JP7620867B2 - Lead frame, manufacturing method of lead frame, and manufacturing method of semiconductor device - Google Patents

Description

This disclosure relates to a lead frame, a method for manufacturing a lead frame, and a method for manufacturing a semiconductor device.

In recent years, there has been a demand for smaller and thinner semiconductor devices mounted on substrates. To meet this demand, various types of so-called QFN (Quad Flat Non-lead) type semiconductor devices have been proposed, which are conventionally constructed using a lead frame, with a semiconductor element mounted on the mounting surface sealed with sealing resin and with a portion of the leads exposed on the back side.

However, traditionally, as the lead frame becomes thinner, it becomes more difficult to maintain the strength of the lead frame, and deformation of the lead frame after etching becomes an issue.

In recent years, there has also been a demand to increase the number of leads (number of pins) without changing the chip size. In response to this, the conventional approach has been to narrow the width of the leads, but as the leads become thinner, they become more susceptible to deformation, creating the problem that stable wire bonding becomes more difficult.

JP 2019-57590 A

Patent Document 1 discloses a technique for providing a resin portion on the back surface of a lead frame and then removing unnecessary portions of the resin portion. However, conventionally, it has been difficult to remove the unnecessary portions of the resin portion in a uniform thickness, and there is a problem in that it is difficult to make the thickness of the die pad and lead portions constant.

This disclosure provides a lead frame, a method for manufacturing a lead frame, and a method for manufacturing a semiconductor device, which are capable of polishing the back side resin of a lead frame having a back side resin to a uniform thickness.

The method for manufacturing a lead frame according to the present disclosure includes the steps of preparing a metal substrate, etching the metal substrate from the rear side to the middle of the thickness direction to form a rear side recess, forming a mark on a portion of the metal substrate other than the rear side recess, forming a rear side resin on the rear side of the metal substrate and covering the rear side recess and the mark with the rear side resin, polishing the rear side resin to a predetermined thickness using the mark as a reference, and either before or after the polishing step, exposing the rear side resin to the front side by etching the metal substrate from the front side to the middle of the thickness direction.

In the manufacturing method of the lead frame according to the present disclosure, in the step of polishing the back surface side resin, after the mark appears, the back surface side resin may be polished until the mark disappears.

In the method for manufacturing a lead frame according to the present disclosure, in the step of polishing the back surface side resin, the back surface side resin may be polished until the mark appears.

In the lead frame manufacturing method according to the present disclosure, the mark may be removed after the step of polishing the back side resin.

The method for manufacturing a lead frame according to the present disclosure includes the steps of preparing a metal substrate, etching the metal substrate from the rear surface side to the middle of the thickness direction to form a rear surface recess, forming a mark on a portion of the metal substrate other than the rear surface recess, forming a rear surface resin on the rear surface side of the metal substrate and forming the rear surface resin on a portion of the thickness direction of the rear surface recess, polishing the rear surface resin to a predetermined thickness using the mark as a reference, and exposing the rear surface resin to the front surface side by etching the metal substrate from the front surface side to the middle of the thickness direction either before or after the step of polishing the rear surface resin.

In the method for manufacturing a lead frame according to the present disclosure, in the step of polishing the back surface side resin, the back surface side resin may be polished until the mark disappears.

In the lead frame manufacturing method according to the present disclosure, the mark may be a solder resist.

In the method for manufacturing a lead frame according to the present disclosure, the step of exposing the back surface side resin to the front surface side may be performed before the step of polishing the back surface side resin.

In the method for manufacturing a lead frame according to the present disclosure, the step of exposing the back surface side resin to the front surface side may be performed after the step of polishing the back surface side resin.

The lead frame according to the present disclosure comprises a die pad, a lead portion arranged around the die pad, and a back surface side resin arranged around the die pad and the lead portion on the back surface side of the lead frame, the back surface of the back surface side resin, the back surface of the die pad, and the back surface of the lead portion being located on the same plane, and rolling marks are present on the back surface of the die pad and the back surface of the lead portion, respectively.

The lead frame according to the present disclosure comprises a die pad, a lead portion arranged around the die pad, and a back side resin arranged around the die pad and the lead portion on the back side of the lead frame, the back side resin protruding further toward the back side than the die pad and the lead portion.

The lead frame according to the present disclosure comprises a die pad, a lead portion arranged around the die pad, and a back side resin arranged around the die pad and the lead portion on the back side of the lead frame, the back side of the back side resin being located closer to the front side than the back side of the die pad and the back side of the lead portion, and rolling marks are present on the back side of the die pad and the back side of the lead portion, respectively.

The method for manufacturing a semiconductor device according to the present disclosure includes the steps of preparing a lead frame according to the present disclosure, mounting a semiconductor element on the lead frame, electrically connecting the semiconductor element and the lead frame with a connecting member, and sealing the lead frame, the semiconductor element, and the connecting member with a sealing resin.

According to the present disclosure, in a lead frame having a back surface resin, the back surface resin can be polished to a uniform thickness.

FIG. 1 is a plan view showing a lead frame according to a first embodiment. FIG. 2 is a bottom view showing the lead frame according to the first embodiment. FIG. 3 is a cross-sectional view showing the lead frame according to the first embodiment (a cross-sectional view taken along line III-III in FIG. 1). FIG. 4 is a plan view showing the semiconductor device according to the first embodiment. FIG. 5 is a cross-sectional view showing the semiconductor device according to the first embodiment (cross-sectional view taken along line VV in FIG. 4). 6(a) to 6(j) are cross-sectional views showing the method for manufacturing the lead frame according to the first embodiment. 7A to 7E are cross-sectional views showing the method for manufacturing the semiconductor device according to the first embodiment. 8A to 8J are cross-sectional views showing a first modified example of the method for manufacturing the lead frame according to the first embodiment. 9A to 9K are cross-sectional views showing a second modified example of the method for manufacturing the lead frame according to the first embodiment. FIG. 10 is a cross-sectional view showing a lead frame according to the second embodiment. FIG. 11 is a cross-sectional view showing a semiconductor device according to a second embodiment. FIG. 12 is a cross-sectional view showing a state in which the semiconductor device according to the second embodiment is mounted on a wiring board. 13A to 13J are cross-sectional views showing a method for manufacturing a lead frame according to the second embodiment. FIG. 14 is a cross-sectional view showing a lead frame according to a third embodiment. FIG. 15 is a cross-sectional view showing a semiconductor device according to a third embodiment. 16(a) to 16(j) are cross-sectional views showing a method for manufacturing a lead frame according to the third embodiment. FIG. 17 is a cross-sectional view showing a state in which the semiconductor device according to the third embodiment is mounted on a wiring board. 18(a) to 18(j) are cross-sectional views showing a first modified example of the method for manufacturing a lead frame according to the third embodiment. 19(a) to 19(k) are cross-sectional views showing a second modified example of the method for manufacturing a lead frame according to the third embodiment.

(First embodiment)
A first embodiment will be described below with reference to Figures 1 to 9. In the following figures, the same parts are denoted by the same reference numerals, and some detailed descriptions may be omitted.

In this specification, the X direction and the Y direction are two directions parallel to each side of the lead frame 10, and the X direction and the Y direction are perpendicular to each other. The Z direction is perpendicular to both the X direction and the Y direction. The terms "inside" and "inner side" refer to the side facing the center of each package area 10a, and the terms "outside" and "outer side" refer to the side away from the center of each package area 10a. The term "front side" refers to the side on which the semiconductor element 21 is mounted (the positive side in the Z direction), and the term "back side" refers to the side opposite the "front side" (the negative side in the Z direction) that is connected to an external wiring board (not shown).

In addition, in this specification, half-etching refers to etching the material to be etched partway in the thickness direction. The thickness of the material to be etched after half-etching is, for example, 30% to 70%, preferably 40% to 60%, of the thickness of the material to be etched before half-etching.

(Lead frame configuration)
First, an outline of the lead frame according to the present embodiment will be described with reference to Figures 1 to 3. Figures 1 to 3 are diagrams showing the lead frame according to the present embodiment.

As shown in Figures 1 and 2, the lead frame 10 includes an outer frame 40 and a package area (unit lead frame) 10a arranged inside the outer frame 40.

In this case, multiple package areas 10a are arranged in multiple rows and columns (in a matrix). However, this is not limited to the above, and it is sufficient that there is one or more package areas 10a. Note that each package area 10a corresponds to a semiconductor device 20 (described below), and is an area located inside the imaginary lines in Figures 1 and 2. Also, the imaginary lines in Figures 1 and 2 correspond to the outer periphery of the semiconductor device 20.

Next, the configuration of the lead frame 10 will be further explained with reference to Figures 1 to 3.

As shown in Figures 1 to 3, each package area 10a of the lead frame 10 includes a die pad 11, a plurality of elongated lead portions 12 that are provided around the die pad 11 and connect the semiconductor element 21 to an external circuit (not shown), and a back side resin 18 that is disposed around the die pad 11 and the lead portions 12 and on the back side of the lead frame 10. The plurality of package areas 10a are connected to each other via support leads (support members) 13. The support leads 13 support the die pad 11 and the lead portions 12, and extend along the X and Y directions, respectively.

The die pad 11 has a substantially square shape in plan. In this case, the die pad 11 is not half-etched and has the same thickness as the metal substrate before processing (metal substrate 31 described later). The planar shape of the die pad 11 is not limited to a square, and may be a polygon such as a rectangle. In addition, suspension leads 14 are connected to the four corners of the die pad 11, and the die pad 11 is connected and supported by the support leads 13 via these four suspension leads 14. Note that the front surface side of the die pad 11 may be partially half-etched to make it thinner.

As shown in FIG. 3, the die pad 11 has a die pad front surface 11a located on the front side and a die pad back surface 11b located on the back side. A semiconductor element 21, which will be described later, is mounted on the die pad front surface 11a. The die pad back surface 11b is exposed to the outside from the lead frame 10. In addition, a first die pad side surface 11c and a second die pad side surface 11d are formed on the side of the die pad 11 facing the lead portion 12. The first die pad side surface 11c is located on the die pad front surface 11a side and is exposed to the outside from the lead frame 10. The second die pad side surface 11d is located on the die pad back surface 11b side and is in close contact with the back surface resin 18.

Each lead 12 is connected to the semiconductor element 21 via a bonding wire 22 as described below, and is disposed with a space between it and the die pad 11. Each lead 12 extends from the support lead 13 or the outer frame 40.

Each lead portion 12 is arranged along the periphery of the die pad 11. An external terminal 17 is formed on the back surface of each lead portion 12, and is electrically connected to an external wiring board (not shown). Each external terminal 17 is exposed to the outside from the semiconductor device 20 after the semiconductor device 20 (described later) is manufactured.

As shown in FIG. 3, the lead portion 12 has an inner lead 51 located on the inside (die pad 11 side) and a terminal portion 53 located on the outside (support lead 13 side). The inner lead 51 extends from the terminal portion 53 to the die pad 11 side, and an internal terminal 15 is formed at the tip portion on the front side. This internal terminal 15 is an area that is electrically connected to the semiconductor element 21 via a bonding wire 22 as described below. A plating layer 25 is provided on the internal terminal 15 to improve adhesion with the bonding wire 22. The plating layer 25 may be made of silver plating, for example.

The inner lead 51 is thinned by half etching from the back side. The inner lead 51 has an inner lead surface 51a and an inner lead back surface 51b. An internal terminal 15 is formed on a part of the inner lead surface 51a. The inner lead back surface 51b is in close contact with the back side resin 18. An inner lead side surface 51c is formed on the side of the inner lead 51 facing the die pad 11. The inner lead side surface 51c is exposed to the outside from the lead frame 10.

The terminal portion 53 extends toward the support lead 13 or the outer frame 40, and its base end is connected to the support lead 13 or the outer frame 40. The above-mentioned external terminal 17 is formed on the back surface of the terminal portion 53. The terminal portion 53 is not half-etched and has the same thickness as the die pad 11.

The back side resin 18 is disposed around the die pad 11 and the lead portion 12. That is, as shown in FIG. 1, when viewed from the front side, the back side resin 18 is located in an area surrounded by one side of the die pad 11, the multiple lead portions 12 facing that side, the support lead 13 or outer frame 40, and the two suspension leads 14. Also, as shown in FIG. 2, when viewed from the back side, the back side resin 18 is located in an area surrounded by one side of the die pad 11, the external terminals 17 of the multiple lead portions 12 facing that side, the support lead 13 or outer frame 40, and the two suspension leads 14. Note that in FIG. 1 and FIG. 2, the back side resin 18 is shown shaded (the same applies to FIG. 4 described later).

The back surface side resin 18 is disposed on the back surface side of the lead frame 10. In other words, the back surface side resin 18 is not present on the front surface side (positive side in the Z direction) of the lead frame 10 relative to the middle position in the thickness direction (Z direction), but is present only on the back surface side (negative side in the Z direction) of the middle position in the thickness direction. Note that the middle position is not limited to the center in the thickness direction of the lead frame 10, and may be located on the front surface side or back surface side of the middle position in the thickness direction.

As shown in FIG. 3, the back surface side resin 18 is disposed in a region surrounded by the terminal portion 53, the inner lead back surface 51b, and the second die pad side surface 11d in a cross-sectional view. The back surface side resin 18 has a resin front surface 18a located on the front surface side and a resin back surface 18b located on the back surface side. Of these, the resin front surface 18a is exposed to the outside from the space between the first die pad side surface 11c and the inner lead side surface 51c. The resin back surface 18b is exposed to the outside from the back surface side of the lead frame 10. The resin back surface 18b, the die pad back surface 11b, and the external terminal 17 are located on the same plane.

The rear surface side resin 18 can be a thermosetting resin such as silicone resin or epoxy resin, or a thermoplastic resin such as PPS resin. In order to improve adhesion between the rear surface side resin 18 and the sealing resin 23 described below, it is preferable to use the same material as the sealing resin 23 for the rear surface side resin 18.

The lead frame 10 described above is generally made of metals such as copper, copper alloy, and 42 alloy (Fe alloy containing 42% Ni). The thickness of the lead frame 10 can be 80 μm or more and 250 μm or less, depending on the configuration of the semiconductor device 20 to be manufactured.

The front and back surfaces of the lead frame 10 have rolling marks formed when rolling the metal substrate 31 (described later) for producing the lead frame 10. FIG. 2 shows, as an example, a case where rolling marks S are formed on the back surface 11b of the die pad 11. In this case, the rolling marks S extend parallel to one side (Y direction) of the die pad 11. The rolling marks S may have, for example, an arithmetic mean roughness Ra of 0.03 μm to 0.20 μm and a depth of 0 μm to 5 μm. In addition, the rolling marks S may be formed at intervals from each other over the entire front and back surfaces of the lead frame 10. As described later, the back surface resin 18 is polished from the back surface side with reference to the mark 37 until the mark 37 disappears. Therefore, the back surface 11b of the die pad 11 and the external terminals 17 of the lead portion 12 are hardly polished, and the rolling marks S are exposed to the outside. In this embodiment, a lead frame 10 is also provided in which rolling marks S are present on the die pad back surface 11b of the die pad 11 and on the external terminals 17 of the lead portion 12.

(Configuration of Semiconductor Device)
Next, the semiconductor device according to the present embodiment will be described with reference to Figures 4 and 5. Figures 4 and 5 are diagrams showing the semiconductor device (QFN type) according to the present embodiment.

As shown in Figures 4 and 5, the semiconductor device (semiconductor package) 20 includes a die pad 11, a plurality of lead portions 12 arranged around the die pad 11, a semiconductor element 21 mounted on the die pad 11, and a plurality of bonding wires (connecting members) 22 that electrically connect the lead portions 12 and the semiconductor element 21. In addition, a back side resin 18 is arranged around the die pad 11 and the lead portions 12 on the back side of the semiconductor device 20. Furthermore, the die pad 11, the lead portions 12, the semiconductor element 21, and the bonding wires 22 are resin-sealed with sealing resin 23.

Of these, the die pad 11, the lead portion 12, and the back side resin 18 are made from the lead frame 10 described above. The configurations of the die pad 11, the lead portion 12, and the back side resin 18 are the same as those shown in Figures 1 to 3 described above, except for the areas not included in the semiconductor device 20, so a detailed description will be omitted here.

The semiconductor element 21 may be any of a variety of commonly used semiconductor elements, including, but not limited to, integrated circuits, large-scale integrated circuits, transistors, thyristors, and diodes. The semiconductor element 21 has a number of electrodes 21a to which bonding wires 22 are attached. The semiconductor element 21 is fixed to the surface of the die pad 11 by an adhesive 24, such as die bonding paste.

Each bonding wire 22 is made of a material with good conductivity, such as gold or copper. One end of each bonding wire 22 is connected to an electrode 21a of the semiconductor element 21, and the other end is connected to a plating layer 25 located on the internal terminal 15 of each lead portion 12.

The sealing resin 23 may be a thermosetting resin such as silicone resin or epoxy resin, or a thermoplastic resin such as PPS resin. The overall thickness of the sealing resin 23 may be about 300 μm or more and 1500 μm or less. Furthermore, one side of the sealing resin 23 (one side of the semiconductor device 20) may be, for example, 0.2 mm or more and 16 mm or less. In the space between the die pad 11 and the lead portion 12, the sealing resin 23 is in close contact with the resin surface 18a of the back surface side resin 18. Note that in FIG. 4, the sealing resin 23 located on the front surface side of the die pad 11, the lead portion 12, and the back surface side resin 18 is omitted.

(Lead frame manufacturing method)
Next, a method for manufacturing the lead frame 10 shown in FIGS. 1 to 3 will be described with reference to FIGS.

First, as shown in FIG. 6(a), a flat metal substrate 31 is prepared. This metal substrate 31 may be made of a metal such as copper, a copper alloy, or alloy 42 (a 42% Ni-Fe alloy). It is preferable to use a metal substrate 31 that has been degreased and cleaned on both sides.

Next, photosensitive resist is applied to the entire front and back surfaces of the metal substrate 31 and dried. The photosensitive resist on the metal substrate 31 is then exposed through a photomask and developed to form etching resist layers 32 and 33 having the desired openings 32b and 33b (FIG. 6(b)).

Next, the metal substrate 31 is thinned from the back side of the metal substrate 31 to the middle of the thickness direction by half etching. In this case, the back side etching resist layer 33 is used as a corrosion-resistant film, and etching is performed on the back side of the metal substrate 31 with a etchant (FIG. 6(c)). At this time, the front side etching resist layer 32 may be covered with a film (not shown). This forms a back side recess 36, which is a non-penetrating recess, on the back side of the metal substrate 31. This back side recess 36 has a shape corresponding to the back side resin 18. The etchant can be appropriately selected depending on the material of the metal substrate 31 used. For example, when copper is used as the metal substrate 31, a ferric chloride aqueous solution is usually used, and this ferric chloride aqueous solution may be spray-etched from one side or both sides of the metal substrate 31.

Next, the etching resist layer 33 on the back side is peeled off and removed, leaving the etching resist layer 32 on the front side, and then the metal substrate 31 is washed with water and dried (Figure 6 (d)).

Next, a mark 37 is formed on the metal substrate 31 other than the rear recess 36, i.e., on the exposed metal surface that is not half-etched (FIG. 6(e)). Specifically, the mark 37 may be formed on the portion 11e corresponding to the rear surface 11b of the die pad 11 and the portion 17a corresponding to the external terminal 17 of the lead portion 12. If the lead frame 10 includes multiple die pads 11, the mark 37 may be formed on all of the portions 11e corresponding to the rear surfaces 11b of the die pads. Alternatively, the mark 37 may be formed on a portion of the portions 11e corresponding to the rear surfaces 11b of the die pads. In this way, in the polishing process (FIG. 6(h)) described later, the polishing thickness of each die pad 11 can be adjusted with reference to the mark 37, thereby preventing the polishing thickness from becoming uneven within the surface of the metal substrate 31.

For example, solder resist can be used as the mark 37. When the mark 37 is made of solder resist, the mark 37 may be formed by a printing method such as screen printing. By making the mark 37 of solder resist, the mark 37 having a desired pattern shape can be easily formed. The thickness of the mark 37 may be, for example, more than 1 μm and 50 μm or less. It is preferable that the mark 37 is provided only in a part of the portion 11e corresponding to the die pad back surface 11b. For example, the mark 37 may be provided at a position separated by a distance D1 from the end 11f of the portion 11e. This distance D1 may be, for example, 50 μm or more and 150 μm or less. As a result, the metal (die pad 11), the resin (back surface side resin 18), and the solder resist (mark 37) do not intersect at one point at the end 11f, and it is possible to suppress the occurrence of cracks around the end 11f when stress is applied to the end 11f in a later process. The same applies to the portion 17a of the lead portion 12 that corresponds to the external terminal 17.

Next, the back side resin 18 is formed on the back side of the metal substrate 31, and the back side recess 36 and the mark 37 are covered by the back side resin 18 (FIG. 6(f)). At this time, a thermosetting resin or a thermoplastic resin may be injection molded or transfer molded on the back side of the metal substrate 31. As a result, the back side resin 18 fills the back side recess 36 and completely covers the mark 37. The thickness T1 of the back side resin 18 from the portion 11e corresponding to the die pad back surface 11b may be 25 μm or more and 200 μm or less. This thickness T1 is thicker than the thickness of the mark 37 described above.

Next, the metal substrate 31 is thinned from the front surface side to the middle of the thickness direction by half etching. In this case, the front surface side etching resist layer 32 is used as a corrosion-resistant film, and etching is performed with an etchant on the front surface side of the metal substrate 31 (FIG. 6(g)). This forms the outlines of the die pad 11, the lead portion 12, and the support lead 13. In addition, by half-etching the front surface side of the metal substrate 31, a gap is formed between the die pad 11 and the lead portion 12, and the back surface side resin 18 is exposed on the front surface side. The etchant may be the same as that used when etching the back surface side of the metal substrate 31 (FIG. 6(c)).

Next, the rear surface side resin 18 is polished to a predetermined thickness using the mark 37 as a reference (FIG. 6(h)). Specifically, the rear surface side resin 18 is polished from the rear surface side, and after the mark 37 appears, the rear surface side resin 18 is polished until the mark 37 disappears. When it is confirmed that the mark 37 has disappeared, the polishing of the rear surface side resin 18 is terminated. This allows the thickness to which the rear surface side resin 18 is polished to be approximately equal to the thickness T1 (FIG. 6(f)) of the rear surface side resin 18 from the portion 11e corresponding to the die pad rear surface 11b described above. At this time, the metal surface constituting the die pad rear surface 11b of the die pad 11 and the external terminal 17 of the lead portion 12 is exposed on the rear surface side. When the mark 37 disappears, the polishing of the rear surface side resin 18 may be immediately terminated. This allows the amount of metal parts (die pad 11 and lead portion 12) polished to be minimized. At this time, the rolling marks S (FIG. 2) formed on the die pad back surface 11b of the die pad 11 and the external terminals 17 of the lead portion 12 are also exposed to the outside. Note that the back surface resin 18 can be polished, for example, by buffing. In this way, by forming the mark 37 on the back surface of the metal substrate 31, the presence or absence of the mark 37 can be visually confirmed, and the amount of polishing of the back surface resin 18 can be maintained constant.

Next, the etching resist layer 32 is peeled off and the metal substrate 31 is washed with water and dried (Figure 6(i)).

Then, electrolytic plating is applied to the inner lead 51 of the lead portion 12. This causes a metal (e.g., silver) to deposit on the inner lead 51 of the lead portion 12, forming a plating layer 25. In this manner, the lead frame 10 shown in Figures 1 to 3 is obtained (Figure 6(j)).

(Method of manufacturing a semiconductor device)
Next, a method for manufacturing the semiconductor device 20 shown in FIGS. 4 and 5 will be described with reference to FIGS.

First, the lead frame 10 is fabricated (FIG. 7(a)) using, for example, the method shown in FIG. 6(a)-(j).

Next, the semiconductor element 21 is mounted on the die pad 11 of the lead frame 10. In this case, the semiconductor element 21 is placed on the die pad 11 and fixed using an adhesive 24 such as die bonding paste (die attachment process) (Figure 7 (b)).

Next, each electrode 21a of the semiconductor element 21 and the plating layer 25 formed on each lead portion 12 are electrically connected to each other by a bonding wire (connecting member) 22 (wire bonding process) (Figure 7 (c)).

Next, the lead frame 10 is molded with, for example, a thermosetting resin or a thermoplastic resin by injection molding or transfer molding to form the sealing resin 23 (FIG. 7(d)). In this way, the lead frame 10, the lead portion 12, the semiconductor element 21, and the bonding wires 22 are sealed.

Next, the sealing resin 23 and the support leads 13 between each semiconductor element 21 are diced to separate the lead frame 10 into each semiconductor device 20. At this time, the sealing resin 23 and the support leads 13 between each semiconductor device 20 may be cut while rotating a blade made of, for example, a diamond grindstone.

In this manner, the semiconductor device 20 shown in Figures 4 and 5 is obtained (Figure 7 (e)).

Thus, according to this embodiment, in the manufacturing process of the lead frame 10, after the mark 37 is formed on the metal substrate 31 in the portion other than the back side recess 36, the back side resin 18 is formed on the back side of the metal substrate 31 to cover the back side recess 36 and the mark 37. Then, using the mark 37 as a reference, the back side resin 18 is polished to a predetermined thickness. In this way, by polishing the back side resin 18 while checking the mark 37, the back side resin 18 can be polished to a uniform thickness.

Furthermore, according to this embodiment, in the process of polishing the back surface side resin 18, the back surface side resin 18 is polished until the mark 37 disappears. This allows the polishing of the back surface side resin 18 to be stopped when the mark 37 disappears, thereby minimizing the amount of the metal parts (die pad 11 and lead portion 12) that are polished. This allows the variation in thickness of the die pad 11 and lead portion 12 to be reduced.

In addition, according to this embodiment, the process of exposing the back surface resin 18 to the front surface by etching (FIG. 6(g)) is performed before the process of polishing the back surface resin 18 (FIG. 6(h)). As a result, when the front surface side of the metal substrate 31 is etched, the back surface side of the metal substrate 31 is covered with the back surface resin 18, so that only the front surface side of the metal substrate 31 can be thinned without a separate process of covering the back surface side of the metal substrate 31 with another member.

In addition, according to this embodiment, the photolithography process for forming the etching resist layers 32 and 33 can be performed only once (Figure 6 (b)), which simplifies the manufacturing process of the lead frame 10.

(First Modification of Lead Frame Manufacturing Method)
Next, a first modified example of the method for manufacturing the lead frame 10 according to the present embodiment will be described with reference to Figures 8(a)-(j). In the modified example shown in Figures 8(a)-(j), the step of exposing the back surface side resin 18 to the front surface side is performed after the step of polishing the back surface side resin 18, and the other configurations are substantially the same as the method for manufacturing the lead frame 10 shown in Figures 6(a)-(j). In Figures 8(a)-(j), the same parts as those in Figures 6(a)-(j) are given the same reference numerals and detailed description will be omitted.

First, a metal substrate 31 is prepared (FIG. 8(a)) in a manner similar to the steps shown in FIGS. 6(a) and 6(b) described above, and etching resist layers 32 and 33 are formed on the front and back of the metal substrate 31 (FIG. 8(b)).

Next, in a manner similar to the process shown in FIG. 6(c) described above, the metal substrate 31 is thinned from the rear surface side of the metal substrate 31 to the middle of its thickness direction by half etching, forming a rear surface recess 36 (FIG. 8(c)).

Next, in a manner similar to the steps shown in Figures 6(d) and (e), the etching resist layer 33 on the back side is peeled off and removed (Figure 8(d)), and a mark 37 is formed on the metal substrate 31 in the area other than the back side recess 36 (Figure 8(e)).

Next, in a manner substantially similar to the process shown in FIG. 6(f), a back surface side resin 18 is formed on the back surface side of the metal substrate 31, and the back surface side recess 36 and the mark 37 are covered with the back surface side resin 18 (FIG. 8(f)).

Next, in a manner similar to the process shown in FIG. 6(h), the back surface side resin 18 is polished to a predetermined thickness using the mark 37 as a reference (FIG. 8(g)). Specifically, the back surface side resin 18 is polished from the back surface side until the mark 37 appears and then the back surface side resin 18 is polished until the mark 37 disappears. When it is confirmed that the mark 37 has disappeared, polishing of the back surface side resin 18 is terminated. At this time, the portion 11e corresponding to the die pad back surface 11b of the die pad 11 and the portion 17a corresponding to the external terminal 17 of the lead portion 12 are each exposed on the back surface side.

Next, in a manner similar to the process shown in FIG. 6(g), the metal substrate 31 is thinned from the front surface side to the middle of the thickness direction by half etching (FIG. 8(h)). This forms the outer shapes of the die pad 11, the lead portion 12, and the support lead 13. In addition, by half-etching the front surface side of the metal substrate 31, a gap is formed between the die pad 11 and the lead portion 12, and the back surface resin 18 is exposed to the front surface side.

Next, in a manner similar to the process shown in FIG. 6(i), the etching resist layer 32 is peeled off and then the metal substrate 31 is washed with water and dried (FIG. 8(i)).

Then, in a manner similar to the process shown in FIG. 6(j), a plating layer 25 is formed on the inner lead 51 of the lead portion 12. In this manner, the lead frame 10 shown in FIGS. 1 to 3 is obtained (FIG. 8(j)).

According to this modified example, the process of exposing the back surface side resin 18 to the front surface side by etching (FIG. 8(h)) is performed after the process of polishing the back surface side resin 18 (FIG. 8(g)). This makes it possible to suppress deformation of the lead frame 10.

(Second Modification of Lead Frame Manufacturing Method)
Next, a second modified example of the method for manufacturing the lead frame 10 according to the present embodiment will be described with reference to Figures 9(a)-(k). In the modified example shown in Figures 9(a)-(k), a process for forming etching resist layers 32A and 33A for etching the back side of the metal substrate 31 and a process for forming an etching resist layer 32B for etching the front side of the metal substrate 31 are separately performed. The other configurations are substantially the same as those in the method for manufacturing the lead frame 10 shown in Figures 6(a)-(j). In Figures 9(a)-(k), the same parts as those in Figures 6(a)-(j) are denoted by the same reference numerals, and detailed description thereof will be omitted.

First, prepare a metal substrate 31 (Figure 9(a)) in a manner similar to the process shown in Figure 6(a) described above.

Next, in a manner similar to the process shown in FIG. 6(b) described above, photosensitive resist is applied to the entire front and back surfaces of the metal substrate 31 and then dried. The photosensitive resist on the metal substrate 31 is then exposed through a photomask and developed to form an etching resist layer 32A on the front surface side that does not have any openings, and an etching resist layer 33A on the back surface side that has the desired openings 33c (FIG. 9(b)).

Next, in a manner similar to the process shown in FIG. 6(c) described above, the metal substrate 31 is thinned from the rear side of the metal substrate 31 to the middle of the thickness direction by half etching, forming a rear side recess 36 (FIG. 9(c)). In this case, the rear side etching resist layer 33A is used as a corrosion-resistant film, and the rear side of the metal substrate 31 is etched with a etchant. Note that the front side of the metal substrate 31 is not etched because it is covered by the etching resist layer 32A, which does not have an opening.

Next, the etching resist layer 32A on the front side and the etching resist layer 33A on the back side are peeled off and removed (Figure 9 (d)).

Next, in a manner similar to the process shown in FIG. 6(e) described above, a mark 37 is formed on the metal substrate 31 in a portion other than the recess 36 on the rear side (FIG. 9(e)).

Next, in a manner similar to the process shown in FIG. 6(f) described above, a back surface resin 18 is formed on the back surface of the metal substrate 31, and the back surface recess 36 and the mark 37 are covered with the back surface resin 18 (FIG. 9(f)).

Next, in a manner similar to the process shown in FIG. 6(h) described above, the back surface side resin 18 is polished to a predetermined thickness using the mark 37 as a reference (FIG. 9(g)). Specifically, the back surface side resin 18 is polished from the back surface side until the mark 37 appears and then the back surface side resin 18 is polished until the mark 37 disappears. When it is confirmed that the mark 37 has disappeared, polishing of the back surface side resin 18 is terminated. At this time, the portion 11e corresponding to the die pad back surface 11b of the die pad 11 and the portion 17a corresponding to the external terminal 17 of the lead portion 12 are each exposed on the back surface side.

Next, a surface-side etching resist layer 32B having the desired openings 32c is formed on the surface of the metal substrate 31 (FIG. 9(h)). In this case, a photosensitive resist is applied to the entire surface of the metal substrate 31 and then dried. Next, the metal substrate 31 is exposed to light through a photomask and developed to form the surface-side etching resist layer 32B.

Next, in a manner similar to the process shown in FIG. 6(g) described above, the metal substrate 31 is thinned from the front surface side to the middle of the thickness direction by half etching (FIG. 9(i)). In this case, the front surface side etching resist layer 32B is used as a corrosion-resistant film, and etching is performed with a corrosive liquid on the front surface side of the metal substrate 31. This forms the outlines of the die pad 11, the lead portion 12, and the support lead 13. In addition, by half-etching the front surface side of the metal substrate 31, a gap is formed between the die pad 11 and the lead portion 12, and the back surface side resin 18 is exposed on the front surface side.

Next, in substantially the same manner as in the process shown in FIG. 6(i) described above, the etching resist layer 32B is peeled off and then the metal substrate 31 is washed with water and dried (FIG. 9(j)).

Then, in a manner similar to the process shown in FIG. 6(j) described above, a plating layer 25 is formed on the inner lead 51 of the lead portion 12. In this manner, the lead frame 10 shown in FIGS. 1 to 3 is obtained (FIG. 6(k)).

According to this modified example, a process of forming etching resist layers 32A and 33A for etching the back side of the metal substrate 31 (FIG. 9(b)) and a process of forming etching resist layer 32B for etching the front side of the metal substrate 31 (FIG. 9(i)) are performed separately. As a result, the etching resist layer 32B is formed immediately before etching, and advance surface preparation can be reliably performed, allowing a stable etching resist layer 32B to be formed.

Second Embodiment
Next, a second embodiment will be described with reference to Figures 10 to 13. Figures 10 to 13 are diagrams showing the second embodiment. The second embodiment shown in Figures 10 to 13 differs mainly in that the back surface side resin 18 protrudes further toward the back surface side (Z direction minus side) than the die pad back surface 11b of the die pad 11 and the external terminals 17 of the lead portion 12, and other configurations are substantially the same as those of the first embodiment described above. In Figures 10 to 13, the same parts as those of the first embodiment shown in Figures 1 to 9 are denoted by the same reference numerals, and detailed description thereof will be omitted.

(Structure of lead frame and semiconductor device)
FIG. 10 is a cross-sectional view showing a lead frame 10A according to the present embodiment, and FIG. 11 is a cross-sectional view showing a semiconductor device 20A according to the present embodiment.

In the lead frame 10A shown in FIG. 10 and the semiconductor device 20A shown in FIG. 11, the back surface side resin 18 protrudes toward the back surface side (negative side in the Z direction) beyond the die pad back surface 11b of the die pad 11 and the external terminals 17 of the lead portion 12. In other words, the resin back surface 18b of the back surface side resin 18, the die pad back surface 11b, and the external terminals 17 are not on the same plane, and the resin back surface 18b is located toward the back surface side (negative side in the Z direction) beyond the die pad back surface 11b and the external terminals 17.

Figure 12 shows the state in which the semiconductor device 20A according to this embodiment is connected to the wiring board 80. At this time, the external terminals 17 of the lead portion 12 and the die pad back surface 11b of the die pad 11 are each connected to the wiring board 80 by solder parts 81. In this embodiment, the back surface side resin 18 protrudes toward the back surface side beyond the die pad back surface 11b of the die pad 11 and the external terminals 17 of the lead portion 12. This makes it possible to prevent short-circuiting between the solder parts 81 provided on adjacent external terminals 17, or between the solder part 81 provided on the die pad back surface 11b and the solder part 81 provided on the external terminal 17.

(Lead frame manufacturing method)
Next, a method for manufacturing the lead frame 10A shown in Fig. 10 will be described with reference to Figs. 13(a) to 13(j). In Figs. 13(a) to 13(j), the same parts as those in Figs. 6(a) to 6(i) are designated by the same reference numerals and detailed description thereof will be omitted.

First, a metal substrate 31 is prepared (FIG. 13(a)) in a manner similar to the steps shown in FIGS. 6(a) and 6(b) described above, and etching resist layers 32 and 33 are formed on the front and back of the metal substrate 31, respectively (FIG. 13(b)).

Next, in a manner similar to the process shown in FIG. 6(c) described above, the metal substrate 31 is thinned from the rear side of the metal substrate 31 to the middle of the thickness direction by half etching, forming the rear side recess 36. Next, in a manner similar to the process shown in FIG. 6(d) described above, the etching resist layer 33 on the rear side is peeled off and removed (FIG. 13(c)).

Next, a mark 37A is formed on the portion of the metal substrate 31 other than the rear recess 36, i.e., on the exposed metal surface that is not half-etched (FIG. 13(d)). Specifically, the mark 37A is formed on the entire area of the portion 11e corresponding to the rear surface 11b of the die pad 11, and on the entire area of the portion 17a corresponding to the external terminal 17 of the lead portion 12. The thickness of the mark 37A may be, for example, more than 1 μm and not more than 50 μm.

Next, in a manner similar to the process shown in FIG. 6(f) described above, a back surface resin 18 is formed on the back surface of the metal substrate 31, and the back surface recess 36 and the mark 37A are covered with the back surface resin 18 (FIG. 13(e)).

Next, in a manner similar to the process shown in FIG. 6(g) described above, the metal substrate 31 is thinned from the front surface side to the middle of the thickness direction by half etching (FIG. 13(f)). This forms the outer shapes of the die pad 11, the lead portion 12, and the support lead 13. In addition, by half etching the front surface side of the metal substrate 31, a gap is formed between the die pad 11 and the lead portion 12, and the back surface resin 18 is exposed on the front surface side.

Next, the rear surface side resin 18 is polished to a predetermined thickness using the mark 37A as a reference (FIG. 13(g)). Specifically, the rear surface side resin 18 is polished from the rear surface side until the mark 37A appears. When it is confirmed that the mark 37A has appeared, the polishing of the rear surface side resin 18 is terminated. This allows the thickness of the rear surface side resin 18 to be polished to a substantially constant thickness. At this time, the mark 37A formed on the rear surface 11b of the die pad 11 and the mark 37A formed on the external terminal 17 of the lead portion 12 are exposed on the rear surface side. When the mark 37A appears, the polishing of the rear surface side resin 18 may be terminated immediately. This allows the amount of protrusion of the rear surface side resin 18 from the rear surface 11b of the die pad 11 and the external terminal 17 of the lead portion 12 to be uniform when the mark 37A is removed as described below (FIG. 13(h)).

Next, the marks 37A are removed from the die pad back surface 11b of the die pad 11 and the external terminals 17 of the lead portions 12 (FIG. 13(h)). If the marks 37A are solder resist, they may be removed by peeling them off. This causes the die pad back surface 11b of the die pad 11 and the external terminals 17 of the lead portions 12 to be exposed to the outside. In addition, the back surface resin 18 protrudes from the die pad back surface 11b of the die pad 11 and the external terminals 17 of the lead portions 12. The amount of this protrusion can be approximately the same as the thickness of the marks 37A.

Next, in a manner similar to the process shown in FIG. 6(i) described above, the etching resist layer 32 is peeled off and then the metal substrate 31 is washed with water and dried (FIG. 13(i)).

Then, in a manner substantially similar to the process shown in FIG. 6(j) described above, a plating layer 25 is formed on the inner lead 51 of the lead portion 12. In this manner, the lead frame 10A shown in FIG. 10 is obtained (FIG. 6(j)).

In this embodiment, similarly to the manufacturing method of the lead frame 10 shown in Figures 8(a)-(j), the process of exposing the back surface side resin 18 to the front surface side by etching (Figure 13(f)) may be performed after the process of polishing the back surface side resin 18 (Figure 13(g)).

(Method of manufacturing a semiconductor device)
The method for manufacturing the semiconductor device 20A according to this embodiment can be performed in a manner substantially similar to the method for manufacturing the semiconductor device 20 shown in FIGS.

Third Embodiment
Next, a third embodiment will be described with reference to Fig. 14 to Fig. 19. Fig. 14 to Fig. 19 are diagrams showing the third embodiment. The third embodiment shown in Fig. 14 to Fig. 19 is different from the first embodiment in that the resin back surface 18b of the back surface side resin 18 is recessed toward the front surface side (positive side in the Z direction) from the die pad back surface 11b of the die pad 11 and the external terminals 17 of the lead portion 12, and other configurations are substantially the same as those of the first embodiment described above. In Fig. 14 to Fig. 19, the same parts as those of the first embodiment shown in Fig. 1 to Fig. 9 are denoted by the same reference numerals, and detailed description thereof will be omitted.

(Structure of lead frame and semiconductor device)
FIG. 14 is a cross-sectional view showing a lead frame 10B according to the present embodiment, and FIG. 15 is a cross-sectional view showing a semiconductor device 20B according to the present embodiment.

In the lead frame 10B shown in FIG. 14 and the semiconductor device 20B shown in FIG. 15, the back surface side resin 18 is recessed toward the front surface side (positive side in the Z direction) from the die pad back surface 11b of the die pad 11 and the back surface (external terminal 17) of the lead portion 12. That is, the resin back surface 18b, the die pad back surface 11b, and the external terminal 17 are not on the same plane, and the resin back surface 18b is located toward the front surface side (positive side in the Z direction) from the die pad back surface 11b and the external terminal 17. In other words, the die pad 11 and the terminal portion 53 protrude toward the back surface side (negative side in the Z direction) from the resin back surface 18b of the back surface side resin 18. The second die pad side surface 11d of the die pad 11 and the side surface 53a of the terminal portion 53 are partially or entirely exposed to the outside.

In this embodiment, the thickness T2 of the back side resin 18 may be 30 μm or more and 90 μm or less, and preferably 45 μm or more and 75 μm or less. The thickness T2 of the back side resin 18 is a length measured in the Z direction (thickness direction), and refers to the length measured at the thickest part of the back side resin 18. The distance T3 by which the back side resin 18 is recessed from the back side may be 25 μm or more and 50 μm or less, and preferably 30 μm or more and 45 μm or less. By setting the distance T3 to 25 μm or more, the effect of self-alignment described later is easily achieved. By setting the distance T3 to 50 μm or less, the back side resin 18 can reliably block the gap between the die pad 11 and the lead portion 12, and it is possible to prevent a gap from occurring between the die pad 11 and the lead portion 12. The distance T3 refers to the length measured in the Z direction (thickness direction) between the resin back surface 18b of the back side resin 18, the die pad back surface 11b, and the external terminal 17.

The planar shape and bottom shape of the lead frame 10B shown in FIG. 14 may be substantially the same as the planar shape and bottom shape of the lead frame 10 shown in FIG. 1 and FIG. 2, respectively. The planar shape of the semiconductor device 20B shown in FIG. 11 may be substantially the same as the planar shape of the semiconductor device 20 shown in FIG. 4. Although not shown in FIG. 14 and FIG. 15, the front and back surfaces of the die pad 11 and the lead portion 12 each have rolling marks that were generated when the metal substrate 31 was rolled (see FIG. 2).

(Lead frame manufacturing method)
Next, a method for manufacturing the lead frame 10B shown in Fig. 14 will be described with reference to Figs. 16(a) to 16(j). In Figs. 16(a) to 16(j), the same parts as those in Figs. 6(a) to 6(i) are given the same reference numerals and detailed description thereof will be omitted.

First, a metal substrate 31 is prepared (FIG. 16(a)) in a manner similar to the steps shown in FIGS. 6(a) and 6(b) described above, and etching resist layers 32 and 33 are formed on the front and back of the metal substrate 31, respectively (FIG. 16(b)).

Next, in a manner similar to the process shown in FIG. 6(c) described above, the metal substrate 31 is thinned from the rear side of the metal substrate 31 to the middle of the thickness direction by half etching, forming a rear side recess 36. Next, in a manner similar to the process shown in FIG. 6(d) described above, the etching resist layer 33 on the rear side is peeled off and removed (FIG. 16(d)).

Next, in a manner similar to the process shown in FIG. 6(e) described above, a mark 37 is formed on the portion of the metal substrate 31 other than the rear recess 36, i.e., on the exposed metal surface that is not half-etched (FIG. 16(e)). Specifically, the mark 37 may be formed on the portion 11e corresponding to the rear surface 11b of the die pad 11 and the portion 17a corresponding to the external terminal 17 of the lead portion 12.

Next, the back side resin 18 is formed on the back side of the metal substrate 31, and the back side recess 36 and the mark 37 are covered with the back side resin 18 (FIG. 16(f)). At this time, the back side resin 18 may be formed on the back side of the metal substrate 31 by a printing method such as screen printing. In this way, the back side resin 18 is formed in a part of the back side recess 36 in the thickness direction (Z direction). The back side resin 18 filled in the back side recess 36 is recessed toward the front side (positive side of the Z direction) from the part 11e corresponding to the die pad back surface 11b of the die pad 11 and the part 17a corresponding to the external terminal 17 of the lead portion 12.

As described above, the thickness T2 of the back side resin 18 filled in the back side recess 36 may be 30 μm or more and 90 μm or less, and preferably 45 μm or more and 75 μm or less. The distance T3 by which the back side resin 18 is recessed from the back side may be 25 μm or more and 50 μm or less, and preferably 30 μm or more and 45 μm or less. The thickness T4 of the back side resin 18 from the portion 11e corresponding to the die pad back side 11b may be 25 μm or more and 50 μm or less. The thickness T4 may be equal to the thickness T2 described above. This thickness T4 is thicker than the thickness of the mark 37, and the mark 37 is completely covered by the back side resin 18. The thickness T4 of the back side resin 18 may be thinner than the thickness of the mark 37, in which case the mark 37 does not have to be covered by the back side resin 18.

Next, in a manner similar to the process shown in FIG. 6(g) described above, the metal substrate 31 is thinned from the front surface side to the middle of the thickness direction by half etching (FIG. 16(g)). This forms the outer shapes of the die pad 11, the lead portion 12, and the support lead 13. In addition, by half etching the front surface side of the metal substrate 31, a gap is formed between the die pad 11 and the lead portion 12, and the back surface resin 18 is exposed on the front surface side.

Next, in a manner similar to the process shown in FIG. 6(h) described above, the back side resin 18 is polished to a predetermined thickness using the mark 37 as a reference (FIG. 16(h)). Specifically, the back side resin 18 is polished from the back side, and after the mark 37 appears, the back side resin 18 is polished until the mark 37 disappears. When it is confirmed that the mark 37 has disappeared, the polishing of the back side resin 18 is terminated. During this time, the back side resin 18 filled in the back side recess 36 maintains the thickness T2 without being polished. Note that, if the mark 37 is not covered by the back side resin 18 from the beginning, the back side resin 18 is polished from the state where the mark 37 appears until the mark 37 disappears.

Next, in a manner similar to the process shown in FIG. 6(i) described above, the etching resist layer 32 is peeled off and removed, and then the metal substrate 31 is washed with water and dried (FIG. 16(i)).

Then, in a manner similar to the process shown in FIG. 6(j) described above, a plating layer 25 is formed on the inner lead 51 of the lead portion 12. In this manner, the lead frame 10B shown in FIG. 14 is obtained (FIG. 6(j)).

(Method of manufacturing a semiconductor device)
The method for manufacturing the semiconductor device 20B according to this embodiment can be performed in a manner substantially similar to the method for manufacturing the semiconductor device 20 shown in FIGS.

Figure 17 shows the state in which the semiconductor device 20B according to this embodiment is connected to the wiring board 80. At this time, the external terminals 17 of the lead portion 12 and the die pad back surface 11b of the die pad 11 are each connected to the wiring board 80 by the solder parts 81. At this time, cream-like solder called cream solder is first printed on the terminals of the wiring board 80, and the semiconductor device 20B is placed on top of it. Next, heat is applied to the wiring board 80 to melt the solder, and the terminals of the wiring board 80 are connected to the external terminals 17 and the die pad back surface 11b of the semiconductor device 20B by the molten solder (solder parts 81) (reflow soldering).

During this reflow soldering, the surface tension of the molten solder portion 81 automatically moves the semiconductor device 20B to the correct position on the wiring board 80 to correct any misalignment (self-alignment phenomenon). In this embodiment, the backside resin 18 is recessed toward the front side from the die pad back surface 11b of the die pad 11 and the external terminals 17 of the lead portion 12. Therefore, during reflow soldering, the solder portion 81 wraps around the side surface 53a of the terminal portion 53 and the second die pad side surface 11d of the die pad 11. This makes it possible to more effectively utilize the self-alignment phenomenon described above.

(First Modification of Lead Frame Manufacturing Method)
Next, a first modified example of the manufacturing method of the lead frame 10B according to the present embodiment will be described with reference to Figures 18(a)-(j). In the modified example shown in Figures 18(a)-(j), the step of exposing the back surface side resin 18 to the front surface side is performed after the step of polishing the back surface side resin 18, and the other configurations are substantially the same as the manufacturing method of the lead frame 10B shown in Figures 16(a)-(j). In Figures 18(a)-(j), the same parts as those in Figures 6(a)-(j), Figures 8(a)-(j), and Figures 16(a)-(j) are given the same reference numerals and detailed description will be omitted.

First, a metal substrate 31 is prepared (FIG. 18(a)) in a manner similar to the process shown in FIGS. 16(a) and 16(b) described above, and etching resist layers 32 and 33 are formed on the front and back of the metal substrate 31 (FIG. 18(b)).

Next, in a manner similar to the process shown in FIG. 16(c) described above, the metal substrate 31 is thinned from the rear surface side of the metal substrate 31 to the middle of its thickness direction by half etching, forming a rear surface recess 36 (FIG. 18(c)).

Next, in a manner similar to the steps shown in Figures 16(d) and (e), the etching resist layer 33 on the back side is peeled off and removed (Figure 18(d)), and a mark 37 is formed on the metal substrate 31 in the area other than the back side recess 36 (Figure 18(e)).

Next, in a manner similar to the process shown in FIG. 16(f), the back side resin 18 is formed on the back side of the metal substrate 31, and the back side recess 36 and the mark 37 are covered by the back side resin 18 (FIG. 18(f)). At this time, the back side resin 18 is formed in a part of the back side recess 36 in the thickness direction (Z direction). The back side resin 18 filled in the back side recess 36 is recessed toward the front side (positive side of the Z direction) from the part 11e corresponding to the die pad back surface 11b of the die pad 11 and the part 17a corresponding to the external terminal 17 of the lead portion 12.

Next, in a manner similar to the process shown in FIG. 16(h), the back surface side resin 18 is polished to a predetermined thickness using the mark 37 as a reference (FIG. 18(g)). Specifically, the back surface side resin 18 is polished from the back surface side until the mark 37 disappears. When it is confirmed that the mark 37 has disappeared, the polishing of the back surface side resin 18 is terminated. At this time, the portion 11e corresponding to the die pad back surface 11b of the die pad 11 and the portion 17a corresponding to the external terminal 17 of the lead portion 12 are each exposed on the back surface side.

Next, in a manner similar to the process shown in FIG. 16(g), the metal substrate 31 is thinned from the front surface side to the middle of the thickness direction by half etching (FIG. 18(h)). This forms the outer shapes of the die pad 11, lead portion 12, and support lead 13. In addition, by half-etching the front surface side of the metal substrate 31, a gap is formed between the die pad 11 and the lead portion 12, and the back surface resin 18 is exposed to the front surface side.

Next, in a manner similar to the process shown in FIG. 16(i), the etching resist layer 32 is peeled off and then the metal substrate 31 is washed with water and dried (FIG. 18(i)).

Then, in a manner similar to the process shown in FIG. 16(j), a plating layer 25 is formed on the inner lead 51 of the lead portion 12. In this manner, the lead frame 10B shown in FIG. 14 is obtained (FIG. 18(j)).

According to this modified example, the process of exposing the back surface side resin 18 to the front surface side by etching (FIG. 18(h)) is performed after the process of polishing the back surface side resin 18 (FIG. 18(g)). This makes it possible to suppress deformation of the lead frame 10B.

(Second Modification of Lead Frame Manufacturing Method)
Next, a second modified example of the method for manufacturing the lead frame 10B according to the present embodiment will be described with reference to Figures 19(a)-(k). In the modified example shown in Figures 19(a)-(k), a process for forming etching resist layers 32A and 33A for etching the back side of the metal substrate 31 and a process for forming an etching resist layer 32B for etching the front side of the metal substrate 31 are separately performed. The other configurations are substantially the same as those of the method for manufacturing the lead frame 10B shown in Figures 16(a)-(j). In Figures 19(a)-(k), the same parts as those in Figures 6(a)-(j), Figures 9(a)-(k) and Figures 16(a)-(j) are denoted by the same reference numerals, and detailed description thereof will be omitted.

First, prepare a metal substrate 31 (Figure 19(a)) in a manner similar to the process shown in Figure 16(a) described above.

Next, in a manner similar to the process shown in FIG. 16(b) described above, photosensitive resist is applied to the entire front and back surfaces of the metal substrate 31 and then dried. The photosensitive resist on the metal substrate 31 is then exposed through a photomask and developed to form an etching resist layer 32A on the front surface side that does not have any openings, and an etching resist layer 33A on the back surface side that has the desired openings 33c (FIG. 19(b)).

Next, in a manner similar to the process shown in FIG. 16(c) described above, the metal substrate 31 is thinned from the back side of the metal substrate 31 to the middle of the thickness direction by half etching, forming a back side recess 36 (FIG. 19(c)). In this case, the back side etching resist layer 33A is used as a corrosion-resistant film, and the back side of the metal substrate 31 is etched with a etchant. Note that the front side of the metal substrate 31 is not etched because it is covered by the etching resist layer 32A, which does not have an opening.

Next, the etching resist layer 32A on the front side and the etching resist layer 33A on the back side are peeled off and removed (Figure 19 (d)).

Next, in a manner similar to the process shown in FIG. 16(e) described above, a mark 37 is formed on the metal substrate 31 in a portion other than the recess 36 on the rear side (FIG. 19(e)).

Next, in a manner similar to the process shown in FIG. 16(f) described above, the back side resin 18 is formed on the back side of the metal substrate 31, and the back side recess 36 and the mark 37 are covered by the back side resin 18 (FIG. 19(f)). At this time, the back side resin 18 is formed in a part of the back side recess 36 in the thickness direction (Z direction). The back side resin 18 filled in the back side recess 36 is recessed toward the front side (positive side of the Z direction) from the part 11e corresponding to the die pad back surface 11b of the die pad 11 and the part 17a corresponding to the external terminal 17 of the lead portion 12.

Next, in a manner similar to the process shown in FIG. 16(h) described above, the back surface side resin 18 is polished to a predetermined thickness using the mark 37 as a reference (FIG. 19(g)). Specifically, the back surface side resin 18 is polished from the back surface side until the mark 37 disappears. When it is confirmed that the mark 37 has disappeared, polishing of the back surface side resin 18 is terminated. At this time, the portion 11e corresponding to the die pad back surface 11b of the die pad 11 and the portion 17a corresponding to the external terminal 17 of the lead portion 12 are each exposed on the back surface side.

Next, a surface-side etching resist layer 32B having the desired openings 32c is formed on the surface of the metal substrate 31 (FIG. 19(h)). In this case, a photosensitive resist is applied to the entire surface of the metal substrate 31 and then dried. Next, the metal substrate 31 is exposed to light through a photomask and developed to form the surface-side etching resist layer 32B.

Next, in a manner similar to the process shown in FIG. 16(g) described above, the metal substrate 31 is thinned from the front surface side to the middle of the thickness direction by half etching (FIG. 19(i)). In this case, the front surface side etching resist layer 32B is used as a corrosion-resistant film, and etching is performed with a corrosive liquid on the front surface side of the metal substrate 31. This forms the outlines of the die pad 11, the lead portion 12, and the support lead 13. In addition, by half-etching the front surface side of the metal substrate 31, a gap is formed between the die pad 11 and the lead portion 12, and the back surface side resin 18 is exposed on the front surface side.

Next, in substantially the same manner as in the process shown in FIG. 16(i) described above, the etching resist layer 32B is peeled off and then the metal substrate 31 is washed with water and dried (FIG. 19(j)).

Then, in a manner similar to the process shown in FIG. 16(j) described above, a plating layer 25 is formed on the inner lead 51 of the lead portion 12. In this manner, the lead frame 10B shown in FIG. 14 is obtained (FIG. 16(k)).

According to this modified example, a process of forming etching resist layers 32A and 33A for etching the back side of the metal substrate 31 (FIG. 19(b)) and a process of forming etching resist layer 32B for etching the front side of the metal substrate 31 (FIG. 19(i)) are performed separately. As a result, the etching resist layer 32B is formed immediately before etching, and a preliminary surface preparation process can be reliably performed to form a stable etching resist layer 32B.

The components disclosed in each of the above embodiments and modifications may be combined as necessary. Alternatively, some components may be deleted from all the components shown in each of the above embodiments and modifications.

REFERENCE SIGNS LIST 10 Lead frame 10a Package area 11 Die pad 12 Lead portion 15 Internal terminal 17 External terminal 18 Back surface resin 20 Semiconductor device 21 Semiconductor element 22 Bonding wire (connecting member)
23 Sealing resin 24 Adhesive 25 Plating layer 31 Metal substrate 36 Back surface recess 37 Mark

Claims (13)

In a method for manufacturing a lead frame,
Providing a metal substrate;
forming a back surface recess by etching the metal substrate from a back surface side to a middle of a thickness direction;
forming a mark on a portion of the metal substrate other than the rear surface side recess;
forming a back surface side resin on a back surface side of the metal substrate, and covering the back surface side recess and the mark with the back surface side resin;
a step of polishing the back surface side resin to a predetermined thickness using the mark as a reference;
A method for manufacturing a lead frame, comprising a process for etching the metal substrate from the front surface side to halfway through the thickness direction, either before or after the process for polishing the rear surface side resin, thereby exposing the rear surface side resin to the front surface side. The method for manufacturing a lead frame according to claim 1, wherein in the step of polishing the backside resin, after the mark appears, the backside resin is polished until the mark disappears. The method for manufacturing a lead frame according to claim 1, wherein in the step of polishing the back side resin, the back side resin is polished until the mark appears. The method for manufacturing a lead frame according to claim 3, wherein the mark is removed after the step of polishing the back side resin. In a method for manufacturing a lead frame,
Providing a metal substrate;
forming a back surface recess by etching the metal substrate from a back surface side to a middle of a thickness direction;
forming a mark on a portion of the metal substrate other than the rear surface side recess;
forming a back surface side resin on a back surface side of the metal substrate, the back surface side resin being formed on a part of the back surface side recess in a thickness direction;
a step of polishing the back surface side resin to a predetermined thickness using the mark as a reference;
A method for manufacturing a lead frame, comprising a process for etching the metal substrate from the front surface side to halfway through the thickness direction, either before or after the process for polishing the rear surface side resin, thereby exposing the rear surface side resin to the front surface side. The method for manufacturing a lead frame according to claim 5, wherein in the step of polishing the back side resin, the back side resin is polished until the mark disappears. The method for manufacturing a lead frame according to any one of claims 1 to 5, wherein the mark is a solder resist. The method for manufacturing a lead frame according to any one of claims 1 to 7, wherein the step of exposing the back side resin to the front side is performed before the step of polishing the back side resin. The method for manufacturing a lead frame according to any one of claims 1 to 7, wherein the step of exposing the back side resin to the front side is performed after the step of polishing the back side resin. In the lead frame,
A die pad;
a lead portion disposed around the die pad;
a back surface side resin disposed around the die pad and the lead portion on a back surface side of the lead frame,
a rear surface of the rear surface-side resin, a rear surface of the die pad, and a rear surface of the lead portion are located on the same plane;
A lead frame, wherein rolling marks are present on a surface of the die pad, a surface of the lead portion, a rear surface of the die pad, and a rear surface of the lead portion. In the lead frame,
A die pad;
a lead portion disposed around the die pad;
a back surface side resin disposed around the die pad and the lead portion on a back surface side of the lead frame,
the back surface side resin protrudes toward the back surface side beyond the die pad and the lead portion,
A lead frame, wherein a thickness of the back surface side resin protruding from the back surface of the die pad and the back surfaces of the lead portions is more than 1 μm and 50 μm or less. In the lead frame,
A die pad;
a lead portion disposed around the die pad;
a back surface side resin disposed around the die pad and the lead portion on a back surface side of the lead frame,
a back surface of the back surface-side resin is located closer to the front surface than a back surface of the die pad and back surfaces of the lead portions;
A lead frame, wherein rolling marks are present on the rear surface of the die pad and on the rear surfaces of the lead portions. In a method for manufacturing a semiconductor device,
Providing a lead frame according to any one of claims 10 to 12 ;
mounting a semiconductor element on the lead frame;
a step of electrically connecting the semiconductor element and the lead frame with a connecting member;
and sealing the lead frame, the semiconductor element, and the connecting member with a sealing resin.

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