JP2002359460A - Solder connection structure and connection method for electronic components - Google Patents

Abstract

(57) [Summary] [Problem] To connect an electronic component to an electronic circuit board by soldering, the formation of a solder connection area is omitted, and the solder connection structure and connection of the electronic component whose solder connection reliability is guaranteed. Provide a way. In an electronic circuit board, a terminal electrode of a conductor wiring protrudes from a protective resist on a board, and an opening portion is formed.
It is exposed in a belt shape. On the other hand, the electronic component 1 is provided with solder bumps 2, and a flux (not shown) is applied to the solder bumps 2, and the solder bumps 2 are made to correspond to the terminal electrodes 4 on the substrate 5. 1 is mounted on the electronic circuit board 7 and heated while applying pressure, so that the flux-coated portion of the solder bump 2 is melted and connected to the terminal electrode 4. In this case, the terminal electrode 4 is not provided with a means for limiting the solder wetting area.
The wet area of the molten solder bump 2 on the terminal electrode 4 has a wide and wide shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure and a method for soldering electronic components to an electronic circuit board in an electronic circuit device.

[0002]

2. Description of the Related Art Conventionally, when an electronic component having a solder bump formed thereon is flip-chip connected, a solder connection area of a terminal electrode on an electronic circuit board is limited in accordance with the size of the solder bump of the electronic component. It is common. In the connection process, the electronic component is positioned and mounted on the electronic circuit board so that the solder bumps provided on the electronic component are located on the solder connection area of the terminal electrodes of the electronic circuit board, and then the temperature is higher than the solder melting point. By heating the solder bumps to melt the solder bumps, the electronic component and the electronic circuit board are connected. In such a connection method, the molten solder spreads over the electrode metal on the electronic circuit board side, and the diffusion of the electrode metal into the molten solder and the formation of an alloy layer occur.
The solder is firmly connected to the terminal electrodes.

[0003] The area for solder connection at the terminal electrode of the electronic circuit board is (1) by coating a cover resist on the terminal electrode or its wiring or by closely attaching a cover film to the area other than the area for solder connection. (2) A ceramic sheet on which conductor wiring is printed is superposed and sintered to form a conductor wiring in an electronic circuit board, and a tip of the conductor wiring appears on the surface of the electronic circuit board. Is formed by using a method of forming terminal electrodes on the surface of the electronic circuit board so as to be connected to the substrate. As described above, a solder connection structure in which a region other than the mounting pad serving as a solder connection area is protected by a protective resist is disclosed in, for example, Japanese Patent Laid-Open No. 5-4 / 1993.
No. 8226.

FIG. 6 shows an example of a conventional solder connection structure, wherein 1 is an electronic component such as an LSI, 2 is a solder bump, 3 is a protective resist, 4 is a terminal electrode, 5 is a substrate,
Reference numeral 6 denotes a solder connection area, and reference numeral 7 denotes an electronic circuit board.

[0005] In FIG. 1A, in the electronic circuit board 7, conductor wiring (not shown) is formed on the surface of the board 5, and the leading end and the like form a terminal electrode 4. A protective resist 3 is formed on the surface of the substrate 5 so as to cover the conductor wiring, and the terminal electrodes 4 of the protective resist 3 are formed.
Is removed so that the terminal electrode 4 is exposed, thereby forming a solder connection area 6 in which the periphery of the terminal electrode 4 is restricted by the protective resist 3.

On the other hand, electrodes (not shown) of the electronic component 1
Electronic circuit board 7 on which solder bumps 2 are formed and solder connection areas 6 are formed by protective resist 3
After the flux is applied to the entire surface of the substrate, that is, including the surface of the terminal electrode 4 in the solder connection area 6, the solder bump 2 is fitted into the solder connection area 6 so that the electronic component 1 is mounted. It is mounted on the electronic circuit board 7.
Then, by pressing the electronic component 1 against the electronic circuit board 7 and heating, the solder connection between the electronic component 1 and the electronic circuit board 7 is performed. In this case, the applied flux removes oxides generated on the surfaces of the terminal electrodes 4 and the solder bumps 2 so that the molten solder and the terminal electrodes 4 are removed.
The electrode metal contacts and diffuses to form an alloy layer, whereby a solder connection is made.

FIG. 6B is a photograph showing the state of the solder connection obtained as a result. As is clear from this, the tip of the solder bump 2 is joined to the terminal electrode 4, as described above, because the flux applied to the surface of the terminal electrode 4 covers the solder bump 2, This is because the solder bump 2 is melted and joined to the terminal electrode 4 as described above.

[0008]

However, in recent years,
With the increase in integration of electronic components, the pitch of solder bumps has been reduced, and the size of solder bumps has also tended to be reduced. Therefore, the solder connection area on the electronic circuit board, particularly on the side where the electronic components are mounted, is also miniaturized, and the pitch between the electrodes in this area is required to be further narrowed. . For this reason, it is necessary to increase the formation accuracy of the solder connection area, which is one factor that increases the cost of the electronic circuit board, and hence the electronic device.

SUMMARY OF THE INVENTION An object of the present invention is to provide a solder connection structure and a connection method for an electronic component in which such a problem is solved, the formation of a solder connection area is omitted, and the reliability of the solder connection is ensured. is there.

[0010]

In order to achieve the above object, a solder connection structure for an electronic component according to the present invention eliminates the limitation of a solder connection area at a terminal electrode of an electronic circuit board, thereby reducing the solderability of the electronic component. The connection is configured.

In this case, the solder connection is performed by applying a flux to the solder bumps, and no means for limiting the solder connection area is provided on the terminal electrodes. Although the wet spread of the molten solder on the terminal electrode is increased, the same connection reliability as the conventional terminal electrode provided with a means for limiting the solder connection area can be achieved.

The shape of the spread of the molten solder can be limited by the flux applied to the solder bumps. In addition, by selecting the solder material, the terminal electrode material, the flux itself, and the combination thereof, The shape of the wet spread of the molten solder can be limited.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory view of an embodiment of a method for soldering electronic components according to the present invention. Reference numeral 8 denotes an opening, and portions corresponding to those in FIG.

In FIG. 1, an electronic component 1 such as an LSI is provided with a plurality of solder bumps 2 along its side, for example, on an outer peripheral portion thereof.

On the other hand, the electronic circuit board 7 has an opening 8 in which the entire outer peripheral portion of the board 5 is covered with the protective resist 3 and the central portion is not covered with the protective resist 3. A conductor wiring (not shown) is provided in a portion covered with the protective resist 3. That is, the conductor wiring is formed on the outer peripheral portion of the surface of the electronic circuit board 5 and is covered with the protective resist 3. It is exposed to. These terminal electrodes 4 correspond to the solder bumps 2 of the electronic component, and are exposed in a strip form from the protective resist 3, and the solder connection area 6 as shown in FIG. 6 is not formed.

The electronic circuit board 7 has a sheet shape as a whole. Such an electronic circuit board 7
Is a sheet in which the entire substrate 5 on which the conductor wiring has been made as described above is covered with the protective resist 3, and all the terminal electrodes 4 are exposed on this sheet,
An opening 8 is formed by removing the protective resist 3 in a region having a shape larger than the size and shape of the electronic component 1 to form the electronic circuit board 7 in this embodiment.

According to the method of manufacturing the electronic circuit board 7, even if the position of the opening 8 is slightly shifted, it is sufficient that all the terminal electrodes 4 are exposed in a belt shape with a predetermined length or more. It does not take.

On the other hand, when the conventional electronic circuit board 7 shown in FIG. 6 is formed using such a sheet, the sheet in which the entire substrate 5 is covered with the protective resist 3 is formed on the substrate 5. Except for the protective resist 3, the terminal electrode 4
It is necessary to provide a hole for exposing the hole, and such an operation is required for each terminal electrode 4. For this reason, the work is troublesome and the work accuracy must be quite high.

When the electronic component 1 is connected to the electronic circuit board 7 by soldering, first, as shown in FIG. 2, the concave portion 10 having a predetermined uniform depth is provided on the flux application dish 9. Fill the flux 11 and ring the surface with a squeegee to form a layer of flux 11 of uniform thickness,
By immersing the solder bumps 2 of the electronic component 1 in this,
The flux 11 is applied to each solder pump 2 with the same thickness.

After the flux 11 is applied to the solder bumps 2 in this manner, the electronic component 1 is placed so that the solder bumps 2 ride on the tips of the respective terminal electrodes 4 on the substrate 5.
Is positioned and mounted on the electronic circuit board 7, and is heated by applying pressure from the electronic component 1 side in a predetermined atmosphere, and the solder bump 2 and the terminal electrode 4 are fusion-connected as described above. After connection, an underfill may be injected and cured by heating for the purpose of reinforcement.

FIG. 3 is a sectional view showing an embodiment of a solder connection structure for an electronic component according to the present invention obtained as described above. Reference numeral 4a denotes a conductor wiring. Have the same reference numerals.

In FIG. 2, the terminal electrode 4 of the electronic circuit board 7 is not provided with a solder connection area for regulating the wetting shape of the solder unlike the conventional electronic circuit board. As compared with the case of the substrate, the solder bump 2 has a shape that is wider and spreads. Even in this case,
As will be described later, the reliability of the connection can be secured to the same degree as in the conventional case. In addition, solder bump 2
Does not spread to a region other than the terminal electrode 2, that is, the surface of the electronic circuit board 5.

The conductor wiring 4a connected to the terminal electrode 4
Is covered with the protective resist 3. The other terminal electrode of the conductor wiring 4a can be exposed to the outside on the substrate 5, for example, although not shown. The terminal electrodes on the substrate side can be provided with a size and a pitch corresponding to the electrodes of the electronic component. The electronic circuit board 7 having such a configuration is mounted on a main board such as a motherboard (not shown) after or before the electronic components 1 are connected. The electronic component 1 can function as a means for converting the pitch of the terminal electrodes to the main substrate.

FIG. 4 shows the flux 11 to the solder bump 2.
FIG. 4 is a photograph of a longitudinal section of a terminal electrode in which a solder connection state is observed at different application thicknesses.

FIG. 4A shows that the depth of the recess 10 is 20 μm.
When the flux 11 is applied to the solder bumps 2 as described above using the coating dish 9 (FIG.
m. FIG. 4B shows the case where the flux 11 is applied to the solder bump 2 with a thickness of 25 μm, and FIG. 4C shows the case where the flux 11 is applied to the solder bump 2 with a thickness of 30 μm. Is shown. Here, the composition of the solder bump is 63% by weight of tin and 3% by weight of lead.
7% by weight, maximum temperature 220
Each time, a fusion connection was made. Further, after connection, an underfill was injected for the purpose of reinforcement, and was cured by heating.

From the observation results shown in FIGS.
As the applied thickness of the flux 11 is larger, the solder bump 2
It can be seen that the wet shape of the sample has spread. This is because the larger the applied thickness of the flux 11, the larger the applied area of the flux 11 on the solder bump 2, and therefore, the larger the amount of the removed solder oxide and the amount of the solder that can spread out of the molten solder. This is due to the large amount of

The connection reliability of these samples was verified. This verification method is performed by charging a temperature cycle test layer at −55 ° C. to 150 ° C., and changing the atmosphere at −55 ° C. to, for example, a state of continuing for 30 min and a state of + 150 ° C. for the same time (30 min) The solder connection is checked for disconnection every 100 to several hundred cycles.

FIG. 5 shows the result of this check. FIGS. 4 (a), 4 (b) and 4 (c) as samples are shown in FIGS.
As a comparative example, the connection structure shown in FIGS. 6A, 6B, and 6C was added as a verification sample to the conventional connection structure shown in FIG. In this conventional connection structure, for example, a circular solder bump connection area 6 is formed on the terminal electrode 4 with the solder resist 3 as conventionally used. Accordingly, as described above, in FIG. 6B, the spread of the solder bumps 2 on the terminal electrodes 4 is limited, but this is due to the solder connection area 6 shown in FIG. is there.

FIG. 5 shows that the above samples were subjected to the above temperature cycle at 100, 200, 300, 500, 7
The connection status was checked every 00, 1000 cycles.
In this case, three samples were used, indicating that no samples were defective. Therefore, even in this embodiment in which the solder bumps are connected to the terminal electrodes 4 of the electronic circuit board 7 to which the electronic components are connected in a widely spread shape, even if the reliability test of 1000 cycles or more is performed, the connection portion is disconnected. No problem occurred, and it was confirmed that there was no problem in reliability as compared with the conventional product.

Although the embodiments of the present invention have been described above, the present invention is not limited to only such embodiments. For example, the above numerical values are shown as an example for convenience of explanation, and the present invention is not limited to such numerical values. Further, in the above embodiment, the connection structure can be applied to the mounting of a package or a module component in which an electronic component such as an LSI is mounted on a substrate such as an interposer, and the shape of the terminal electrode and the type of flux used for the connection are limited. Not something.

[0032]

As described above, according to the present invention,
Even if the solder connection restricted area corresponding to the solder bump is not particularly provided on the electronic circuit board side, the solder bump connection with sufficient connection reliability can be obtained, and the cost of the product can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of one embodiment of a method for soldering electronic components according to the present invention.

FIG. 2 is a view showing a specific example of a method of applying a flux to solder bumps of an electronic component in the embodiment shown in FIG.

FIG. 3 is a cross-sectional view showing one embodiment of a solder connection structure for an electronic component according to the present invention obtained by the solder connection method shown in FIGS. 1 and 2;

FIG. 4 is an observation photograph of a solder bump according to a difference in the amount of applied flux of a solder connection structure of an electronic component according to the present invention.

5 is a diagram showing a test result of connection reliability between the solder connection structure of the electronic component shown in FIG. 4 and a solder connection structure of a conventional electronic component.

FIG. 6 is a diagram illustrating an example of a conventional solder connection structure of an electronic component.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electronic component 2 Solder bump 3 Protective resist 4 Terminal electrode 4a Conductor wiring 5 Substrate 7 Electronic circuit board 8 Opening 9 Flux coating plate 10 Depressed part 11 Flux

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takehide Yokozuka 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside of Hitachi, Ltd. Hitachi, Ltd. Semiconductor Group (72) Inventor Tomio Yamada Kojiro, Komoro City, Nagano Prefecture 190, Kashiwagi, Hitachi, Ltd. F term (reference) 5E319 AA03 AA06 AB05 AC01 AC13 BB04 CC12 CD21 CD25 GG01 GG03 5F044 KK09 KK11 KK12 LL13 QQ01

Claims (5)

[Claims] 1. A structure for connecting an electronic component to an electronic circuit board using a solder bump, wherein the electronic circuit board has a terminal electrode provided with no means for limiting a region corresponding to the solder bump of the electronic component. An electronic component solder connection structure, wherein the terminal component is soldered to the electronic component. 2. The solder connection structure for an electronic component according to claim 1, wherein the terminal electrode of the electronic circuit board has a band shape. 3. The solder connection structure for an electronic component according to claim 2, wherein the electronic component is soldered to a tip end of the strip-shaped terminal electrode. 4. The solder connection of an electronic component according to claim 1, wherein the solder spreads greatly on the terminal electrodes on the electronic circuit board side compared to a normal solder bump connection structure. Construction. 5. A method for connecting an electronic component to an electronic circuit board using solder bumps, wherein a terminal is provided without means for applying a flux to the solder bumps and defining a soldering area on the electronic circuit board. A method for soldering electronic components, wherein the method is connected to electrodes.