JP2741611B2 - Substrate for flip chip bonding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a flip chip method or a CCB (Controlle
The present invention relates to an electronic component mounting substrate used when electronic components such as semiconductor elements are mounted face-down on an insulating substrate by using a connection method (hereinafter, referred to as a flip chip method) called a d Collapse Bonding method.

2. Description of the Related Art Conventionally, as a connection method for connecting electrodes of an electronic component such as a semiconductor element to connection terminals formed on an insulating substrate or a package (hereinafter, referred to as an insulating substrate including a package), as described above, There is a connection method called a simple flip chip method.

In this connection method, a substantially spherical solder bump formed on an electrode of an electronic component is superimposed directly on a connection terminal formed on an insulating substrate or on a solder layer provided on the connection terminal. The solder forming the solder bumps and the solder layers is reflowed. The electrodes of the electronic component are connected to the connection terminals formed on the insulating substrate by soldering using the reflowed solder. And
Electronic components are mounted face down on an insulating substrate.

In this connection method, the solder bumps formed on the electrodes of the electronic component are entirely formed of solder only, and a Cu ball is used as a core material, and the periphery of the ball is covered with solder. There is something we do.

According to the flip-chip method, an electronic component such as a highly integrated semiconductor element, in which a large number of electrodes are provided in a grid or the like on the inside and outside of the upper surface, without using wires or the like, It can be easily and accurately mounted face down on an insulating substrate.

[Problems to be Solved by the Invention] By the way, when the electronic component is mounted face down on the insulating substrate by the flip-chip method as described above, the electronic component mounted on the insulating substrate is normally It is checked whether it operates. If it is found that the electronic component mounted on the insulating substrate is a defective product that does not operate normally, the electronic component mounted on the insulating substrate is generally replaced with another good electronic component. doing.

However, in order to replace the electronic component mounted on the insulating substrate with another electronic component, the solder connecting each of the plurality of electrodes of the electronic component to each of the plurality of connection terminals of the insulating substrate is reflowed. When the electronic component is detached from the insulating substrate, the solder adhered over the plurality of electrodes of the electronic component and the plurality of connection terminals of the insulating substrate to which the electrodes are connected by soldering. However, the solder is not randomly divided and adhered to each of the electrodes and the connection terminals, and the solder is randomly or excessively adhered to the respective electrodes and the connection terminals. Alternatively, the core Cu balls forming the solder bumps may be randomly attached to one of the electrodes of the electronic component or the connection terminals of the insulating substrate. After that, it becomes difficult to mount another electronic component face down again by the flip-chip method on the insulating substrate from which the electronic component has been detached as described above.

In other words, on each connection terminal of the insulating substrate after the electronic component is detached, the solder layer is randomly or excessively or insufficiently adhered, or the Cu ball is adhered or not adhered. Then, using the solder bumps formed on the respective electrodes, the respective electrodes of the other electronic components are securely re-soldered to the respective connection terminals of the insulating substrate from which the electronic components have been separated by the flip chip method. It becomes difficult.

Therefore, conventionally, as described above, if it is determined by the flip-chip method that the electronic component mounted face-down on the insulating substrate is a defective product that does not operate properly, the electronic component, The electronic component has to be discarded together with the insulating substrate mounted thereon.

However, in recent years, highly integrated insulating substrates for mounting electronic components are expensive, such as multilayer ceramic substrates and ceramic packages having complicated connection circuits, and as described above. Discarding the insulating substrate, together with the defective electronic components mounted on it,
Electronic devices formed by mounting electronic components face down on an insulating substrate have become expensive.

This is particularly remarkable in a modular expensive insulating substrate having a large number of complicated connection circuits for mounting a plurality of electronic components together.

Also, forming solder bumps on the electrodes of electronic components and forming a layered glass dam for forming solder bumps around the electrodes of the electronic components requires high heat to be applied to the electronic components. The function of the weak electronic component and its reliability may be impaired.

The present inventors have conceived that the solder bumps may be formed on the insulating substrate side so that heat for forming the solder bumps is not applied to the electronic component. An electronic component mounting substrate having solder bumps formed on the insulating substrate side. The electronic component mounting substrate is capable of repeatedly and accurately mounting the electronic component face down on the insulating substrate by a flip chip method. A substrate was developed.

That is, the present invention provides an electronic component mounting substrate in which solder bumps are formed on the insulating substrate side, wherein the electronic component can be repeatedly mounted face down by flip-chip method. It is intended to be.

[Means for Solving the Problems] In order to achieve the above object, in the electronic component mounting substrate of the present invention, a solder bump forming ball is formed on a connection terminal formed on an insulating substrate by solder melting. A solder bump formed by joining via a metal that does not melt even when subjected to a high temperature, and surrounding the ball except for a portion joined to the connection terminal with solder.

Further, in the electronic component mounting board of the present invention, it is preferable that the ball is brazed to the connection terminal via a silver solder.

Alternatively, it is preferable that the ball be bonded to the connection terminal by thermocompression bonding via a metal plating layer formed on the terminal or a metal plating layer formed on the surface of the ball.

[Operation] In the electronic component mounting board of the present invention, the electronic component is mounted face down on the insulating substrate, and the electrodes of the electronic component are insulated directly or via the solder layer formed on the electrode. By reflowing the solder forming the solder bumps and the solder layer in a state of being superimposed on the solder bumps formed on the connection terminals of the insulating substrate, the electrodes of the electronic component are reflowed to the connection terminals of the insulating substrate. It can be connected by using solder. Then, the electronic component can be mounted face down on the insulating substrate by the flip chip method.

Also, since the balls are bonded to the connection terminals via a metal that does not melt even when the temperature at which the solder melts, the solder connecting the electrodes of the electronic components to the connection terminals of the insulating substrate is reflowed. Thus, when the electronic component is detached from the insulating substrate, the ball can be reliably left on the connection terminal.

At the same time, using the surface tension acting on the peripheral surface of the ball left on the connection terminal, the solder connecting the electrode of the electronic component to the connection terminal of the insulating substrate was left on the connection terminal. The electronic component can be detached from the insulating substrate in a state where the electronic component is always sufficiently adhered and remained around the ball.

In other words, the electronic component can be detached from the insulating substrate with the solder bumps on the connection terminals where the periphery of the ball is covered with the solder without any shortage always being accurately left.

Then, using the solder bumps left on the connection terminals, another electronic component can be repeatedly and accurately mounted face-down by the flip-chip method on the insulating substrate from which the electronic component has been detached.

Further, in the electronic component mounting board of the present invention in which the balls are bonded to the connection terminals via a silver solder or a metal plating layer, the balls are connected to the connection terminals even if the temperature at which the solder melts is applied. Can be firmly bonded through a silver brazing or metal plating layer having a high melting point so that

Example Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 or FIG. 2 shows a preferred embodiment of the electronic component mounting substrate of the present invention, and is an enlarged front sectional view near the solder bumps thereof. Hereinafter, the electronic component mounting board will be described.

In the figure, reference numeral 12 denotes an insulating substrate having a multilayer structure. The insulating substrate 12 is formed by laminating and firing a plurality of alumina ceramic green sheets.

As shown in FIG. 1 or FIG. 2, the insulating substrate 12 has a plurality of connection terminals 10 made of tungsten metallization or the like for connecting electrodes of electronic components to be described later, as shown in FIG.
Are arranged at a predetermined pitch. Then, each of the connection terminals 10 is connected to an internal circuit (not shown) formed between the layers of the insulating substrate 12 through a circuit 26 formed vertically penetrating the layer of the insulating substrate 12. doing.

The upper surface 12a of the uppermost layer of the insulating substrate and the surface peripheral portion of each of the plurality of connection terminals 10 formed on the uppermost surface 12a are the first
As shown in FIG. 2 or FIG.
It is continuously covered with b. A plurality of connection terminals 10 of the insulating substrate are provided inside the alumina ceramic layer 12b.
The central part of the surface is exposed. An alumina ceramic layer 12 is formed around the plurality of connection terminals 10 on the insulating substrate.
A dam for forming a solder bump made of b is formed.

When forming this alumina ceramic layer 12b,
A plurality of connection terminal forming layers made of a tungsten metallized paste or the like are formed on the upper surface of the uppermost layer of the insulating substrate forming member before firing formed by laminating a plurality of alumina ceramic green sheets at a predetermined pitch using a screen printing method or the like. Are formed side by side. Next, the alumina ceramic paste is continuously applied by screen printing or the like over the upper surface of the uppermost layer of the insulating substrate forming member and the peripheral portions of the surfaces of the plurality of connection terminal forming layers formed on the uppermost layer. It is applied in layers. Then, when the insulating substrate forming member is fired together with the connection terminal forming layer to form the insulating substrate 12, at the same time, the alumina ceramic paste is fired, and the upper surface 12a of the insulating substrate is coated with alumina. The ceramic layer 12b is formed integrally.

At the center of the surface of each connection terminal 10 exposed inside the alumina ceramic layer 12b, a spherical ball 14 for forming a solder bump described later is mounted. The bottom of the ball 14 is joined to each connection terminal 10 via a metal that does not melt even when a temperature of, for example, 200 ° C. at which the solder melts is applied.

Specifically, a ball made of, for example, spherical gold, copper, or Kovar (Fe—Ni—Co alloy) having a diameter of 50 to 100 μm is used as the ball 14.

As shown in FIG. 1, the ball 14 is heated at a temperature of about 800 ° C. using a silver solder 28 having a high melting point so that each connection terminal 1
It is brazed on 0.

Alternatively, as shown in FIG. 2, the ball 14 is bonded to each connection terminal 10 on which a metal plating layer such as gold plating is formed by applying a high temperature of about 500 ° C. by thermocompression bonding.

Further, when the ball 14 is formed of Kovar or the like and it is difficult to directly thermocompress the ball 14 onto the connection terminal 10,
Form a plating layer such as gold plating on the peripheral surface of the ball 14,
The balls 14 are securely and firmly joined to the connection terminals 10 by thermocompression bonding via the plating layers.

The periphery of the ball 14 bonded on each connection terminal 10 is covered with the solder 16 almost uniformly without a gap except for the portion bonded to the connection terminal 10.

When the periphery of the ball 14 is covered with the solder 16, as shown in FIG. 3, a sheet-like solder is formed over the ball 14 bonded on each of the plurality of connection terminals 10 of the insulating substrate 12. Then, the solder 16 is reflowed. Then, the solder 16 that melts and falls on the surface of the alumina ceramic layer 12b formed on the uppermost layer upper surface 12a of the insulating substrate is applied to each of the connection terminals 1 exposed inside the alumina ceramic layer 12b.
The self-alignment is automatically performed at the center of the surface of 0 to converge. Then, the collected solder 16 is connected to each connection terminal 10 exposed inside the alumina ceramic layer 12b.
Each ball 14 bonded on the center of the surface of the
Utilizing the surface tension acting on the peripheral surface of each ball, the self-alignment is automatically performed over the center of the surface of each connection terminal 10 and the periphery of each ball 14 so that they are almost uniformly attached without any gap. I have.

Then, on each of the plurality of connection terminals 10 formed on the upper surface 12a of the uppermost layer of the insulating substrate, a substantially spherical solder bump 18 is formed, in which the periphery of the ball 14 is covered almost uniformly with the solder 16 without any gap. ing.

The electronic component mounting substrate shown in FIG. 1 or FIG. 2 is configured as described above.

Next, an example of use of the electronic component mounting board and its operation will be described.

First, a method of mounting the electronic component 20 face down on the insulating substrate 12 by the flip chip method will be described.

As shown in FIG. 4, a solder layer 24 is formed on a plurality of electrodes 22 provided in a grid or the like on the electronic component 20 by using a screen printing method or the like. Then, the electronic component 20 is mounted face down on the insulating substrate 12,
The solder layer 24 on each of the plurality of electrodes 22 of the electronic component is connected to the corresponding solder bump on each of the plurality of connection terminals 10 of the insulating substrate.
Overlay on 18. Then, the solder layer 24 on each electrode 22 of the electronic component and the solder 16 around the ball 14 on each connection terminal 10 on the insulating substrate are reflowed together.

Alternatively, each electrode 22 of the electronic component is directly superimposed on the solder bump 18 on each connection terminal 10 of the insulating substrate without forming the solder layer 24 on each electrode 22 of the electronic component. Then, the solder 16 around the ball 14 is reflowed.

Then, as shown in FIG. 5, the solder layer 24 on each electrode 22 and the solder 16 around each ball 14 are melted and integrated, and these solders correspond to each electrode 22 of the electronic component and the corresponding electrode 22. It is in a state of being attached to each connection terminal 10 of the insulating substrate.

Alternatively, the solder 16 around the ball 14 is melted, and the solder adheres to each electrode 22 of the electronic component and the corresponding connection terminal 10 of the insulating substrate.

As a result, each electrode 22 of the electronic component is soldered and connected to each corresponding connection terminal 10 of the insulating substrate, and the electronic component 20 is mounted face-down on the insulating substrate 12. .

Next, a method of replacing the electronic component 20 mounted face down on the insulating substrate 12 by the flip-chip method as described above with another electronic component will be described.

As shown in FIG. 5, the solder 16 connecting each electrode 22 of the electronic component to each corresponding connection terminal 10 of the insulating substrate is heated to a temperature of about 200 ° C. and reflowed. Then, the electronic component 20 is separated from above the insulating substrate 12 upward.

Then, on each connection terminal 10 of the insulating substrate, the bottom of the ball 14 is joined via a metal silver solder or a metal plating layer which does not melt even when a temperature of about 200 ° C. at which the solder 16 melts is applied. As described above, when the electronic component 20 is detached from the insulating substrate 12, the ball 14
It remains reliably in a state of being joined on each of the 12 connection terminals 10.

At the same time, the solder 16 that receives the surface tension acting on the peripheral surface of the ball 14 and connects each electrode 22 of the electronic component to each connection terminal 10 of the corresponding insulating substrate,
The reflowed solder 16 in the molten state always remains accurately and sufficiently attached around the ball 14.

In other words, with the solder bump 18 in a state where the solder 16 is sufficiently adhered and remaining around the ball 14 on the connection terminals 10 of the insulating substrate, the electronic component 20 is mounted on the insulating substrate. 12 Leave from above.

As a result, using the solder bumps 18 remaining on each connection terminal 10 of the insulating substrate, the other electronic components are accurately and repeatedly face-down by flip-chip method to the insulating substrate 12 from which the electronic component 20 has been detached. Can be reimplemented.

[Effects of the Invention] As described above, according to the electronic component mounting substrate of the present invention, electronic components such as semiconductor elements can be accurately mounted face-down on the insulating substrate by the flip chip method.

Also, if it is determined that the electronic component mounted on the insulating substrate is a defective product that does not operate properly, the electronic component is separated from the insulating substrate, and another electronic component is placed on the insulating substrate. Can be repeatedly and accurately mounted face down by the flip chip method. Then, the insulating substrate such as an expensive ceramic substrate or a ceramic package having a multilayer structure having a complicated circuit can be effectively used without wasting the waste.

Also, there is no need to form a solder bump on the electrode side of the electronic component for mounting the electronic component on the insulating substrate by the flip chip method, and when forming the solder bump, high heat is applied to the electronic component, The function and reliability of the electronic component can be prevented from being impaired.

In addition, since a ball is used as a core material and the periphery of the ball is covered with solder to form a solder bump, an almost accurate and orderly spherical solder bump is easily and accurately formed on the connection terminal of the insulating substrate. Or use the surface tension acting on the peripheral surface of the ball to easily and accurately form solder bumps, which cover the periphery of the ball with solder, almost uniformly and without gaps, on the connection terminals of the insulating substrate. Can be.

In addition, when the electronic component is mounted face down by the flip chip method on the insulating substrate, the amount of solder that connects the electrodes of the electronic component to the connection terminals of the insulating substrate is interposed in the solder. Can reduce the volume of the ball. Then, the solder having a large thermal expansion coefficient as compared with the electronic component or the insulating substrate can reduce the adverse effect of thermal stress on the fragile electronic component or the insulating substrate, based on the difference between the two thermal expansion coefficients. it can.

[Brief description of the drawings]

1 or 2 is an enlarged front sectional view of the vicinity of a solder bump of an electronic component mounting board according to the present invention. FIG. 3 is an explanatory view of a case where the periphery of a ball for forming a solder bump is covered with solder. FIG. 5 is an enlarged front sectional view showing a state in which an electronic component is mounted face-down on the electronic component mounting board of the present invention by the flip-chip method. FIG. It is an enlarged front sectional view showing the state where it was mounted face down. 10 connection terminals, 12 insulating substrate, 12a top surface of uppermost layer, 12b alumina ceramic layer, 14 balls, 16
…… Solder, 18 …… Solder bump, 20 …… Electronic component, 22
... electrodes, 24 ... solder layers.

Claims (3)

(57) [Claims] A solder bump forming ball is bonded to a connection terminal formed on an insulating substrate via a metal that does not melt even when a temperature at which the solder melts is applied, and is bonded to the connection terminal. An electronic component mounting board, wherein a solder bump is formed by covering the periphery of the ball except for a portion with solder. 2. The electronic component mounting board according to claim 1, wherein the ball is brazed to the connection terminal via a silver solder. 3. The electronic component board according to claim 1, wherein the ball is bonded to the connection terminal via a metal plating layer formed on the surface of the terminal or a metal plating layer formed on the surface of the ball.