectional area formed by the gap 22G is equal to the cross-sectional area formed by the groove 21U as a condition for obtaining the effect of effectively feeding cooling air into the groove 21U. That is, it is only necessary to satisfy Expression (5) as a condition for the interval HG from Expression (4).

HG × (WU + WT) ≦ HU × WU (4)
HG ≦ HU × WU / (WU + WT) (5)
Conditions satisfying such conditions vary depending on the shape and arrangement of the groove 21U, but a specific value is preferably in the range of 0.3% to 40% of the depth HU of the groove 21U.

Incidentally, since the cooling effect can be expected as the number of the 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 is increased, it is desirable to increase the depth within a range in which the heating resistor is not hindered. Here, increasing the number of grooves 21U and increasing the depth HU decreases the mechanical strength of the wall 21W, but the upper portion 21T of the wall 21W does not contact the heat insulating block 22 as described above. So it will not be stressed. For this reason, as compared with the prior art, the groove 21U can be formed deeper and deeper, which is effective in improving the cooling effect.

Thus, 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. For this reason, in the mounting apparatus 1 using the bonding head 2 of the present embodiment, the tact time of electronic component mounting can be shortened without adversely affecting the mounting quality.

As described above, the example in which the gap 22G is provided in the heat insulating block 22 has been described with reference to FIG. 1, but the present invention is not particularly limited as long as the upper portion 21T of the wall 21W does not contact the heat insulating block 22. That is, as in another embodiment shown in FIG. 3, a gap 21 </ b> G that lowers the upper portion 21 </ b> T of the wall 21 </ b> W may be provided with respect to the upper surface 22 </ b> S of the heater 21. That is, the same effect as the configuration of FIG. 1 can be obtained by using the heater 21 shown in FIG. 4 in combination with the heat insulating block 22 shown in FIG. Here, the gap 21G of the heater 21 is also preferably set in the same range as the gap HG of the gap formed by the step between the lower surface 22S of the heat insulation 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 perform heating and cooling from both sides. good. When the electronic component C is small and the volume on the substrate B side is large and the amount of heat from the head side cannot be sufficiently transmitted, it is effective to heat from the substrate B side with a heater, and both the electronic component C and the substrate B are very small. In such a case, it is effective to heat from both sides with a heater.

DESCRIPTION OF SYMBOLS 1 Mounting apparatus 2 Bonding head 3 Bonding unit 4 Substrate 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 Wall which forms a groove 22 Thermal insulation block 22C Second lower surface 22D Dimple 22G Gap 22S Heat insulation block lower surface 22V Vent hole 23 Holder 24 Head body B Substrate C Electronic component AB Wall scraped part BP Fragment BR Wall damaged part HG Gap spacing HU Groove depth PW Wear powder WT Wall width (thickness)
WU groove width

Claims (4)

A bonding head used for thermocompression bonding of electronic components,
An attachment tool for holding electronic components on the bottom surface;
A heater disposed on top of the attachment tool;
A heat insulation block disposed on top of the heater;
A plurality of grooves are formed on the upper surface of the heater,
The bonding head which provided the clearance gap in the range which includes the area | region where the said groove | channel was provided in the interface of the upper surface of the said heater, and the lower surface of the said heat insulation block. The bonding head according to claim 1,
The bonding head is characterized in that an interval of the gap is 0.3% or more and 40% or less of the depth of the groove. The bonding head according to claim 1 or claim 2,
The bonding head is characterized in that the gap is formed by providing a recess on the lower surface of the heat insulating block. A mounting apparatus comprising the bonding head according to any one of claims 1 to 3.

Images