Manufacturing method for leadless semiconductor package component

Abstract

To provide a manufacturing method for a leadless semiconductor package component which improves bond strength of lead and a plastic molding material, improves airtightness of the package component, and improves stability and quality of a package unit.SOLUTION: In a manufacturing method for a leadless semiconductor package component, a chip is mounted on a metal frame, and the metal frame includes two short metal connection bars; an upper metal contact point and a lower metal contact point are electrically connected to respective two X direction connection metal bars, bonding or soldering is performed; plastic package molding is performed; a Y direction connection bar is cut by a first cutter so as to expose whole side surfaces of a plurality of metal contact points; solderable metal layers are applied to all the plurality of metal contact points that are exposed in an electric plating step; a plastic molding material is cut with a second cutter having a diameter smaller than a diameter of the first cutter; and one semiconductor package component is obtained.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to the technical field of semiconductor package components, and more particularly to the technical field of leadless semiconductor package components. [Background technology]

[0002] The Quad Flat No-lead Package (QFN) is an advanced package component that uses a conventional lead frame and is similar to the Chip Size Package (CSP). QFN uses dual or quad flat no-lead packaging technology with solder pads only on the bottom and two sides, and has the advantages of small volume, light weight, excellent heat dissipation, excellent electrical performance, and high reliability.

[0003] As shown in Figure 1, conventional metal-bonded (I / O contact) packages are typically singulated into the entire unit component by cutting after the packaging process. After singulation, component 1 exposes bare copper bottom surfaces 20 of leads 2 as metal contacts, and side surfaces 21 of leads 2 are flush with sidewalls 10 of component 1 as metal contacts. Current manufacturing processes only form a solder plating layer 3 on bottom surfaces 20 of leads 2 by electroplating. Therefore, when soldering a package unit to a circuit board 4, it is difficult to determine the soldering locations from the appearance of the package unit in this package configuration, where conventional pins are replaced with metal-bonded packages. In particular, the condition of the tin on bottom surface 20 can only be determined by perspective methods such as X-ray, and it is not possible to determine the quality of the soldering. Furthermore, because the metal contacts on side surfaces 21 of leads 2 are exposed to air, oxidation can cause solder wetting defects.

[0004] To address this issue, we wet the side 21 of the lead 2 with solder material to achieve creepage of the metal contacts on the side of the package unit. The current standard method involves first making a step cut on the lead frame, then electroplating the side of the lead frame where the step cut was made to create a creepage finish, as shown in Figure 2. After cutting, the solder material is applied to the metal contacts on the side 21 by electroplating, and finally, the lead frame is single-crystallized. The step cut on the lead 2 ensures electrical serial connection of the metal units, thereby maintaining complete electrical conductivity and facilitating electroplating. However, because the step cut or half cut is made on the side metal connection bar, the full creepage height of the side metal contacts is rarely achieved during the subsequent soldering process on the circuit board 4. The creepage height of the tin material 6 depends on the cut depth. Furthermore, because the side metal contacts are half-cut, there is a step on the side 21 of the lead 2. This can easily reduce the creepage height at the step when the package unit is soldered to the circuit board 4, potentially leaving air gaps 5 at the step.

[0005] A common method is to first cut the entire lead frame 300. To ensure that the exposed metal on the cut side is covered with solder material, an electroplating process is usually performed after cutting the lead frame 300, thereby covering the exposed metal with solder material. It is necessary to ensure that the exposed metal pads are in a series circuit. For example, as shown in the schematic diagram of conventional lead connection in FIG. 3 (U.S. Pat. No. 9,640,463), each lead 30 is connected to a metal connection bar 31 for connecting 16 leads 30 in series, and then connected to a surrounding metal frame 32, thereby allowing for the electroplating process. However, in this embodiment, the number of connection bars 31 depends on the number of leads 30, which imposes strict design constraints, complicates the manufacturing process, and reduces quality reliability.

[0006] Thus, in order to improve the electrical and thermal conductivity of the lead frame 300, effectively maximize the surface wettability of the side metal contacts, and ensure the reliability of the soldering process, an optimized cutting process and an improved design of the connection bars of the lead frame 300 are required. Summary of the Invention [Problem to be solved by the invention]

[0007] The present disclosure provides a method for manufacturing a leadless semiconductor package component, thereby ensuring the stability and soldering quality of the soldering process when soldering a package unit to a circuit board, allowing the package unit to be soldered more firmly, simplifying the inspection of soldering quality, reducing the inspection time and cost, and improving the competitiveness of the package unit, thereby solving the technical problems. [Means for solving the problem]

[0008] To solve the technical problem, the present disclosure uses a manufacturing method for a leadless semiconductor package component, which includes the following steps:

[0009] The chip is mounted on a metal frame, and the metal frame includes two Y-direction connecting metal bars and two X-direction connecting metal bars connected to each other, each of the two Y-direction connecting metal bars being electrically connected to a plurality of metal contacts, the plurality of metal contacts including at least an upper metal contact and a lower metal contact along the Y direction, and the upper metal contact and the lower metal contact are respectively connected to two short metal connecting bars, thereby being electrically connected to the two X-direction connecting metal bars.

[0010] Using a plastic molding material, a plastic package is molded onto a metal frame on which the chip is mounted.

[0011] The Y-direction connection bar is cut, and a portion of the plastic molding material is cut by a first cutter so that the Y-direction connection bar exposes the entire side surface of the plurality of metal contacts.

[0012] A solderable metal layer is applied to all of the plurality of metal contacts exposed by the electroplating process.

[0013] The plastic molding material is cut by a second cutter to obtain one semiconductor package unit, where the diameter of the second cutter is smaller than the diameter of the first cutter. [Effects of the Invention]

[0014] With the above technical solutions, the present disclosure has the following advantages:

[0015] According to the manufacturing method of the leadless semiconductor package component provided by the present disclosure, the metal contacts and the X-direction metal connection bars are connected to each other. Therefore, the metal pads can be formed by a half-etching process. In this way, on the one hand, the soldering area of ​​the wiring is enlarged. On the other hand, stepped notches can be formed in the metal pads and the metal on the bottom surface. This improves the bonding strength between the leads and the plastic molding compound, improves the hermeticity of the package component, and improves the stability and quality of the package unit.

[0016] Furthermore, all metal contacts are in a series circuit, and the front and rear surfaces of the chip fixed to the metal frame are connected on the metal frame via ribbons or clips. Thus, due to the equipotential principle, the front and rear surfaces of the chip are short-circuited during the electroplating process, providing ESD (Electrostatic Discharge) protection. Even though the electrical conduction on the metal frame along the X direction is cut off during the cutting process, the present disclosure further provides a clamp for rack plating to form a series electrical connection, thereby simplifying the electroplating process. [Brief explanation of the drawings]

[0017] The present disclosure will be better understood from the detailed description given herein below and the accompanying drawings.

[0018] [Figure 1] 1 is a schematic diagram showing a conventional package of a type of metal contact. [Figure 2] FIG. 1 is a schematic diagram showing electroplated tin material on the side where a conventional lead frame is cut. [Figure 3] FIG. 1 is a schematic diagram showing a conventional lead connection. [Figure 4] 1 is a flowchart illustrating a manufacturing process of the present disclosure. [Figure 5] 1 is a schematic diagram illustrating the wetting effect of side metal contacts of the present disclosure. [Figure 6] 1 is a structural schematic diagram of a metal frame of the present disclosure. FIG. [Figure 7] FIG. 1 is a schematic diagram of a backside structure showing the chip of the present disclosure mounted on a metal frame. [Figure 8] FIG. 2 is a schematic diagram of the rear structure of the package unit of the present disclosure. [Figure 9] FIG. 2 is a schematic diagram of the front structure of one packaging unit of the present disclosure. [Figure 10] FIG. 2 is a schematic diagram showing the current flow during the electroplating step of the present disclosure. [Figure 11] FIG. 10 is a cross-sectional view of the package unit of the present disclosure after plastic package molding has been performed. [Figure 12] 10 is a cross-sectional view showing a cut of a long connection bar in the Y direction of the present disclosure. FIG. [Figure 13] 1 is a cross-sectional view showing the first cutting step of the present disclosure completed; [Figure 14] 1 is a cross-sectional view showing a plastic molding compound of the present disclosure being cut. [Figure 15] FIG. 10 is a cross-sectional view showing the completed singulation of the present disclosure. [Figure 16] 1 is a cross-sectional view showing a cutting direction of a Y-direction connection bar according to the present disclosure. [Figure 17]1 is a cross-sectional view showing the cutting direction of a Y-direction plastic molding material, an X-direction metal connection bar, and a plastic molding material according to the present disclosure. [Figure 18] FIG. 1 is a top view of a metal frame according to a first embodiment of the present disclosure. [Figure 19] FIG. 19 is a schematic diagram of the metal frame of FIG. 18. [Figure 20] FIG. 10 is a top view of a metal frame according to a second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0019] In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are diagrammatically shown to simplify the drawings.

[0020] Please refer to Figure 4, which shows a schematic flow chart of the present disclosure. The present disclosure will be explained in further detail in conjunction with Figures 5-17 and specific embodiments.

[0021] 5, which is a cross-sectional view taken along the YZ plane. This is to ensure that the creepage height (Hc) covers the height of the side surface 510 of the lead 51. In the manufacturing method of the leadless semiconductor package component of the present disclosure, a wafer is placed in a cutting machine and divided into multiple chips using a diamond cutter, laser, or the like, and then the following steps are performed.

[0022] In step A, one chip 101 is mounted on a matrix-like metal frame 102, and the chip 101 is assembled to the matrix-like metal frame 102 via, for example, a bond, a solder bump, or the like.

[0023] In a specific embodiment, as shown in FIGS. 6, 7, and 9, a plurality of package units 200 are disposed on a matrix-like metal frame 102. The peripheral portion of the matrix-like metal frame 102 is not covered with a plastic molding material, and an edge metal frame 208 is exposed. The edge metal frame 208 has a frame shape, such as a rectangle or square, surrounding the matrix-like metal frame 102 and connects the X-direction connection bar 205 and the Y-direction connection bar 201. After the chips 101 are mounted one by one on the matrix-like metal frame 102, the Y-direction connection bar 201 is electrically connected to the chips 101 via left metal contacts (including the upper left metal contact 203 and the lower left metal contact 204) via ribbons or clips, thereby forming the package unit 200. In FIGS. 7, 9, and 10, the white portions indicate unetched portions of the matrix-like metal frame 102, the portions with dividing lines indicate etched portions of the matrix-like metal frame 102, and the gray dotted portions indicate hollow portions of the metal frame. The package unit 200 may also be called a semiconductor package component. The dotted line in Figure 9 indicates, for example, an outer edge 1050 of the package unit 200.

[0024] Referring now to FIG. 8 , a chip soldering area 207 is disposed inside the package unit 200. Four metal contacts, including a right-side metal contact 206 and a left-side metal contact, are disposed on the left and right sides of the chip soldering area 207. The right-side metal contact 206 is directly connected to the chip soldering area 207. The left-side metal contact includes three interconnected upper-left metal contacts 203 and one lower-left metal contact 204. A short metal connection bar 202 parallel to the Y-direction connection bar 201 is arranged to connect to the upper-left metal contact 203, and another short metal connection bar 202 is arranged to connect to the lower-left metal contact 204. The two short metal connection bars 202 electrically connect the two left-side metal contacts to the two X-direction connection bars 205, respectively. The upper-left metal contact 203 and the lower-left metal contact 204 are connected to the matrix-like metal frame 102 via the short metal connection bar 202 and the X-direction connection bar 205, respectively. With this design, even if the Y-direction connection bar 201 is cut, the two left metal contacts can still be electrically connected to the upper and lower X-direction connection bars 205 of the matrix-like metal frame 102 by the two short metal connection bars 202. The dotted lines in Figure 8 indicate, for example, the outline of the etched portion (shown as a cross-section line) of the Y-direction connection bar 201 of the matrix-like metal frame 102 in Figure 7.

[0025] 11 to 15 are cross-sectional views taken along the XZ plane, for example. For the process of mounting the chip 101 on the matrix-like metal frame 102, see FIGS. 11 and 7. First, the chip 101 is placed on the chip soldering area 207 on the front surface of the matrix-like metal frame 102, and the rear surface 101b of the chip 101 is bonded or soldered to the chip soldering area 207 of the matrix-like metal frame 102 through a bonding or soldering process. Preferably, as shown in FIG. 9, the front surface 101a of the chip 101 and the metal contacts are connected by bonding or soldering using connection structures such as clips 103 or ribbons 104.

[0026] In one embodiment, the clip 103 is preferably made of copper, and the ribbon 104 is preferably made of gold, silver, copper, aluminum, or an alloy. The ribbon 104 may be in the form of a ribbon or a band.

[0027] In the embodiment, the upper three metal contacts 203 on the upper left are further subjected to a half-etching technique to remove the upper portion of the matrix-like metal frame 102 and partially thin the matrix-like metal frame 102, thereby forming three metal pads with bottom connections. The half-etched matrix-like metal frame 102 can increase the bonding strength between the matrix-like metal frame 102 and the plastic molding compound 105 and reduce the risk of peeling of the package unit.

[0028] Step B: Using the plastic molding material 105, a plastic package is molded on the matrix-shaped metal frame 102 on which the chip 101 is mounted. Note that the plastic molding material 105 is not shown in FIGS.

[0029] 11 and 8. The plastic package is implemented on a matrix-shaped metal frame 102 to which the chip is soldered using a plastic molding compound 105, and each package unit 200 is entirely surrounded by the plastic molding compound 105. Each package unit 200 includes a chip 101, metal contacts (including an upper left metal contact 203, a lower left metal contact 204, and a right metal contact 206), a ribbon 104, and a clip 103. Plastic package molding involves injecting an encapsulant to complete the plastic package, completely surrounding the matrix-shaped metal frame 102, the chip soldering area 207, the Y-direction connection bar 201, and the X-direction connection bar 205 with the plastic molding compound 105. Only the periphery of the matrix-shaped metal frame 102 is not surrounded by the plastic molding compound, and the edge metal frame 208 is exposed to facilitate the subsequent cutting process. The plastic molding compound 105 can be epoxy resin, ABF resin, or other types of plastic molding compounds.

[0030] Step C: Cut the Y-direction connection bar 201 and cut a portion of the plastic molding compound 105 so as to expose the entire side surface of the metal contact.

[0031] 12, 13, and 16, a cutter 301 is used to cut the matrix-like metal frame 102 surrounded by the plastic molding material 105 in a direction from the bottom surface 102a of the matrix-like metal frame 102 toward the chip 101. A vertical cut is then made to cut the Y-direction connection bar 201 until a portion of the plastic molding material 105 is cut without cutting the plastic molding material 105, thereby forming a scribe line 106. The cut depth H2 is preferably equal to 1 / 3 of the body thickness H of the package unit 200, and the remaining thickness H3 is 2 / 3 of the body thickness H. This forms the scribe line 106 as a reference scribe line for the final singulation process. The cutter 301 cuts a portion of the plastic molding material 105, completely cutting the Y-direction connection bar 201 and forming a cutout 320 that allows the entire side surface of the Y-direction connection bar 201 to be exposed (see FIG. 7).

[0032] Step D applies a solderable metal layer 400 onto all exposed metal contacts, the rear and side surfaces of the matrix-like metal frame 102 by an electroplating process.

[0033] Referring to FIG. 10 , in step C, the Y-direction connection bar 201 is completely cut, and the three spaced-apart upper-left metal contacts 204 are electrically connected to the short metal connection bar 202, allowing the current flowing from the upper X-direction connection bar 205 to form a series circuit, thereby realizing horizontal and vertical electrical conduction through the upper-left metal contact 203. Additionally, the current flowing from the lower X-direction connection bar 205 flows to the lower-left metal contact 204 via the short metal connection bar 202, realizing horizontal and vertical electrical conduction. Furthermore, the four right-side metal contacts 206 located on the sides of the chip soldering area 207 can also receive current flowing from the X-direction connection bar 205, thereby completing electroplating. After the cutting process in step C, even after the electrical connection along the Y direction is severed, the left-side metal contacts remain electrically connected to the upper and lower X-direction connection bars 205 via the two short metal connection bars 202. Therefore, electrical conductivity between the left metal contact and other components is maintained as electroplating is performed by the current barrel, thereby ensuring that the solderable metal layer 400 is applied to all metal contacts, maintaining electrical conductivity. Also, for example, the positive electrode label in FIG. 10 corresponds to the negative electrode of the electroplating device, and the negative electrode label in FIG. 10 corresponds to the positive electrode of the electroplating device. Even if the Y-direction connection bar 201 is cut, the end metal frame 208 is not cut. In this way, the end metal frame 208 connects the anode and cathode of the electroplating device in different directions, and functions as a conductive path for the flow of electricity.

[0034] 5 and 13. Electroplating is preferably performed by rack plating or high-speed plating, and a side solderable metal layer 400a can be applied to the entire bare copper on the side surfaces exposed after cutting the Y-direction connection bar 201, and a bottom solderable metal layer 400b can be applied to cover the bottom surface 102a of the matrix-like metal frame 102.

[0035] 9 and 11 , the front surface 101 a of the chip 101 connected to the matrix-like metal frame 102 is electrically connected to the left metal contact 203 via the ribbon 104 or the connecting sheet 103, the left metal contact 203 is electrically connected to the X-direction connecting bar 205 via the short metal connecting bar 202, and the X-direction connecting bar 205 is electrically connected to the chip soldering area 207 via the connecting bar 209, and the rear surface 101 b of the chip 101 is electrically connected to the chip soldering area 207 of the matrix-like metal frame 102. Therefore, the front surface 101 a and the rear surface 101 b of the chip 101 are short-circuited by the connection of the matrix-like metal frame 102. Due to the equipotential principle, the chip provides ESD protection during the electroplating process.

[0036] Step E is to cut the plastic molding material 105 by the thin cutter 302 to obtain one package unit.

[0037] Next, reference is made to FIGS. 14, 15, and 17. A full cut is performed along the scribe line 106 from the side of the matrix-like metal frame 102 using a thin cutter 302, preferably with a diameter smaller than that of the cutter 301, to cut the electroplated package components. The thin cutter 302 then completely cuts the plastic molding material 105 along the Y direction, and completely cuts the plastic molding material 105 and the X-direction connection bar 205 along the X direction. Because the diameter of the thin cutter 302 is smaller than the width of the scribe line 106, a single package unit 200 as shown in FIG. 15 is obtained after the full cut. The wall surfaces of the cutout 320 adjacent to the plastic molding material 105 and the Y-direction connection bar 201 are correspondingly recessed inward from the side solderable metal layer 400a along the thickness direction. The cutout 320 is located at 1 / 3 of the body thickness H of the package unit 200. This 1 / 3 of the body thickness H is, for example, in the range of 0.2 mm to 0.4 mm, preferably 0.22 mm to 0.35 mm. Both the bottom and side surfaces of the Y-directional connection bar 201 are covered with the solder metal material. Therefore, when the bottom surface 102a and part of the side surface of the matrix-like metal frame 102 are wetted with the solder material (see FIG. 5, where the lead 51 in FIG. 5 corresponds to the upper-left metal contact 203 exposed after the Y-directional connection bar 201 is completely cut in FIG. 7), the solder material S0 covers the side solderable metal layer 400a and the bottom solderable metal layer 400b. Furthermore, the recess 320 recessed inward from the peripheral wall of the plastic molding compound 105 allows the creeping height Hc of the solder material S0 on the lead 51 along the solderable metal layer 400a on the side surface 510 to be higher than the height of the lead 51. This allows the entire side surface of the lead 51 to be covered with the tin material, improving mechanical stress resistance.

[0038] <Embodiment 1> See FIG. 18. In this embodiment, the Y-direction width L of the end metal frame 208 of the matrix-shaped metal frame 102 in the X-direction is increased. In step C, after cutting the Y-direction connection bar 201, only one-third of the thickness of the package unit 200 is cut to complete the cutting process, thereby preventing the end metal frame 208 from being cut. See FIG. 9. After the cutting process is completed, the left metal contacts of each unit are fully exposed and connected to the X-direction connection bar 205 via the short connection bar 202. Alternatively, the short connection bar 202 may function as a Y-direction connecting wire, forming an electrical circuit along the Y direction for all metal contacts, and connecting each package unit 200 via the rear plastic molding compound 105. Because the end metal frame 208 in the X-direction on the matrix-shaped metal frame 102 covered by the rear plastic molding compound 105 is not cut, subsequent electroplating and second cutting processes are facilitated. The Y-direction width L of the end metal frame 208 in the X-direction and a portion of the matrix-shaped metal frame 102 is adjusted, for example, by cutting parameters to omit clamps for rack plating. For example, as shown in FIG. 19, the Y-direction width L satisfies the following inequality (Equation 1):

[0039]

number

[0040] In the above inequality (Equation 1), L is the Y-direction width L of the end metal frame 208 and a portion of the matrix-like metal frame 102 in the X-direction, R is the radius of the cutter 301, D is the cutting depth of the cutter 301, A is the safety margin width, and P is the electroplating preservation width. Also, in FIG. 19, the cutter 301 has a center point C, and the radius R of the cutter 301 is generally in the range of 25 mm to 35 mm. The cutting depth D is generally in the range of 0.2 mm to 0.4 mm, preferably in the range of 0.22 mm to 0.35 mm. The safety margin width A is generally in the range of 0.3 mm to 0.7 mm, preferably 0.5 mm. The electroplating preservation width P is generally in the range of 0.22 mm to 1.2 mm, preferably 1 mm.

[0041] TIFF2025168306000003.tif150163

[0042] As a result, in this disclosure, the bottom of the upper left metal contact 203 is electrically connected, which triples the practical soldering area and improves the heat dissipation capability of the package unit. Meanwhile, the metal pad is cut out in a stepped shape, which improves the bonding strength between the metal frame and the plastic molding material, improves the airtightness of the package component, and improves the stability and quality of the package unit.

[0043] It will be apparent to those skilled in the art that various modifications and variations can be made to the present disclosure. It is intended that the specification and examples be considered as exemplary embodiments only, with the scope of the present disclosure being indicated by the following claims and their equivalents.

Claims

1. a chip is mounted on a metal frame, the metal frame including two Y-axis connecting bars and two X-direction connecting metal bars connected to each other, each of the two Y-direction connecting metal bars being connected to a plurality of metal contacts, the plurality of metal contacts including at least an upper metal contact and a lower metal contact, the upper metal contact and the lower metal contact being connected to the two short metal connecting bars, respectively, thereby being electrically connected to the two X-direction connecting metal bars; a plastic molding material is used to mold a plastic package on the metal frame on which the chip is mounted; cutting the Y-direction connection bar and cutting a portion of the plastic molding material with a first cutter so that the Y-direction connection bar exposes side surfaces of the plurality of metal contacts; applying a solderable metal layer to all of the plurality of metal contacts exposed by the electroplating process; cutting the plastic molding material with a second cutter to obtain one semiconductor package component, the diameter of the second cutter being smaller than the diameter of the first cutter; A method for manufacturing leadless semiconductor package components.

2. In the step of molding the plastic package, a plurality of package units electrically connected to the Y-direction connection bar and the X-direction connection bar are further arranged on the metal frame, a chip soldering area is arranged on each of the plurality of package units, and four of the plurality of metal contacts are respectively arranged on the left and right sides of the chip soldering area. A method for manufacturing the leadless semiconductor package component of claim 1 .

3. In the step of mounting the chip on the metal frame, the rear surface of the chip is further bonded or soldered to the chip soldering area of ​​the metal frame. A method for manufacturing the leadless semiconductor package component of claim 2 .

4. In the step of mounting the chip on the metal frame, the front surface of the chip is further bonded to be connected to the upper metal contact by a clip. A method for manufacturing the leadless semiconductor package component of claim 1 .

5. In the step of mounting the chip on the metal frame, the front surface of the chip is further connected to the upper metal contact by a ribbon by bonding or soldering; A method for manufacturing the leadless semiconductor package component of claim 1 .

6. In the step of cutting the Y-direction connection bar with the first cutter, the cutting depth is equal to 1 / 3 of the thickness of the semiconductor package component; A method for manufacturing the leadless semiconductor package component of claim 1 .

Images