JP2000286368A - Electronic circuit module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure a good heat transfer path to a wiring board for a semiconductor element mounted on the wiring board in a flip-chip mounting manner. SOLUTION: A semiconductor element 3 is mounted on a wiring board 1, and the terminal electrode 4 of the element 3 and the opposed electrode pads 2 formed on the surface of the wiring board 1 are connected together into an electronic circuit module with a bonding member composed of metal particles 5 which are 30 to 100 μm in diameter and arranged at an interval of 50 μm or smaller. Heat released from the semiconductor element 3 can be efficiently transferred to the wiring board 1, and the electronic circuit module can be improved in electric connection reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic circuit module having a semiconductor element mounted on a wiring board, and more particularly to an electronic circuit module used for an important part of various electronic apparatuses and electronic devices, and more particularly, to a heat radiation from the semiconductor element to the wiring board. The present invention relates to an electronic circuit module having a higher level.

[0002]

2. Description of the Related Art The demand for smaller, thinner, more functional, and lower cost electronic devices and electronic devices has been constantly increasing. In the same way, studies on miniaturization, thinning, high functionality, and low cost of electronic circuit modules, which are semiconductor devices constituting electronic devices, have been rapidly advanced.

[0003] Such electronic circuit modules generally constitute electronic circuits by mounting electronic components and semiconductor elements on a circuit board that constitutes a circuit board, and furthermore, these electronic components are used for protection of the electronic circuits and electromagnetic shielding. And a metal case is attached so as to cover the semiconductor element.

The substrate constituting the electronic circuit module includes, for example, a ceramic material mainly composed of an aluminum oxide sintered body, a high thermal conductive ceramic material mainly composed of an aluminum nitride sintered body, or glass. Glass epoxy made of a material and an organic material, glass ceramics that can be fired at a lower temperature than ceramic materials, and the like are used. Regarding these substrate materials, in the electronic circuit module, the respective substrate materials are properly used depending on the application as follows.

For example, a ceramic material containing an aluminum oxide sintered body as a main component is a highly stable and reliable insulating material. However, since it must be fired at a high temperature of about 1400 to 1650 ° C., wiring It is necessary to use a high melting point metal such as tungsten or molybdenum as the material of the conductor, and since such a high melting point metal is a high specific resistance metal material, it is difficult to apply it to an electronic circuit module that performs high-speed signal processing.

A ceramic material having a high thermal conductivity, which is mainly composed of an aluminum nitride sintered body, is effective in that it has good heat dissipation, but is not suitable for general electronic circuit modules in the consumer field. It is expensive and it is difficult to reduce the cost.

Further, glass epoxy comprising a glass material and an organic material is inexpensive but has insufficient heat resistance.
It is not suitable for electronic circuit modules that also require thermal stability.

On the other hand, glass ceramics which can be fired at a lower temperature and in a shorter time than ceramic materials can be manufactured at a low cost, and further, a low melting point metal material such as Au or Ag is used as a wiring conductor material. -Since a low resistivity metal material such as Cu can be used, it is advantageous for an electronic circuit module that performs high-speed signal processing.

In addition, these substrate materials are properly used depending on the application. In order to attain the miniaturization by directly mounting the semiconductor element in response to the recent enhancement of the function of the electronic circuit module, the miniaturization and the high density of the semiconductor element are required. An important issue is how to dissipate the heat generated by the semiconductor element due to the higher power. As a measure for the heat radiation, for example, a method of directly mounting a semiconductor element on a substrate made of a material having a high thermal conductivity or a method of forming a large number of thermal via holes through a heat radiation member called a thermal via hole in a substrate immediately below the semiconductor element is formed. And the like.

On the other hand, as for the electrical connection method for mounting a semiconductor element, a method such as so-called flip-chip mounting using metal bumps has been put into practical use instead of conventional wire bonding in order to reduce the mounting area. ing.

[0011]

However, in order to ensure the reliability of a semiconductor device in which the amount of generated heat tends to increase, better heat dissipation than before is required, and furthermore, the electrical characteristics are also reduced. In order to ensure stable operation of the semiconductor element, the ground is required to be strengthened, and there is an increasing demand for an electronic circuit module that achieves both smaller size and lower cost than ever before.

As a conventional heat dissipation measure, a so-called thermal via penetrating from the front surface to the rear surface of the substrate is provided, connected to a metal electrode portion on the substrate surface, and a semiconductor element is provided with a metal bump on the metal electrode portion. By mounting and connecting via a semiconductor device, heat generated by a semiconductor element is transmitted to a thermal via. Also, by injecting a high thermal conductivity underfill material into the gap between the semiconductor element and the substrate,
Further, heat dissipation is also improved.

However, the transfer of heat generated from the semiconductor element is dominated by metal bumps from the viewpoint of thermal conductivity, and the heat dissipation ability is affected by the number of metal bumps. In other words, the heat dissipation efficiency can be improved by forming a large number of metal bumps on the semiconductor element. However, the number of metal bumps that can be formed is determined by the bump shape and the capability of the bump pitch forming apparatus. There was a limit to improving the heat dissipation by increasing the number.

Further, from the viewpoint of electrical characteristics, the higher the operating frequency of the semiconductor device, the greater the effect of ground stability on electrical characteristics. However, this is also limited by the number of metal bumps that can be formed. Since the number of metal bumps that can be formed is determined by the capability of the bump forming apparatus, there is a limit to increasing the number of bumps from the viewpoint of further stabilizing the ground.

The present invention has been made in view of the above circumstances, and has as its object to efficiently radiate heat generated from a semiconductor element mounted on a wiring board and to stabilize the electrical characteristics of the semiconductor element. In order to obtain a highly reliable electronic circuit module.
An object of the present invention is to provide a highly reliable electronic circuit module that can respond to a demand for miniaturization.

[0016]

An electronic circuit module according to the present invention has a semiconductor element mounted on a wiring board,
A joining member formed by joining a plurality of metal particles having a diameter of 30 to 100 μm, which are arranged at an interval of 50 μm or less and having a diameter of 30 to 100 μm, to a terminal electrode of the semiconductor element and an electrode pad on the surface of the wiring board opposed thereto The connection is characterized by the following.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an electronic circuit module according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a top view showing an example of a wiring board constituting the electronic circuit module of the present invention. FIG. 2 is a bottom view showing an example of a semiconductor element constituting the electronic circuit module of the present invention. (A) and (b) are each shown in FIG.
FIG. 3 is a cross-sectional view corresponding to the line AA ′ and the line BB in FIG. 2 showing a state where the semiconductor element shown in FIG.

In these figures, reference numeral 1 denotes a wiring board serving as a substrate main body of an electronic circuit module, 2 denotes an electrode pad formed on an upper surface of the wiring board 1, 3 denotes a semiconductor element, and 4 denotes a lower surface of the semiconductor element. The terminal electrodes 5, 5 are metal grains, and 6 is a brazing metal. Reference numeral 7 denotes a so-called underfill material filled between the wiring board 1 and the semiconductor element 3, and reference numeral 8 denotes various electronic parts such as chip parts mounted on the upper surface of the wiring board 1 together with the semiconductor element 3. is there. In FIG. 1, the mounting position of the semiconductor element 3 is indicated by a chain line.

The wiring board 1 forms a circuit board with a plurality of insulating layers, circuit wiring layers, through conductors and the like. As the wiring board 1, substrates made of various materials such as a ceramic epoxy wiring board, a glass ceramic multilayer wiring board, and a glass epoxy board can be used.

The electrode pad 2 is formed on the upper surface of the wiring board 1 so as to face the terminal electrode 4 of the semiconductor element 3. The electrode pad 2 is made of a thick film using a conductive paste like the conductive layer and the through conductor of the wiring board 1. It is formed by a method or the like. For example, in the case of forming on the upper surface of the wiring board 1 made of a ceramic insulating layer, the insulating layer of the wiring board 1 is formed by using a metal paste such as Ag / Au / Cu and a conductive paste prepared with an organic binder or the like. After printing in a predetermined pattern on the surface of the ceramic green sheet, the electrode pad 2 having a desired shape and dimensions may be formed by firing together with the ceramic green sheet.

The semiconductor element 3 is, for example, a semiconductor integrated circuit element such as an IC or LSI, and the amount of heat generated during operation tends to increase with the recent increase in density. Terminal electrodes 4 for performing so-called flip-chip mounting are formed on the lower surface of the semiconductor element 3. Here, as shown in FIG. 2, metal particles 5 for mounting and connecting to the wiring board 1 are formed.
Have an area in which a plurality are arranged. Note that the terminal electrode 4 is not limited to an elongated shape in which a plurality of metal grains 5 are arranged in a line as shown in FIG. 2, but has a wide area in which a plurality of metal grains 5 are dispersed and arranged on a plane. Pattern shape.

The metal particles 5 connecting the terminal electrodes 4 of the semiconductor element 3 and the electrode pads 2 of the wiring board 1 do not melt at the melting temperature of the metal brazing material 6, and have the same shape even after joining with the metal brazing material 6. And a metal having excellent thermal conductivity. The metal particles 5 are made of Au (thermal conductivity: 318 W / m · K) or Cu (394 W / m) used for general metal bumps.
· K) · Al (229 W / m · K) or the like, and is formed and arranged on the surface of the terminal electrode 4 or the electrode pad 2 using a wire bonding apparatus in the same manner as in the method of forming a metal bump. It is possible to

As the main substance of the metal particles 5, it is preferable to use Au which is chemically stable among the above materials, has small electric conductor loss, and is excellent in thermal conductivity.

It is preferable that the diameter of the metal particles 5 is 30 to 100 μm.

The metal grains 5 reduce the conductor loss by increasing the diameter, but when the diameter exceeds 100 μm,
The size of the semiconductor element 3 is unsuitable for high-density and highly-integrated semiconductor elements 3, and it is difficult to reduce the size of the electronic circuit module. In addition, the volume of the metal particles 5 becomes unnecessarily large, which is unsuitable in terms of cost reduction. On the other hand, when the diameter of the metal particle 5 is less than 30 μm, the capacity for the current and heat transmitted through the metal particle 5 becomes insufficient, and the transmission loss for a high-frequency signal increases. In addition, it is difficult to stably form and arrange such fine metal particles 5.

Although the shape of the metal particles 5 is basically spherical, it is not necessarily required to be a true sphere. In addition to an elliptical sphere or a column, the metal particles 5 can function as the metal particles 5 in the present invention. If so, various shapes may be used.

Such metal particles 5 can be formed by using, for example, a wire bonding apparatus. The formation of the metal particles 5 by this wire bonding apparatus can form the desired metal particles 5 at a lower cost and in a shorter time than the formation method by metal plating or the formation method by metal evaporation. Further, a method of forming the metal particles 5 by supplying a solder paste or the like to the surface of the terminal electrode 4 or the electrode pad 2 by using a printing method or the like and melting it by heating may be adopted. It is somewhat difficult to form fine metal particles 5 as compared with the forming method using a bonding apparatus.

In the connecting member according to the present invention,
The interval between the plurality of metal grains 5 joined by the metal brazing material 6 is preferably 50 μm or less. The reason for this is 50
By arranging the metal particles 5 at intervals of not more than μm, when the semiconductor element 3 is mounted on the wiring board 1 and connected by a bonding member, the metal particles 5 are adjacent to the metal particles 5 arranged between the terminal electrode 4 and the electrode pad 2. The fitting space can be filled with the metal brazing material 6 without any gap, and the metal brazing material 6 can be interposed therebetween, and the connection area between the terminal electrode 4 and the electrode pad 2 by the connecting member composed of the metal grains 5 and the metal brazing material 6 can be sufficiently ensured. As a result, the connection area can be greatly increased as compared with the conventional case using metal bumps, and a sufficient heat radiation path can be secured for the heat generated from the semiconductor element 3 and the electrical connection reliability can be improved. Can be done.

When the interval between the metal grains 5 exceeds 50 μm, when the metal grains 5 are joined with the metal brazing material 6 to form a connecting member, the metal brazing material 2 is interposed between the metal grains 5 to reduce the gap. It becomes difficult to fill the gap sufficiently, and stress concentration in the gaps occurs, causing cracks in the connection member.It also becomes difficult to secure a sufficient heat dissipation path and improve the reliability of electrical connection by the connection member. It is in.

It is preferable that the interval between the plurality of metal grains 5 be as narrow as possible with an interval of 50 μm or less, which is more advantageous for heat radiation and is preferable.

The metal brazing material 6 is formed by joining a plurality of metal grains 5 arranged at a predetermined interval of 50 μm or less between the electrode pad 2 of the wiring board 1 and the terminal electrode 4 of the semiconductor element 3. Together with the bonding member, thereby forming the electrode pad 2
And the terminal electrode 4 are electrically connected.

According to such a joining member, it is possible to secure a sufficient connection area between the terminal electrode 4 of the semiconductor element 3 and the electrode pad 2 of the wiring board 1 to secure an effective heat transfer path. Thus, the heat generated by the semiconductor element 3 can be transmitted to the wiring board 1 and radiated with high heat transfer efficiency.

[0034] Such a metal brazing material 6 is required to maintain the shape of the metal particles 5 in the joining member, and at the lowest possible temperature due to the problem of thermal protection of the semiconductor element 3 and residual thermal stress. It is preferable to select a material that can be melted. For example, basically, any melting temperature lower than the melting point of the metal particles 5 can be used, but Pb / Sn or Au / S
When solder such as n.Au/Si is used, the melting temperature of these is 180 to 460.degree. C., whereas the melting temperature of metal particles 5 is around 900.degree. be able to. When the metal brazing material 6 is melted, a solid solution may be generated with the metal of the metal particles 5 to lower the melting point of the metal particles 5. Therefore, in order to maintain the shape of the metal particles 5 in good condition, The melting temperature of the brazing metal 6 is Au
It is desirable to select a material having a / Sn of about 330 ° C. or less.

It is important that the metal brazing material 6 be made of a material having good thermal conductivity as much as possible. As such a metal brazing material 6, for example, Au / S
n (thermal conductivity: 250 W / m · K) or Au (318 W / m · K)
K) ・ Cu (394 W / m ・ K) ・ Al (220 W / m ・
K) · Pb / Sn (40 W / m · K) or the like can be used.

As the metal brazing material 6, in particular, solder which is a low melting point metal brazing material is used so that the joining member can be formed while maintaining the shape of the metal particles 5. This is preferable in that damage to the first or electronic component 8 due to temperature can be suppressed. Specific examples of such solder include Au / Sn and Sn / Pb.Sn.
/ Ag etc. can be applied widely. In particular, when considering the influence on the environment, it is preferable to use Sn / Ag solder.

In order to connect the terminal electrode 4 of the semiconductor element 3 and the electrode pad 2 of the wiring board 1 with a joining member composed of a plurality of metal grains 5 and a metal brazing material 6, for example, A plurality of metal particles 5 having a diameter of 30 to 100 μm are arranged and attached on the surface of the terminal electrode 4 at intervals of 50 μm or less, while a metal brazing material 6 is previously placed on the electrode pads 2 of the wiring board 1. By mounting the semiconductor element 3 thereon with good positional accuracy and melting the metal brazing material 6 by reflow or substrate heating, the metal particles 5 are joined with the metal brazing material 6 and the joining member is formed. And the terminal electrode 4 and the electrode pad 2 may be connected.

At this time, it is necessary to supply an amount of the metal brazing material 6 such that the metal brazing material 6 can sufficiently wet and spread between the metal particles 5 and fill the space between the metal particles 5 and join them. In order to improve the wettability of the metal brazing material 6 to the metal particles 5, a rosin-based flux is mixed with an organic solvent and mixed with the metal brazing material 6, and is used in an inert atmosphere or in a reducing atmosphere. It is also effective to heat and join in an atmosphere.

After the semiconductor element 3 is mounted on the wiring board 1 and the electrode pads 2 and the terminal electrodes 4 are connected by a joining member, if necessary, an underfill material is provided between the wiring board 1 and the semiconductor element 3. By implanting 7, the mounting reliability of the semiconductor element 3 can be improved. Such an underfill material 7 is an insulating resin having good heat conduction injected and filled between the lower surface of the semiconductor element 3 and the wiring board 1, thereby connecting the wiring board 1 and the semiconductor element 3. Can be stabilized.

Further, by using an epoxy resin or the like to which an inorganic filler having a high thermal conductivity is added as the underfill material 7, it is possible to provide more sufficient heat radiation from the semiconductor element 3 to the wiring board 1. It is. The underfill material 7 is used as needed, and is not always necessary for the electronic circuit module.

By mounting various electronic components 8 at predetermined positions on the wiring board 1, a desired electric circuit can be formed, and an electronic circuit module is completed.

Thereafter, the semiconductor element 3 may be sealed with a sealing resin such as an epoxy resin for sealing the semiconductor element or a silicone resin for the purpose of protecting the element and the bonding member after mounting. Alternatively, a cover covering the semiconductor element 3 and the electronic component 8 is attached to the upper surface of the wiring board 1 to protect them,
Alternatively, it may be electromagnetically shielded.

The various electronic components 8 mounted and mounted on the upper surface of the wiring board 1 together with the semiconductor element 3 include:
For example, chip capacitors, chip resistors, chip inductors, and the like are used. The mounting of these electronic components 8 is as follows.
For example, a solder paste may be printed and applied to the mounting electrodes of the electronic component 8 in advance, and after mounting the electronic component 8 on the wiring board 1, it may be soldered by passing it through a belt-type reflow furnace or the like.

According to the electronic circuit module of the present invention as described above, the terminal electrode 4 of the semiconductor element 3 and the electrode pad 2 of the wiring board 1 facing the terminal electrode 4 are arranged at an interval of 50 μm or less and have a diameter of 30 to 30 μm. Since a plurality of metal grains 5 of 100 μm are connected by a joining member joined by a metal brazing material 6, the metal grains 5 having high thermal conductivity and the metal brazing material 6 having good thermal conductivity are connected. A sufficient heat transfer path can be ensured by the joining members configured in a suitable combination, and the heat generated by the semiconductor element 3 can be efficiently transmitted to the wiring board 1 side via the joining members to dissipate the heat. In addition, the area of the electrical connection can be sufficiently secured, the ground can be stabilized, the transmission loss of the high-frequency signal can be suppressed, and the connection reliability can be improved.

It should be noted that the present invention is not limited to the above-described embodiments, and that various changes and improvements can be made without departing from the scope of the present invention.

[0046]

According to the electronic circuit module of the present invention,
The terminal electrodes of the semiconductor element and the electrode pads of the wiring board opposed thereto are arranged at an interval of 50 μm or less and have a diameter of 30 to
Since a plurality of metal particles of 100 μm are connected by a joining member joined by a brazing metal, a sufficient heat transfer path can be secured by such joining members, and the heat generated by the semiconductor element can be efficiently generated on the wiring board side. The heat can be transmitted to the radiator to dissipate heat, and the electrical connection area can be sufficiently ensured to stabilize the ground and reduce transmission loss of high-frequency signals, thereby improving connection reliability. You can also.

As described above, according to the present invention, heat generated from a semiconductor element mounted on a wiring board is efficiently radiated,
Furthermore, the electrical characteristics of the semiconductor element can be stabilized, and a highly reliable electronic circuit module that can meet the demand for high density and small size at low cost can be provided.

[Brief description of the drawings]

FIG. 1 is a top view showing an example of a wiring board used for an electronic circuit module of the present invention.

FIG. 2 is a bottom view showing an example of a semiconductor element constituting the electronic circuit module of the present invention.

FIGS. 3 (a) and (b) show a state where the semiconductor element shown in FIG. 2 is mounted on a portion shown by a dashed line in FIG. 1, respectively, and are taken along lines AA 'and BB in FIG. It is sectional drawing corresponding to FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Wiring board 2 ... Electrode pad 3 ... Semiconductor element 4 ... Terminal electrode 5 ... Metal particles 6 ... Metal brazing material

Claims (1)

[Claims] A semiconductor device is mounted on a wiring substrate, and a terminal electrode of the semiconductor device and an electrode pad on the surface of the wiring substrate facing the semiconductor device are arranged at an interval of 50 μm or less and have a diameter of 30 to 100 μm. An electronic circuit module, wherein a plurality of metal particles are connected by a joining member joined by a brazing metal.