A method for preparing a pre-coated solder cover plate

Abstract

This invention discloses a method for preparing a pre-coated solder cover plate, belonging to the field of electronic component packaging. The method includes: processing a metal substrate according to preset conditions; rolling a smelted gold-tin alloy ingot into a gold-tin foil strip; punching the gold-tin foil strip to obtain gold-tin solder, which has a hollow structure; etching annular grooves on the metal substrate; cleaning impurities from the surface of the metal substrate after etching; electroplating the surface of the metal substrate using an electrochemical method to form an electroplated layer; placing the formed gold-tin solder on the metal substrate, with the grooves located within the inner frame of the gold-tin solder; heating the gold-tin solder to a semi-molten state to adhere it to the metal substrate, forming a pre-coated solder cover plate; checking whether the pre-coated solder cover plate meets the requirements and rejecting defective products. This invention uses grooves to restrict the semi-molten gold-tin solder, preventing the solder from diffusing into the central area of ​​the pre-coated solder cover plate.

Description

Technical Field

[0001] This invention belongs to the field of electronic component packaging, and specifically relates to a method for preparing a pre-coated solder cover plate. Background Technology

[0002] For electronic components such as quartz crystals, the base and top cover need to be sealed and soldered in an inert atmosphere or vacuum environment to protect the internal components. After placing the crystal on a ceramic base, a pre-coated solder-coated hermetic encapsulation cover is placed on top. The cover is then heated to the soldering temperature. The molten solder, due to its high fluidity and wettability, quickly fills the gap between the cover and the ceramic base, achieving hermetic encapsulation.

[0003] However, due to its high fluidity and wettability, the solder is prone to disordered overflow during the high-temperature semi-molten process of being pre-coated onto the cover plate, with a small amount of solder randomly diffusing towards the central area. When this pre-coated gold-tin cover plate, with a small amount of solder diffusing towards the central area, is used for the hermetic packaging of electronic components such as quartz crystals, the solder, in addition to quickly filling the gap between the metal cover plate and the ceramic substrate, will randomly overflow near the central area onto pre-placed components such as quartz crystals and microcircuits on the ceramic substrate, causing damage to the entire electronic component. This results in low reliability and low yield of pre-coated solder cover plates obtained by existing methods, and poses risks such as internal circuit short circuits and damage. Therefore, how to provide a pre-coated solder cover plate preparation method that can avoid solder overflowing to components is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the present invention provides a method for preparing a pre-coated solder cover plate, which can prevent solder from overflowing into components and reduce the risk of internal circuit short circuits and damage.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing a pre-coated solder cover plate, comprising:

[0007] S10: Material Pretreatment

[0008] According to the preset conditions, a metal base plate that meets the requirements is processed, and the gold-tin alloy ingot obtained by melting is rolled into gold-tin foil strip. Then, the gold-tin foil strip is punched to obtain gold-tin solder, which has a hollow structure.

[0009] S20: Metal base plate etching

[0010] A ring-shaped groove is etched into the metal base plate;

[0011] S30: Electroplated metal base plate

[0012] After the groove etching is completed, the impurities on the surface of the metal base plate are cleaned, and an electroplating layer is formed on the surface of the metal base plate by an electrochemical method.

[0013] S40: Pre-coated gold-tin solder

[0014] After electroplating, the formed gold-tin solder is placed on the metal base plate, with the groove located in the inner frame of the gold-tin solder; the gold-tin solder is heated to a semi-molten state and adheres to the metal base plate to form a pre-coated solder cover plate.

[0015] S50: Finished Product Inspection

[0016] Check whether the pre-coated solder cover plate meets the requirements and reject unqualified products.

[0017] Preferably, in step S10, the thickness of the gold-tin solder is 10-25 μm, and the distance between the outer frame and the inner frame of the gold-tin solder is 0.1-0.2 mm.

[0018] Preferably, in step S20, the shape of the groove is the same as the outer edge shape of the metal base plate.

[0019] Preferably, the groove in step S20 is etched using a laser, and the laser is equipped with a control device for adjusting the laser spot size and the laser dwell time.

[0020] Preferably, in step S30, an electrochemical method is used to electroplate the surface of the metal substrate, and the electroplated layer has multiple layers with a total thickness of less than or equal to 5 μm.

[0021] Preferably, in step S30, the electroplating layer includes a first nickel plating layer and a second gold plating layer. The first nickel plating layer is disposed between the metal base plate and the second gold plating layer. The thickness of the first nickel plating layer is 2.5 to 4.5 μm, and the thickness of the second gold plating layer is 0.01 to 0.05 μm.

[0022] Preferably, in step S40, a high-temperature tunnel furnace is used to heat the gold-tin solder at high temperature. The temperature of the high-temperature tunnel furnace is set at 305-310°C, and the high-temperature tunnel furnace is filled with inert reducing gas or evacuated.

[0023] The beneficial effects of this invention are as follows:

[0024] This invention, by setting a groove within the inner frame of the gold-tin solder, confines the small amount of solder that randomly overflows into the metal substrate in a semi-molten state within the groove. This prevents the solder from diffusing into the central area of ​​the pre-coated solder cover plate, thus preventing solder overflow onto pre-arranged components such as quartz crystals and microcircuits on the ceramic substrate, which could lead to short circuits or damage. This improves the reliability and yield of the pre-coated solder metal substrate package. Additional aspects and advantages of this invention will be set forth in part in the description which follows, and will become apparent from the description. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0026] Figure 1 This is a cross-sectional schematic diagram of the packaged finished product of the present invention;

[0027] Figure 2 This is a cross-sectional schematic diagram of the metal base plate of the present invention;

[0028] Figure 3 This is a cross-sectional schematic diagram of the pre-coated solder cover plate of the present invention;

[0029] Figure 4 This is a top view of the pre-coated solder cover plate of the present invention.

[0030] In the figure:

[0031] 1. Pre-coated solder cover plate; 2. Gold-tin solder; 3. Transition layer; 4. Ceramic base; 5. Metal base plate; 6. Groove. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] See appendix Figure 1-4 This invention discloses a method for preparing a pre-coated solder cover plate, comprising:

[0034] S10: Material pretreatment, processing according to preset conditions to obtain a metal base plate 5 that meets the requirements, and rolling the smelted gold-tin alloy ingot into gold-tin foil strip, and then punching the gold-tin foil strip to obtain gold-tin solder 2, which has a hollow structure; the shape and size requirements of the metal base plate 5 are determined according to the parameters of the ceramic base 4, and the thickness is determined according to the impact strength. The material of the metal base plate 5 is preferably Kovar alloy, and the forming of the metal base plate 5 is preferably carried out by etching and punching processes. The distance between the outer frame of the gold-tin solder 2 and the outer edge of the metal base plate 5 is preferably 50μm.

[0035] S20: Etching of the metal base plate 5, etching an annular groove 6 on the metal base plate 5; preferably, the depth of the groove 6 is 10μm, the distance between the outer frame of the groove 6 and the inner frame of the gold solder 2 is 40μm, and the distance between the outer frame and the inner frame of the groove 6 is 20μm.

[0036] S30: After the metal base plate 5 is electroplated and the groove 6 is etched, the impurities on the surface of the metal base plate 5 are cleaned, and an electroplating layer is formed on the surface of the metal base plate 5 by an electrochemical method.

[0037] S40: Pre-coated gold-tin solder 2. After electroplating, the formed gold-tin solder 2 is placed on the metal base plate 5, and the groove 6 is located in the inner frame of the gold-tin solder 2. The gold-tin solder 2 is heated to a semi-molten state and adheres to the metal base plate 5 to form a pre-coated solder cover plate 1. In a semi-molten state, a small amount of gold-tin solder 2 flows randomly into the central area of ​​the pre-coated solder cover plate 1 until it flows into the groove 6 and is then confined in the groove 6, thereby completely preventing the gold-tin solder 2 from further diffusing into the central area of ​​the pre-coated solder cover plate 1.

[0038] S50: Finished product inspection, check whether the pre-coated solder cover plate 1 meets the requirements, and reject unqualified products; preferably use an automatic optical inspection instrument, through image analysis and processing, check whether the gold-tin solder 2 is pre-coated on the metal base plate 5 as required to form a standard pre-coated solder cover plate 1, and remove the pre-coated solder cover plate 1 that does not meet the requirements.

[0039] By setting the groove 6 and placing it within the inner frame of the gold-tin solder 2, the small amount of gold-tin solder 2 that is randomly overflowing into the central area of ​​the pre-coated solder cover plate 1 in a semi-molten state is confined within the groove 6. This prevents the gold-tin solder 2 from spreading into the central area of ​​the pre-coated solder cover plate 1 and prevents the gold-tin solder 2 from further overflowing into the components inside the ceramic base 4 during the sealing process, which could lead to short circuits or damage to the components. This improves the reliability and yield of the pre-coated solder metal base plate 5 encapsulation.

[0040] In this embodiment, preferably, in step S10, the thickness of the gold-tin solder 2 is 10-25 μm, and the distance between the outer frame and the inner frame of the gold-tin solder 2 is 0.1-0.2 mm.

[0041] In this embodiment, preferably, in step S20, the shape of the groove 6 is the same as the outer edge shape of the metal base plate 5.

[0042] In this embodiment, preferably, in step S20, the groove 6 is etched using a laser. The laser is equipped with a control device for adjusting the laser spot size and the laser dwell time. The width of the groove 6 is adjusted by the laser spot size, and the depth of the groove 6 is adjusted by the laser etching dwell time. According to the parameters of the groove 6 to be etched, the laser spot size and the laser dwell time are adjusted by the control device to achieve precise etching.

[0043] In this embodiment, preferably, in step S30, an electrochemical method is used to electroplate the surface of the metal base plate 5, and the electroplating layer has multiple layers, with a total thickness of less than or equal to 5 μm.

[0044] In this embodiment, preferably, in step S30, the electroplating layer includes a first nickel plating layer and a second gold plating layer. The first nickel plating layer is disposed between the metal base plate 5 and the second gold plating layer. The thickness of the first nickel plating layer is 2.5 to 4.5 μm, and the thickness of the second gold plating layer is 0.01 to 0.05 μm.

[0045] In this embodiment, preferably, in step S40, a high-temperature tunnel furnace is used to heat the gold-tin solder 2 at high temperature. The temperature of the high-temperature tunnel furnace is set to 305-310°C, and the high-temperature tunnel furnace is filled with inert reducing gas or evacuated.

[0046] This invention can pre-coat the metal substrate 5 with gold-tin solder 2, ensuring the quality of hermetic packaging while preventing the solder from overflowing disorderly into the central area of ​​the pre-coated solder cover 1. This prevents the gold-tin solder 2 overflowing into the internal circuit of electronic components from causing short circuits or damage during subsequent packaging processes, thereby significantly improving the reliability and yield of the pre-coated solder cover 1. In subsequent packaging processes of electronic components, this invention can achieve high-quality hermetic packaging while preventing the disorderly overflow of gold-tin solder 2 into the components, thus avoiding short circuits or damage and improving the reliability and stability of component packaging.

[0047] Example 1

[0048] S10: Material pretreatment. The metal base plate 5 is made of Kovar alloy, and is rectangular in shape with a length of 1.2mm, a width of 1.0mm, and a thickness of 0.04mm. It is formed by precision etching. The gold-tin alloy ingot obtained by melting is rolled into gold-tin foil strip, and then the foil strip is punched to obtain gold-tin solder 2. Gold-tin solder 2 is a hollow ring structure with a thickness of 10μm. The outer frame of the gold-tin solder ring is 1.15mm long and 0.95mm wide, and the inner frame is 0.95mm long and 0.75mm wide.

[0049] S20: Etching of the metal base plate 5. The laser parameters are adjusted by the control device to quickly etch a groove 6 on the metal base plate 5. The groove 6 is rectangular, with a depth of 10μm. The outer frame of the groove 6 is 0.91mm long and 0.71mm wide, the inner frame of the groove 6 is 0.89mm long and 0.69mm wide, and the width of the groove 6 is 20μm.

[0050] S30: Electroplating of metal base plate 5. After removing impurities from the surface of metal base plate 5, two layers of electroplating are performed on the surface of metal base plate 5 using an electrochemical method. The first plating layer is nickel plating with a thickness of 3μm, and the second plating layer is gold plating with a thickness of 0.015μm.

[0051] S40: Pre-coated gold-tin solder 2. After electroplating, the gold-tin solder 2 is accurately placed on the metal base plate 5, and the groove 6 is located in the inner frame of the gold-tin solder 2. Then it is transferred to a high-temperature tunnel kiln. The temperature of the high-temperature tunnel kiln during sintering is 305°C. The high-temperature tunnel kiln is filled with inert reducing gas. The gold-tin solder 2 is rapidly attached to the metal base plate 5 in a semi-molten state to form a pre-coated gold-tin solder 2 cover plate.

[0052] S50: Finished product inspection. An automatic optical inspection instrument is used to check whether the gold-tin solder 2 is pre-coated on the metal base plate 5 as required through image analysis and processing, and to remove the pre-coated solder cover plate 1 that does not meet the requirements.

[0053] S60: During the sealing process, a transition layer 3 is provided between the pre-coated solder cover plate 1 and the ceramic base 4. The gold-tin solder 2 is matched with the transition layer 3. The pre-coated solder cover plate 1 is placed on the ceramic base 4 where the crystal has been placed, and it is transferred to the high-temperature tunnel furnace. At the welding temperature, the molten gold-tin solder 2, due to its high fluidity and high wettability, can quickly fill the gap between the pre-coated solder cover plate 1 and the ceramic base 4 to achieve hermetic sealing. The small amount of gold-tin solder 2 that overflows disorderly into the central area of ​​the pre-coated solder cover plate 1 after melting is restricted by the groove 6 to prevent the gold-tin solder 2 overflowing into the central area from causing short circuits or damage to the internal circuits of electronic components.

[0054] Example 2

[0055] S10: Material pretreatment. The metal base plate 5 is made of Kovar alloy, and is rectangular in shape with a length of 1.6mm, a width of 1.2mm, and a thickness of 0.06mm. It is formed by precision etching. The gold-tin alloy ingot obtained by melting is rolled into gold-tin foil strip, and then the foil strip is punched to obtain gold-tin solder 2. Gold-tin solder 2 is a hollow ring structure with a thickness of 13μm. The outer frame of gold-tin solder 2 is 1.55mm long and 1.15mm wide, and the inner frame is 1.35mm long and 0.95mm wide.

[0056] S20: Etching of the metal base plate 5. The laser parameters are adjusted by the control device to quickly etch a groove 6 on the metal base plate 5. The groove 6 is rectangular, with a depth of 12μm. The outer frame of the groove 6 is 1.31mm long and 0.91mm wide, the inner frame of the groove 6 is 1.29mm long and 0.89mm wide, and the width of the groove 6 is 20μm.

[0057] S30: Electroplating of metal base plate 5. After removing impurities from the surface of metal base plate 5, two layers of electroplating are performed on the surface of metal base plate 5 using an electrochemical method. The first plating layer is nickel plating with a thickness of 3.5μm, and the second plating layer is gold plating with a thickness of 0.02μm.

[0058] S40: Pre-coated gold-tin solder 2. After electroplating, the gold-tin solder 2 is accurately placed on the metal base plate 5, and the groove 6 is located in the inner frame of the gold-tin solder 2. Then it is transferred to the high-temperature tunnel kiln. The temperature of the high-temperature tunnel kiln during sintering is 308°C. The high-temperature tunnel kiln is evacuated. The gold-tin solder 2 is rapidly attached to the metal base plate 5 in a semi-molten state to form the pre-coated gold-tin solder 2 cover plate.

[0059] S50: Finished product inspection. An automatic optical inspection instrument is used to check whether the gold-tin solder 2 is pre-coated on the metal base plate 5 as required through image analysis and processing, and to remove the pre-coated solder cover plate 1 that does not meet the requirements.

[0060] S60: During the sealing process, a transition layer 3 is provided between the pre-coated solder cover plate 1 and the ceramic base 4. The gold-tin solder 2 is matched with the transition layer 3. The pre-coated solder cover plate 1 is placed on the ceramic base 4 where the crystal has been placed, and it is transferred to the high-temperature tunnel furnace. At the welding temperature, the molten gold-tin solder 2, due to its high fluidity and high wettability, can quickly fill the gap between the pre-coated solder cover plate 1 and the ceramic base 4 to achieve hermetic sealing. The small amount of gold-tin solder 2 that overflows disorderly into the central area of ​​the pre-coated solder cover plate 1 after melting is restricted by the groove 6 to prevent the gold-tin solder 2 overflowing into the central area from causing short circuits or damage to the internal circuits of electronic components.

[0061] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to the embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a pre-coated solder cover plate, characterized in that, include: S10: Material Pretreatment According to the preset conditions, a metal base plate that meets the requirements is processed, and the gold-tin alloy ingot obtained by melting is rolled into gold-tin foil strip. Then, the gold-tin foil strip is punched to obtain gold-tin solder, which has a hollow structure. S20: Metal base plate etching A ring-shaped groove is etched into the metal base plate; S30: Electroplated metal base plate After the groove etching is completed, impurities on the surface of the metal base plate are cleaned, and electroplating is performed on the surface of the metal base plate using an electrochemical method to form an electroplated layer. The electroplated layer includes a first nickel plating layer and a second gold plating layer. The first nickel plating layer is disposed between the metal base plate and the second gold plating layer. The total thickness of the electroplated layer is less than or equal to 5 μm, the thickness of the first nickel plating layer is 2.5 to 4.5 μm, and the thickness of the second gold plating layer is 0.01 to 0.05 μm. S40: Pre-coated gold-tin solder After electroplating, the formed gold-tin solder is placed on the metal base plate, with the groove located within the inner frame of the gold-tin solder. A gold-tin solder is heated to a semi-molten state at high temperature and adhered to a metal base plate to form a pre-coated solder cover plate. The gold-tin solder is heated at a high temperature of 305°C using a high-temperature tunnel furnace. 310℃; the distance between the outer frame of the gold-tin solder and the outer edge of the metal base plate is 50μm, the distance between the outer frame of the groove and the inner frame of the gold-tin solder is 40μm, and the distance between the outer frame of the groove and the inner frame of the groove is 20μm; S50: Finished Product Inspection Check whether the pre-coated solder cover plate meets the requirements and reject unqualified products; During the sealing process, a transition layer is set between the pre-coated solder cover plate and the ceramic base. The gold-tin solder matches the transition layer. The pre-coated solder cover plate is then placed on the ceramic base where the crystal has been placed, and the ceramic base is then transferred to a high-temperature tunnel kiln.

2. The method for preparing a pre-coated solder cover plate according to claim 1, characterized in that, In step S10, the thickness of the gold-tin solder is 10-25 μm, and the distance between the outer frame and the inner frame of the gold-tin solder is 0.1-0.2 mm.

3. The method for preparing a pre-coated solder cover plate according to claim 1, characterized in that, In step S20, the shape of the groove is the same as the outer edge shape of the metal base plate.

4. The method for preparing a pre-coated solder cover plate according to claim 1, characterized in that, The groove described in step S20 is etched using a laser, and the laser is equipped with a control device for adjusting the laser spot size and the laser dwell time.

5. The method for preparing a pre-coated solder cover plate according to claim 1, characterized in that, In step S40, the high-temperature tunnel kiln is filled with inert reducing gas or evacuated.

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