JPH0317238B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a method for mounting a resin-sealed semiconductor device, and relates to a technique that is effective when applied to improve the reliability of electronic equipment formed by mounting the semiconductor device. It is something.

[Background technology]

A method for mounting a semiconductor device is to fix the external terminal of the device to an electrode portion on a substrate using a brazing material such as solder.

At this time, as a method of melting the brazing material, there is a method of heating the entire semiconductor device to a temperature higher than the melting point of the brazing material using hot air or infrared irradiation.

By the way, among semiconductor devices, resin-sealed semiconductor devices are inherently prone to package cracks, such as cracks in the resin part or gaps at the interface between the resin and the leads, due to differences in the physical properties of their constituent materials. Even after the product is completed, corrosive substances such as moisture can enter the inside of the package from the crack and corrode the electrical system, resulting in poor continuity. It is something that can be considered.

Therefore, in order to improve the reliability of the semiconductor device, it is necessary to prevent the occurrence of package cracks as much as possible.

However, even after the semiconductor device is resin-molded and packaged, there are various steps that are affected by heat, and these steps are also a major cause of the occurrence of package cracks.

Among these, the aging process of the package after resin molding and the brazing mounting process of the semiconductor device, which is the first step, are considered to be the processes most likely to cause package cracks, as the entire device is exposed to extremely high temperatures. .

When mounting the entire semiconductor device by heating it with infrared rays to melt the brazing material, the package part is usually heated to a much higher temperature than the lead parts because the resin that makes up the package is black. The present inventor has clarified that there is a Therefore, the present inventor has found that the occurrence of package cracks due to thermal shock caused by differences in physical properties such as thermal expansion coefficients of the materials constituting the semiconductor device becomes a particularly important problem when the above-mentioned mounting method is adopted. It was.

Furthermore, as mentioned above, the entire semiconductor device is exposed to high temperatures during the mounting process, etc., and in addition to differences in the physical properties such as the coefficient of thermal expansion of the constituent materials, there is also a problem with the low boiling point of trace amounts of moisture incorporated into the package. The present inventor has also discovered that the so-called volumetric impact accompanying vaporization, which is caused by the vaporization of a substance and the thermal expansion of the vapor of the substance, is a major cause of the occurrence of the package crack.

The low-boiling point substances such as water present in the package may still exist to some extent even in the package after molding before aging, and even after aging, the external leads cannot be plated. If the product is left in the air for a long time, the water in the air may gradually seep into the inside of the package. It's also something that makes you feel tired. This is because resin is not completely airtight.

From the above facts, the problem of package cracks occurring in the mounting process can be seen in thin packages, small packages, and even semiconductors made of small and thin packages, where moisture easily penetrates and the resin strength is low, even among resin-sealed semiconductor devices. It has been found by the inventors to be of particular importance in devices.

[Purpose of the invention]

An object of the present invention is to provide an effective technique for mounting a resin-sealed semiconductor device, which can be applied to improve the reliability of electronic equipment in which the semiconductor device is mounted.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

That is, in a mounting method for a resin-sealed semiconductor device in which external leads of a resin-sealed semiconductor device are connected to a mounting board via a brazing material, before placing the resin-sealed semiconductor device on the mounting board, a pre-drying step for the resin-sealed semiconductor device in which the resin-sealed semiconductor device is heat-treated in an atmosphere at a temperature lower than the melting temperature of the brazing material in order to dry the entire resin-sealed semiconductor device; A pre-dried semiconductor device is placed on the mounting board via the brazing material, and the pre-dried semiconductor device, the mounting board, and the brazing material on the mounting board are heated to a temperature higher than the melting temperature of the brazing material as a whole. The soldering material is melted by exposing it to an atmosphere at a temperature of Even when the package is heated to a high temperature in the process, it is possible to prevent the occurrence of package cracks caused by vaporization of low boiling point substances, thereby achieving the above object.

In addition, when electromagnetic wave irradiation is used as a heating means in the brazing metal melting process and resin-sealed semiconductor devices are brazed and mounted, an electromagnetic wave reflecting plate is attached to the package surface in the direction receiving the electromagnetic wave irradiation. Since it is possible to suppress the temperature rise of the package part even in the case of heat transfer, it is possible to suppress the occurrence of package cracks due to thermal shock.
This achieves the above objective.

〔Example〕

Embodiment 1 of the present invention relates to a method for mounting a resin-sealed semiconductor device.

In the mounting method of Example 1, when a completed resin-sealed semiconductor device is mounted on a board using solder, which is one of the brazing materials, the semiconductor device is heated to a temperature lower than the solder melting temperature before the solder melting process. temperature, for example 100
This method is characterized in that the resin part of the package is pre-dried by heat treatment at ~150 DEG C. for a sufficient time to dry the resin-type semiconductor device, and in some cases under reduced pressure.

Further, extremely effective specific conditions include a temperature of 125° C.±5° C., a pressure of 1 to 5 mmHg, and a time of 5 to 10 hours. After pre-drying the semiconductor device under these conditions,
When mounted on a board by heating it to 250°C and melting the solder, package cracks can be greatly reduced.

As a heating means suitable for such a mounting method, any means that exposes the entire semiconductor device to a high temperature higher than the solder melting temperature, such as hot air heating or infrared heating, can be employed. Therefore, it is an effective method that can be applied to any type of resin-sealed semiconductor device.

Note that when the semiconductor device goes through the pre-drying process, low-boiling substances such as moisture trapped inside the package resin can be removed under mild conditions, so that it can be heated to a higher temperature in the subsequent solder melting process. It is possible to avoid the effects of moisture and other vapors even when exposed to water.

Furthermore, according to this implementation method, the range
Since multiple or large numbers of semiconductor devices such as ICs can be pre-dryed at once, it is possible to achieve the desired purpose with relatively simple equipment that occupies a small volume for pre-drying. Depending on the situation, a reduced pressure can be applied to easily achieve more complete pre-drying.

〔effect〕

(1) In a method of mounting a resin-sealed semiconductor device on a board by heating the entire device and melting the brazing material, the moisture present in the package is removed by pre-drying the package before the brazing material melting process. Since low boiling point substances such as the like can be removed in advance, it is possible to effectively prevent the occurrence of package cracks even when the brazing filler metal is subsequently heated to a high temperature to melt it.

(2) According to (1) above, the reliability of the semiconductor device can be improved.

(3) By performing preliminary drying at 100-150℃,
Low boiling point substances can be evaporated gently and efficiently.

(4) By performing preliminary drying under reduced pressure, packages can be dried more efficiently than when simply heating.

(5) Pre-drying is particularly effective for semiconductor devices made of thin packages, as moisture and the like can easily penetrate into the inside of the package.

(6) By using solder as a brazing material, the present mounting method can be applied to provide a highly reliable and inexpensive semiconductor device.

(7) If the semiconductor device is formed in a small package, the buried part of the internal lead is short, so
This semiconductor device is particularly suitable to which this mounting method is applied, since moisture and the like are likely to enter through the interface between the internal leads and the package resin.

(8) From (1) and (7) above, it is possible to provide an extremely reliable electronic device.

(9) As for electronic equipment mounted with a semiconductor device made of a flat package, it is possible to provide an electronic device with extremely high reliability compared to the above (5).

(10) By making the printed circuit board black like the package body, the infrared absorption rate can be made to be on the same level as the package, increasing thermal efficiency during soldering.

Although the invention made by the present inventor has been specifically explained based on Examples above, the present invention is not limited to the Examples described above, and it is understood that various changes can be made without departing from the gist of the invention. Needless to say.

For example, although specific package forms were not explained in the embodiments, if the entire semiconductor device is heated and soldered, it may be socket-mounted or surface-mounted. , it can be applied to anything.

Furthermore, it goes without saying that the pre-drying conditions are not limited to those shown in the Examples.

[Application field]

The above explanation has mainly been about the case where the invention made by the present invention is applied to the mounting method of a resin-sealed semiconductor device, which is the background field of application, but the invention is not limited thereto.
For example, the present invention relates to a technique that can be applied to any process in which high-temperature heat treatment is performed after package molding, such as aging.

Claims (1)

[Claims] 1. A method for mounting a resin-sealed semiconductor device in which external leads of the resin-sealed semiconductor device are connected to a mounting board via a brazing material, wherein the resin-sealed semiconductor device is mounted on the mounting board. a pre-drying step for the semiconductor device, in which the resin-sealed semiconductor device is heat-treated in an atmosphere at a temperature lower than the melting temperature of the brazing material in order to dry the entire resin-sealed semiconductor device before placement; Thereafter, the pre-dried semiconductor device is placed on the mounting board via the brazing material, and the pre-dried semiconductor device, the mounting board, and the brazing material on the mounting board are entirely covered with the wax. A brazing material melting step of melting the brazing material by exposing it to an atmosphere at a temperature higher than the melting temperature of the material and connecting the external leads of the pre-dried semiconductor device to the mounting board. A method for mounting semiconductor devices. 2. The method of mounting a semiconductor device according to claim 1, wherein solder is used as the brazing material and the preliminary drying step is performed at a temperature range of 100 to 150°C. 3. The semiconductor device mounting method according to claim 1 or 2, wherein the preliminary drying step is performed under reduced pressure. 4 Claim 1, characterized in that the semiconductor device is a semiconductor device consisting of a thin package.
A method for mounting a semiconductor device as described in . 5. The semiconductor device mounting method according to claim 1, wherein the brazing material melting step employs an infrared irradiation heating method. 6. The method for mounting a semiconductor device according to any one of claims 1 to 5, wherein the brazing material is solder.