JPH08316629A - Method for soldering multi-chip-module substrate by solder post - Google Patents

Abstract

PURPOSE: To achieve a stable and reliable soldering treatment without any short-circuiting even at a narrow-pitch solder pad by mounting a high part both on the front and reverse sides of a multi-chip-module substrate. CONSTITUTION: A solder post 16 which is in cylindrical shape, includes a copper cylinder 18, and has a solder 18 outside is arranged on a pad between an MCM substrate 14 and a large-scale substrate 15 for packaging it, the solder 18 of the solder post 16 is melted for performing alloy connection to the pad part of both substrates, the copper cylinder 19 plays a role of constantly maintaining the distance between both substrates, high parts can be mounted on the reverse side of the MCM substrate 14, and a reliable soldering quality which is stable also for a narrow pitch at the pad part due to the increase in the number of signals caused by the high integration of the MCM substrate 14 is secured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-chip module substrate (hereinafter referred to as an MCM substrate) and a reflow soldering method for a substrate on which it is mounted.

[0002]

2. Description of the Related Art In a reflow soldering process of an MCM board and a board on which the MCM board is mounted, a conventional method is a solder in which a spherical metal such as copper is internally contained on a soldering point (hereinafter referred to as a pad) of both boards. The ball is placed as a soldering medium, and the solder part of the solder ball is melted by the heat treatment in the reflow process to be alloyed and connected to the copper foil pads of both boards. At this time, the spherical metal included in the solder ball (Hereinafter, copper spheres) play a role of a spacer that secures a stable distance between both substrates, and a method of implementing the backside mounting of the MCM substrate within the secured distance is adopted.

FIG. 2 shows this conventional method and configuration.
Is shown in. The MCM board 24 has a SOP on the surface.
An IC, a memory IC 21, a chip resistor, a chip capacitor 22, a QFP LSI 23 are mounted, and a bare chip (IC / LSI) 27 is mounted on the back surface. This MCM
When the board 24 is soldered onto a board (hereinafter referred to as a large-scale board) 25 on which an MCM is mounted, a reflow process is performed through a solder ball 26 as a soldering medium. That is, the solder balls 26 are arranged on the pads of both the MCM board 24 and the large-scale board 25,
When the reflow process is performed, the solder balls 26 shown in FIG.
The solder 28 is melted and the MCM board 24 and the large-scale board 2 are melted.
5, the MCM substrate 24 and the large-scale substrate 25 were electrically connected in a low resistance state in the form of being alloyed and connected to both pad portions, and using the copper balls 29 as spacers with the interval dimension b.

[0004]

In the reflow soldering process between the MCM board and the board on which the MCM board is mounted, the conventional method using solder balls as a soldering medium increases the number of signals wired between the boards. However, in the case of high integration, there are the following problems.

(1) Since the copper balls inside the solder balls, which play the role of spacers between the two substrates at the time of reflow, are spherical, the solder portion melts during reflow processing, and the solder balls move from the pads on both substrates by the force of the solder surface tension. Therefore, when the pad pitch becomes narrow due to high-density mounting, an electrical short circuit between adjacent pads is likely to occur, which is a factor that prevents high-density mounting.

(2) When mounting both sides of the MCM board, the distance between the MCM board and the board on which the MCM board is mounted is
Although it depends on the diameter of the copper sphere inside the solder ball, if the diameter of the copper sphere is increased in order to increase the height of the mounted components on the back surface of the MCM board, the dimension also increases in the lateral direction.
It is not possible to deal with the narrow pad spacing during high-density mounting. That is, since it is not possible to secure a large distance between both substrates, MC
It is practically impossible to mount the back surface of the M board, and basically it is possible to mount only bare chips of IC / LSI as low-profile components, which makes it difficult to realize high-density mounting on both boards. Was there.

An object of the present invention is to enable mounting of ordinary parts on the back surface of the MCM board and to provide flexibility in mounting the parts of the MCM board to achieve high integration. It is to provide a method of soldering a module substrate.

[0008]

A method of soldering a multi-chip module substrate by means of a solder pillar according to the present invention is I
A multi-chip module substrate in which circuit components such as C, LSI, resistors and capacitors are densely mounted on a small-scale substrate, and themselves are one mounting component on a large-scale substrate, and this multi-chip module Within the range of the reflow soldering process with the large-scale board on which the board is mounted, a columnar metal serving as a spacer between the multi-chip module board and the large-scale board is internally contained and externally. Is using a solder column composed of a solder component as a soldering medium.

[0009]

Next, the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, (a) is a side view, and (b) is an enlarged perspective view of a solder column used in this embodiment.

In this embodiment, in the reflow soldering process of the MCM board 14 and the board on which the MCM board 14 is mounted, that is, the large-scale board 15, a solder pillar 16 as a soldering medium is provided between both boards.
Arrange and configure. As shown in FIG. 1B, the solder column 16 has a columnar shape, contains a copper column 19 inside, and has a solder 18 on the outer periphery thereof to form a soldering medium.

The MCM substrate 14 has a SOP I on the surface.
C, memory IC 11, chip resistor, chip capacitor 1
2. The QFP LSI 13 is mounted, and the bare chip (IC / LSI) 17 is mounted on the back surface. The solder pillars 16 are arranged on the pads of both the MCM board 14 and the large-scale board 15, and one side is in a state of being bonded and fixed on the pads of the MCM board 14 perpendicularly to the pad surface by a conductive adhesive. ing.

When the reflow process is performed in this state, the solder 18 of the solder column 16 is melted and alloyed and connected to both pads of the MCM substrate 14 and the large-scale substrate 15, and the copper column 19 is used as a spacer. Both substrates are electrically connected in a low resistance state. According to this embodiment, the solder pillar 1 is used as a spacer between the MCM board 14 and the large-scale board 15.
By using 6, even when the MCM is highly integrated and the number of connection signals is increased, the following merits can be achieved.

(1) Since the solder column 16 which plays the role of the spacer is cylindrical, it is more difficult to move from the pad portion than the conventional copper ball spacer during the reflow process, which makes it possible to reduce the pad interval. High density pattern mounting of the MCM board 14 and the large scale board 15 is possible.

(2) Only by reducing the bottom area of the copper cylinder 19, the pad interval can be narrowed, and high integration can be facilitated.

(3) Since the solder column 16 which plays the role of the spacer is cylindrical, it is easy to secure the dimension of the spacer in the height direction without expanding the dimension in the lateral direction unlike the conventional copper ball spacer. Will be feasible. Further, as the number of signals increases with higher integration, the distance a between both substrates shows a tendency of a> b as compared with the conventional distance b (FIG. 2). Therefore, when high integration is performed and the MCM board 14 is mounted on both sides, in the case of the conventional copper ball spacer, the dimension expansion of the spacer is limited to prevent short circuit between the narrow pads, and as a result, On the back surface of the MCM substrate, only bare chips of low-profile parts could be mounted, whereas in the present embodiment,
Since it is easy to secure the dimension in the height direction of the spacers even with a narrow pad spacing, as a result, in addition to the bare chip 17 on the back surface of the MCM substrate 14, as shown in FIG. It is possible to mount high-height components equivalent to the surface of the MCM board 14, such as the chip capacitor 12, and it is possible to easily realize high-density pattern mounting of the MCM board 14.

As described above, according to this embodiment, the MC
It is possible to easily realize high-density pattern mounting on both the M board 14 and the large-scale board 15 on which the M board 14 is mounted.

[0018]

As described above, the present invention has the following effects by using the solder columns for the reflow soldering process between the MCM board and the board on which the MCM board is mounted.

(1) Since the inner copper material of the solder pillar which plays the role of a spacer between both substrates at the time of reflow is columnar, it is difficult to move against the force due to the solder surface tension from the pads of both boards at the time of reflow processing. As a result, stable soldering quality can be easily secured even in high-density mounting with a narrow pad interval.

(2) As in the above item (1), since the copper material inside the solder column is columnar, the dimension of the spacer in the height direction can be easily secured without increasing the dimension in the lateral direction. Therefore, it is possible to easily secure the dimension in the height direction of the spacer even under the condition that the pad spacing is narrowed by high-density mounting, and as a result, the height of the mounted component on the back surface of the MCM substrate is increased, and M
High-density pattern mounting on both the CM board and the board on which the CM board is mounted can be realized with high reliability, and flexibility can be provided in component mounting arrangement on the MCM board.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, (a) is a side view,
(B) is an enlarged perspective view of a solder column used in this embodiment.

FIG. 2 shows an example of a conventional soldering treatment method, (a)
Is a side view and (b) is a sectional view showing a solder ball used for this.

[Explanation of symbols]

 11,21 SOP IC, memory IC 12,22 Chip resistor, chip capacitor 13,23 QFP LSI 14,24 MCM substrate 15,25 Large-scale substrate 16 Solder pillar 17,27 Bare chip (IC / LSI) 18,28 Solder 19 Copper Cylinder 26 Solder ball 29 Copper ball

Claims (1)

[Claims] 1. A multi-chip module substrate in which circuit components such as ICs, LSIs, resistors, and capacitors are mounted on a small-scale substrate with high density, and are themselves mounted as one mounting component on a large-scale substrate. Within the range of the reflow soldering process with the large-scale board on which the multi-chip module board is mounted, a columnar metal serving as a spacer between the multi-chip module board and the large-scale board is internally formed. A method of soldering a multi-chip module substrate using a solder pillar, characterized in that a solder pillar which is included in the above and whose outside is composed of a solder component is used as a soldering medium.