SUPPORT AND/OR CLIP FOR SEMICONDUCTOR ELEMENTS, SEMICONDUCTOR COMPONENT, AND PRODUCTION METHOD

Abstract

The invention relates to a support and/or clip for at least one semiconductor element with at least one functional surface (10) for connecting to the semiconductor element. The invention is further characterized by at least one solder resist cavity (12) with at least one flank wall (13), in particular a straight flank wall (13), and a delimiting edge (14) which adjoins the flank wall (13) and delimits the functional surface (10) at least on one side. The delimiting edge (14) forms a protrusion (15) which protrudes past the functional surface (10) in order to retain solder, and/or the flank wall (13) forms an undercut (16) for retaining solder at the delimiting edge (14).

Claims

1. A support for a semiconductor element, the support comprising: a functional surface for connecting to the semiconductor element; at least one solder resist cavity comprising a flank wall and a delimiting edge, the delimiting edge adjoining the flank wall and delimiting the functional surface on a first edge of the functional surface; wherein the delimiting edge forms a protrusion, the protrusion protruding past the functional surface for holding back solder, or wherein the flank wall comprises an undercut for holding back solder at the delimiting edge.

2. The support as claimed in claim 1, wherein a depth of the at least one solder resist cavity ranges from 10% to 80% of a thickness of the support.

3. The support as claimed in claim 1, wherein a width of the at least one solder resist cavity ranges from 0.05 mm to 2 mm.

4. The support as claimed in claim 1, wherein a height of the protrusion ranges from 5% to 80% of a thickness of the support.

5. The support as claimed in claim 1, wherein the at least one solder resist cavity comprises a first base side and a second base side, the second base side being longer than the first base side, and wherein the first solder resist cavity comprises a trapezoidal cross section, wherein the second base side is an opening of the trapezoidal cross-section.

6. The support as claimed in claim 1, wherein the at least one solder resist cavity is a plurality of solder resist cavities, wherein a first solder resist cavity is arranged side-by-side in parallel to a second solder resist cavity on a same side of the functional surface. wherein the delimiting edge is formed at the first solder resist cavity, the solder resist cavity directly bordering the functional surface.

7. The support as claimed in claim 1, wherein the at least one solder resist cavity is a plurality of solder resist cavities, wherein a first solder resist cavity is arranged on opposite side of the functional surface to a second solder resist cavity, wherein the delimiting edge is formed at the first solder resist cavity, the solder resist cavity directly bordering the functional surface.

8. The support as claimed in claim 1, wherein an acute angle between a reference plane perpendicular to the support and the flank wall of the undercut ranges from 5 to 45.

9. The support as claimed in claim 1, wherein the delimiting edge of the flank wall of the undercut forms a bead-free, sharp edge.

10. The support as claimed in claim 1, wherein the delimiting edge of the flank wall of the undercut forms the protrusion.

11. The support as claimed in claim 1, wherein at least one solder resist cavity is embossed or stamped or laser-cut or milled.

12. In combination, a semiconductor component and a support, the combination comprising: the semiconductor component comprising a device edge, and the support comprising a functional surface for connecting to the semiconductor element; at least one solder resist cavity comprising a flank wall and a delimiting edge, the delimiting edge adjoining the flank wall and delimiting the functional surface on a first edge of the functional surface; wherein the delimiting edge forms a protrusion, the protrusion protruding past the functional surface for holding back solder, or wherein the flank wall comprises an undercut for holding back solder at the delimiting edge. wherein the device edge of the semiconductor element lies against the delimiting edge of the at least one solder resist cavity or wherein the device edge of the semiconductor element is arranged at a distance from the at least one solder resist cavity.

13. A method of making a support for a semiconductor element the support being structured, the method comprising the steps of: stamping the support to having a functional surface for connecting to the semiconductor element; using a punch, embossing or stamping into at least one side of the support at least one solder resist cavity with a delimiting edge, the punch forming a protrusion at the delimiting edge from the material of the support, or using a laser cutter, cutting at least on one side of the functional surface at least one solder resist cavity with a flank wall, wherein the laser cutter is angled to form an undercut at the flank wall, or using a punch, embossing or stamping into the support at least on one side of the functional surface at least one solder resist cavity with a flank wall, a plunging angle of the punch being set in such a way that the flank wall forms an undercut, or milling at least one solder resist cavity into the support.

14. The method as claimed in claim 13, wherein after embossing or stamping or milling of the solder resist cavity using the punch, the protrusion is formed at the delimiting edge, a forming cavity is embossed or stamped into the support next to the delimiting edge and displaces the delimiting edge and a flank wall of the solder resist cavity extending from the delimiting edge to form the undercut.

15. The support as claimed in claim 1, wherein the flank wall is planar.

16. The support as claimed in claim 1, wherein a depth of the at least one solder resist cavity is from 30% to 50% of a thickness of the support.

17. The support as claimed in claim 1, wherein a width of the solder resist cavity ranges from 0.3 mm to 1.2 mm.

18. The support as claimed in claim 1, wherein a height of the protrusion ranges from 10% to 30% of the thickness of the support.

19. The support as claimed in claim 1, wherein the at least one solder resist cavity a wedge-shaped cross section.

20. The support as claimed in claim 1, wherein an acute angle between a reference plane perpendicular to the support and the flank wall of the undercut ranges from 10 to 30.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The invention will be explained in greater detail hereinafter on the basis of exemplary embodiments with further details with reference to the accompanying schematic drawings, in which:

[0037] FIG. 1a shows a plan view of a support in accordance with an exemplary embodiment according to the invention with a trapezoidal solder resist cavity;

[0038] FIG. 1b shows a side view of the support according to FIG. 1a;

[0039] FIG. 2a shows a plan view of a support in accordance with an exemplary embodiment according to the invention with a wedge-shaped solder resist cavity;

[0040] FIG. 2b shows a side view of the support according to FIG. 2a;

[0041] FIG. 3 shows a detailed view of the protrusion at the delimiting edge of the solder resist cavity;

[0042] FIG. 4a shows a variant of the support according to FIG. 2a, in which a plurality of solder resist cavities are provided;

[0043] FIG. 4b shows a side view of the support according to FIG. 4a;

[0044] FIG. 5a shows step 1 of the production of the undercut of the solder resist cavity;

[0045] FIG. 5b shows step 2 of the production of the undercut of the solder resist cavity; and

[0046] FIG. 6 shows an alternative method of producing the undercut of the solder resist cavity.

DETAILED DESCRIPTION OF THE INVENTION

[0047] FIGS. 1a and 1b show a support, i.e. a lead frame for a semiconductor element, which has a functional surface 10 (on the right-hand side in FIGS. 1a and 1b), which is intended for connecting to a semiconductor element. The functional surface is connected to the semiconductor element by soldering. The surface of the semiconductor element is the same size as the functional surface 10 or slightly smaller. The semiconductor element is thus prevented from protruding past the functional surface 10 into the region of the solder resist cavity 12. The solder resist cavity 12 delimits the functional surface 10 and forms an effective barrier against the undesirable flow of the liquid solder.

[0048] For this purpose, the solder resist cavity 12 has a straight flank wall 13, specifically two straight flank walls 13, which are each inclined. The cross section of the solder resist cavity is trapezoidal, wherein the longer base line of the trapezoidal solder resist cavity 12 forms the opening thereof. In other words, the solder resist cavity 12 tapers. The transition from the right-hand flank 13 in FIGS. 1a and 1b to the functional surface 10 is formed by the delimiting edge 14, which adjoins the flank wall 13 and delimits the functional surface 10 on one side.

[0049] The objective of the cavity is primarily to form the delimiting edge 14 during production of the cavity so that said delimiting edge acts as a barrier for the solder. This does not rule out the fact that the cavity acts as a second barrier for the solder and can fill with solder in part. However, a situation in which the solder overcomes the delimiting edge 14 is to be avoided.

[0050] A variant of the solder resist cavity 12 is illustrated in FIGS. 2a and 2b, in which the cavity 12 has a wedge-shaped cross section. This cross section also has two inclined flanks, which taper to a point in the base of the cavity 12, as can be clearly seen in FIG. 2b. The delimiting edge 14 at the flank wall 13 shown on the right-hand side in FIG. 2b at the same time delimits the functional surface 10 on one side.

[0051] The retaining function of the delimiting edge 14 is achieved by a protrusion, specifically by a bead 15, which is raised on the delimiting edge 14 by the embossing of the solder resist cavity 12. As can be clearly seen in FIG. 3, the bead 15 or generally the protrusion 15 protrudes past the functional surface 10 and thus forms a barrier, which effectively holds back the solder in the region of the functional surface 10. The height of the barrier or bead 15 is determined by the forming process. The more material that is displaced during the embossing, the higher the bead 15 or the protrusion. The bead 15 is not removed in exemplary embodiments 1-2, but is an important feature of the final support or lead frame.

[0052] All the features according to FIGS. 1a, 1b and 2a, 2b are also disclosed and claimed in conjunction with a clip for a semiconductor element.

[0053] The clip, similarly to the bonding wires, serves to electrically connect the semiconductor element in a suitable manner. The semiconductor element and the clip are connected by soldering, as is also the case with the support. The solder resist disclosed and described in conjunction with the support is therefore also disclosed and described in conjunction with the clip.

[0054] A variant of the solder resist cavity according to FIGS. 2a, 2b is illustrated in FIGS. 4a and 4b. The difference from FIG. 2a lies in the fact that in FIG. 2a a single solder resist cavity 12 is provided, which delimits the functional region 10, whereas in FIGS. 4a and 4b a number of wedge-shaped solder resist cavities 12 are provided on the same side of the functional region 10 and border one another in a sawtooth-shaped manner. The security against undesirable flow of the solder is thus further increased.

[0055] A further possibility of the solder resist cavity 12 is illustrated in FIGS. 5a and 5b. Here, an undercut 16 is formed in the support or in the clip. An undercut is understood to mean a depth profile which has an upper edge, i.e. the delimiting edge 14, which in relation to a vertical plane protrudes further than a lower edge, specifically the edge at the transition to the base of the cavity 12. In other words, the inclined flank 13 at the delimiting edge 14 protrudes back and shadows the region of the solder resist cavity 12 directly below the delimiting edge 14. A sharp-edged transition from the functional surface 10 to the inclined flank wall 13 adjacent to the functional surface 10 can thus be formed, as illustrated in the example according to FIG. 6.

[0056] Alternatively, as is made possible by the method steps according to FIGS. 5a and 5b, a bead can be formed at the delimiting edge 14 of the undercut 16. For this purpose, a solder resist cavity 16 having a trapezoidal cross section (see also FIGS. 1a and 1b) is impressed in the support in the first step according to FIG. 5a. In so doing, the bead shown in FIG. 3 is formed at the delimiting edge 14 toward the functional surface 10. In the second step according to FIG. 5b, a forming cavity 17 is made in the support close to the delimiting edge 14. The forming cavity 17 displaces the material between the forming cavity and the delimiting edge 14 of the solder resist cavity 12. This results in a movement of the delimiting edge 14 inclusive of the inclined flank wall adjoining the delimiting edge 14, such that said flank wall is urged inwardly into the solder resist cavity 16. The originally outwardly inclined flank wall 13 (see FIG. 5a) is shifted back by the urging effect of the forming cavity 17 and is inclined, as can be seen in FIG. 5b, inwardly into the solder resist cavity 12. The above-explained undercut is thus formed.

[0057] An alternative possibility for producing the undercut is shown in FIG. 6. An inclined punch 18 is used for this purpose, which plunges into the support at an angle in relation to the surface thereof. The acute punch 18 impresses the desired solder resist cavity 12 into the material of the support or the clip, forming the undercut 16 in the region of the tip of the punch. In this exemplary embodiment a particularly sharp delimiting edge 14 is formed. This is adjacent to the holding-down means 19, which prevents material from being raised in the region of the delimiting edge 14.

[0058] The above-explained method has the advantage that it can be combined easily and quickly with a stamping method for producing the support. For this purpose, the tools provided for the stamping can be converted so that, in a 2-step method, they first punch out the support and then in the next step form the desired embossing structure in the surface in order to form the solder resist or the solder resist cavity.

LIST OF REFERENCE SIGNS

[0059] 10 functional surface

[0060] 12 solder resist cavity

[0061] 13 flank wall

[0062] 14 delimiting edge

[0063] 15 protrusion/bead

[0064] 16 undercut

[0065] 17 forming cavity

[0066] 18 punch

[0067] 19 holding-down means