JP4040551B2 - Semiconductor device mounting method - Google Patents

Description

  The present invention relates to a semiconductor element mounting method for mounting a semiconductor element on a substrate by solder bonding.

Conventionally, when a semiconductor element such as a power element is mounted on a substrate by solder bonding, a high positional accuracy of the semiconductor element with respect to the substrate is required. The element was mounted on the substrate.
For example, as shown in FIG. 9, the jig 121 is set on the substrate 101 while positioning the jig 121 with respect to the substrate 101 in a lower recess 121 a formed in accordance with the outer dimensions of the substrate 101.
On the upper side of the jig 121, an upper recess 121b is formed in accordance with the outer dimensions of the semiconductor element 102. The solder foil 103 and the semiconductor element 102 are fitted into the upper recess 121b and placed on the substrate 101. By setting, the semiconductor element 102 can be mounted on the substrate 101 by solder bonding while positioning the semiconductor element 102 with respect to the substrate 101.

However, in order to solder-bond the semiconductor element 102 and the substrate 101 using such a jig 121, it is necessary to manufacture the jig 121 according to the shape of each semiconductor element 102 and the substrate 101. First, since various jigs 121 must be held, the cost increases.
Further, the dimensions of the upper recess 121b of the jig 121 are the ease of setting the semiconductor element 102, the linear expansion coefficient of the constituent elements of the semiconductor element 102 and the jig 121, and the dimensional accuracy of the semiconductor element 102 and the jig 121. In view of the above, since it is necessary to form the semiconductor element 102 slightly larger than the outer shape of the semiconductor element 102, a predetermined clearance d is generated between the jig 121 and the semiconductor element 102. The mounting position of the semiconductor element 102 with respect to the substrate 101 cannot be controlled with high accuracy.
Furthermore, the solder thickness after joining depends on the thickness of the solder foil before joining, and the solder thickness varies depending on the presence or absence of voids generated in the solder and the wettability / spreadability of the solder. In particular, since there is nothing to support the semiconductor element 102 at the time of soldering, as shown in FIG. 10, the semiconductor element 102 may tilt while the solder is melted, and the solder may solidify as it is.

As described above, a technique described in Patent Document 1 is known as a technique for suppressing a change in solder thickness and a tilt of a semiconductor element that occur when a semiconductor element is soldered to a substrate.
That is, when a semiconductor element on which solder bumps are formed is mounted on a substrate, a paste-like thermosetting resin is supplied between the semiconductor element and the substrate, and the thermosetting resin is thermally cured to provide a substrate for the semiconductor element. Japanese Patent Application Laid-Open No. H10-228688 describes a technique in which solder bumps are melted by reflow and the bonding is performed after the position and interval with respect to is kept constant.

JP 2000-58597 A

As described above, the technology of supplying paste-like thermosetting resin between the semiconductor element and the substrate and thermosetting the thermosetting resin before solder bonding is mounted on the substrate by solder bonding. If it is applied, a paste-like thermosetting resin enters between the semiconductor element and the solder foil or between the solder foil and the substrate, resulting in a defective portion.
In particular, a solder foil that joins a semiconductor element and a substrate has a small area and, unlike a solder bump that touches the substrate, has a large joint area between the semiconductor element and the substrate. Therefore, the solder foil is interposed between the semiconductor element and the substrate. Even if pressure is applied to the semiconductor element while the resin is supplied and the resin is supplied, the thermosetting resin that has entered between the semiconductor element and the solder foil or between the solder foil and the substrate is expelled by the pressure. It is difficult.

The semiconductor element mounting method of the present invention that solves the above problems has the following characteristics.
That is, in claim 1, a semiconductor element mounting method for mounting a semiconductor element on a substrate by solder bonding, wherein the semiconductor element is set on a substrate on which a thermosetting resin tape member is adhered, The step of temporarily fixing the mounting position of the semiconductor element with the tape member, the step of crushing the tape member to the thickness of the solder foil and thermosetting it by thermocompression bonding the set semiconductor element to the substrate, and the semiconductor element by reflow And a step of soldering the substrate and the substrate.
Thereby, when performing reflow, since the position of the semiconductor element is already fixed with respect to the substrate, the position of the semiconductor element is not shifted or tilted by melting of the solder.
Therefore, even if the reflow process is performed without using a jig, the semiconductor element can be mounted by performing solder bonding with high positional accuracy.
In addition, since the distance between the semiconductor element and the substrate is fixed at the time of thermocompression bonding, it is possible to control the solder film thickness after soldering to a constant thickness.
Furthermore, cost reduction can be achieved.

Further, in claim 2, a semiconductor element mounting method for mounting a semiconductor element on a substrate by solder bonding, wherein the semiconductor element is set on a substrate to which a thermosetting resin tape member is attached, A step of temporarily fixing a mounting position of the semiconductor element with a tape member; a step of placing solid solder on a position close to the semiconductor element on the substrate; and a step of soldering the semiconductor element and the substrate by reflow.
As a result, the mounting position of the semiconductor element can be obtained without using a jig for positioning the semiconductor element with respect to the substrate and without providing a special mechanism for maintaining a space for solder injection between the substrate and the semiconductor element. -It is possible to reduce the cost while mounting the semiconductor element by performing solder joining while controlling the tilt and the solder thickness with high accuracy.

According to a third aspect of the present invention, an uneven portion for controlling the flow direction of solder melted during reflow is formed on the substrate surface.
Thereby, the wet spreading property of the melted solder can be improved.
Improved solder wettability allows the solder to spread easily over the entire lower surface of the semiconductor element, resulting in voids in the solidified solder and places where solder joints are insufficient. It is possible to prevent the thermal conductivity from the semiconductor element to the substrate from being lowered.

According to the present invention,
Even if the reflow process is performed without using a jig, the semiconductor element can be mounted by soldering with high positional accuracy. In addition, the solder film thickness after soldering can be controlled to a constant thickness, and the cost can be reduced.
In addition, the wet spreadability of the molten solder can be improved, and voids in the solidified solder can be prevented, and inadequate solder joints can be generated. It is possible to prevent the heat conductivity from being lowered.

  The best mode for carrying out the present invention will be described with reference to the accompanying drawings.

First, a first embodiment of the semiconductor element mounting method of the present invention will be described.
As shown in FIGS. 1 and 2, the solder foil 3 and the fixing tape 5 are set on the upper surface of the substrate 1 to which the semiconductor element 2 is bonded in accordance with the bonding position of the semiconductor element 2 (FIG. 1A, S01). ).
The solder foil 3 is formed in a foil shape having substantially the same size as the bottom surface of the semiconductor element 2. The fixing tape 5 is formed by forming a thermosetting resin in a tape shape using a heat-resistant resin such as polyimide as a base material, and is disposed at a plurality of locations around the solder foil 3. In FIG. 1, the fixing tape 5 is arranged at four locations around the solder foil 3, but it is sufficient that the semiconductor element 2 can be stably set when the semiconductor element 2 is placed on the fixing tape 5. It only has to be arranged in.

Thereafter, the semiconductor element 2 is placed on the plurality of fixed tapes 5 set (S02), and as shown in FIG. 1B, pressure and heat are applied from above the semiconductor element 2 to perform thermocompression bonding (S03). .
In the thermocompression bonding, the fixing tape 5 is crushed until the distance between the substrate 1 and the semiconductor element 2 becomes substantially the same as the thickness of the solder foil 3, and the fixing tape 5 is heated to remove the thermosetting resin of the fixing tape 5. Harden.

As the thermosetting resin of the fixing tape 5 is cured, the position of the semiconductor element 2 relative to the substrate 1 and the distance between the semiconductor element 2 and the substrate 1 are maintained.
In order to prevent the solder foil 3 from melting in the thermocompression bonding process, the fixing tape 5 uses a thermosetting resin having a curing temperature equal to or lower than the melting temperature of the solder foil, and is fixed by heating by thermocompression bonding. The heating temperature of the tape 5 is not higher than the melting temperature of the solder foil.
Further, the thickness of the fixing tape 5 after the pressure bonding is, for example, about several tens μm to several hundreds μm.

As shown in FIG. 1C, after the semiconductor element 2 is positioned, reflow is performed to melt the solder foil 3 and solder the semiconductor element 2 and the substrate 1 (S04).
At the time of reflow, since the position of the semiconductor element 2 is already fixed with respect to the substrate 1, the position of the semiconductor element 2 is not shifted or tilted due to melting of the solder.
Accordingly, when the semiconductor element 2 is set on the substrate 1, if the semiconductor element 2 is placed on the fixing tape 5 with high positional accuracy and thermocompression bonded, high positional accuracy can be achieved even if reflow processing is performed without using a jig. Can be soldered and mounted.
Moreover, since the space | interval of the semiconductor element 2 and the board | substrate 1 is fixed at the time of thermocompression bonding, it is possible to control the solder film thickness after solder joining to fixed thickness.

When the semiconductor element 2 is configured as a power element that generates heat during operation, the substrate 1 on which the semiconductor element 2 is mounted is further soldered to a heat radiating plate to increase heat dissipation efficiency.
Even when the substrate 1 is soldered to the heat radiating plate, the position of the substrate 1 is fixed to the heat radiating plate by the fixing tape 5 so that high-precision soldering can be performed.

For example, first, as shown in FIGS. 3A and 3B, the solder foil 7 and the fixing tape 5 are set on the upper surface of the heat radiating plate 6 in accordance with the bonding position of the substrate 1, and the substrate is formed by thermocompression bonding. 1 is fixed to the heat sink 6. The solder foil 7 is formed in a foil shape having substantially the same size as the bottom surface of the substrate 1.
Next, as shown in FIGS. 3C and 3D, the solder foil 3 and the fixing tape 5 are set on the upper surface of the substrate 1 positioned and fixed to the heat sink 6, and the semiconductor element 2 is mounted as described above. The semiconductor element 2 is positioned and fixed with respect to the substrate 1 by thermocompression bonding.

Thereafter, as shown in FIG. 3 (e), the heat radiating plate 6, the substrate 1 and the semiconductor element 2 which are fixed to each other by the fixing tape 5 are reflowed, and the heat radiating plate 6 and the substrate 1 are soldered by the solder foil 7. While joining, the board | substrate 1 and the semiconductor element 2 are solder-joined with the solder foil 3. FIG.
Also in this case, the positioning and fixing of the semiconductor element 2 with respect to the substrate 1 and the positioning and fixing of the substrate 1 with respect to the heat radiating plate 6 are performed by the fixing tape 5, so that the semiconductor element 2 can be mounted with high accuracy without using a jig. It is possible to reduce the cost.

Next, a second embodiment in the semiconductor element mounting method of the present invention will be described.
In the present embodiment, as shown in FIG. 4A, a plurality of fixing tapes 5 are set on the upper surface of the substrate 1 to which the semiconductor element 2 is bonded. The fixing tape 5 is disposed so as to be positioned at the peripheral edge of the semiconductor element 2 in accordance with the mounting position of the semiconductor element 2.
Next, the semiconductor element 2 is placed on the fixing tape 5 and the fixing tape 5 is thermally cured by thermocompression bonding, and the position of the semiconductor element 2 relative to the substrate 1 and the distance between the semiconductor element 2 and the substrate 1 are determined. Fix it. In this case, the thickness of the fixing tape 5 after pressure bonding is, for example, about several tens of μm to several hundreds of μm.

Next, as shown in FIG. 4B, solid solder 13 such as thread solder or solder pellets is installed in the vicinity of the semiconductor element 2 on the substrate 1.
As shown in FIG. 4C, when reflow is performed after the solid solder 13 is installed, the solid solder 13 is melted and is formed between the substrate 1 and the semiconductor element 2 by the thickness of the fixing tape 5. Solder flows into the gap by capillary action, and the substrate 1 and the semiconductor element 2 are soldered.

  Thus, even when solder bonding is performed using solid solder arranged close to the semiconductor element 2, a jig for positioning the semiconductor element 2 with respect to the substrate 1 is used, or solder injection between the substrate 1 and the semiconductor element 2 is performed. The semiconductor element 2 can be mounted by performing solder bonding while controlling the position / inclination of the semiconductor element 2 and the solder thickness with high accuracy without providing a special mechanism for maintaining the space for Cost can be reduced.

  Further, when solder bonding is performed using the solid solder 13 installed in the vicinity of the semiconductor element 2, the wettability of the solder to the surface of the substrate 1 is improved by forming irregularities on the surface of the substrate 1 as follows. Can do.

That is, for example, as shown in FIG. 5 (a), the solder placement recess 1a is formed in the portion where the solid solder 13 is placed on the surface of the substrate 1, and the solder placement recess 1a is connected to the semiconductor element 2 side (in FIG. 5). A flow recess 1b extending in a slit shape is formed on the center side of the substrate 1).
When the solid solder 13 is placed in the solder installation recess 1a of the substrate 1 and the semiconductor element 2 is thermocompression bonded via the fixing tape 5 as shown in FIG. 5B, reflow is performed. ), The molten solder wets and spreads below the semiconductor element 2 through the flow recess 1b, and the solder spreads over the entire bottom surface of the semiconductor element 2.
Note that although only one flow recess 1b is formed in FIG. 5, a plurality of flow recesses 1b may be formed.

If the surface of the substrate 1 is uniformly flat without forming the solder installation recess 1a and the flow recess 1b, the solder does not spread evenly over the entire surface of the substrate 1 due to the difference in solder wettability of the surface. There is a risk that a location where solder bonding between the substrate 1 and the semiconductor element 2 is insufficient will occur or a void will occur in the solder.
However, by forming the solder installation recess 1a and the flow recess 1b in this way, the molten solder can easily flow from the solder installation recess 1a through the flow recess 1b, thereby improving the wetting spreadability. it can.
By improving the wettability of the solder, it becomes possible for the solder to spread easily over the entire lower surface of the semiconductor element 2, resulting in voids in the solidified solder and places where solder bonding is insufficient. This can be prevented, and the thermal conductivity from the semiconductor element 2 to the substrate 1 is not lowered.

  Further, in order to further improve the wet spreading property of the molten solder, the flow recess 1b formed on the surface of the substrate 1 is extended from one end of the semiconductor element 2 to the other end (in FIG. 6, the semiconductor element 2). A plurality of branch recesses 1c may be formed obliquely from the flow recess 1b. The branch recess 1 c extends from the flow recess 1 b toward the other side of the semiconductor element 2, and the flow recess 1 b and the branch recess 1 c cover substantially the entire bottom surface area of the semiconductor element 2. .

Thus, by forming a plurality of branch recesses 1c in addition to the flow recesses 1b, as shown in FIG. 7, it becomes even easier for the solder to spread over the entire bottom surface of the semiconductor element 2, Generation of voids in the solder can be reliably suppressed.
Note that the flow direction and amount of solder can be controlled by changing the bottom surface height of the flow recess 1b and the branch recess 1c depending on the location.
The flow recess 1b and the branch recess 1c have a concave shape with respect to the surface of the substrate 1, but even if a convex slit portion is formed on the surface of the substrate 1, the wettability of the solder is similarly improved. It is possible.

  Further, in the case of a configuration in which the semiconductor element 2 is thermocompression bonded to the substrate 1 via the fixing tape 5 and the solder flows into the gap corresponding to the thickness of the fixing tape 5 by capillary action, the solid solder 13 is brought close to the semiconductor element 2. In addition, the molten solder can be directly injected between the semiconductor element 2 and the substrate 1.

  For example, as shown in FIG. 8A, after the semiconductor element 2 is thermocompression bonded to the substrate 1 via the fixing tape 5, the gap between the semiconductor element 2 and the substrate 1 is obtained as shown in FIG. When the molten solder 8 is injected into this space, as shown in FIG. 8C, the molten solder is filled into the entire space by capillary action.

  As described above, even when molten solder is injected into the space between the semiconductor element 2 and the substrate 1, a jig for positioning the semiconductor element 2 with respect to the substrate 1 is used, or the substrate 1, the semiconductor element 2, The semiconductor element 2 is formed by performing solder bonding while controlling the position / inclination of the semiconductor element 2 and the solder thickness with high accuracy without providing a special mechanism for maintaining the space for solder injection between the two. While being able to mount, cost reduction can be achieved.

It is a figure which shows the semiconductor element mounting method in 1st embodiment of this invention. It is a figure which shows the flow of the semiconductor element mounting method in 1st embodiment. In 1st embodiment, in addition to joining of a semiconductor element and a board | substrate, it is a figure which shows the semiconductor element mounting method at the time of also joining a board | substrate and a heat sink. It is a figure which shows the semiconductor element mounting method in 2nd embodiment of this invention. In 2nd embodiment of this invention, it is a figure which shows the board | substrate in which the recessed part which controls the flow of a solder was formed. In 2nd embodiment of this invention, it is a top view which shows the board | substrate which formed the several branch recessed part in addition to the recessed part for flow as a recessed part which controls the flow of solder. It is a figure which shows the flow of the molten solder in the board | substrate shown in FIG. It is a figure which shows the semiconductor element mounting method which inject | pours molten solder between a board | substrate and a semiconductor element. It is side surface sectional drawing which shows the jig | tool used for the conventional semiconductor element mounting method. It is side surface sectional drawing which shows a mode that the semiconductor element was mounted in the board | substrate in the inclined state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Semiconductor element 3 Solder foil 5 Fixing tape 6 Heat sink

Claims (3)

A semiconductor element mounting method for mounting a semiconductor element on a substrate by solder bonding,
Setting a semiconductor element via a solder foil on a substrate on which a thermosetting resin tape member is adhered, temporarily fixing the mounting position of the semiconductor element by the tape member;
By thermocompression bonding the set semiconductor element to the substrate, the process of crushing the tape member to the thickness of the solder foil and thermosetting,
A step of soldering the semiconductor element and the substrate by reflow;
A method for mounting a semiconductor element, comprising: A semiconductor element mounting method for mounting a semiconductor element on a substrate by solder bonding,
Setting a semiconductor element on a substrate to which a tape member made of a thermosetting resin is attached, and temporarily fixing the mounting position of the semiconductor element by the tape member;
A step of placing solid solder on the substrate in the vicinity of the semiconductor element;
A step of soldering the semiconductor element and the substrate by reflow;
A method for mounting a semiconductor element, comprising: 3. The semiconductor element mounting method according to claim 2, wherein an uneven portion for controlling a flow direction of solder melted during reflow is formed on the surface of the substrate.

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