High-reliability ceramic magnetic shielding packaging structure for MRAM (Magnetic Random Access Memory)

Abstract

The invention belongs to the technical field of magnetic shielding packaging, and particularly relates to a high-reliability ceramic magnetic shielding packaging structure for an MRAM (Magnetic Random Access Memory). The packaging structure is composed of a ceramic base, a sealing ring, a magnetic shielding cover plate and a magnetic shielding bottom plate. The magnetic shielding bottom plate is welded to the bottom of an inner cavity of the ceramic base, the sealing ring is welded to the side walls of the periphery of the inner cavity of the ceramic base, the magnetic shielding cover plate is welded or bonded to the top of the sealing ring, and a chip to be packaged is bonded to the top of the magnetic shielding bottom plate. The packaging structure provided by the invention has an excellent shielding effect on a magnetic field at the chip. Compared with a tetrahedral packaging form, the packaging structure has the advantages that the shielding effect is ensured, the internal chip can be isolated from external factors such as water, gas and salt, and the packaging reliability is greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetic shielding packaging, and in particular relates to a high-reliability ceramic magnetic shielding packaging structure for MRAM. Background Art

[0002] Magnetic random access memory (MRAM) has attracted more and more attention due to its excellent performance such as high read and write speed, nearly unlimited read and write times and low power consumption. It uses the direction of the magnetic field to operate the storage bit, and the external magnetic field can easily interfere with the magnetic junction and cause read and write errors. Therefore, it is of great significance to use a magnetic shielding packaging structure to reduce the impact of the external magnetic field on the memory.

[0003] At present, for STT-MRAM, in order to ensure the magnetic shielding effect, a shell-and-tube packaging structure is mostly used for magnetic shielding. This method mostly uses a hexahedral shell and opens holes in the shell to facilitate pin routing. This method has high process requirements and may have reliability problems. There will be magnetic leakage at the opening, which may cause read and write errors in the chip at the opening. Another method is a tetrahedral shell, which has two opposite faces without magnetic shielding materials. This method can simplify the shell-and-tube process, but the open structure may have reliability problems such as poor sealing. Summary of the invention

[0004] The purpose of the present invention is to provide a high-reliability ceramic magnetic shielding packaging structure for MRAM, which can take into account both magnetic shielding effect and packaging reliability. The present invention adopts an integrally formed sealing ring and magnetic shielding bottom plate structure, leaves the bonding area on both sides of the magnetic shielding bottom plate, and then welds it on the ceramic base, thereby ensuring the shielding effect while greatly improving the sealing reliability of the package body, and also allows the bonding wire to be easily led out.

[0005] In order to solve the above technical problems, the present invention provides a high-reliability ceramic magnetic shielding packaging structure for MRAM, which is composed of a ceramic base, a sealing ring, a magnetic shielding cover plate and a magnetic shielding bottom plate; the magnetic shielding bottom plate is welded to the bottom of the inner cavity of the ceramic base, the sealing ring is welded to the side walls around the inner cavity of the ceramic base, the top of the sealing ring is welded or bonded to the magnetic shielding cover plate, and the top of the magnetic shielding bottom plate is bonded to the chip to be packaged;

[0006] A certain distance is maintained between the left and right ends of the magnetic shielding bottom plate and the sealing rings on the left and right sides to form a hollow bonding area, so that the bonding wires of the chip to be packaged can be connected to the bonding fingers on the ceramic base.

[0007] Preferably, the sealing ring is connected to the magnetic shielding cover plate by parallel seam welding or bonding, and the thickness of the magnetic shielding cover plate is 0.2 mm to 0.8 mm.

[0008] Preferably, the bonding method includes bonding using magnetic solder or magnetic glue, wherein the magnetic glue uses epoxy resin doped with magnetic iron-nickel-molybdenum alloy particles, wherein the mass ratio of the doped iron and nickel is 2:5, and the mass of the doped molybdenum is 4% of the total mass of the iron-nickel-molybdenum alloy.

[0009] Preferably, the thickness of the magnetic shielding bottom plate and the sealing ring are both 0.5 mm to 1.5 mm.

[0010] Preferably, the magnetic shielding bottom plate and the sealing ring are an integrally formed structure, and are formed in one step by chemical etching or machining.

[0011] Preferably, the magnetic shielding bottom plate, the sealing ring and the magnetic shielding cover plate are all made of iron-silicon-manganese alloy material, wherein the iron-silicon mass ratio is 2:5 or 3:5, and the mass of manganese is 3% or 5% of the total mass of the iron-silicon-manganese alloy.

[0012] Preferably, the connection process of the magnetic shielding bottom plate and the sealing ring to the ceramic base is as follows:

[0013] First, the unprocessed magnetic shielding bottom plate and sealing ring are welded to the ceramic base, and then the magnetic shielding bottom plate and sealing ring are processed by chemical etching or machining; the above operations can prevent stress deformation of the magnetic shielding bottom plate and the sealing ring.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The present invention has an excellent shielding effect, can better isolate the chip from external interference factors, and improve the reliability of magnetic shielding packaging. Compared with the traditional hexahedral tube shell, while ensuring the shielding effect, the bonding wire can be easily led out. Compared with the tetrahedral open packaging structure, the airtightness is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a front cross-sectional view of the high-reliability magnetic shielding packaging structure of the present invention.

[0017] Figure 2 It is a side cross-sectional view of the high-reliability magnetic shielding packaging structure of the present invention.

[0018] Figure 3 It is a top view of the high-reliability magnetic shielding packaging structure of the present invention.

[0019] Figure 4 It is a schematic diagram of the magnetic field distribution in the chip area of ​​embodiments 1 to 4 of the present invention.

[0020] In the figure: 1-ceramic base, 2-magnetic shielding cover plate, 3-sealing ring, 4-bonding wire, 5-magnetic shielding bottom plate, 6-chip. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the accompanying drawings are in very simplified form and in non-precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0022] like Figures 1 to 4 As shown, the embodiment of the present invention specifically provides a high-reliability ceramic magnetic shielding packaging structure for MRAM, which is composed of a ceramic base 1, a sealing ring 3, a magnetic shielding cover plate 2, and a magnetic shielding bottom plate 5.

[0023] The above-mentioned magnetic shielding cover plate 2, magnetic shielding bottom plate 5 and sealing ring 3 are composed of the following magnetic materials, but are not limited to the following magnetic materials: iron-nickel alloy (any proportion), which may be doped with elements such as niobium, tantalum, vanadium, tungsten, titanium, silicon, manganese, and aluminum; iron-silicon alloy (any proportion), which may be doped with elements such as niobium, tantalum, vanadium, tungsten, titanium, nickel, manganese, and aluminum; ferrite material composed of iron and oxygen elements and one or more other metal elements (such as niobium, tantalum, vanadium, tungsten, titanium, nickel, aluminum, and manganese).

[0024] The magnetic shielding cover plate 2 is connected to the sealing ring 3 by parallel seam welding or bonding, and has a thickness of 0.2 mm to 0.8 mm.

[0025] The magnetic shielding bottom plate 5 and the sealing ring 3 are connected to the ceramic base 1 by welding.

[0026] The magnetic shielding bottom plate 5 and the sealing ring 3 are thin-walled workpieces that are easily warped and deformed due to thermal stress during welding. Therefore, the unprocessed magnetic shielding bottom plate 5 and the sealing ring 3 are first welded to the ceramic base 1, and are formed in one step by chemical etching or machining. The specific manufacturing process is as follows:

[0027] 1) Remove the unnecessary parts of the whole magnetic material by machining;

[0028] 2) Remove the unnecessary parts of the whole magnetic material by chemical etching method.

[0029] There are hollow parts on both sides of the magnetic shielding bottom plate 5 and the sealing ring 3, so that the bonding wire 4 of the chip 6 can be connected to the bonding finger. The thickness of the sealing ring 3 and the magnetic shielding bottom plate 5 is 0.5-1.5 mm.

[0030] The connection process of the magnetic shielding bottom plate 5 and the sealing ring 3 with the ceramic substrate is as follows:

[0031] First, the unprocessed magnetic shielding bottom plate 5 and the sealing ring 3 are welded to the ceramic substrate, and then the magnetic shielding bottom plate 5 and the sealing ring 3 are processed by chemical etching or machining. The above operation can prevent stress deformation of the magnetic shielding bottom plate 5 and the sealing ring 3.

[0032] The above bonding method adopts magnetic solder or magnetic glue, and the magnetic solder is composed of the following magnetic materials, but not limited to the following magnetic materials: iron-nickel alloy (any proportion), which can be doped with niobium, tantalum, vanadium, tungsten, titanium, silicon, manganese, aluminum and other elements; iron-silicon alloy (any proportion), which can be doped with niobium, tantalum, vanadium, tungsten, titanium, nickel, manganese, aluminum and other elements. The magnetic glue is composed of epoxy resin mixed with magnetic particles, wherein the magnetic particles are composed of the following magnetic materials, but not limited to the following magnetic materials: iron-nickel alloy (any proportion), which can be doped with niobium, tantalum, vanadium, tungsten, titanium, silicon, manganese, aluminum and other elements; iron-silicon alloy (any proportion), which can be doped with niobium, tantalum, vanadium, tungsten, titanium, nickel, manganese, aluminum and other elements; ferrite material composed of iron and oxygen elements and one or more other metal elements (such as niobium, tantalum, vanadium, tungsten, titanium, nickel, aluminum, manganese).

[0033] Embodiment 1:

[0034] The selected ceramic package includes a ceramic base 1, a magnetic shielding bottom plate 5, a sealing ring 3, a magnetic shielding cover plate 2, bonding fingers, bonding wires 4, etc. The unprocessed workpiece of the magnetic shielding bottom plate 5 and the sealing ring 3 is welded to the ceramic base 1. The unprocessed workpiece is composed of an iron-nickel-molybdenum (iron-nickel ratio: 1:5, molybdenum content 5%) alloy. The magnetic shielding bottom plate 5 and the sealing ring 3 are constructed by machining, wherein the thickness of the magnetic shielding bottom plate 5 is 0.5mm and the thickness of the sealing ring 3 is 1mm. The magnetic shielding cover plate 2 is welded to the sealing ring 3 by a parallel seam welding process. The magnetic shielding cover plate 2 is 0.3mm thick and is composed of an iron-nickel-molybdenum (iron-nickel ratio: 1:5, molybdenum content 5%) alloy.

[0035] Embodiment 2:

[0036] The selected ceramic package includes a ceramic base 1, a magnetic shielding bottom plate 5, a sealing ring 3, a magnetic shielding cover plate 2, bonding fingers, bonding wires 4, etc. The unprocessed workpiece of the magnetic shielding bottom plate 5 and the sealing ring 3 is welded to the ceramic base 1. The unprocessed workpiece is composed of an iron-silicon-manganese (iron-silicon ratio: 3:5, manganese content 5%) alloy. The magnetic shielding bottom plate 5 and the sealing ring 3 are constructed by machining, wherein the thickness of the magnetic shielding bottom plate 5 is 0.5mm and the thickness of the sealing ring 3 is 1mm. The magnetic shielding cover plate 2 is bonded to the sealing ring 3, and the magnetic shielding cover plate 2 is 0.3mm thick and is composed of an iron-silicon-manganese (iron-silicon ratio: 3:5, manganese content 5%) alloy. The bonding material is an epoxy resin containing iron-nickel-molybdenum (iron-nickel ratio: 1:5, molybdenum content 5%) alloy particles, and the magnetic shielding substrate is bonded to the magnetic shielding top cover by bonding material. The magnetic shielding substrate is made by milling.

[0037] Embodiment 3:

[0038] The selected ceramic package includes a ceramic base 1, a magnetic shielding bottom plate 5, a sealing ring 3, a magnetic shielding cover plate 2, bonding fingers, bonding wires 4, etc. The unprocessed workpiece of the magnetic shielding bottom plate 5 and the sealing ring 3 is welded to the ceramic base 1. The unprocessed workpiece is composed of an iron-nickel-molybdenum (iron-nickel ratio: 1:5, molybdenum content 5%) alloy. The magnetic shielding bottom plate 5 and the sealing ring 3 are constructed by machining, wherein the thickness of the magnetic shielding bottom plate 5 is 0.3mm and the thickness of the sealing ring 3 is 0.8mm. The magnetic shielding cover plate 2 is welded to the sealing ring 3 by a parallel seam welding process. The magnetic shielding cover plate 2 is 0.5mm thick and is composed of an iron-nickel-molybdenum (iron-nickel ratio: 2:5, molybdenum content 4%) alloy.

[0039] Embodiment 4:

[0040] The selected ceramic package includes a ceramic base 1, a magnetic shielding bottom plate 5, a sealing ring 3, a magnetic shielding cover plate 2, bonding fingers, bonding wires 4, etc. The unprocessed workpiece of the magnetic shielding bottom plate 5 and the sealing ring 3 is welded to the ceramic base 1. The unprocessed workpiece is composed of an iron-silicon-manganese (iron-silicon ratio: 2:5, manganese content 3%) alloy. The magnetic shielding bottom plate 5 and the sealing ring 3 are constructed by machining, wherein the thickness of the magnetic shielding bottom plate 5 is 0.5mm and the thickness of the sealing ring 3 is 1mm. The magnetic shielding cover plate 2 is bonded to the sealing ring 3, and the magnetic shielding cover plate 2 is 0.2mm thick and is composed of an iron-silicon-manganese (iron-silicon ratio: 2:5, manganese content 3%) alloy. The bonding material is an epoxy resin containing iron-nickel-molybdenum (iron-nickel ratio: 2:5, molybdenum content 4%) alloy particles, and the magnetic shielding substrate is bonded to the magnetic shielding top cover by bonding material. The magnetic shielding substrate is made by milling.

[0041] like Figure 4 As shown, the simulation results are implemented by Examples 1 to 4, and finite element analysis and calculation are performed on the invented package. It is found that when an external magnetic field of 24000A / m is applied, the magnetic field in the hollow area of ​​the magnetic shielding base plate 5 is relatively large, about 20000A / m, while the magnetic field strength in the area where the chip 6 is located is greatly weakened, and the minimum can reach 10A / m.

[0042] The above results prove that the packaging structure of the present invention has an excellent shielding effect on the magnetic field at the chip. Compared with the tetrahedral packaging form, while ensuring the shielding effect, it can isolate the internal chip from external factors such as water, air, and salt, greatly improving the packaging reliability. In addition, the chip bonding wire can be easily led out. It provides a new idea for the high-reliability magnetic shielding packaging of MRAM chips.

[0043] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A high-reliability ceramic magnetic shielding packaging structure for MRAM, characterized in that: The packaging structure is composed of a ceramic base, a sealing ring, a magnetic shielding cover plate and a magnetic shielding bottom plate; the magnetic shielding bottom plate is welded to the bottom of the inner cavity of the ceramic base, the sealing ring is welded to the side walls around the inner cavity of the ceramic base, the magnetic shielding cover plate is welded or bonded to the top of the sealing ring, and the chip to be packaged is bonded to the top of the magnetic shielding bottom plate; A certain distance is maintained between the left and right ends of the magnetic shielding bottom plate and the sealing rings on the left and right sides to form a hollow bonding area, so that the bonding wires of the chip to be packaged can be connected to the bonding fingers on the ceramic base.

2. A high-reliability ceramic magnetic shielding packaging structure for MRAM as claimed in claim 1, characterized in that: The sealing ring is connected to the magnetic shielding cover plate by parallel seam welding or bonding, and the thickness of the magnetic shielding cover plate is 0.2 mm to 0.8 mm.

3. A high-reliability ceramic magnetic shielding packaging structure for MRAM as claimed in claim 2, characterized in that: The bonding method includes bonding using magnetic solder or magnetic glue, wherein the magnetic glue uses epoxy resin doped with magnetic iron-nickel-molybdenum alloy particles, wherein the mass ratio of the doped iron and nickel is 2:5, and the mass of the doped molybdenum is 4% of the total mass of the iron-nickel-molybdenum alloy.

4. A high-reliability ceramic magnetic shielding packaging structure for MRAM as claimed in claim 1, characterized in that: The thickness of the magnetic shielding bottom plate and the sealing ring are both 0.5 mm to 1.5 mm.

5. The high-reliability ceramic magnetic shielding packaging structure for MRAM as claimed in claim 1, characterized in that: The magnetic shielding bottom plate and the sealing ring are an integrally formed structure, and are formed in one step by chemical etching or machining.

6. A high-reliability ceramic magnetic shielding packaging structure for MRAM as claimed in claim 1, characterized in that: The magnetic shielding bottom plate, the sealing ring and the magnetic shielding cover plate are all made of iron-silicon-manganese alloy material, wherein the iron-silicon mass ratio is 2:5 or 3:5, and the mass of manganese is 3% or 5% of the total mass of the iron-silicon-manganese alloy.

7. A high-reliability ceramic magnetic shielding packaging structure for MRAM as claimed in any one of claims 1 to 6, characterized in that: The connection process of the magnetic shielding bottom plate and the sealing ring to the ceramic base is as follows: First, the unprocessed magnetic shielding bottom plate and sealing ring are welded to the ceramic base, and then the magnetic shielding bottom plate and sealing ring are processed by chemical etching or machining; the above operations can prevent stress deformation of the magnetic shielding bottom plate and the sealing ring.

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