Aluminum nitride CLCC packaging shell and preparation method thereof

Abstract

The invention belongs to the technical field of integrated circuit packaging, and particularly relates to an aluminum nitride CLCC packaging shell and a preparation method thereof. The method comprises the following steps: S1, carrying out first cavity opening on the surface of a printed surface-mounted bonding pad to form a circular through hole penetrating through the surface-mounted bonding pad; s2, carrying out slurry wall hanging in the circular through hole to form a side surface bonding pad; s3, opening the circular through hole for the second time to form a special-shaped structure; s5, sequentially laminating, sintering and plating the aluminum nitride raw material tape to obtain an aluminum nitride ceramic base material; and S6, grinding wheel scribing is conducted on the surface of the aluminum nitride ceramic base material, and the aluminum nitride CLCC packaging shell is prepared. According to the method, a repeated cavity opening design is adopted, so that the completeness of the surface-mounted bonding pad and side metallization of the aluminum nitride CLCC packaging shell is reserved, and the problem that the gold layer of the surface-mounted bonding pad is curled due to the fact that a blade makes contact with the gold layer in the grinding wheel scribing process is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated circuit packaging, and in particular relates to an aluminum nitride CLCC packaging shell and a preparation method thereof. Background Art

[0002] The CLCC (Ceramic Leaded Chip Carrier) package is a ceramic chip carrier with pins extending from the four sides of the package bottom. The side pads are interconnected with the bottom surface-mount pads in an L-shape. Due to its large number of pins, small size, and the L-shaped pads that increase assembly reliability, this package is particularly suitable for electronic devices that require high reliability and small size. Due to the high integration and large number of pins, electronic devices have higher requirements for the heat dissipation performance of this type of package. Due to the excellent high thermal conductivity and low thermal expansion coefficient of aluminum nitride ceramics, CLCC packages made of aluminum nitride ceramics have excellent heat dissipation, thermal matching, and high integration. They are particularly suitable for high-power devices such as IGBTs, MOSFETs, and laser diodes, as well as aerospace, automotive electronics, and industrial control systems.

[0003] In the existing CLCC package, the aluminum nitride ceramic shell is generally made into an outer shape by means of grinding wheel scribing. However, since the surface mount pads and the side pads at the bottom of the CLCC package are interconnected, the grinding wheel will inevitably contact the connection between the surface mount pads and the side pads during cutting. Since gold has good ductility, this will cause the gold layer plated at the interconnection position between the surface mount pads and the side pads to curl up during the grinding wheel scribing, causing the problem of curling of the gold layer on the pads, thereby affecting the quality of the CLCC package. Summary of the Invention

[0004] To overcome the above-mentioned shortcomings of the prior art, the present invention provides an aluminum nitride CLCC package and a method for manufacturing the same. This method not only preserves the integrity of the aluminum nitride CLCC package's surface-mount pads and side metallization, but also prevents the gold layer on the surface-mount pads from curling due to contact with the gold layer during grinding wheel scribing.

[0005] To achieve one of the above purposes, the present invention adopts the following technical solutions:

[0006] A method for preparing an aluminum nitride CLCC package shell comprises the following steps:

[0007] S1. Surface mount pads are printed on the surface of the aluminum nitride raw tape by screen printing.

[0008] S2. Through laser positioning and laser cavity opening technology, the first cavity is opened on the surface of the printed surface mount pad to form a circular through hole that penetrates the surface mount pad;

[0009] S3, applying slurry to the inner wall of the circular through hole formed in step S2, so that the slurry is attached to the inner wall of the through hole to form a side pad;

[0010] S4. Based on step S3, the laser positioning and laser cavity opening technology is used again to open the circular through hole for the second time, and the circular through hole is processed into a special-shaped structure with a plane difference between the surface of the circular through hole and the side wall of the aluminum nitride raw tape, while retaining the slurry on the inner side wall of the special-shaped through hole;

[0011] S5, sequentially laminating, sintering, and plating the aluminum nitride ceramic substrate to obtain an aluminum nitride ceramic substrate;

[0012] S6. Use ceramic surface scribing mark alignment technology to scribble the surface of the aluminum nitride ceramic substrate with a grinding wheel to produce an aluminum nitride CLCC packaging shell.

[0013] Preferably, the slurry used to print the surface mount pads in step S1 and the slurry in step S3 are both tungsten conductors, which are composed of 95% tungsten and 5% solvent, so as to facilitate the interconnection between the surface mount pads and the side pads.

[0014] Preferably, in step S5, the surface of the sintered aluminum nitride raw tape is subjected to surface treatment before plating. The surface treatment can clean the ceramic surface and make the subsequently produced composite thick film have a certain bonding strength.

[0015] Preferably, in step S5, nickel plating and gold plating are applied to make the surface mount pads and side pads of the aluminum nitride ceramic substrate solderable to ensure the subsequent assembly requirements of the user.

[0016] Preferably, the thickness of the nickel-plated layer is 2.5-8.9 μm; the thickness of the gold-plated layer is 0.1-0.5 μm.

[0017] Preferably, in step S4 , the range of the plane difference d is 0<d≤0.3 μm.

[0018] Preferably, in step S6, the ceramic surface scribing mark alignment technology is: the main shaft drives the grinding wheel blade to rotate rapidly, and at the same time, the grinding wheel blade is accurately guided to move along the designed scribing mark, so that it contacts the aluminum nitride ceramic substrate and cuts. During the cutting process, the main shaft drives the blade to move in a straight line to achieve precise cutting of aluminum nitride ceramics.

[0019] To achieve the second of the above-mentioned purposes, the present invention provides an aluminum nitride CLCC packaging shell prepared by a method for preparing an aluminum nitride CLCC packaging shell, the shell comprising an aluminum nitride ceramic substrate, the side wall of the aluminum nitride ceramic substrate being embedded with a plurality of side pads at intervals along the length direction of the side wall, the cross-section of the side pads being arc-shaped, and a plane difference being provided between the surface of the side pad and the surface of the side wall of the aluminum nitride ceramic substrate.

[0020] Preferably, the bottom of the aluminum nitride ceramic substrate is provided with a surface mount pad, and the surface mount pad and the side pad are interconnected to form an "L" shape, so as to improve the welding strength and increase the welding area.

[0021] The present application has the advantages of:

[0022] (1) The method for avoiding the curling of the surface mount pad gold layer of the aluminum nitride CLCC package shell by using the abrasive wheel dicing machine to cut the material, realizes the size control and appearance control of the aluminum nitride CLCC package. The aluminum nitride multilayer ceramic substrate with high thermal conductivity and low thermal expansion coefficient is used as the CLCC package shell substrate, and the secondary cavity design and dicing mark alignment technology are used to avoid the curling of the surface mount pad gold layer of the aluminum nitride CLCC package shell caused by the abrasive wheel dicing, so as to realize the effective control of the size and appearance of the aluminum nitride CLCC package shell.

[0023] (2) The high-thermal-conductivity CLCC package shell can not only realize the electrical connection with the subsequent platform of the user, but also can be in close contact with the subsequent assembly platform, so as to achieve good heat dissipation function and form good thermal matching with the chip assembled in the CLCC package shell.

[0024] (3) The multiple cavity design is adopted, the integrity of the surface mount pad and the side metallization of the aluminum nitride CLCC package shell is reserved, the curling of the surface mount pad gold layer caused by the contact of the blade with the gold layer during the abrasive wheel dicing process is avoided, and the abrasive wheel dicing realizes the high-precision requirement of the size of the aluminum nitride CLCC package shell, and the size tolerance can be controlled within ±0.03mm. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The present application is a schematic diagram.

[0026] Figure 2 The present application is a first cavity structure schematic diagram.

[0027] Figure 3 The present application is a second cavity structure schematic diagram.

[0028] Figure 4 The present application is an abrasive wheel dicing schematic diagram.

[0029] Figure 5 The present application is a side structure schematic diagram.

[0030] Figure 6 The present application is a flowchart of Example 1.

[0031] The meanings of the symbols in the figure are as follows:

[0032] 1-Aluminum nitride ceramic substrate, 2-Surface mount pad, 3-Side pad, 4-Surface pad, 5-Lead-tin solder, 6-User assembly platform, 7-Circular through hole, 8-Grinding wheel blade. DETAILED DESCRIPTION

[0033] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0034] A method for preparing an aluminum nitride CLCC package shell comprises the following steps:

[0035] Step 1: Surface mount pads 2 are printed on the bottom surface of the aluminum nitride raw tape by screen printing;

[0036] Step 2: Using laser positioning and laser cavity opening technology, a first cavity is opened on the surface of the printed surface mount pad 2 to form a circular through hole 7 that penetrates the surface mount pad 2.

[0037] Step 3: Apply slurry to the inner wall of the circular through hole 7 formed in step 2, so that the slurry is attached to the inner wall of the circular through hole 7 to form a side pad 3;

[0038] Step 4: Based on step 3, laser positioning and laser cavity opening technology are used again to open the circular through hole 7 for the second time, and the circular through hole 7 is processed into a special-shaped structure (such as Figure 3 As shown, the surface of the circular through hole 7 forms a level difference / step difference with the side wall of the aluminum nitride raw tape, and the level difference d is in the range of 0 < d ≤ 0.3 μm. This prevents the grinding wheel blade 8 from contacting the side pad 3 during subsequent scribing, thereby preventing the problem of gold layer curling. At the same time, the slurry is retained on the inner side wall of the irregular through hole. Subsequently, the aluminum nitride ceramic substrate 1 is laminated, sintered, and plated as normal until scribing.

[0039] The grinding wheel scribing adopts the ceramic surface scribing mark alignment technology. The main shaft drives the grinding wheel blade to rotate rapidly, and at the same time, the grinding wheel blade 8 accurately guides the grinding wheel movement along the designed scribing mark, so that it contacts and cuts the aluminum nitride ceramic substrate 1. During the cutting process, the main shaft drives the blade to move linearly to achieve precise cutting of the aluminum nitride ceramic substrate 1.

[0040] like Figure 1-5Figure 1 shows an aluminum nitride CLCC package housing. The housing comprises an aluminum nitride ceramic substrate 1. A plurality of side pads 3 are embedded along the sidewalls of the aluminum nitride ceramic substrate 1 at intervals. The side pads 3 have an arcuate cross-section, and a plane difference exists between the surface of the side pads 3 and the sidewall of the aluminum nitride ceramic substrate 1. A surface-mount pad 2 is provided on the bottom of the aluminum nitride ceramic substrate 1. The surface-mount pad 2 and the side pad 3 are interconnected to form an "L" shape. Figure 1 In order to apply the prepared aluminum nitride CLCC package shell, the aluminum nitride CLCC package shell is placed on the user assembly platform 6, the surface pads 4 on the user assembly platform 6 correspond to and are connected to the surface mount pads 2, and then lead-tin solder 5 is used to connect the surface pads 4 to the side pads 3, so that the aluminum nitride CLCC package shell is firmly installed on the user assembly platform 6.

[0041] Example 1

[0042] like Figure 6 As shown, a method for preparing an aluminum nitride CLCC package shell, the specific steps are as follows:

[0043] Step 1, preparing an aluminum nitride ceramic substrate 1;

[0044] Specifically, step 1 includes the following steps:

[0045] Step 1.1: Cast aluminum nitride raw tape of the required thickness for the product, and perform patching and punching of the aluminum nitride raw tape according to the design requirements.

[0046] Step 1.2: Based on the design requirements, via filling and conductive strip printing are performed on each layer of aluminum nitride green tape. Via filling and conductive strip printing are performed by screen printing. The conductive paste is tungsten conductor, which is composed of 95% tungsten and 5% solvent. The vias are used to achieve vertical conductivity, and the conductive strips are used to achieve horizontal conductivity.

[0047] Step 1.3: After the hole filling and printing, the aluminum nitride raw tape is opened for the first time to form the metal sidewall metallization in the cavity. Laser positioning and laser cavity opening technology are used. The cavity opening position penetrates the conductive paste at the position of the surface mount pad 2 to form a circular through hole 7.

[0048] Step 1.4: The inner wall of the circular through hole 7 formed after the first cavity opening is subjected to slurry hanging, so that the inner wall of the circular through hole 7 is evenly covered with conductor slurry to form a side pad 3. The conductor slurry is a tungsten conductor, which is composed of 95% tungsten and 5% solvent and can be interconnected with the surface mount pad 2.

[0049] Step 1.5: After step 1.4 is completed, a second cavity is opened. Laser positioning and laser cavity opening technology are used to process the circular through hole 7 into a special-shaped structure, while retaining the conductive paste on part of the inner wall of the circular through hole 7.

[0050] Step 1.6: Place the aluminum nitride raw tape that has completed the slurry hanging on the wall and the second cavity opening on the mold for stacking, and perform isostatic pressing on the stacked porcelain body so that each layer of aluminum nitride raw tape is firmly combined together. Then, the stacked porcelain body is cut.

[0051] Step 1.7: Sintering the cut aluminum nitride green ceramic blocks to complete the preparation of the aluminum nitride ceramic-based substrate 1.

[0052] Step 2: Prepare an aluminum nitride CLCC package with a surface-coated structure. The outer surface of the sintered aluminum nitride ceramic substrate 1 is surface treated to clean the ceramic surface and ensure sufficient bonding strength for the subsequently fabricated composite thick film. After surface treatment, nickel and gold are electroplated sequentially on the surface of the aluminum nitride ceramic substrate 1 to ensure solderability of the surface-mount pads 2 and side pads 3 of the aluminum nitride ceramic substrate 1, ensuring subsequent assembly requirements.

[0053] The preparation steps of nickel plating and gold plating on the surface of aluminum nitride multilayer ceramics are as follows:

[0054] Step 2.1: Electroplating nickel and gold is performed on the surface-mount pads 2 and side pads 3 of the aluminum nitride ceramic-based substrate 1 after surface treatment. The thickness of the nickel layer is 5 μm, and the thickness of the gold layer is 0.3 μm.

[0055] Through step 2, a surface metallization suitable for welding is obtained. Combining steps 1 and 2, an aluminum nitride ceramic-based substrate 1 having solderable surface mount pads 2 and side pads 3 is realized.

[0056] Step 3, perform grinding wheel scribing on the surface of the obtained aluminum nitride CLCC package shell with solderable surface mount pads 2 and side pads 3, and adopt ceramic surface scribing mark alignment technology. The main shaft drives the grinding wheel blade to rotate rapidly, and at the same time, the grinding wheel blade 8 is accurately guided to move along the designed scribing mark, so that it contacts the aluminum nitride CLCC package shell and cuts. During the cutting process, the main shaft drives the blade to move in a straight line to achieve precise cutting of the aluminum nitride ceramic shape. At the same time, since the design of step 1 has made the surface mount pads 2 and side pads 3 of the aluminum nitride CLCC package shell avoid the grinding wheel scribing path, the surface gold layer of the surface mount pads 2 and side pads 3 of the aluminum nitride CLCC package shell obtained after grinding wheel scribing can be completely protected without curling.

[0057] Through steps 1-3, an aluminum nitride CLCC package shell with solderable surface mount pads 2 and side pads 3 is obtained, and solder welding assembly of the user platform can be performed at the bottom of the shell.

[0058] Embodiment 1 of the present invention can ensure that the aluminum nitride CLCC packaging shell has good thermal matching, heat dissipation performance and packaging reliability, and ultimately forms a packaging structure that meets the requirements of high-power chip circuit products.

[0059] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing an aluminum nitride CLCC package shell, characterized in that: The steps include: S1. Printing a surface mount solder pad (2) on the surface of the aluminum nitride raw tape by screen printing; S2, performing a first cavity opening on the surface of the printed surface mount pad (2) by laser positioning and laser cavity opening technology, thereby forming a circular through hole (7) penetrating the surface mount pad (2); S3, applying slurry to the circular through hole (7) formed in step S2 to form a side solder pad (3); S4, based on step S3, laser positioning and laser cavity opening technology are used again to open the circular through hole (7) for the second time, and the circular through hole (7) is processed into a special-shaped structure with a plane difference between the surface of the circular through hole and the side wall of the aluminum nitride raw tape, while retaining the slurry on the inner side wall of the special-shaped through hole; S5, laminating, sintering and plating the aluminum nitride ceramic substrate (1) in sequence to obtain the aluminum nitride ceramic substrate (1); S6. Using a ceramic surface scribing mark alignment technology, the surface of the aluminum nitride ceramic substrate (1) is scribed with a grinding wheel to obtain an aluminum nitride CLCC packaging shell.

2. The method for preparing an aluminum nitride CLCC package shell according to claim 1, characterized in that: The slurry used to print the surface mount pad (2) in step S1 and the slurry used in step S3 are both tungsten conductors, and the tungsten conductors are composed of 95% tungsten and 5% solvent.

3. The method for preparing an aluminum nitride CLCC package shell according to claim 1, wherein: In step S5, the surface of the sintered aluminum nitride raw tape is surface treated and then plated.

4. The method for preparing an aluminum nitride CLCC package shell according to claim 1, wherein: In step S5, the plating is nickel plating layer and gold plating layer.

5. The method for preparing an aluminum nitride CLCC package shell according to claim 4, characterized in that: The thickness of the nickel-plated layer is 2.5-8.9 μm; the thickness of the gold-plated layer is 0.1-0.5 μm.

6. The method for preparing an aluminum nitride CLCC package shell according to claim 1, wherein: In step S4 , the range of the plane difference d is 0<d≤0.3 μm.

7. The method for preparing an aluminum nitride CLCC package shell according to claim 1, characterized in that: In step S6, the ceramic surface scribing mark alignment technology is as follows: the grinding wheel blade (8) is driven to rotate by the main shaft, and the grinding wheel blade (8) is guided to move along the designed scribing mark so that the grinding wheel contacts the aluminum nitride ceramic substrate (1) and cuts.

8. An aluminum nitride CLCC package shell prepared by the method for preparing an aluminum nitride CLCC package shell according to any one of claims 1 to 7, characterized in that: The housing comprises an aluminum nitride ceramic substrate (1), wherein a plurality of side pads (3) are embedded at intervals along the length direction of the side wall of the aluminum nitride ceramic substrate (1), wherein the cross section of the side pads (3) is arc-shaped, and a plane difference is provided between the surface of the side pads (3) and the surface of the side wall of the aluminum nitride ceramic substrate (1).

9. The aluminum nitride CLCC package shell prepared by the method for preparing an aluminum nitride CLCC package shell according to claim 8, characterized in that: A surface-mount pad (2) is provided at the bottom of the aluminum nitride ceramic substrate (1), and the surface-mount pad (2) and the side pad (3) are interconnected to form an "L" shape.

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