Ceramic adapter substrate and surface BGA manufacturing method thereof

Abstract

The present application relates to a kind of ceramic adapter substrate and its surface BGA manufacturing method, the back surface of the ceramic adapter substrate is BGA pad structure, the BGA pad structure includes via pad and ball pad, it is characterized in that, the top surface height of the via pad is higher than the top surface height of the ball pad, and the process design height difference of overhang between the two is formed.The present application sets up overhang height difference in the BGA pad structure of ceramic adapter substrate, so that the top surface height of via pad is higher than the top surface height of ball pad, in subsequent front surface multilayer wiring process, equipment mesa and suction disc are only contacted with the higher height via pad, effectively avoid ball pad and its surface plating layer from being abraded, completely solve the problem of ball pad easy to damage and poor welding reliability from structure.

Description

Technical Field

[0001] This invention relates to the field of ceramic adapter substrate manufacturing technology for semiconductor packaging and testing, and particularly to a ceramic adapter substrate and a method for fabricating BGA on its surface. Background Technology

[0002] MLC probe cards typically use ceramic substrates for space conversion. This requires fabricating multiple layers of metal wiring and insulating layers on the front side of the substrate, and creating BGA pad structures on the back side. A single BGA pad structure usually consists of two parts: a via pad for interconnection with the MLC's internal structure, and a ball pad for soldering to the PCB board.

[0003] Current processes typically involve fabricating a complete BGA pad structure on the back side first, followed by multi-layer routing on the front side to facilitate flying probe testing after each layer is fabricated. Specifically, the existing BGA fabrication process is as follows: ① Magnetron sputtering to deposit a Ti / Cu seed layer; ② Spreading, photolithography, and development; ③ One-time electroplating of Cu+Au to form a complete BGA pad structure; ④ Resin removal; ⑤ Wet etching to remove the seed layer. In subsequent multi-layer routing processes on the front side, the back side (BGA side) of the ceramic interposer substrate fabricated using this process frequently comes into contact with the tables and suction cups of equipment such as exposure machines, spreaders, and hot / cold plates. This easily causes wear on the Au layer on the ball pad surface, severely affecting product appearance consistency and damaging the solder interface between the ball pads and solder balls. This directly reduces the reliability of subsequent soldering to the PCB board, ultimately leading to a significant decrease in the mass production yield of the ceramic interposer substrate. Summary of the Invention

[0004] This invention provides a ceramic adapter substrate and a method for fabricating BGA on its surface to solve the above-mentioned technical problems.

[0005] To solve the above technical problems, the present invention provides a ceramic adapter substrate, the back side of which is a BGA pad structure, the BGA pad structure including via pads and ball pads, the top surface height of the via pads being higher than the top surface height of the ball pads, forming a suspended height difference between the two by process design.

[0006] Preferably, the height difference is 1 μm to 10 μm.

[0007] Preferably, the height difference is 5 μm.

[0008] Preferably, the via pad is a 12μm thick Cu layer.

[0009] Preferably, the ball pad comprises an 8μm thick Cu layer and a 0.1μm thick Au layer.

[0010] The present invention also provides a method for fabricating a surface BGA for preparing a ceramic adapter substrate as described above, comprising the following steps:

[0011] Step 1: Deposit a seed layer on the back side of the ceramic adapter substrate;

[0012] Step 2: Coat the surface of the seed layer with photoresist, and form a first pattern that matches the via pads through photolithography and development processes;

[0013] Step 3: Electroplating to form primary via pads based on the first pattern;

[0014] Step 4: Remove the photoresist from the surface of the ceramic adapter substrate using a wet process;

[0015] Step 5: Coat the ceramic adapter substrate with photoresist again, and the thickness of the photoresist coating is higher than the height of the primary via pad. Then, form a second pattern that matches the complete BGA pad structure through photolithography and development processes.

[0016] Step 6: Based on the second pattern, electroplating is used to thicken the via pads and form the ball pads;

[0017] Step 7: Remove the photoresist from the surface of the ceramic adapter substrate using a wet process;

[0018] Step 8: Use wet etching process to remove the seed layer not covered by the electroplating layer, and the BGA pad structure on the back side is completed.

[0019] Preferably, the seed layer is a Ti / Cu composite layer.

[0020] Preferably, the thickness of the primary via pad is 5 μm.

[0021] Compared with the prior art, the ceramic adapter substrate and its surface BGA fabrication method provided by the present invention have the following advantages:

[0022] 1. This invention sets a height difference in the BGA pad structure so that the top surface of the via pad is higher than the top surface of the ball pad. In subsequent processes, only the via pad contacts the equipment, which structurally avoids wear on the ball pad and plating, and greatly improves the welding reliability and production yield of the product.

[0023] 2. The present invention adopts a two-step electroplating process, which is simple, easy to control, and low in cost, making it suitable for the mass production of ceramic adapter substrate BGA structure. Attached Figure Description

[0024] Figure 1 and Figure 2 This is a flowchart of a method for fabricating a surface BGA on a ceramic adapter substrate according to a specific embodiment of the present invention.

[0025] In the diagram: 1-Ceramic adapter substrate, 2-via, 3-Primary via pad, 4-via pad, 5-Ball pad. Detailed Implementation

[0026] To illustrate the technical solutions of the invention in more detail, specific embodiments are listed below to demonstrate the technical effects; it should be emphasized that these embodiments are used to illustrate the invention and not to limit the scope of the invention.

[0027] like Figure 2 As shown, the back side of the ceramic adapter substrate 1 provided by this invention has a BGA pad structure. The BGA pad structure includes via pads 4 (corresponding to the position of via 2) and ball pads 5. The top surface height of the via pad 4 is higher than the top surface height of the ball pad 5, forming a height difference designed by the process. This height difference ensures that the equipment table surface only contacts the via pad 4 in subsequent processes, effectively preventing wear on the surface plating of the ball pad 5 and ensuring a complete and reliable soldering interface.

[0028] In some embodiments, the height difference is 1μm to 10μm, preferably 5μm, which can adapt to different process environments and substrate specifications, and has greater versatility.

[0029] In some embodiments, the via pad 4 is a 12μm thick Cu layer, which has high structural strength and stable conductivity, and can serve as a support structure to withstand process contact friction without affecting functionality. In some embodiments, the ball pad 5 includes an 8μm thick Cu layer and a 0.1μm thick Au layer. The Au layer is intact and wear-free, which can significantly improve the solder wettability and bonding reliability with the solder ball.

[0030] The present invention also provides a method for fabricating a surface BGA for preparing a ceramic adapter substrate as described above, comprising the following steps:

[0031] Step 1: A seed layer is deposited on the back side of the ceramic adapter substrate 1. In this embodiment, the seed layer is a Ti / Cu composite layer to improve the adhesion of the coating and ensure uniform and stable subsequent electroplating.

[0032] Step 2: Coat the surface of the seed layer with photoresist, and form a first pattern that matches the via pad 4 through photolithography and development processes.

[0033] Step 3: Electroplating is performed to form a primary via pad 3 based on the first pattern. In some embodiments, the thickness of the primary via pad is 5 μm, providing a basic structure for subsequent thickening molding.

[0034] Step 4: Remove the photoresist from the surface of the ceramic adapter substrate 1 using a wet process to expose the primary via pad 3 and the seed layer below, such as... Figure 1 As shown.

[0035] Step 5: Coat the surface of the ceramic adapter substrate 1 with photoresist again, and the thickness of the photoresist coating is higher than the height of the primary via pad 3. After photolithography and development processes, a second pattern matching the complete BGA pad structure is formed, thereby forming a stepped structure to achieve the suspended height difference.

[0036] Step 6: Based on the second pattern, the via pad 4 is thickened by electroplating, and the ball pad 5 is formed simultaneously, realizing the one-time forming of the height difference structure. The process is simple and controllable.

[0037] Step 7: Remove the photoresist from the surface of the ceramic adapter substrate 1 using a wet process.

[0038] Step 8: Use a wet etching process to remove the seed layer not covered by the electroplating layer. The BGA pad structure on the back side is now complete. Figure 2 As shown.

[0039] In summary, by setting a suspended height difference structure, this invention fundamentally avoids wear on the ball pad 5 and its surface Au layer, significantly improving product yield and welding reliability. At the same time, the two-step electroplating process is simple, easy to mass-produce, and suitable for the large-scale manufacturing of ceramic adapter substrates.

[0040] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A ceramic adapter substrate, wherein the back side of the ceramic adapter substrate has a BGA pad structure, the BGA pad structure including via pads and ball pads, characterized in that, The top surface height of the via pad is higher than the top surface height of the ball pad, creating a height difference in the process design.

2. The ceramic adapter substrate according to claim 1, characterized in that, The height difference is 1μm to 10μm.

3. The ceramic adapter substrate according to claim 2, characterized in that, The height difference is 5 μm.

4. The ceramic adapter substrate according to claim 2, characterized in that, The via pad is a 12μm thick Cu layer.

5. The ceramic adapter substrate according to claim 2, characterized in that, The ball pads consist of an 8μm thick Cu layer and a 0.1μm thick Au layer.

6. A method for fabricating a surface-mount BGA for a ceramic interposer substrate according to any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1: Deposit a seed layer on the back side of the ceramic adapter substrate; Step 2: Coat the surface of the seed layer with photoresist, and form a first pattern that matches the via pads through photolithography and development processes; Step 3: Electroplating to form primary via pads based on the first pattern; Step 4: Remove the photoresist from the surface of the ceramic adapter substrate using a wet process; Step 5: Coat the ceramic adapter substrate with photoresist again, and the thickness of the photoresist coating is higher than the height of the primary via pad. Then, form a second pattern that matches the complete BGA pad structure through photolithography and development processes. Step 6: Based on the second pattern, electroplating is used to thicken the via pads and form the ball pads; Step 7: Remove the photoresist from the surface of the ceramic adapter substrate using a wet process; Step 8: Use wet etching process to remove the seed layer not covered by the electroplating layer, and the BGA pad structure on the back side is completed.

7. The method for fabricating a surface BGA according to claim 6, characterized in that, The seed layer is a Ti / Cu composite layer.

8. The method for fabricating a surface BGA according to claim 6, characterized in that, The thickness of the primary via pad is 5 μm.

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