JP4045985B2 - Resin-sealed electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a resin from peeling off at the tip of an inner lead at the time of reflow, in a resin-sealed electronic device in which a semiconductor chip and a lead frame are connected by a bonding wire and these are sealed with resin so as to be wrapped. <P>SOLUTION: A QFP (quad flat package) 100 as a resin-sealed electronic device is provided with a semiconductor chip 10, a resin member 20 for sealing the semiconductor chip 10 so as to wrap it, a lead frame 30 extending and entering from outside the resin member 20 to its inside, and a bonding wire 40 for connecting the semiconductor chip 10 to an inner lead 31 of the lead frame 30 inside the resin member 20. In the inner lead 31, a plating layer 50 for ensuring a bonding property with the wire 40 is formed on the uppermost layer of a portion to be connected to the wire 40, and the plating layer 50 is not formed on the uppermost surface of a portion nearer to an end of the plating layer 50. <P>COPYRIGHT: (C)2005,JPO&amp;NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a resin-sealed electronic device in which an electronic component and a lead frame are connected by a bonding wire and are sealed so as to be wrapped by a resin member.
[0002]
[Prior art]
In recent years, using this type of resin-encapsulated electronic device as a surface mounting package and reflow mounting it on a substrate via solder has been widely performed because it can be mounted at low cost. However, in this mounting method, since the temperature becomes high at the time of solder reflow, the package has a very large thermal stress, which may affect the reliability.
[0003]
In particular, recently, surface mounting using a lead-free solder that requires a higher reflow temperature, that is, a solder having a higher melting point such as a Sn—Ag—Cu solder, has started, and thermal stress tends to further increase.
[0004]
This deterioration due to thermal stress occurs when the lead frame and the resin member are peeled off due to thermal stress or water vapor pressure. Here, the water vapor pressure is a pressure at which moisture in the hygroscopic resin member evaporates due to a high temperature during reflow.
[0005]
In order to suppress such peeling between the lead frame and the resin member, conventionally, a coating that hinders the adhesion between the lead frame and the resin member is provided on the suspension lead of the lead frame, so that the coating portion is actively peeled off. A technique has been proposed in which water in the resin member is discharged as water vapor (see Patent Document 1).
[0006]
In addition, a method has been proposed in which one surface of the lead frame is covered with an inorganic thin film to strengthen the adhesion between the thin film portion and the resin member, and to suppress the peeling between the lead frame and the resin member. (See Patent Document 2).
[0007]
[Patent Document 1]
Japanese Patent No. 2845600 [0008]
[Patent Document 2]
Japanese Patent Laid-Open No. 6-13516
[Problems to be solved by the invention]
However, in each of the above-described methods, peeling between the lead frame and the resin member can be suppressed, but in order to suppress the peeling, it is necessary to separately form the coating film or the thin film on the lead frame. This leads to an increase in cost, such as time-consuming manufacturing.
[0010]
The present inventors have examined the problem of peeling between the lead frame and the resin member. This examination will be described with reference to FIG. FIG. 5 is a perspective view of a resin mold QFP (quad flat package) as a conventional typical resin-encapsulated electronic device.
[0011]
The QFP includes a semiconductor chip 10 as an electronic component, a resin member 20 that encapsulates the semiconductor chip 10, a lead frame 30 that extends from the outside to the inside of the resin member 20, and the resin member 20. A bonding wire 40 for connecting and electrically connecting the semiconductor chip 10 and the inner lead 31 of the lead frame 30. In FIG. 5, the outer shape of the resin member 20 is indicated by a two-dot chain line.
[0012]
Further, a plating layer for ensuring the bonding property to the bonding wire 31 is formed on the surface of the connecting portion of the bonding wire 40 in the inner lead 31, that is, the surface of the tip portion of the inner lead 31, as indicated by the point hatching in FIG. 5. 50 is formed. The plating layer 50 is usually made of a noble metal plating such as an Ag plating.
[0013]
By reflow mounting such a QFP on the substrate, the inner lead 31 and the resin member 20 were separated as shown in FIG. The peeled portion K1 is indicated by hatching in FIG. As described above, it was confirmed that the peeling between the lead frame 30 and the resin member 20 occurred from the front end portion of the inner lead 31 where stress was concentrated during reflow.
[0014]
Therefore, in order to suppress the peeling between the lead frame and the resin member, it is necessary to suppress the peeling of the resin at the tip of the inner lead 31, but as described above, the surface of the tip of the inner lead 31 is not affected. The plating layer 50 for ensuring the bonding property of the bonding wire 40 is formed.
[0015]
The plated layer 50 is made of a noble metal as described above, but generally has a low adhesive force to the resin against the noble metal. Therefore, when stress concentrates on the tip portion of the inner lead 31 during reflow, the resin is easily peeled off from the tip portion. And when peeling of a certain magnitude | size generate | occur | produces, since this peeling will advance to a wire bond part, reliability will be reduced.
[0016]
In view of the above problems, the present invention provides a resin-sealed electronic device in which an electronic component and a lead frame are connected by a bonding wire and sealed so as to be wrapped with a resin member. It aims at preventing exfoliation of resin in a tip part.
[0017]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, an electronic component (10), a resin member (20) that is sealed so as to enclose the electronic component, and a lead that extends from the outside to the inside of the resin member are extended. In a resin-sealed electronic device including a frame (30) and a bonding wire (40) for connecting and electrically connecting an electronic component and an inner lead (31) of a lead frame (30) inside a resin member In the inner lead (31), a plating layer (50) is formed on the outermost surface of the portion connected to the bonding wire (40) to ensure the bonding property with the bonding wire (40). only the outermost surface portions of the front end portion of the layer (50) inner lead (31) than an excellent member adhesion between the resin member (20) than the plating layer (50) Characterized in that it is coated.
[0018]
According to this, on the outermost surface of the inner lead (31), the plating layer (50) exists substantially only at the connection portion with the bonding wire (40). A member having better adhesion to the resin member (20) than the plated layer (50) on the outermost surface of the portion (51) on the tip side of the plated layer (50) in the inner lead (31). Is coated, and there is no plating layer (50) having poor adhesion to the resin.
[0019]
Therefore, the bonding property between the inner lead (31) and the bonding wire (40) can be ensured, and the lead frame (30) is provided at the inner lead (31) portion on the tip side of the connecting portion of the bonding wire (40). And the resin member (20) can be secured. Therefore, according to the resin-encapsulated electronic device of the present invention, it is possible to prevent the resin from peeling off at the tip of the inner lead during reflow. In addition, as a member excellent in adhesiveness with the resin member (20) rather than a plating layer (50), it can be made into a polyimide or polyamide as described in Claim 6.
[0020]
The invention according to claim 2 is characterized in that the plating layer (50) is made of noble metal plating. The plating layer (50) in the resin-encapsulated electronic device according to claim 1 can be composed of noble metal plating.
[0021]
The invention according to claim 3 is characterized in that the noble metal plating is Ag plating. As the noble metal plating in the resin-encapsulated electronic device according to claim 2, Ag plating can be adopted.
[0022]
The invention according to claim 4 is characterized in that the resin member (20) is made of an epoxy resin. The resin member (20) in the resin-encapsulated electronic device according to any one of claims 1 to 3 can be made of an epoxy resin.
[0023]
The invention according to claim 5 is characterized in that the lead frame (30) is made of a Cu alloy or an alloy containing Ni. The lead frame (30) in the resin-encapsulated electronic device according to any one of claims 1 to 4 can be made of a Cu alloy or an alloy containing Ni.
[0024]
In addition, the code | symbol in the bracket | parenthesis of each said means is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments shown in the drawings will be described below. FIG. 1 is a diagram showing a schematic planar configuration as seen through a resin member 20 of a resin mold QFP 100 as a resin-encapsulated electronic device according to an embodiment of the present invention. In FIG. 1, the resin member 20 is indicated by a two-dot chain line, and the surface of the plating layer 50 is hatched for identification for convenience.
[0026]
The QFP 100 includes a semiconductor chip 10 as an electronic component, a resin member 20 that seals the semiconductor chip 10 so as to enclose the electronic component, a lead frame 30 that extends from the outside to the inside of the resin member 20, and a resin member 20. Inside, a bonding wire 40 is provided for connecting and electrically connecting the semiconductor chip 10 and the inner lead 31 of the lead frame 30.
[0027]
The semiconductor chip 10 can be a normal semiconductor chip constituting an IC chip, and is mounted on the island 30a of the lead frame 30 via an adhesive or the like. The resin member 20 has, for example, a large amount of filler with good reflow resistance and a small coefficient of thermal expansion, and a mold resin in which a glass filler is contained in an epoxy resin or the like can be used.
[0028]
Each lead frame 30 can be formed into an elongated plate shape using a Cu alloy or an alloy containing Ni. As a material for such a lead frame 30, Cu, 42 alloy, or the like, or a material obtained by applying Ni plating to the surface of Cu as a base material can be used. The materials of the resin member 20 and the lead frame 30 are usually used for resin-sealed electronic devices as having excellent adhesion to each other.
[0029]
The portion of the lead frame 30 embedded in the resin member 20 is the inner lead 31, and the portion protruding from the resin member 20 is the outer lead 32. Although not shown, the QFP 100 is reflow-mounted on the substrate via the solder in the outer leads 32.
[0030]
The bonding wire 40 is formed by wire bonding such as gold or aluminum. In such a QFP 100, signal exchange between the semiconductor chip 10 and the outside is performed via the lead frame 30 and the bonding wire 40. The semiconductor chip 10 and the electrical connection portion are protected by the resin member 20.
[0031]
Here, in the inner lead 31, a plating layer 50 is formed on the outermost surface of the portion connected to the bonding wire 40 to ensure the bonding property with the bonding wire 40. As the plating layer 50, noble metal plating such as Ag plating suitable for securing wire bondability in a normal resin-sealed electronic device can be employed.
[0032]
At the same time, the plating layer 50 is not formed on the outermost surface of the portion of the inner lead 31 closer to the tip than the plating layer 50. In FIG. 1, a region where the plated layer 50 is not formed on the tip end side is shown as a non-plated forming portion 51.
[0033]
According to this, the plating layer 50 exists in the outermost surface of the inner lead 31 substantially only at the connection portion with the bonding wire 40. Therefore, the plating layer 50 having poor adhesion to the resin member 20 does not exist on the inner lead 31 on the tip side of the plating layer 50, that is, on the outermost surface of the non-plating formation portion 51. And the outermost surface of the non-plating formation part 51 is comprised with the raw material of the lead frame 30 excellent in adhesiveness with resin.
[0034]
In other words, in the present embodiment, the inner lead 31 includes the first region connected to the bonding wire 40 and the second region from the first region to the tip of the inner lead 31 (that is, the non-plated forming portion 51). ) And a plating layer 50 for ensuring wire bond bonding is formed in the first region, and the plating layer 50 is not formed in the second region. The adhesiveness with the resin member 20 is superior to that of the first region.
[0035]
Therefore, the bondability between the inner lead 31 and the bonding wire 40 can be ensured, and the adhesion between the lead frame 30 and the resin member 20 is ensured at the inner lead 31 portion closer to the tip than the connecting portion of the bonding wire 40. can do.
[0036]
Therefore, according to the present embodiment, when the QFP 100 is reflow-mounted using solder on a substrate (not shown) or the like via the outer lead 32, the resin is prevented from being peeled off at the tip of the inner lead 31 during the reflow. be able to.
[0037]
Here, the plating layer 50 can be selectively formed on the surface of the lead frame 30 by an ordinary plating method in which plating such as electroplating or electroless plating is selectively performed by masking. As a mask, a mask made of rubber or the like can be used in the same manner as the partial plating that is usually performed. If high-precision formation is required, masking may be performed using a resist.
[0038]
Then, the semiconductor chip 10 is mounted on the lead frame 30 on which such a plated layer 50 is formed, wire bonding is performed, and the lead frame 30 and the semiconductor chip 10 are connected by the bonding wire 40. Thereafter, this is put into a mold and sealed with the resin member 20. In this way, the QFP 100 shown in FIG. 1 is completed.
[0039]
Hereinafter, various modifications of the present embodiment will be described. First, as a method for forming the plating layer 50, the following method may be used in addition to the selective plating using the mask.
[0040]
A method of forming a plating layer 50 by using a paste containing a noble metal powder such as Ag, applying the paste only to a necessary portion of the lead frame 30 by an ink jet method, and thereafter performing baking or the like. Alternatively, the lead frame 30 is immersed in a plating solution, and a laser is applied to the lead frame 30, and drawing is performed by the laser to perform surface treatment only on necessary portions, thereby depositing or welding the plating layer 50.
[0041]
Further, the pattern of the plating layer 50 may be a flat circular pattern as shown in FIGS. 2A and 2B, for example, besides the flat rectangular pattern as shown in FIG. Such a circular plating layer 50 is preferable because stress applied to the plating layer 50 can be dispersed.
[0042]
In some cases, a plurality of bonding wires 40 are connected to one lead frame 30 (inner lead 31). In such a case, when the circular plating layer 50 shown in FIG. 2 is used, the area of the plating layer 50 required for bonding may be insufficient.
[0043]
In order to prevent such a problem from occurring, in particular, as shown in FIG. 2B, a plurality of circular plating layers 50 (in the illustrated example) are provided corresponding to the number of bonding wires to be connected. (Two).
[0044]
In this way, by providing a plurality of small-area plating layers 50, it is possible to increase the area of the portion where the plating layer 50 does not exist, compared to the case where a single large-area plating layer 50 is provided. The adhesion between the frame and the resin can be improved. Moreover, relaxation of the stress of the plating layer 50 can also be expected.
[0045]
In the resin-encapsulated electronic device according to the present embodiment, as shown in FIG. 3, the semiconductor chip 10 and the lead frame 30 (that is, the inner lead 31) are arranged so as to overlap each other, so-called chip-on-lead ( LOC) type may be used.
[0046]
In this LOC type configuration, the inner lead 31 overlapping the semiconductor chip 10 is fixed to the semiconductor chip 10 using a double-sided adhesive tape made of polyimide or the like (not shown).
[0047]
In this case, the plating layer 50 is formed so as to avoid the front end side of the inner lead 31 and also avoid the outermost surface of the portion of the inner lead 31 located at the end 11 of the semiconductor chip 10. Thereby, the peeling between the lead frame 30 and the resin due to the stress applied to the end portion 11 of the semiconductor chip 10 is avoided.
[0048]
Further, in the present embodiment, the portion connected to the bonding wire 40 in the inner lead 31 and the shape of the tip portion of the portion corresponding to the portion are deformed as shown in FIGS. It is good also as a shape which heightened the effect.
[0049]
In the shape example shown in FIG. 4 (a), the portion of the inner lead 31 on which the plating layer 50 having relatively weak adhesion to the resin is formed is used as a protruding portion 31a having a shape protruding more than other portions. The anchor effect is increased by increasing the contact area.
[0050]
Further, in the shape example shown in FIG. 4B, the through hole 31 b is formed on the tip portion side, that is, the non-plating formation portion 51 with respect to the formation portion of the plating layer 50 in the inner lead 31. In this case, the resin member 20 is filled in the through hole 31b, and the resin member 20 is engaged with the inner lead 31 in the through hole 31b, thereby increasing the anchor effect.
[0051]
If these shapes are as shown in FIG. 4, even if the resin peels off at the tip of the inner lead 31, a resin such as a protruding portion 31a in FIG. 4 (a) and a through hole 31b in FIG. 4 (b). The progress of the peeling can be stopped at a portion having excellent adhesion to the member 20. That is, a further effect of preventing peeling is obtained.
[0052]
Further, in the present embodiment, in the inner lead 31, the plating layer 50 is formed on the outermost surface of the portion connected to the bonding wire 40, and the outermost surface of the non-plating forming portion 51 on the tip end side is more than that. The lead frame 30 is made of a material such as Cu alloy.
[0053]
On the other hand, even if the outermost surface of the non-plating forming part 51 is coated with, for example, a member having better adhesion to the resin member 20 than the plated layer 50, the same effect can be obtained. For example, a resin such as polyimide or polyamide may be coated by a printing method or the like.
[0054]
In this case, after the plating layer 50 is once formed from the plating layer 50 formation portion on the inner lead 31 to the outermost surface on the tip side, the polyimide described above is applied only to the portion that becomes the non-plating formation portion 51. Alternatively, a resin such as polyamide or a polyamide may be selectively coated.
[Brief description of the drawings]
FIG. 1 is a schematic plan view of a resin mold QFP (quad flat package) as a resin-encapsulated electronic device according to an embodiment of the present invention as seen through a resin member.
FIG. 2 is a diagram showing an example in which a planar circular plating layer is formed on the surface of an inner lead.
FIG. 3 is a plan view showing an example in which a plating layer is formed on an inner lead when a chip-on-lead (LOC) type is used.
FIG. 4 is a diagram illustrating an example in which a shape with an enhanced anchor effect on a resin member is applied to an inner lead.
FIG. 5 is a perspective view of a resin mold QFP as a conventional typical resin-sealed electronic device.
6 is a view showing a state when the resin member is peeled off at the inner lead tip portion in FIG. 5;
[Explanation of symbols]
10 ... Semiconductor chip as an electronic component, 20 ... Resin member,
30 ... lead frame, 31 ... inner lead of the lead frame,
40 ... bonding wire, 50 ... plated layer.

Claims (6)

An electronic component (10);
A resin member (20) for sealing so as to enclose the electronic component;
A lead frame (30) extending from the outside to the inside of the resin member;
In a resin-encapsulated electronic device comprising a bonding wire (40) for connecting and electrically connecting the electronic component and an inner lead (31) of the lead frame (30) inside the resin member,
In the inner lead (31), a plating layer (50) is formed on the outermost surface of the portion connected to the bonding wire (40) to ensure the bonding property with the bonding wire (40). A member having better adhesion to the resin member (20) than the plated layer (50) is provided only on the outermost surface of the inner lead (31) on the tip side of the plated layer (50). A resin-sealed electronic device characterized by being coated.   The resin-sealed electronic device according to claim 1, wherein the plating layer (50) is made of noble metal plating.   3. The resin-encapsulated electronic device according to claim 2, wherein the noble metal plating is Ag plating.   The resin-sealed electronic device according to any one of claims 1 to 3, wherein the resin member (20) is made of an epoxy resin.   5. The resin-encapsulated electronic device according to claim 1, wherein the lead frame (30) is made of a Cu alloy or an alloy containing Ni. The resin-sealed electronic device according to claim 1, wherein the member is polyimide or polyamide.

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