JP4978294B2 - Semiconductor device and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure a bonding force between an inner lead and a mold resin even when Pd is deposited on the surface of the inner lead in a resin sealed semiconductor device using a Pd-PPF (Pre Plated Flame). <P>SOLUTION: Wire bonding is carried out between a semiconductor element 30 and a lead frame 40 as a laminate having a Ni plated layer 40b, a Pd plated layer 40c, and an Au plated layer 40d sequentially laminated on a surface of a Cu-made base material 40a; an inner lead 41 of the lead frame 40 is heat treated at a temperature higher than the temperature of the inner lead 41 applied upon the wire bonding; the amount of Cu present in the outermost surface of the inner lead 41 when the surface of the inner lead is analyzed by an Auger electron spectroscopy is set not to be smaller than 40% of the amount of Pd present in the outermost surface thereof; and then the inner lead is sealed with a mold resin 60. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a resin-encapsulated semiconductor device using a Pd-PPF (Pre Plated Frame) obtained by laminating Ni, Pd, and Au plating on a base material made of Cu, and a method for manufacturing the same.

  Conventionally, this type of semiconductor device is obtained by electrically connecting Pd-PPF as a lead frame and a semiconductor element with a bonding wire and then sealing the lead frame, the bonding wire and the semiconductor element with a mold resin. It is.

  Since Pd-PPF is used as the lead frame, the inner lead, which is a portion sealed with the mold resin, of the lead frame is formed on the surface of the base material made of Cu by Ni plating from the base material side. The Ni layer, the Pd plating layer made of Pd plating, and the Au plating layer made of Au are sequentially laminated.

  Here, Pd-PPF is covered with Au as a metal component on the outermost surface of the plating that comes into contact with the mold resin at the time of manufacturing the frame. However, Pd-PPF is exposed to a thermal history such as die mount or wire bonding. There is a phenomenon in which the adhesion strength with the mold resin is reduced due to the relief of the resin.

  In order to suppress the surface diffusion of the base metal, in Pd-PPF, it is necessary to form a thick Au, which is an expensive metal. However, normally, the Au plating layer on the surface cannot be formed so thick in consideration of the cost, so that Pd diffuses to the outermost surface of the inner lead through the thermal history described above.

  As a result, for example, Pd diffuses to the outermost surface of the inner lead due to the heating temperature at the time of wire bonding, and the adhesion between Pd-PPF and the mold resin tends to decrease. That is, in the state where the adhesive force between the Pd-PPF and the mold resin that has undergone the current wire bonding conditions is reduced, molding with the mold resin is performed, and the adhesive force varies.

In order to improve the adhesion between the Pd-PPF and the mold resin, conventionally, as described in Patent Document 1, the Pd that has been exposed on the surface of the inner lead is oxidized to improve the adhesion with the mold resin. Proposed lead frame manufacturing methods have been proposed.
JP-A-10-16397

  However, according to the method described in Patent Document 1, since a Pd oxide film is formed on the inner lead of the lead frame in advance, an electrode such as Au or Al is formed on the Pd oxide film during wire bonding. It becomes. Therefore, this Pd oxide film becomes an obstacle to the electrode formation, and there is a problem that the bonding strength is reduced compared to the initial stage.

  The present invention has been made in view of the above problems, and in a resin-encapsulated semiconductor device using Pd-PPF, even when Pd is deposited on the surface of the inner lead, the inner lead and the molding resin are adhered to each other. The purpose is to ensure power.

  In order to achieve the above object, the present inventor investigated the adhesion between each metal such as Au, Pd, Cu, and Ni constituting Pd-PPF and a mold resin made of an epoxy resin. As a result, it was found that the adhesion strength with Pd was reduced by about 30% while Au and Cu showed the same strength (see FIG. 5 described later).

  In addition, when Pd-PPF is heat-treated at a temperature exceeding the heating temperature at the time of wire bonding, for example, 275 ° C., the base material Cu is exposed to the outermost surface through the Ni plating layer, the Pd plating layer, and the Au plating layer. I found the phenomenon.

  Further, the amounts of Cu and Pd present on the outermost surface of the inner lead were obtained by surface analysis by Auger electron spectroscopy, and the relationship between the amount of Cu and the above-mentioned adhesion was investigated. As a result, it has been found that if the amount of Cu is 40% or more of the amount of Pd on the outermost surface of the inner lead, an adhesive force capable of preventing the mold resin from peeling can be realized (see FIGS. 4, see FIG. 6)).

The present invention has been found experimentally as a result of the above-described studies. When the outermost surface of the inner lead (41) is subjected to surface analysis by Auger electron spectroscopy, Cu present on the outermost surface is analyzed. The amount is 40% or more of the amount of Pd present on the outermost surface, and the thickness of each of the Ni plating layer (40b), the Pd plating layer (40c), and the Au plating layer (40d) is 0. The first feature is that it is 3 μm or more and less than 2.3 μm, 0.005 μm or more and less than 0.05 μm, or 0.003 μm or more and less than 0.02 μm .

  As described above, the amount of Cu existing on the outermost surface of the inner lead (41) is 40% or more of the amount of Pd existing on the outermost surface as compared with the atomic ratio when surface analysis is performed by Auger electron spectroscopy. Then, even if Pd is deposited on the inner lead (41), the adhesion between the inner lead (41) and the mold resin (60) can be secured.

In the present invention, the Ni plating layer (40b), the Pd plating layer (40c), and the Au plating layer (40d), which are plating layers constituting the inner lead (41), each have a film thickness of 0.3 μm to 2 μm. .3μm, 0.005μm~0.05μm, are assumed to be 0.003μm~0.02μm. The present invention has been confirmed to be effective for such a general Pd-PPF. The mold resin (60) can be made of an epoxy resin.

  Further, as described above, by heat-treating Pd-PPF at a temperature exceeding the heating temperature at the time of wire bonding, Cu is deposited on the outermost surface of the inner lead (41), and the amount of Cu on the outermost surface is reduced. It can be 40% or more of the amount of Pd.

  However, if a Cu oxide film is present on the outermost surface of Pd—PPF, wire bonding performance is degraded, and in the worst case, bonding may not be possible. In view of this, the present inventor decided to carry out the above heat treatment after wire bonding. In consideration of this point, the present inventor has created the following semiconductor device manufacturing method.

  That is, according to the present invention, after wire bonding is performed between the lead frame (40) and the semiconductor element (30), the inner lead (41) of the lead frame (40) is used as the inner lead (41) during wire bonding. The amount of Cu present on the outermost surface when the outermost surface of the inner lead (41) is subjected to surface analysis by Auger electron spectroscopy is present on the outermost surface. The second feature is that the amount is 40% or more of the amount of Pd, and thereafter sealing with the mold resin (60) is performed.

  Accordingly, the semiconductor device having the first feature can be manufactured without deteriorating the wire bonding property. Here, the temperature of the step of heat-treating the inner lead (41) is preferably 275 ° C. or higher, more preferably 295 ° C. or higher.

  In addition, in the Pd-PPF, when the semiconductor element (30) is mounted on the island (10) other than the inner lead (41), the semiconductor element (30) and the inner lead (41) are connected by the bonding wire (50). The above heat treatment is performed in a connected state. In this case, the semiconductor element (30) mounted on the island (10) is also heated at the same time, and the bonding strength on the semiconductor element (30) side can be deteriorated.

  Therefore, in this case, the island (10) on which the semiconductor element (30) is mounted is substantially unheated to prevent the temperature rise of the semiconductor element (30) and the bonding portion in the semiconductor element (30). desirable. Considering this point, it is preferable that the step of heat-treating the inner lead (41) heats the inner lead (41) in a state where the island (10) is set to a temperature lower than the temperature of the heat-treatment.

  In addition, the code | symbol in the bracket | parenthesis of each means described in the claim and this column is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, parts that are the same or equivalent to each other are given the same reference numerals in the drawings for the sake of simplicity.

  FIG. 1A is a view showing a schematic cross-sectional configuration of a resin-encapsulated semiconductor device 100 according to an embodiment of the present invention, and FIG. 1B is a view inside the mold resin 60 in FIG. 2 is an enlarged schematic cross-sectional view of a lead frame 40, that is, an inner lead 41. FIG.

  As shown in FIG. 1, in a semiconductor device 100, a semiconductor chip 30 as a semiconductor element is mounted on an island 10 via a die mount material 20 such as a conductive adhesive or solder. The semiconductor chip 30 and the lead frame 40 are connected and electrically connected via the bonding wire 50.

  Here, the semiconductor chip 30 is formed by forming a transistor element or the like on a silicon semiconductor substrate using a well-known semiconductor manufacturing technique. The bonding wire 50 is a wire made of gold (Au) or aluminum (Al) formed by wire bonding.

  The semiconductor chip 30, the bonding wire 50, and the inner lead 41 in the lead frame 40 are molded and sealed so as to be encased in a molding resin 60. That is, the inner lead 41 is a portion of the lead frame 10 that is covered with the mold resin 60.

  The mold resin 60 is made of a general epoxy resin used for ordinary Pd-PPF, and is formed by a transfer molding method using a mold or the like. The mold resin 60 constitutes the main body of the semiconductor device, that is, the package body.

  Here, the mold resin 60 employs, for example, an epoxy resin containing a sulfur component in order to improve the adhesion with the Au plating layer 40d constituting the outermost surface of the inner lead 41. However, other materials may be used as the mold resin 60 as long as the adhesion with the Au plating layer 40d can be maintained.

  Here, the outer leads 42 of the lead frame 40 protrude from the mold resin 60. As shown in FIG. 1, the outer lead 42 has a shape bent at an intermediate portion between the root portion and the tip portion on the mold resin 60 side.

  In the present embodiment, the outer lead 42 has a bent shape that is bent at two locations at the intermediate portion. The semiconductor device 100 is connected to a substrate (not shown) (for example, a printed circuit board) by solder or the like via the outer lead 42.

  Here, the configuration in the vicinity of the surface of the lead frame 40 of the present embodiment is shown in FIG. As shown in FIG. 1B, the lead frame 40 of this embodiment uses a lead frame material made of Cu, for example, as a base material 40a. Here, that the base material 40a is made of Cu is not limited to only copper, but also includes a copper alloy.

  A Ni plating layer 40b made of Ni (nickel) plating, a Pd plating layer 40c made of Pd (palladium) plating, and an Au plating layer 40d made of Au plating are sequentially formed on the surface of the base material 40a. It is. Here, in the lead frame 40, the inner lead 41 and the outer lead 42 have the same configuration.

  For example, in the lead frame 40 of this example, the base material 40a is a plate made of copper, and the plate thickness can be about 0.125 mm to 0.25 mm and the width can be about 0.2 mm to 0.5 mm. Further, the plating layers 40b to 40e are formed by patterning a lead frame material plate into a lead frame shape by etching or stamping and then performing a plating process.

  The thicknesses of the Ni plating layer 40b, the Pd plating layer 40c, and the Au plating layer 40d are the same as those of a general Pd-PPF, and the Ni plating layer 40b has a thickness of 0.3 μm to 2.3 μm, respectively. The layer 40c is 0.005 μm to 0.05 μm, and the Au plating layer 40d is 0.003 μm to 0.02 μm.

  In this example, the plated layer on the surface of the lead frame 40 is roughened. That is, the surface roughness of the Au plating layer 40d as the outermost surface is larger than the surface roughness of the base material 40a.

  Formation of such a rough plating layer in Pd-PPF is known, and can be realized, for example, by roughening the Ni plating layer 40b. In this case, for example, the thickness of the Ni plating layer 40b is about 0.6 μm to 1.4 μm, and the specific surface area value is about 1.05 to 1.25. Here, the specific surface area indicates a surface area value including unevenness per unit area, and a value measured using an atomic force microscope (Nonpics 2000: manufactured by SII Nanotechnology) was used.

  Moreover, each plating layer 40b-40d in the lead frame 40 of this embodiment can be formed by a general plating method, and may be formed by any method of electroplating or electroless plating. Further, the rough Ni plating layer 40b can be formed, for example, by adjusting plating conditions or chemical components during plating film formation.

  In this embodiment, when the outermost surface of the inner lead 41 of such a lead frame 40 is subjected to surface analysis by Auger electron spectroscopy, the amount of Cu present on the outermost surface is Pd present on the outermost surface. 40% or more of the amount.

  That is, in this embodiment, when the surface of the Au plating layer 40d in the inner lead 41 is subjected to surface analysis by Auger electron spectroscopy, and the amount of Cu and the amount of Pd present on the outermost surface are determined by this analysis, the Cu Is 40% or more of the amount of Pd. Details of this will be described later.

  Next, a method for manufacturing the resin-encapsulated semiconductor device 100 of this embodiment will be described. First, after patterning the base material 40a of the lead frame 40 into a lead frame shape by etching or stamping, a plating process is performed to form the above-described plating layers 40b to 40d.

  In the present embodiment, the island 10 is integrally connected to the lead frame 40 and finally divided by a cutting process. The island 10 is formed by the plating process of the lead frame 40. This surface also has the same plating structure as the inner lead 41.

  Next, in order to mount the semiconductor chip 30 on the island 10 of the lead frame 40, the semiconductor chip 30 is mounted after applying the die mount material 20 such as Ag paste on the island 10 (die mounting step). Thereafter, the die mount material 20 is cured in an oven at about 180 ° C.

  Next, wire bonding is performed between the lead frame 40 and the semiconductor chip 30 mounted on the island 10, and the bonding wires 50 are electrically connected to each other (wire bonding process). This wire bonding is performed by a general method, and the temperature of the lead frame 40 is about 230 ° C. to 250 ° C.

  Next, the inner lead 41 of the lead frame 40 is heat-treated at a temperature higher than the temperature (for example, 230 ° C. to 250 ° C.) applied to the inner lead 41 during wire bonding. Specifically, the temperature is 275 ° C. or higher, preferably 295 ° C. or higher. For example, heat treatment is performed at 295 ° C. ± 5 ° C. for 1 hour.

  Thereby, when the outermost surface of the inner lead 41 is subjected to surface analysis by Auger electron spectroscopy, the amount of Cu existing on the outermost surface can be set to 40% or more of the amount of Pd existing on the outermost surface. Become.

  FIG. 2 is a diagram showing a specific heating method in the process of heat-treating the inner lead 41. As shown in FIG. In addition, this process is not limited to the method of this FIG. Here, the first temperature regulator 200 that adjusts the temperature of the inner lead 41 by contacting only the inner lead 41 of the lead frame 40 and the second temperature controller that adjusts the temperature of the island 10 by contacting only the island 10. A temperature regulator 210 is used.

  These temperature regulators 200 and 210 can employ energizing heaters, for example. In this heat treatment step, the inner lead 41 is heated in a state where the semiconductor chip 30 and the inner lead 41 are connected by the bonding wire 50. At this time, the island 10 is set to a temperature lower than the temperature of the heat treatment.

  Specifically, the first temperature regulator 200 is in a heated state, the second temperature regulator 210 is in a non-heated state, the temperature of the first temperature regulator 200 is about 295 ° C., and the second temperature regulator. The inner lead 41 is heat-treated in a state where the temperature of the vessel 210 is, for example, 230 ° C. or lower. As a result, the temperature of the inner lead 41 can be maintained at about 295 ° C., and the temperature of the semiconductor chip 30 on the island 10 is suppressed to about 230 ° C. or less.

  Thereby, deterioration of each part on the island 10, for example, the semiconductor chip 30, due to heat can be prevented. Furthermore, since the heating zone of the main heating process is only the inner lead 41, the portion to which the outer lead 42 is subjected to the soldering process is freed from the foundation due to heating, and good solderability can be ensured.

  Thus, after the heat treatment of the inner lead 41 is performed, the semiconductor chip 30, the bonding wire 50, and the lead frame 40 are sealed with the mold resin 60. Thereafter, the semiconductor device 100 of this embodiment is completed by performing dicing, molding of the outer leads 42, and the like.

  When the heating method shown in FIG. 2 is used, the temperature of the inner lead 41 and the island 10 can be adjusted separately. Therefore, in the state shown in FIG. 2, the die mounting step and the wire bonding are performed. A process can also be performed.

  For example, die mounting is performed in a state where the island 10 is maintained at 180 ° C. by the second temperature regulator 210, or the inner leads 41 and the island 10 are formed by the first and second temperature regulators 200 and 210. Wire bonding may be performed while the semiconductor chip 30 is maintained at about 230 ° C.

  In the present embodiment, as described above, the amount of Cu by Auger electron spectroscopy on the outermost surface of the inner lead 41 is 40% or more of the amount of Pd. Even if deposited, the adhesion between the inner lead 41 and the mold resin 60 is secured. This has been obtained as a result of the experimental study conducted by the present inventor, and specific examples of the study will be described below.

  FIG. 3 shows the relationship between the heating temperature (frame heating temperature, unit: ° C.) and the amounts of Pd and Cu on the outermost surface of the lead frame 40 when the lead frame 40 of this embodiment as Pd-PPF is heated. It is a figure which shows the result of having investigated.

  Here, the amounts of Pd and Cu are abundance ratios obtained by measuring the outermost surface of the lead frame 40 after heat treatment by general Auger electron spectroscopy, and are the outermost surface of the lead frame 40, that is, the Au plating layer. The sum of the abundances of Au, Pd, and Cu existing on the surface of 40d is expressed as 100%. In addition, the measurement by this Auger electron spectroscopy is generally performed, and the amount of atoms detected from the spectrum is obtained.

  As shown in FIG. 3, when Pd—PPF as the lead frame 40 is heat-treated, the underlying Pd and Cu are deposited on the outermost surface. And it turns out that the precipitation amount also increases as this heating temperature is made high.

  Here, when the heating temperature is set to 230 to 250 ° C. corresponding to the wire bonding step in the above manufacturing method, the base Pd is diffused on the surface in addition to Au on the outermost surface of the lead frame 40. This is also confirmed from observation with an electron microscope.

  However, at this temperature, Pd has diffused on the surface, but as shown in FIG. 3, many are covered with Au, and wire bonding such as wire bonding with an oxide layer interposed. There are few factors that degrade strength. Therefore, in the above manufacturing method, the wire bonding property can be kept in a good state.

  Further, as shown in FIG. 3, when the heating temperature is 275 ° C. in which the inner lead 41 is heat-treated in the above manufacturing method, the amount of Cu is 16%, the amount of Pd is 40%, and the amount of Cu Is 2/5 of the amount of Pd, that is, 40%. At 275 ° C. or higher, the amount of Cu further increases and becomes 40% or more of the amount of Pd.

  Here, FIG. 4 is a diagram showing a result of investigating the relationship of the adhesion strength between the inner lead 41 and the mold resin 60 with respect to the heating temperature in FIG. The adhesion strength was measured by the shear strength at room temperature between the lead frame 40 and the mold resin 60 after heating, specifically, the pudding cup strength (unit: MPa).

  As shown in FIG. 4, at the heating temperature of about 250 ° C., as shown in the background art column, the adhesion strength with the mold resin 60 is reduced due to the precipitation of Pd. However, if the heating temperature is 275 ° C. or higher, the adhesion strength is improved again.

  Specifically, the heat treatment of the inner lead 41 in the above manufacturing method may be performed at a temperature of 275 ° C. or higher although it depends on the required strength of adhesion with the mold resin 60. As shown in FIG. 4, at a temperature of 275 ° C., the strength of about 90% can be recovered with respect to the adhesion to the mold resin 60 at the initial stage of lead frame manufacture.

  Further, based on the result of FIG. 4, at a temperature of 295 or higher, the adhesion strength with the mold resin 60 is substantially equal to the strength at the time of manufacturing the lead frame. It is desirable to carry out at a temperature of 295 ° C. or higher. However, it is of course necessary not to exceed the heat resistance temperature of other parts such as the bonding wire 50.

  From the results shown in FIG. 3 and FIG. 4, if the amount of Cu by Auger electron spectroscopy on the outermost surface of the inner lead 41 is 40% or more of the amount of Pd, the adhesion strength is improved as compared with the conventional case. It was found that the strength could be secured.

  FIG. 5 is a diagram showing the results of investigating the adhesive force between each metal such as Au, Pd, Cu, and Ni constituting Ag and Pd-PPF and the mold resin made of epoxy resin. This investigation is based on a sample in which the above-described metal plating is formed on a Cu plate and a mold resin is adhered thereon. This adhesive strength is the same as the shear strength in FIG. is there.

  As shown in FIG. 5, the adhesion strength between the mold resin and the metal plating is approximately the same as that between Au and Cu, whereas the adhesion strength with Pd is reduced to about 70%. I found out that

  From this, in this embodiment, the following mechanism is presumed that sufficient adhesion strength can be realized by setting the amount of Cu to 40% or more of the amount of Pd. That is, the adhesion strength once decreases due to the surface diffusion of Pd by heating, and the underlying Cu diffuses to the surface through the Ni grain boundary due to further high-temperature heating, and Au and Cu that have high adhesion to the mold resin as the abundance ratio. It is thought that there was a tendency that the adhesion strength with the mold resin was improved again.

  In the lead frame 40, when the Ni plating layer 40b is thick, the temperature region where the amount of Cu is 40% or more of the amount of Pd shifts to the high temperature side. However, in reality, when the thickness of the Ni plating layer 40b exceeds 2.3 μm, cracks in the bent portion are generated at the time of lead forming in the subsequent process, and the function as a lead frame is deteriorated.

  Therefore, the thickness of the Ni plating layer 40b is 2.3 μm or less. However, if the thickness is so far, the amount of Cu is substantially 40% of the amount of Pd in the temperature range of 275 ° C. or more. This can be done.

  However, in the case of a lead frame such as a QFN package in which lead bending is not performed, the thickness of the Ni plating layer 40b may be thicker than 2.3 μm. In that case, the heat treatment of the inner lead 41 may be performed in a temperature range in which the material characteristics do not vary significantly.

  When the Ni plating layer 40b is thin, the temperature region where the amount of Cu is 40% or more of the amount of Pd shifts to the low temperature side. However, in reality, when the thickness of the Ni plating layer 40b is 0.3 μm or less, the base Pd diffuses to the outermost surface by heating at 200 to 250 ° C. which is a normal Au wire bonding condition. The wire bond strength will be reduced.

  Therefore, the lower limit value of the thickness of the Ni plating layer 40b is 0.3 μm. If the thickness is 0.3 μm or more, the amount of Cu can be made 40% or more of the amount of Pd in the temperature range of 275 ° C. or more.

  In addition, regarding the time for the heat treatment of the inner lead 41, it has been found by the inventor's examination that in the case of a treatment at 300 ° C. or less, it is difficult to obtain an effect by heating for about 5 minutes. By applying the heating time, a sufficient effect can be exhibited. Furthermore, in the case of a treatment at a temperature exceeding 300 ° C., it has been confirmed that the effect can be obtained even in a heat treatment time of about 5 to 10 minutes because the diffusion rate is increased.

  Further, in the above manufacturing method, the step of sealing with the mold resin 60 made of epoxy resin is performed at a molding temperature of about 175 ± 5 ° C., and then cured to completely cure the mold resin 60. Is normal. In this sealing process, since the temperature is lower than that in the wire bonding process, the surface state of the lead frame 40 does not change.

  Thus, according to the present embodiment, even if Pd is deposited on the inner lead 41 by making the amount of Cu 40% or more of the amount of Pd on the outermost surface of the inner lead 41, the inner lead 41 And the mold resin 60 can be secured.

  FIG. 6 is a diagram showing a specific example of the effect of improving the resin adhesion of the present embodiment. FIG. 6 shows the results of a hygroscopic reflow test conducted on the semiconductor device 100 of this embodiment and a conventional semiconductor device manufactured without performing the heat treatment of the inner lead 41 in the above manufacturing method as a comparative example. Show.

  In this moisture absorption reflow test, 120 semiconductor devices of this embodiment and comparative examples were each left in an atmosphere of 30 ° C. and 70 RH% continuously for 2 weeks (336 hours), and then subjected to solder reflow at 250 ° C. Is.

  The vertical axis of FIG. 6 is the peeling occurrence rate (unit:%), and represents the ratio of the number of peeling of the mold resin 60 in 120 units for each of the embodiment and the comparative example. In addition, this peeling evaluation was implemented by the ultrasonic flaw detection method.

  As shown in FIG. 6, in the conventional semiconductor device, peeling occurs between the inner lead 41 and the mold resin 60, whereas in the present embodiment, the peeling is not observed. Thus, on the outermost surface of the inner lead 41, if the amount of Cu is 40% or more of the amount of Pd, an adhesion force that can prevent the mold resin 60 from peeling off is realized.

  In the manufacturing method of the present embodiment described above, the step of heat-treating the inner lead 41 is performed after the wire bonding. When this heat treatment is performed before wire bonding, an oxide of Cu diffused on the outermost surface of the lead frame 40 is formed as described above. For example, when bonding an Au wire on the lead frame 40, Au and A Cu oxide film is interposed between Au.

  Then, by applying a cooling / heating cycle, the Cu oxide is deteriorated, the bonding strength on the lead frame 40 is lowered, and in the worst case, it is disconnected. In that respect, according to the manufacturing method of the present embodiment, such a problem can be avoided, and the adhesion strength with the mold resin 60 can be improved while maintaining the bonding strength.

  Further, it has been confirmed that the effect of improving the adhesion strength with the mold resin 60 by the heat treatment of the inner lead 41 is exhibited regardless of the roughened state employed in this type of Pd-PPF. That is, the lead frame 40 as the Pd-PPF of this embodiment does not have to have a specific surface area of about 1.05 to 1.25, and has a specific surface area other than that or is not roughened. It may be.

  Specifically, a Ni plating layer 40b having a film thickness of 0.3 μm to 2.3 μm, a Pd plating layer 40c having a film thickness of 0.005 μm to 0.05 μm, and a film thickness of 0.003 μm to 0 are formed on the base material 40a made of Cu. In the lead frame 40 formed by forming the 0.02 μm Au plating layer 40d, the above-mentioned effects were examined for the outermost surface with the roughened state changed.

  Here, the temperature applied to the lead frame 40 at the time of die mounting is 180 ° C., and the heating temperature at the time of wire bonding is 200 to 250 ° C. Thereafter, the heating treatment of the inner lead 41 is performed, and the heating temperature at the time of wire bonding is set. The temperature was exceeded (for example, a temperature of about 290 ° C.).

  If the amount of Cu on the outermost surface is 40% or more of the amount of Pd regardless of the roughened state, the adhesiveness to the mold resin 60 is the same as shown in FIG. 3 and FIG. There was a tendency for power to recover.

  Specifically, in the case where the outermost surface of the lead frame 40 is a flat surface without being roughened, the adhesion strength is about 7 to 8 MPa in the initial stage, whereas the thermal history due to wire bonding. Was reduced to 5 to 6 MPa, and was improved (recovered) to 7 to 8 MPa by subjecting the inner lead to heat treatment after wire bonding.

  Further, when the outermost surface of the lead frame 40 is roughened, for example, when the specific surface area is about 1.1 to 1.3, the adhesion strength is 8 when the thermal history by wire bonding is applied. Whereas it was ˜9 MPa, the adhesive strength was improved (recovered) to 10 to 12 MPa by subjecting the inner lead to heat treatment after wire bonding.

  Furthermore, when the specific surface area is 1.4 to 1.5, the unevenness of the surface of the lead frame 40 becomes severe and is not easily affected by the surface state. Although it does not appear remarkably as compared with a lead frame having a specific surface area of 1.1 to 1.3, it still has an adhesive strength of about 15 to 18 MPa when subjected to a thermal history by wire bonding, A tendency to increase to 17 to 20 MPa was observed by performing the heat treatment of the inner lead.

(Other embodiments)
In addition, since the purpose of the heat treatment of the inner lead 41 in the above embodiment is to improve the resin adhesion of the inner lead 41 inside the mold resin 60, as a method of locally heating, for example, laser heating Such a method may be used. Further, the lead frame 10 is not limited to the above embodiment as long as it is a Pd-PPF and has a surface configuration in consideration of the amount of Cu described above.

  In the above embodiment, in the lead frame 40, the inner lead 41 and the outer lead 42 have the same configuration, but only the inner lead 41 may have the above-described plating and surface configuration. The outer lead 42 may have a different plating configuration and surface state from the inner lead 41 as necessary.

  That is, the structure and the manufacturing method according to the above embodiment relate to the inner lead 41 inside the mold resin 60, and the characteristics relating to the outside of the mold resin 60, that is, the outer lead 42 are not particularly limited. For example, when the position of the outer lead 42 is detected by optical interference as an inspection for positioning at the time of mounting on a printed circuit board, the specific surface area for obtaining the surface gloss is limited (for example, 1.. 23 or less) may be used.

  Further, it may be a partially roughened lead frame in which only the inner lead is roughened to improve the resin adhesion strength and the outer lead is in a non-roughened state in order to improve the positioning inspection property. Furthermore, the above-described configuration and manufacturing method can be applied not only to a semiconductor package for surface mounting, but also to a component that brings a lead frame such as a general sensor component into close contact with a mold resin.

(A) is a schematic sectional drawing of the resin-encapsulated semiconductor device which concerns on embodiment of this invention, (b) is an enlarged view of the inner lead in (a). It is a figure which shows the specific heating method which heat-processes an inner lead. It is a figure which shows the relationship between the heating temperature of a lead frame, and the quantity of Pd and Cu in the outermost surface of a lead frame. It is a figure which shows the relationship of the adhesion strength of the inner lead and mold resin with respect to the heating temperature in the said FIG. It is a figure which shows the adhesive force with mold resin about each metal and Ag which comprise Pd-PPF. It is a figure which shows an example of the improvement effect of resin contact | adhesion power.

Explanation of symbols

10 ... island, 30 ... semiconductor chip as a semiconductor element,
40 ... Lead frame, 40a ... Base material of lead frame,
40b ... Ni plating layer, 40c ... Pd plating layer, 40d ... Au plating layer,
41: inner leads, 42: outer leads, 50: bonding wires.

Claims (6)

A semiconductor element (30), a lead frame (40) electrically connected to the semiconductor element (30) via a bonding wire (50), the semiconductor element (30), the bonding wire (50), and the A mold resin (60) for sealing the lead frame (40),
An inner lead (41) which is a portion sealed with the mold resin (60) in the lead frame (40) is formed on the surface of the base material (40a) made of Cu from the base material (40a) side. In a semiconductor device in which a Ni plating layer (40b) made of Ni plating, a Pd plating layer (40c) made of Pd plating, and an Au plating layer (40d) made of Au are sequentially laminated.
When the outermost surface of the inner lead (41) is subjected to surface analysis by Auger electron spectroscopy, the amount of Cu present on the outermost surface is 40% or more of the amount of Pd present on the outermost surface ,
The thicknesses of the Ni plating layer (40b), the Pd plating layer (40c), and the Au plating layer (40d) are 0.3 μm or more and less than 2.3 μm, 0.005 μm or more and less than 0.05 μm, and 0.0. A semiconductor device having a thickness of 003 μm or more and less than 0.02 μm . The semiconductor device according to claim 1, wherein the mold resin is made of an epoxy resin. The Ni lead layer (40b) made of Ni plating from the base material (40a) side on the surface of the base material (40a) where the inner lead (41), which is the portion sealed with the mold resin (60), is formed. A lead frame (40) constituted by sequentially laminating a Pd plating layer (40c) made of Pd plating and an Au plating layer (40d) made of Au is bonded to the semiconductor element (30). Electrically connected by wire (50),
In the method of manufacturing a semiconductor device, wherein the lead frame (40), the bonding wire (50), and the semiconductor element (30) are sealed with the mold resin (60).
After performing the wire bonding between the lead frame (40) and the semiconductor element (30) and performing the connection by the bonding wire (50),
By heating the inner lead (41) of the lead frame (40) at a temperature higher than the temperature applied to the inner lead (41) during wire bonding, the outermost surface of the inner lead (41) is formed. The amount of Cu present on the outermost surface when surface analysis is performed by Auger electron spectroscopy is 40% or more of the amount of Pd present on the outermost surface,
Thereafter, the semiconductor device is sealed with the mold resin (60). 4. The method of manufacturing a semiconductor device according to claim 3 , wherein the temperature of the step of heat-treating the inner lead (41) is 275 [deg.] C. or higher. The method of manufacturing a semiconductor device according to claim 4 , wherein the temperature of the heat treatment of the inner lead (41) is 295 ° C. or higher. In the step of heat-treating the inner lead (41), the semiconductor element (30) is mounted on the island (10) of the lead frame (40), and the semiconductor element (30) and the inner lead (41) are connected. In the state connected by the bonding wire (50), the heat treatment is performed.
To the heat treatment, said island (10) is any one of claims 3, characterized in that for heating the while the temperature lower than the temperature of the heat treatment inner lead (41) 5 The manufacturing method of the semiconductor device of description.

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