JP7453035B2 - Crimping head, mounting device using the same, and mounting method - Google Patents

Description

The present invention relates to a pressure bonding head for stacking and mounting electronic components such as semiconductor chips in multiple stages on various substrates such as silicon substrates, glass epoxy substrates, glass substrates, etc., a mounting apparatus using the same, and a mounting method.

Flip chip mounting is a well-known method for mounting electronic components such as semiconductor chips on a substrate. In flip-chip mounting, bumps formed on a semiconductor chip are aligned with electrode pads on a circuit board and then bonded by thermocompression.

In conventional flip-chip mounting, the bumps, which are mainly made of solder, are melted and bonded to electrode pads on the board using thermocompression bonding, and then a liquid sealing resin adhesive is injected into the gap between the semiconductor chip and the board and allowed to harden. It was a target. In contrast, in recent years, a non-conductive film (hereinafter referred to as "NCF") whose main component is a thermosetting adhesive is attached to the bump surface of a semiconductor chip, and then it is temporarily fixed to a substrate. A method (for example, Patent Document 1) of performing thermal compression bonding (main compression bonding) after (temporary compression bonding) is attracting attention.

In the method of temporarily fixing using NCF and then thermocompression bonding, it is also possible to temporarily fix the semiconductor chip C on the entire surface of the substrate S (FIG. 6(a)) and then thermocompression bonding. ) It is possible to bond a plurality of semiconductor chips C at the same time by thermocompression.

Furthermore, if the semiconductor chip C has an electrode on the side opposite to the bump surface using a through electrode, as shown in FIG. 7(b), thermocompression bonding can also be performed, and so-called 3D mounting can be performed with high efficiency.

Unexamined Japanese Patent Publication No. 2016-9850

In mounting using NCF, the relationship between the hardening state of NCF and the melting timing of the bump is important, and it is necessary to set an appropriate NCF temperature rise curve during thermocompression bonding. In other words, if the bump melts while the NCF is insufficiently hardened, the bump will collapse, and if the NCF hardens and reaches the bump melting temperature, it becomes difficult for the bump and the electrodes of the substrate (or semiconductor chip) to approach each other, resulting in poor bonding. becomes.

Therefore, the temperature of the heater 31 built into the head body 3 that heats the attachment 40 in FIGS. 6 and 7 is adjusted so as to obtain an NCF temperature increase curve that melts the bump while the NCF is appropriately hardened. It is necessary to appropriately set the temperature of the substrate stage 2. In particular, when the semiconductor chips C are stacked in multiple stages as shown in FIG. 7, it is necessary to perform settings such that the NCF temperature rise curves of all the semiconductor chips stacked in multiple stages fall within an allowable range.

However, it has been found that even if the temperatures of the heater 31 and the substrate stage 2 are set, the temperature increase curve changes greatly if the type of substrate S is different. In other words, if the substrate is used as substrate B under the same conditions as when an appropriate NCF temperature rise curve such as substrate A in FIG. A defect has occurred. This is caused by the difference in thermal conductivity between the materials of substrate A and substrate B, and the temperature of the NCF increases faster when substrate B, which has low thermal conductivity, is used compared to substrate A, which has high thermal conductivity.

Furthermore, while the difference in NCF temperature rise curves between multi-layered semiconductor chips was suppressed for substrate A, it widened for substrate B. For this reason, in the substrate B, it is difficult to set the NCF temperature rise curves of all the semiconductor chips stacked in multiple stages within an allowable range.

The present invention has been made in view of the above-mentioned problems, and when thermocompression bonding is performed after electronic components such as semiconductor chips are temporarily fixed to a substrate in a laminated state via a thermosetting adhesive, the material of the substrate is The present invention provides a crimping head, a mounting device using the same, and a mounting method that can perform mounting with excellent bonding quality under various conditions even if the bonding conditions are different.

In order to solve the above problem, the invention according to claim 1,
A crimping head for mounting electronic components on a board,
An attachment comprising a head body incorporating a constant heater with a constant temperature , a pressing member that presses an electronic component mounted on a lower part of the head body, and an elastic member interposed between the head body and the pressing member. Prepare,
The pressure bonding head is provided with a laminate made of a material different from that of the pressing member on a surface of the pressing member facing the electronic component.

The invention according to claim 2 is a crimping head for mounting electronic components on a substrate,
An attachment comprising a head body incorporating a constant heater with a constant temperature , a pressing member that presses an electronic component mounted on a lower part of the head body, and an elastic member interposed between the head body and the pressing member. Prepare,
The crimping head is a crimping head in which a sheet material made of a material different from that of the pressing member is arranged between the pressing member and the electronic component.

The invention according to claim 4 is the crimping head according to claim 3,
In the crimping head, the pressing member is made of metal, and a material different from the pressing member is glass, ceramics, or heat-resistant resin.

The invention according to claim 5 is the crimping head according to any one of claims 1 to 4,
This is a crimping head that can simultaneously mount multiple electronic components.

The invention according to claim 6 includes the crimping head according to any one of claims 1 to 5;
Pressure means that allows the pressure bonding head to move up and down and applies pressure toward the substrate;
The mounting apparatus includes a substrate stage that supports the pressure surface of the attachment from the substrate side.

The invention according to claim 7 is the mounting device according to claim 6,
The mounting apparatus has a configuration in which an attachment protection film is arranged between the pressure bonding head and the substrate in parallel with the substrate.

The invention according to claim 8 uses the mounting apparatus according to claim 6 or claim 7,
This is a mounting method for mounting the electronic component, which has a thermosetting adhesive layer formed on the electrode surface, on the board.

The invention according to claim 9 is the mounting method according to claim 8,
In this mounting method, a material and/or a thickness of a different material from the pressing member are changed depending on the type of the substrate.

According to the present invention, when electronic components such as semiconductor chips are temporarily fixed to a board in a laminated state via a thermosetting adhesive and then thermocompression bonded, the bonding quality can be maintained under each condition even if the material of the board is different. It has become possible to perform excellent implementations.

This is a diagram illustrating how semiconductor chips temporarily fixed in a multi-stage stacked state are mounted using a crimping head according to an embodiment of the present invention, and (a) is a diagram showing a state after alignment, and (b) is a diagram showing a state after alignment. It is a figure which shows the state during thermocompression bonding. It is a figure which shows the modification of the crimping head based on embodiment of this invention. 3 is a temperature increase curve for explaining the effect of the crimping head according to the embodiment of the present invention. FIG. 2 is a diagram illustrating an example of implementing the present invention with a configuration different from the embodiment. FIG. 3 is a diagram illustrating an example in which the same effect as the present invention is achieved using a method different from that of the embodiment. A pressure bonding head capable of mounting a plurality of semiconductor chips on a substrate will be described, and FIG. 3A is a diagram showing a state after alignment, and FIG. 3B is a diagram showing a state during thermocompression bonding. This is a diagram illustrating how semiconductor chips temporarily fixed in a multi-stage stacked state are mounted using a pressure bonding head capable of mounting a plurality of semiconductor chips on a substrate, and (a) is a diagram showing a state after alignment; (b) A diagram showing a state during thermocompression bonding. FIG. 7 is a diagram illustrating an example in which the temperature rise curves differ for different substrates even when the same pressure bonding head is used.

Embodiments of the present invention will be described using the drawings. FIG. 1 shows an example in which stacked semiconductor chips C are mounted on a substrate S using a pressure bonding head 1 according to an embodiment of the present invention. In FIG. 1A, a semiconductor chip C, which is an electronic component, is temporarily fixed on a substrate S in a stacked state in multiple stages via uncured NCF. Here, NCF is a non-conductive film containing a thermosetting adhesive such as epoxy as a main component and insulating fine particles dispersed therein. Further, although not shown, electrode pads are provided at positions facing the bumps of the semiconductor chip C. Note that although FIG. 1 shows an example in which the semiconductor chips C are stacked in four stages, the number of stacked stages is not limited to this, and may be less than this, but the effect of the present invention is achieved when the semiconductor chips C are stacked in four or more stages. It is beneficial if

FIG. 1A shows a state in which the pressure bonding head 1 and the semiconductor chips C temporarily fixed to the substrate S (in a multi-stage stacked state) are aligned.

The crimping head 1 includes a head body 3 and an attachment 4. In the example of FIG. 1, the head main body 3 has a head housing 30 and a heater 31, and the attachment 4 has an elastic member 41, a pressing member 42, a support holder 43, and a laminate 44.

The crimping head 1 is driven by a pressure means (not shown) to move up and down and to apply a predetermined pressure to the semiconductor chip C.

The crimping head 1 is used to thermocompress multiple semiconductor chips C on a substrate S at the same time, and in order to cope with variations in the thickness of the semiconductor chips C and variations in the height of the bumps B, the crimping head 1 has an elasticity that corresponds to the number of simultaneous presses. It has a member 41, a pressing member 42, and a laminate 44, and the elastic member 41 made of heat-resistant rubber or the like absorbs height variations during pressing.

During thermocompression bonding, heat generated by the heater 31 built into the head body 3 is transmitted to the laminate 44 via the head housing 31, the elastic member 41, and the pressing member 42. Here, since the material of the elastic member 41 generally has low thermal conductivity, the pressing member 42 is made of a material with high heat conductivity. Specifically, aluminum and copper may be used, but the material is not limited to these and may be selected in consideration of thermal conductivity, workability, dimensional stability, price, etc.

The support holder 43 suppresses the inclination of the pressurizing surface caused by the deformation of the elastic member 41 and maintains parallelism.

The laminate 44 is not present in the configurations shown in FIGS. 6 and 7, but is a component included in the present invention. The laminate 44 constitutes a pressurizing surface of the crimping head 1 and plays a role in regulating heat flow via the pressing member 42. Therefore, the material of the laminate 44 needs to have a thermal conductivity lower than that of the pressing member 42, and in consideration of reducing the thickness, the thermal conductivity is preferably 1/30 or less. Specific materials include glass, ceramics, and heat-resistant resin.

The substrate stage 2 supports the area pressurized by the pressure bonding head 1 from the substrate S side, and may have a built-in heater.

By the way, when the attachment 4 directly pressurizes the semiconductor chip C while heating it, the heated and softened NCF may protrude to the surroundings and stain the pressurizing surface of the attachment 4. If the pressurizing surface of the attachment 4 becomes dirty, unevenness or inclination may occur on the pressurizing surface, which may cause inconvenience during subsequent pressurization. Therefore, the attachment protection film 5 is used to prevent NCF from adhering to the surface of the attachment 4. The attachment protection film 5 is arranged parallel to the pressure surface and is sequentially transported by a transport mechanism (not shown).

The attachment protective film 5 is preferably a fluorine film from the viewpoint of heat resistance and releasability against NCF. Further, the attachment protective film must have a minimum thickness that does not break during transportation or thermocompression bonding, and specifically, it is 20 μm or more.

The above-mentioned crimping head 1, substrate stage 2, mechanism for supplying the attachment protective film 5, and pressure means for driving the crimping head 1 are constituent elements of the mounting apparatus.

FIG. 1(b) shows a state in which thermocompression bonding is performed using the crimping tool 1 in the configuration of the mounting apparatus shown in FIG. 1(a). In FIG. 1B, T1 indicates the measured temperature of the semiconductor chip C in the first stage from the substrate S, and T4 indicates the measured temperature of the semiconductor chip C in the fourth stage. Here, the measured temperature of each semiconductor chip C is approximately equal to the NCF temperature of each semiconductor chip C.

By the way, in FIG. 1, a constant heater with a constant temperature is used as the heater 31, and a silicon substrate is used as the substrate S, so that the conditions are optimized. FIG. 3 is a graph showing the measured temperature of each semiconductor chip C when a glass epoxy substrate was used as the substrate S under such conditions.

In FIG. 3, T1A and T4A indicate T1 and T4 when using an attachment 40 with a conventional configuration that does not have the laminate 44, and the time it takes to reach the melting temperature Tm of the bump is short. Bump collapse has occurred. Furthermore, there are differences in the curves of T1A and T4A, and there are also differences in the NCF temperature increase curves.

On the other hand, in FIG. 3, T1B and T4B indicate T1 and T4 when glass with a thickness of 880 μm is used as the laminate 44. In addition to the fact that the difference in the curves of T1B and T4B is smaller than that of T1A and T4A, the time from the temperature rise at the start of thermocompression bonding until the bump melting temperature Tm is reached (approximately (compared to 2 seconds) and became approximately 4.5 seconds. This is almost the same as when a silicon substrate is used as the substrate S, and all of the semiconductor chips C from the first stage to the fourth stage have good bonding without crushed bumps or poor connections. Ta.

Further, in FIG. 3, T1C and T4C indicate T1 and T4 when a fluororesin having a thickness of 300 μm is used as the laminate 44. Although T1C and T4C had different temperature rise curves from T1B and T4B, the time from the temperature rise at the start of thermocompression bonding until the bump melting temperature Tm was reached was about 4.5 seconds. As a result, good bonding was obtained for all of the semiconductor chips C from the first stage to the semiconductor chips C from the fourth stage, with no bump collapse or poor connection.

As described above, by providing a laminate made of a material different from that of the pressing member of the attachment on the pressing surface of a conventional attachment, even if the type of substrate S is different, it is possible to process multi-stage semiconductors without changing conditions such as heater temperature. It becomes possible to bond the chips C without quality variations.

Note that when providing the laminate on the pressing member, a heat-resistant adhesive can be used, but it is necessary to select one that not only has excellent adhesive strength but also takes long-term durability into consideration.

If a fluororesin is used as the laminate 44 in the embodiment of FIG. 1, the flexibility of the fluororesin can be utilized, so instead of providing a laminate 44 for each pressing member 42, the modified example of FIG. A sheet material 45 made of a material different from that of the pressing members may be arranged so as to cover the plurality of pressing members 42 as shown in FIG. In this case, it is not necessary to laminate the sheet material 45 on the pressing member 42, and the sheet material 45 may be arranged under the pressing member 44 each time thermocompression bonding is performed.

In the examples shown in FIGS. 1 and 2, one head body 3 has an attachment 4 configured to press a plurality of semiconductor chips C, but as shown in FIG. The attachment 4 for pressurizing one semiconductor chip C may be configured as a crimping head having a plurality of head bodies 3.

By the way, when the laminate 44 or the sheet material 45 is made of fluororesin, the state is equivalent to a laminate of the same material as the attachment protective film 5, that is, an increased thickness. Therefore, the effect of the thickness of the attachment protective film 5 was examined in FIG. 5. While the temperature curve shown in FIG. 5(a) is obtained when the attachment 40 shown in FIGS. 6 and 7 is used and the thickness of the attachment protective film 5 (denoted as "insulation sheet" in the figures) is 30 μm, Since the temperature curve when the thickness was set to 360 μm was as shown in FIG. 5(b), it was found that a similar tendency appeared when the thickness of the laminate 44 was set to 300 μm. However, since the attachment protective film 5 is a consumable item that needs to be transported for each thermocompression bonding process, the process cost increases.

1 Crimp head 2 Substrate stage 3 Head body 4, 40 Attachment
5 Attachment protective film 30 Head housing 31 Heater 41 Elastic member 42 Pressing member 43 Support holder 44 Laminated body 45 Sheet material B Bump C Semiconductor chip S Substrate NCF Thermosetting adhesive film T1 Temperature of the first semiconductor chip from the substrate side T4 Temperature of the fourth semiconductor chip from the substrate side

Claims (9)

A crimping head for mounting electronic components on a board,
The head body has a built-in constant heater that maintains a constant temperature ,
a pressing member that presses an electronic component mounted on the lower part of the head main body;
an attachment having an elastic member interposed between the head main body and the pressing member;
A crimping head, wherein a laminate made of a material different from that of the pressing member is provided on a surface of the pressing member facing the electronic component. A crimping head for mounting electronic components on a board,
The head body has a built-in constant heater that maintains a constant temperature ,
a pressing member that presses an electronic component mounted on the lower part of the head main body;
an attachment having an elastic member interposed between the head main body and the pressing member;
A crimping head in which a sheet material made of a material different from that of the pressing member is arranged between the pressing member and the electronic component. The crimping head according to claim 1 or 2,
A crimping head, wherein the thermal conductivity of a material different from that of the pressing member is 1/30 or less of that of the pressing member. The crimping head according to claim 3,
The pressure bonding head is characterized in that the pressing member is made of metal, and the material different from the pressing member is glass, ceramics, or heat-resistant resin. The crimping head according to any one of claims 1 to 4,
A crimping head that can mount multiple electronic components at the same time. A crimping head according to any one of claims 1 to 5,
Pressure means that allows the pressure bonding head to move up and down and applies pressure toward the substrate;
A mounting device comprising: a substrate stage that supports a pressure surface of the attachment from the substrate side. The mounting device according to claim 6,
A mounting apparatus configured to arrange an attachment protection film between the pressure bonding head and the substrate in parallel with the substrate. Using the mounting apparatus according to claim 6 or claim 7,
A mounting method for mounting the electronic component having a thermosetting adhesive layer formed on the electrode surface on the substrate. The mounting method according to claim 8,
A mounting method that changes a material and/or a thickness of a different material from the pressing member depending on the type of the substrate.