Kovar process of 3DDPC metal tube shell

Abstract

The invention discloses a Kovar process of a 3DDPC metal tube shell. The Kovar process is characterized by comprising the following steps: completing circuit metal copper processing of a bottom plate; electroplating processing is carried out on the metal copper of the bottom plate, and thickening processing is carried out on a metal area used for signal transmission wiring; after the bottom plate and the thickened area are electroplated, the bottom plate is subjected to film removal and bottom layer etching treatment; an enclosure frame is manufactured, and an inner cavity of the enclosure frame is removed in a laser cutting mode; electroplating the enclosure frame, wherein the total plate thickness of the enclosure frame is equal to or slightly higher than the thickened height of the bottom plate; and cutting the electroplated enclosure frame into single pieces, fixing the single pieces on a bottom plate in an aligned manner by using gold-tin solder, and putting the single pieces into a reflow soldering furnace to complete welding to obtain the metal tube shell. The method has the beneficial effects that Kovar process development of the metal tube shell is achieved, 300 DEG C high-temperature welding is carried out under the Kovar process condition, the stress between the bottom plate and the enclosure frame is low, and the problem that the reliability of the metal tube shell is poor is solved.

Description

Technical Field

[0001] The invention relates to the technical field of ceramic substrates, and in particular to a kovable process for a 3DDPC metal tube shell. Background Art

[0002] As electronic packaging technology gradually develops towards miniaturization, high density, multi-function and high reliability, the market has higher and higher requirements for ceramic metal packaging tube shells. The main difficulty of the current ceramic metal tube shells is that the expansion coefficients of the ceramic substrate and the dam layer metal do not match during the 300℃ reflow soldering process, which easily leads to stress imbalance and reliability failure of the ceramic substrate, while the Kovar frame product cannot realize signal wiring.

[0003] China Invention Patent Publication No. CN109904138A discloses a three-dimensional ceramic substrate and its preparation method, firstly, a planar ceramic substrate containing an independent circuit layer is made on a ceramic substrate, then through holes are processed on the dam structure material to form a hollow structure, and then a high-temperature resistant inorganic glue is used to align the dam structure material containing the hollow holes with the planar ceramic substrate and bond them, and after curing, they are cut to obtain one or more three-dimensional ceramic substrates containing cavity structures or dams. This patent uses bonding instead of reflow soldering, and does not solve the problem of metal stress imbalance between the ceramic substrate and the dam layer caused by reflow soldering.

[0004] Chinese invention patent authorization announcement number CN106783755B discloses a method for preparing a ceramic packaging substrate with a copper-plated dam, comprising the following steps: (1) thin film metallization; (2) making an independent circuit and an annular copper-plated layer on a ceramic base; (3) leveling; (4) electroplating thickening. The present invention manufactures a ceramic base circuit layer by adopting thin film metallization, dry film pasting, exposure and development, copper electroplating and leveling, and then manufactures a copper-plated dam around the independent circuit by repeated dry film pasting, exposure and development, and electroplating thickening processes to obtain a ceramic packaging substrate with a copper-plated dam. In this method, the copper-plated dam and the ceramic base are integrally formed and connected, but it requires repeated dry film pasting, exposure and development, and electroplating thickening processes, which is cumbersome to operate, costly and inefficient. Summary of the invention

[0005] The technical problem to be solved by the present invention is that the existing ceramic substrate and the dam layer metal cause stress imbalance due to the mismatch of expansion coefficients during reflow soldering, and a 3DDPC metal tube shell calendering process is provided for this purpose.

[0006] The technical solution of the present invention is: a 3D PC metal tube shell cavitation process, comprising the following steps: completing the metal copper processing of the circuit of the bottom plate; performing electroplating on the metal copper of the bottom plate, and thickening the metal area used for signal transmission wiring; after the bottom plate and the thickened area are electroplated, the bottom plate is stripped and the bottom layer is etched; a surrounding frame is made, the surrounding frame includes upper dam copper, lower dam copper and dam ceramic, and the inner cavity of the dam ceramic is removed by laser cutting; the dam ceramic is electroplated, so that the upper surface of the dam ceramic forms an upper dam copper layer, the lower surface of the dam ceramic forms a lower dam copper layer, and the total plate thickness of the surrounding frame is equal to or slightly higher than the thickening height of the bottom plate; after the electroplated surrounding frame is cut into single pieces, gold-tin solder is used to fix them on the bottom plate, and they are placed in a reflow oven at 300° C. to complete welding to obtain a metal tube shell.

[0007] The improvement of the above solution is that the metal tube shell is polished so that the overall flatness of the thickened area and the surrounding frame is within 10 μm.

[0008] The beneficial effect of the present invention is to realize the development of the felling process of the metal tube shell, and to carry out 300°C high-temperature welding under the felling process conditions, so that the stress between the bottom plate and the surrounding frame is low, and the problem of poor reliability of the metal tube shell is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a flow chart of metal tube shell assembly of the present invention; Figure 2 This is a photo of the metal tube shell product of the present invention; Figure 3 This is a photo of a metal tube shell product using existing technology. DETAILED DESCRIPTION

[0010] The technical solutions in the embodiments of the present invention are described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0011] like Figure 1 As shown, a 3DDPC metal tube shell cavitation process includes the following steps: Step 1: Complete the circuit metal copper processing of the bottom plate; Step 2: Electroplating is performed on the bottom plate metal to thicken the metal area used for signal transmission wiring. Currently, the minimum diameter of the thickened area metal can be 300μm and the height is 1mm; Step 3: After the bottom plate and the thickened area are electroplated, the bottom plate is stripped and the bottom layer is etched; Step 4: Make a frame. The frame includes upper copper, lower copper and ceramic. The upper copper and lower copper are located on the upper and lower surfaces of the ceramic. Use laser cutting to remove the inner cavity of the frame. Note that the slag on the side wall must be removed cleanly. Step 5: electroplating the frame, requiring the total thickness of the frame to be equal to or slightly higher than the thickened height of the bottom plate; Step 6: Cut the electroplated frame into individual pieces, and fix them on the base plate with gold-tin solder. Place them in a reflow oven to complete the soldering. Step 7: Grind the welded metal tube shell so that the overall flatness of the thickened layer and the surrounding frame is within 10 μm, which is convenient for airtight packaging.

[0012] like Figure 3 As shown in the figure, in conventional ceramic metal tube shells, the dam and the bottom copper are plated together. Since the thickness of the dam is close to 1mm, due to the large difference in linear expansion coefficients between copper and the ceramic substrate, the thermal expansion coefficient is relatively large, which will cause stress to the substrate during the heating process, seriously endangering the performance of the product. In a high-temperature reliability test environment above 300°C, the stress between copper and the substrate is not compatible. The frame of the present invention is connected to the bottom copper by gold-tin welding, such as Figure 2 As shown in the figure, in a high temperature environment above 300°C, the gold-tin solder will melt and recrystallize, offsetting the stress adaptation caused by thermal expansion. The thermal expansion coefficients of the dam layer and the substrate are small and basically close, so no large stress will be generated during the heating process, ensuring the performance reliability of customers during the welding process.

Claims

1. A 3DDPC metal shell kovable process, characterized by: The following steps are involved: Complete the circuit metal copper processing of the base plate; Electroplating is performed on the copper metal of the base plate to thicken the metal area used for signal transmission wiring; After the bottom plate and the thickened area are electroplated, the bottom plate is stripped and the bottom layer is etched; a frame is made, the frame includes upper dam copper, lower dam copper and dam ceramic, and the inner cavity of the dam ceramic is removed by laser cutting; the dam ceramic is electroplated so that an upper dam copper layer is formed on the upper surface of the dam ceramic, and a lower dam copper layer is formed on the lower surface of the dam ceramic, and the total plate thickness of the frame is equal to or slightly higher than the thickened height of the bottom plate; the electroplated frame is cut into single pieces, and fixed on the bottom plate with gold-tin solder, and placed in a reflow oven at 300°C to complete welding to obtain a metal tube shell.

2. The kovable process of a 3DDPC metal tube shell as claimed in claim 1, characterized in that: The metal tube shell is polished so that the overall flatness of the thickened area and the surrounding frame is within 10 μm.

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