JP3441194B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device used for an information processing device such as a computer. 2. Description of the Related Art Conventionally, a semiconductor device used for an information processing apparatus such as a computer includes a semiconductor element, a die pad on which the semiconductor element is mounted, and a plurality of semiconductor elements surrounding the die pad and extending at predetermined intervals from the vicinity of the die pad. And the semiconductor element, the die pad, and a mold resin covering a part of the external lead terminal. The die pad and a large number of external lead terminals are integrally connected via a frame-shaped connecting band. A lead frame is prepared and a semiconductor element is mounted and fixed on the upper surface of the die pad of the lead frame. Next, each electrode of the semiconductor element is electrically connected to an external lead terminal via a bonding wire, and the semiconductor element and the die pad are connected. And manufactured by coating a part of the external lead terminals with mold resin. I have. The lead frame is made of a metal mainly composed of copper, a metal mainly composed of iron, or the like. And the like. However, a lead frame formed by a conventional punching process or etching process has a width of external lead terminals and a distance between adjacent external lead terminals of 0.3 mm.
mm, it is difficult to make it extremely narrow, so if a semiconductor device with a large number of electrodes has been mounted due to recent high integration, a large number of external lead terminals will be required in close proximity to the semiconductor device. It becomes impossible to arrange. Accordingly, the length of the bonding wire for electrically connecting each electrode of the semiconductor element to the external lead terminal becomes long. As a result, when the semiconductor element, the die pad, and a part of the external lead terminal are covered with the mold resin, the bonding wire becomes long. When an external force is applied to the bonding wire, the bonding wire is easily deformed by a slight external force, and adjacent bonding wires come into contact with each other to cause an electric short circuit. Therefore, in order to solve the above-mentioned drawbacks, it is made of an electrically insulating material such as an aluminum oxide sintered body, and has a mounting portion on which the semiconductor element is mounted on the upper surface, and a high density fan-out from the periphery to the outer peripheral portion of the mounting portion. An insulating base having a large number of metallized wiring layers, and a large number of external lead terminals whose inner ends are arranged at substantially the same intervals as the intervals of the metallized wiring layers at the outer peripheral portion of the insulating base are formed in a frame shape at the outer ends. A lead frame integrally connected by a connecting band is prepared, and the inner ends of the external lead terminals are joined to the metallized wiring layer of the insulating base via a brazing material such as silver brazing, solder, or gold-tin brazing. Thereafter, a semiconductor element is mounted and fixed on the mounting portion of the insulating base, and each electrode of the semiconductor element is electrically connected to a metallized wiring layer via a bonding wire. It said insulating substrate, a semiconductor device has been proposed in which a part of the semiconductor element and the external lead terminals so as to cover a mold resin. In such a semiconductor device, after the insulating base, the semiconductor element, and a part of the external lead terminals are covered with a mold resin, the external lead terminals are cut and separated from the frame-shaped connecting band, and each external lead terminal is electrically connected. By making them independent and connecting each external lead terminal to an external electric circuit, the internal semiconductor element is electrically connected to the external electric circuit. However, when the metallized wiring layer of the insulating base and the external lead terminals are joined via, for example, a silver braze, the semiconductor device has an aluminum oxide material which forms the insulating base. The coefficient of thermal expansion of the sintered body and the coefficient of thermal expansion of the metal containing copper as a main component constituting the lead frame are significantly different from each other. Since the melting point is as high as about 800 ° C., when the metallized wiring layer of the insulating base and the external lead terminal are joined via a silver brazing material, the difference in the amount of thermal expansion between the two becomes large. The position of the external lead terminal is displaced, making it difficult to join them accurately. Also, there is a large heat between the lead frame and the metallized wiring layer. The stress causes the external lead terminal to be broken or peeled off from the metallized wiring layer due to the stress, causing a drawback that the internal semiconductor element cannot be accurately and reliably electrically connected to the outside. Further, when the metallized wiring layer of the insulating base and the external lead terminals are joined via solder, the melting point of the solder is as low as 183 ° C., so that the insulating base, the semiconductor element, and a part of the external lead terminals are removed. When coating with mold resin,
Heat for thermosetting the mold resin (usually about 200 ° C)
Is applied, the solder melts due to the heat, and the bonding between the metallized wiring layer and the external lead terminals is disengaged or displaced, so that the internal semiconductor element is also accurately and reliably electrically connected to the external electric circuit. Induced the disadvantage of not being able to. Further, when the metallized wiring layer of the insulating base and the external lead terminals are joined via a gold-tin solder,
Gold-tin brazing material has a hard and brittle property, so when bonding and fixing the semiconductor element to the insulating base, or when electrically connecting the electrode of the semiconductor element and the metallized wiring layer via a bonding wire, Alternatively, when an unnecessary external force is applied to the external lead terminal when, for example, covering a part of the insulating base, the semiconductor element, and the external lead terminal with the mold resin, the external force causes a crack in the gold-tin brazing material, and the external lead The terminal was peeled off from the metallized wiring layer together with the brazing material, causing a disadvantage that the internal semiconductor element could not be accurately and reliably electrically connected to an external electric circuit. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and has as its object to electrically and accurately connect an internal semiconductor element to an external electric circuit. It is an object of the present invention to provide a possible semiconductor device. According to the present invention, there is provided a mounting portion on which a semiconductor element is mounted at a central portion of an upper surface, and a metallized wiring derived from a periphery of the mounting portion to an outer peripheral portion. an insulating substrate having a layer, the being mounted on the mounting portion of the insulating substrate, a semiconductor element electrode is connected to the metallized wiring layer, and the external lead terminal which is engaged against the metallized wiring layer, the insulating substrate, A semiconductor device comprising a semiconductor element and a mold resin covering a part of an external lead terminal, wherein the metallized wiring layer and the external lead terminal are as follows (1):
It is characterized by being joined by the steps (3) to (3). (1) A step of depositing a plating metal layer made of gold on the surface of the metallized wiring layer of the insulating base. (2) A plating metal layer made of silver or palladium and a plating metal layer made of tin are sequentially formed on the surface of the external lead terminals. And (3) contacting the metallized wiring layer of the insulating base with the external lead terminals and attaching the metallized wiring layers to the metallized wiring layer and a part of the plated metal layer made of gold and the external lead terminals. A portion of the plated metal layer made of tin is heated to a temperature equal to or higher than a temperature at which a gold-tin alloy is formed to form a gold-tin alloy between the metallized wiring layer and the external lead terminals. A part of a plating metal layer made of silver or palladium adhered to an external lead terminal is diffused and melted in a gold-tin alloy to form a gold-tin-silver alloy or a gold-tin-palladium alloy. And bonding the metallized wiring layer and the external lead terminals via the gold-tin-silver alloy or the gold-tin-palladium alloy. According to the manufacturing method of the present invention, the plating made of gold is performed. The metallized wiring layer on which the metal layer is adhered is brought into contact with an external lead terminal on which a plated metal layer made of silver or palladium and a plated metal layer made of tin are sequentially adhered, and these are adhered to the metallized wiring layer. The metallized wiring layer is heated to a temperature equal to or higher than a temperature at which a gold-tin alloy is formed by a part of the plated metal layer made of gold and a part of the plated metal layer made of tin applied to the external lead terminals. A gold-tin alloy is formed between the metal and the external lead terminal, and a plated metal layer made of silver or palladium adhered to the external lead terminal is formed in the gold-tin alloy. The portion is diffused and melted to form a gold-tin-silver alloy or a gold-tin-palladium alloy, and the metallized wiring layer and the external lead terminals are joined via the gold-tin-silver alloy or the gold-tin-palladium alloy. Therefore, the metallized wiring layer and the external lead terminal can be joined at a low temperature of about 240 ° C. where the gold-tin alloy is formed. As a result, when the metallized wiring layer and the external lead terminal are joined together, The difference in the amount of thermal expansion is extremely small, so that the two can be joined accurately and firmly. The brazing material made of the gold-tin-silver alloy or the gold-tin-palladium alloy once solidified is about
If it is not heated to 250 ° C. or higher, it will not melt, and will not melt even when heat is applied to cure the mold resin. The present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an embodiment of a semiconductor device according to the method of manufacturing a semiconductor device according to the present invention.
Is an external lead terminal, and 3 is a semiconductor element. The insulating substrate 1 has a mounting portion 1a for mounting a semiconductor element at the center of the upper surface thereof.
The semiconductor element 3 is bonded and fixed to a through an adhesive such as resin, glass, brazing material or the like. The insulating substrate 1 is made of an aluminum oxide sintered body, an aluminum nitride sintered body, a mullite sintered body,
It is made of an electrically insulating material such as a silicon carbide sintered body or a glass ceramic sintered body. For example, in the case of an aluminum oxide sintered body, it is suitable for a raw material powder such as aluminum oxide, silicon oxide, calcium oxide, and magnesium oxide. A ceramic green sheet is obtained by adding and mixing a binder and a solvent to form a slurry and forming the sheet into a sheet by employing a conventionally known doctor blade method. Thereafter, the ceramic green sheet is subjected to a punching method or the like. It is manufactured by punching into an appropriate shape, laminating a plurality of sheets as necessary, and finally firing the ceramic green sheet at a temperature of about 1600 ° C. in a reducing atmosphere. The insulating substrate 1 has a large number of metallized wiring layers 4 spread in a fan shape from the periphery of the upper surface mounting portion 1a to the outer peripheral portion thereof. Each of the electrodes of the semiconductor element 3 is electrically connected via a bonding wire 5, and external lead terminals 2 connected to an external electric circuit are provided on the outer peripheral portion of the insulating base 1, with plated metal layers 8, 9, and 10. Are joined via a brazing material 6 formed by heating the brazing material. The metallized wiring layer 4 is made of a high melting point metal powder such as tungsten, molybdenum, manganese or the like. A metal paste obtained by adding a suitable binder and solvent to the high melting point powder such as tungsten is mixed with the insulating base. By printing and applying a predetermined pattern on the ceramic green sheet to be used as the ceramic green sheet 1 by using a conventionally known screen printing method or the like, a fan-like shape is formed from the upper surface around the mounting portion 1a of the insulating substrate 1 to the upper surface of the outer peripheral portion of the insulating substrate 1. It is formed so as to spread out. Since the metallized wiring layer 4 is printed and applied by a screen printing method, its line width and the distance between adjacent metallized wiring layers 4 can be made as narrow as about 0.05 mm or less. A large number of metallized wiring layers 4 are arranged in the vicinity of the semiconductor
Bonding wire 5 with metallized wiring layer 4
, And electrical short-circuiting between adjacent bonding wires 5 can be effectively prevented. The external lead terminal 2 joined to the metallized wiring layer 4 via the brazing material 6 serves to connect the semiconductor element 3 housed therein to an external electric circuit, and connects the external lead terminal 2 to the external. By connecting to the wiring conductor of the electric circuit board, the semiconductor element 3 is electrically connected to the external electric circuit via the metallized wiring layer 4 and the external lead terminal 2. The external lead terminal 2 is made of a metal such as a copper-based alloy containing copper as a main component or an iron-based alloy containing iron as a main component. For example, an ingot of a copper-based alloy is formed by a conventionally known rolling method. Then, a plate having a predetermined thickness is formed, and the plate is etched and punched to form a predetermined shape. When the external lead terminal 2 is formed of a metal containing copper as a main component, the metal containing copper as a main component is as follows.
It has excellent thermal conductivity and satisfactorily dissipates the heat generated during operation of the semiconductor element 3 to the outside atmosphere via the lead terminals 2 so that the semiconductor element 3 can always be operated stably at a low temperature. Therefore, it is preferable that the external lead terminal 3 is formed of a metal containing copper as a main component. The brazing material 6 joining the external lead terminal 2 to the metallized wiring layer 4 is made of a gold-tin-silver alloy or a gold-tin-palladium alloy, and the external lead terminal 4 is firmly attached to the metallized wiring layer. It acts to join to. Since the gold-tin-silver alloy or the gold-tin-palladium alloy constituting the brazing material 6 has high toughness, even if an unnecessary external force is applied to the external lead terminal 2, the external lead terminal 2 is soldered. It is not easily separated from the metallized wiring layer 4 together with the material 6 and has a melting point of about 25
Since the temperature is 0 ° C. or higher, the brazing material 6 is not melted by heat generated when the mold resin described below is thermally cured, and the external lead terminals 2 can be securely and firmly joined to the metallized wiring layer 4. When the brazing material 6 is made of a gold-tin-silver alloy, the gold contained in the brazing material 6 made of the gold-tin-silver alloy determines the wettability of the brazing material 6 to the metallized wiring layer 4. When the content is less than 1.0% by weight, the wettability of the brazing material 6 becomes poor, and 30.0% by weight.
Is exceeded, a large amount of brittle gold-tin intermetallic compound is formed in the brazing material 6, and the strength of the brazing material 6 becomes weak. Therefore, the amount of gold contained in the brazing material 6 made of the gold-tin-silver alloy is preferably in the range of 1.0 to 30.0% by weight. Further, the brazing material 6 made of the gold-tin-silver alloy
The tin contained in the brazing material has an effect of reducing the brazing temperature of the brazing material 6 to about 240 ° C. If the content is less than 55.0% by weight, the brazing temperature of the brazing material 6 becomes high, and 98.0% by weight If it exceeds, the wettability of the brazing material 6 to the metallized wiring layer 4 tends to decrease. Accordingly, the content of tin in the brazing material 6 made of the gold-tin-silver alloy is preferably in the range of 55.0 to 98.0% by weight. Further, the brazing material 6 made of the gold-tin-silver alloy
Acts to prevent the formation of a brittle gold-tin intermetallic compound in the brazing material 6, and the content of
If it is less than 1.0% by weight, it is not possible to effectively prevent the formation of a brittle gold-tin intermetallic compound in the brazing material 6, and if it exceeds 15.0% by weight, the brazing temperature of the brazing material 6 is high. Becomes Therefore, the silver contained in the brazing material 6 made of the gold-tin-silver alloy is preferably in the range of 1.0 to 15.0% by weight. When the brazing material 6 is made of a gold-tin-palladium alloy, the gold contained in the brazing material 6 made of the gold-tin-palladium alloy reduces the wettability of the brazing material 6 with respect to the metallized wiring layer 4. When the content is less than 1.0% by weight, the wettability of the brazing material 6 becomes poor, and when the content exceeds 30.0% by weight, the fragile gold-
A large amount of the tin intermetallic compound is formed, and the strength of the brazing material 6 becomes weak. Therefore, the amount of gold contained in the brazing material 6 made of the gold-tin-palladium alloy is preferably in the range of 1.0 to 30.0% by weight. The tin contained in the brazing material 6 made of the gold-tin-palladium alloy has a brazing temperature of the brazing material 6 of about
Works at about 240 ° C and contains 55.0% by weight
If it is less than 9%, the brazing temperature of the brazing material 6 is high, and if it exceeds 98.0% by weight, the metallized wiring layer 4
There is a tendency for the wettability to water to decrease. Accordingly, the content of tin contained in the brazing material 6 made of the gold-tin-palladium alloy is preferably in the range of 55.0 to 98.0% by weight. Further, the palladium contained in the brazing material 6 made of the gold-tin-palladium alloy serves to prevent the formation of a brittle gold-tin intermetallic compound in the brazing material 6. If the amount is less than 1.0% by weight, it is not possible to effectively prevent the formation of brittle gold-tin intermetallic compounds in the brazing material 6, and if it exceeds 15.0% by weight, the brazing temperature of the brazing material 6 is reduced. It will be expensive. Therefore, the gold-
The palladium contained in the brazing material 6 made of a tin-palladium alloy is preferably in the range of 1.0 to 15.0% by weight. On the other hand, the insulating base 1, the semiconductor element 3
A part of the external lead terminal 2 is covered with a mold resin 7 such as an epoxy resin, whereby the semiconductor element 3 is hermetically sealed inside. In order to cover a part of the insulating base, the semiconductor element and the external lead terminals with the mold resin 7, the insulating base 1 to which the semiconductor element 3 and the external lead terminals 2 are joined is disposed in a predetermined mold. At the same time, a mold resin such as an epoxy resin is injected into the mold, and thereafter, the injected resin is thermally cured by applying a temperature of about 200 ° C. and a pressure of 100 kgf / mm ² . Next, in the above-described semiconductor device, the external lead terminals 2 are connected to the metallized wiring layer 4 of the insulating base 1 by gold-tin-tin.
A method of joining via a brazing material 6 made of a silver alloy or a gold-tin-palladium alloy will be described with reference to FIGS. First, as shown in FIG. 2A, an insulating base 1 having a metallized wiring layer 4 and an external lead terminal 2 are prepared. Next, as shown in FIG. 2B, a plating metal layer 8 made of gold is applied to the outer surface of the metallized wiring layer 4 of the insulating substrate 1 to a thickness of 0.05 to 2.0 μm and the external lead terminals 2 are formed. A plating metal layer 9 made of silver or palladium and a plating metal layer 10 made of tin are successively deposited on the surface of the substrate at a thickness of 0.05 to 2.0 μm and at a thickness of 3.0 to 100.0 μm. Next, as shown in FIG. 2C, the inner ends of the external lead terminals 2 are placed on the metallized wiring layer 4 of the insulating base 1 and these are heated to a temperature of about 240.degree. A gold-tin alloy is formed by a part of the plating metal layer 8 made of gold adhered to the layer 4 and a part of the plating metal layer 10 made of tin adhered to the external lead terminals 2. A gold-tin-silver alloy is formed between the metallized wiring layer 4 and the external lead terminal 2 by diffusing and melting a part of the plating metal layer 9 made of silver or palladium deposited on the external lead terminal 2 in a tin alloy. Alternatively, by forming a gold-tin-palladium alloy and finally cooling and solidifying the gold-tin-silver alloy or the gold-tin-palladium alloy, the metallized wiring layer 4 of the insulating substrate 1 as shown in FIG. Outside lee The terminal 2 is joined via a brazing material 6 made of a gold-tin-silver alloy or a gold-tin-palladium alloy. In this case, since the metallized wiring layer 4 of the insulating base 1 and the external lead terminals 2 can be joined at a low temperature of about 240 ° C., when the metallized wiring layer 4 and the external lead terminals 2 are joined, The difference in the amount of thermal expansion between the external lead terminal 2 and the external lead terminal 2 is extremely small, so that the position between the metallized wiring layer 4 and the external lead terminal 2 does not shift. No large thermal stress is generated. Further, the brazing material 6 made of the gold-tin-silver alloy or the gold-tin-palladium alloy once cooled and solidified does not re-melt unless it is heated to a temperature of about 250 ° C. or more.
The semiconductor element 3 and a part of the external lead terminal 2 are not melted by the heat when the resin is covered with the mold resin 7. Therefore, according to the manufacturing method of the present invention, the external lead terminal 2 can be accurately and firmly joined to the metallized wiring layer 4 of the insulating base 1. It should be noted that the present invention is not limited to the above-described embodiment, and various changes can be made without departing from the scope of the present invention. Although a plating metal layer made of silver or palladium and a plating metal layer made of tin were sequentially applied on the entire surface, the plating metal layer made of tin may be applied only to the tip of the external lead terminal to be brazed. good. According to the manufacturing method of the present invention, a plating metal layer made of gold is applied, and a metallized wiring layer, a plating metal layer made of silver or palladium, and a plating metal layer made of tin are sequentially applied. An external lead terminal is brought into contact with the metallized wiring layer, and a part of the plated metal layer made of gold and a part of the plated metal layer made of tin adhered to the external lead terminal are used to form gold. Heating to a temperature equal to or higher than the temperature at which the tin alloy is formed, forming a gold-tin alloy between the metallized wiring layer and the external lead terminals, and silver deposited on the external lead terminals in the gold-tin alloy Alternatively, a part of a plating metal layer made of palladium is diffused and melted to form a gold-tin-silver alloy or a gold-tin-palladium alloy, and the gold-tin-silver alloy or gold-tin-palladium Since the metallized wiring layer and the external lead terminal are bonded via the alloy, the metallized wiring layer and the external lead terminal can be bonded at a low temperature of about 240 ° C. at which the gold-tin alloy is formed. Therefore, when joining the metallized wiring layer and the external lead terminal, the difference in the amount of thermal expansion between the two can be made extremely small. As a result, the position of the metallized wiring layer and the external lead terminal do not shift,
Also, no large thermal stress occurs between the two. Furthermore, the gold-tin-silver alloy or the gold-tin-palladium alloy once solidified does not melt again unless heated to about 250 ° C. or more, and does not melt due to heat at the time of thermosetting the mold resin. Therefore, according to the manufacturing method of the present invention, the external lead terminals can be accurately and firmly bonded to the metallized wiring layer of the insulating base, and as a result, the internal semiconductor elements can be accurately and reliably connected to the external electric circuit. Can be connected.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing one embodiment of a semiconductor device of the present invention. 2 (a) to 2 (d) are cross-sectional views for explaining steps in a method for manufacturing the semiconductor device shown in FIG. 1; [Description of Signs] 1 ... Insulating base 1a ... Mounting section 2 ... External lead terminal 3 ... Semiconductor element 4 ... Metalized wiring layer 5 ... Bonding wire 6 ... ... brazing material 7 ... molding resin 8 ... plating metal layer 9 made of gold ... plating metal layer 10 made of silver or palladium ... plating metal layer made of tin

Claims (1)

(57) Claims: 1. An insulating base having a mounting portion on which a semiconductor element is mounted at a central portion of an upper surface, and a metallized wiring layer extending from a periphery of the mounting portion to an outer peripheral portion; coated are mounted on the mounting portion, a semiconductor element electrode is connected to the metallized wiring layer, and the external lead terminal which is engaged against the metallized wiring layer, the insulating substrate, a part of the semiconductor element and the external lead terminal A method of manufacturing a semiconductor device, comprising: bonding a metallized wiring layer to an external lead terminal by the following steps (1) to (3). (1) A step of depositing a plating metal layer made of gold on the surface of the metallized wiring layer of the insulating substrate. (2) A plating metal layer made of silver or palladium and a plating metal layer made of tin are sequentially formed on the surface of the external lead terminals. And (3) contacting the metallized wiring layer of the insulating base with the external lead terminals and attaching the metallized wiring layers to the metallized wiring layer and a part of the plated metal layer made of gold and the external lead terminals. A portion of the plated metal layer made of tin is heated to a temperature equal to or higher than a temperature at which a gold-tin alloy is formed to form a gold-tin alloy between the metallized wiring layer and the external lead terminals. A part of a plating metal layer made of silver or palladium adhered to an external lead terminal is diffused and melted in a gold-tin alloy to form a gold-tin-silver alloy or a gold-tin-palladium alloy. And, gold - tin - silver alloy or gold - tin - step through the palladium alloy to bond the metallized wiring layer and the external lead terminal