A parallel sealing process with ultra-low void rate suitable for pre-plated gold-tin solder cap

Abstract

The application provides a parallel sealing process with ultra-low cavity rate suitable for pre-setting gold-tin solder cover plates, and comprises the following steps: S1, a plurality of pre-fixing points are arranged on the first pair of edges and the second pair of edges of the cover plate respectively, so that the cover plate is pre-fixed on the pipe shell through the double-edge multi-point pre-fixing mode; and S2, the first pair of edges and the second pair of edges of the cover plate are continuously sealed respectively.

Description

Technical Field

[0001] This invention relates to the field of component packaging technology, and in particular to a parallel sealing process with ultra-low void ratio suitable for pre-placed gold-tin solder cover plates. Background Technology

[0002] Hybrid integrated circuits (HICs) and semiconductor devices are core components in industries such as industrial, aerospace, and high-end electronic equipment. The sealing and reliability of their packaging directly determine the reliability and lifespan of the products. Parallel sealing has become the mainstream packaging technology in the HIC and semiconductor industries due to its high packaging efficiency and excellent sealing performance. Taking a rectangular tube shell as an example, the traditional parallel sealing process is as follows: first, a single-point welding pre-fixation is performed at the midpoint of one pair of parallel edges between the shell and the cover plate; then, continuous sealing welding is performed on the pre-fixed pair of parallel edges; finally, continuous sealing welding is performed on the remaining pair of parallel edges.

[0003] This process has significant technical drawbacks in practical applications: 1. When pre-fixed at a single point, the cover plate is connected to the outer shell only through a single welding point. The pressure applied during the operation of the electrode wheel and the thermal stress generated during the welding process continue to accumulate and concentrate on the unfixed side. The two stresses cannot be effectively dispersed, causing the cover plate to be in an asymmetrical stress state, which causes the cover plate on the unfixed side to warp. In particular, the warping of thin cover plates with weak structural rigidity and small size is more severe.

[0004] 2. Warping caused by welding the first pair of sides will increase the gap between the second pair of side cover plates and the pipe shell. After sealing, the internal stress (mainly tensile stress) of the second pair of parallel side welds will be greater, making them more prone to fatigue during long-term use, thus initiating cracks and ultimately leading to seal failure.

[0005] 3. For pre-placed gold solder cover plates, cover plate warping will cause uneven distribution of pre-placed gold solder, requiring more solder to fill the gaps (involving changes to the cover plate solder ring structure, leading to increased costs). This not only affects the flatness of the outer shell appearance, but also, at best, leads to a reduction in the welding width of the sealing edge and a sharp increase in the solder void rate, and at worst, leads to sealing failure and product scrap.

[0006] Existing improvements mainly focus on optimizing the cover plate material or plating, without addressing the issue of uneven stress distribution from the perspective of the sealing process principle. Therefore, there is an urgent need for a new parallel sealing process based on innovative solder joint layout that can effectively disperse stress, suppress cover plate warping, and without increasing costs, in order to achieve low warping and ultra-low void ratio encapsulation of gold-tin solder cover plates. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide an ultra-low void ratio parallel sealing process suitable for pre-placed gold-tin solder cover plates, which addresses the shortcomings of the prior art.

[0008] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: a parallel sealing process with ultra-low void ratio suitable for pre-placed gold-tin solder cover plates, comprising: S1, setting multiple pre-fixing points on the first and second opposite sides of the cover plate to pre-fix the cover plate to the tube shell by means of double-sided multi-point pre-fixing; S2, continuously sealing the first and second opposite sides of the cover plate.

[0009] The beneficial effects of adopting the technical solution of this invention are that, by designing a new parallel sealing process based on innovative solder joint layout, effectively dispersing stress, suppressing cover plate warping, and without increasing costs, the pre-fixing method of the cover plate is changed from single-sided single-point to double-sided multi-point pre-fixing, followed by continuous sealing. By setting multiple pre-fixing points on two pairs of parallel sides, the stress state and constraint conditions of the cover plate during the sealing process are changed. The pre-fixing points around the perimeter are similar to "anchor points," stably "anchoring" the cover plate to the shell, forming a symmetrical constraint system. During the sealing of the first pair of parallel sides, the electrode wheel pressure and welding thermal stress are shared and buffered by the pre-fixing points around the perimeter, effectively preventing stress accumulation at local positions on the second pair of parallel sides, which could lead to cover plate warping and solder voids. This achieves low warping and ultra-low void rate encapsulation of gold-tin solder cover plates.

[0010] Furthermore, in step S1, the first pair of sides and the second pair of sides are two pairs of parallel sides; the number of pre-fixed points on each of the first pair of sides and the second pair of sides ranges from 4 to 6.

[0011] The beneficial effect of adopting the above-mentioned further technical solution is that by setting multiple pre-fixing points on two pairs of parallel sides, the stress state and constraint conditions of the cover plate during the sealing and welding process are changed. The pre-fixing points on the four sides are similar to "anchor points", which stably "anchor" the cover plate to the pipe shell, forming a symmetrical constraint system.

[0012] Further, step S1 includes: S11, setting 5 pre-fixed points on the first opposite side and 6 pre-fixed points on the second opposite side; S12, using the first preset parallel sealing welding parameters, welding the pre-fixed points to anchor the cover plate to the pipe shell; step S2 includes: using the first preset parallel sealing welding parameters, first welding the first opposite side with 5 pre-fixed points, and then welding the second opposite side with 6 pre-fixed points.

[0013] The beneficial effect of adopting the above-mentioned further technical solution is that by setting multiple pre-fixing points on the two pairs of parallel edges, the stress state and constraint conditions of the cover plate during the sealing process are changed. The pre-fixing points on the four perimeter are similar to "anchor points," stably "anchoring" the cover plate to the shell, forming a symmetrical constraint system. During the sealing of the first pair of parallel edges, the electrode wheel pressure and welding thermal stress are shared and buffered by the pre-fixing points on the four perimeter, effectively preventing stress accumulation at local positions on the second pair of parallel edges, which could lead to cover plate warping and solder voids. This achieves low warping and ultra-low void ratio encapsulation of the gold-tin solder cover plate.

[0014] Furthermore, before step S1, the following steps are included: pre-processing the cover plate and the tube shell; checking the integrity of the gold solder; and positioning and assembling the cover plate and the tube shell.

[0015] The beneficial effects of adopting the above-mentioned further technical solutions are to improve welding quality and product quality.

[0016] Furthermore, the pretreatment steps for the cover plate and the tube shell include: cleaning the cover plate; wiping the outer sealing area on the tube shell; and baking the tube shell and cover plate before packaging to control the moisture content inside the product.

[0017] The beneficial effects of adopting the above-mentioned further technical solution are that baking the tube shell and cover plate before packaging controls the moisture content inside the product and improves welding quality.

[0018] Furthermore, the steps for cleaning the cover plate include: ultrasonically cleaning the cover plate using a cleaning solution and ethanol; the steps for wiping the outer casing sealing area on the tube shell include: wiping the outer casing sealing area with acetone.

[0019] The beneficial effects of adopting the above-mentioned further technical solutions are that the cover plate is ultrasonically cleaned using environmentally friendly cleaning fluid and ethanol; and the sealing area of ​​the outer shell is wiped with acetone. This removes dirt from the welding positions and improves the welding quality.

[0020] Further steps to check the integrity of the gold solder include: confirming that the pre-applied gold solder has not fallen off or been damaged.

[0021] The beneficial effect of adopting the above-mentioned further technical solution is that it can check the integrity of the solder, confirm that the pre-placed gold-tin solder has not fallen off or been damaged, and improve product quality.

[0022] Furthermore, the steps for positioning and assembling the cover plate and the tube shell include: aligning and assembling the cover plate and the tube shell using a suction nozzle to avoid scratching or damaging the gold solder.

[0023] The beneficial effects of adopting the above-mentioned further technical solution are that aligning and assembling the cover plate and the tube shell using a special suction nozzle avoids scratching or damaging the solder, thus improving stability and reliability.

[0024] Furthermore, after step S2, the following steps are performed: fine leak testing and rough leak testing are carried out on the finished product in sequence to ensure that the seal is qualified.

[0025] The beneficial effect of adopting the above-mentioned further technical solution is that, in accordance with relevant standard requirements, the finished product is subjected to fine leak inspection and rough leak inspection in sequence to ensure that the sealing is qualified.

[0026] Furthermore, in step S1, the cover plate is pre-filled with a 4J42 Kovar alloy cover plate with a gold-tin solder thickness of 0.05mm; the tube shell is a metal shell or a ceramic shell; the cover plate has a cubic structure with a side length of 9.8mm and a thickness of 0.3mm.

[0027] The beneficial effect of adopting the above-mentioned further technical solutions is that they are applicable to parallel sealing and encapsulation of various metal and ceramic shells, thus improving applicability.

[0028] The advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic flowchart illustrating an ultra-low void ratio parallel sealing process for a pre-placed gold-tin solder cover plate, provided in an embodiment of the present invention.

[0031] Figure 2 This is a schematic diagram of the tube shell provided in an embodiment of the present invention.

[0032] Figure 3 This is a schematic diagram of the cover plate provided in an embodiment of the present invention.

[0033] Figure 4 This is a parallel sealing process diagram for an ultra-low void ratio suitable for a pre-placed gold-tin solder cover plate, provided as an embodiment of the present invention.

[0034] The following are the symbols in the attached diagram: 1. Tube shell; 2. Sealing area; 3. Cover plate; 4. Inside of the cavity. Detailed Implementation

[0035] The principles and features of the present invention are described below with reference to the accompanying drawings. The embodiments described are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0037] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0038] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0039] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0040] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0041] like Figure 1 As shown, this embodiment of the invention provides an ultra-low void ratio parallel sealing process suitable for pre-placed gold-tin solder cover plates, including: S1, setting multiple pre-fixing points on the first and second opposite sides of the cover plate to pre-fix the cover plate to the tube shell through a double-sided multi-point pre-fixing method; S2, continuously sealing the first and second opposite sides of the cover plate.

[0042] The beneficial effects of adopting the technical solution of this invention are that, by designing a new parallel sealing process based on innovative solder joint layout, effectively dispersing stress, suppressing cover plate warping, and without increasing costs, the pre-fixing method of the cover plate is changed from single-sided single-point to double-sided multi-point pre-fixing, followed by continuous sealing. By setting multiple pre-fixing points on two pairs of parallel sides, the stress state and constraint conditions of the cover plate during the sealing process are changed. The pre-fixing points around the perimeter are similar to "anchor points," stably "anchoring" the cover plate to the shell, forming a symmetrical constraint system. During the sealing of the first pair of parallel sides, the electrode wheel pressure and welding thermal stress are shared and buffered by the pre-fixing points around the perimeter, effectively preventing stress accumulation at local positions on the second pair of parallel sides, which could lead to cover plate warping and solder voids. This achieves low warping and ultra-low void rate encapsulation of gold-tin solder cover plates.

[0043] Furthermore, in step S1, the first pair of sides and the second pair of sides are two pairs of parallel sides; the number of pre-fixed points on each of the first pair of sides and the second pair of sides ranges from 4 to 6.

[0044] The beneficial effect of adopting the above-mentioned further technical solution is that by setting multiple pre-fixing points on two pairs of parallel sides, the stress state and constraint conditions of the cover plate during the sealing and welding process are changed. The pre-fixing points on the four sides are similar to "anchor points", which stably "anchor" the cover plate to the pipe shell, forming a symmetrical constraint system.

[0045] Further, step S1 includes: S11, setting 5 pre-fixed points on the first opposite side and 6 pre-fixed points on the second opposite side; S12, using the first preset parallel sealing welding parameters, welding the pre-fixed points to anchor the cover plate to the pipe shell; step S2 includes: using the first preset parallel sealing welding parameters, first welding the first opposite side with 5 pre-fixed points, and then welding the second opposite side with 6 pre-fixed points.

[0046] The beneficial effect of adopting the above-mentioned further technical solution is that by setting multiple pre-fixing points on the two pairs of parallel edges, the stress state and constraint conditions of the cover plate during the sealing process are changed. The pre-fixing points on the four perimeter are similar to "anchor points," stably "anchoring" the cover plate to the shell, forming a symmetrical constraint system. During the sealing of the first pair of parallel edges, the electrode wheel pressure and welding thermal stress are shared and buffered by the pre-fixing points on the four perimeter, effectively preventing stress accumulation at local positions on the second pair of parallel edges, which could lead to cover plate warping and solder voids. This achieves low warping and ultra-low void ratio encapsulation of the gold-tin solder cover plate.

[0047] Furthermore, before step S1, the following steps are included: pre-processing the cover plate and the tube shell; checking the integrity of the gold solder; and positioning and assembling the cover plate and the tube shell.

[0048] The beneficial effects of adopting the above-mentioned further technical solutions are to improve welding quality and product quality.

[0049] Furthermore, the pretreatment steps for the cover plate and the tube shell include: cleaning the cover plate; wiping the outer sealing area on the tube shell; and baking the tube shell and cover plate before packaging to control the moisture content inside the product.

[0050] The beneficial effects of adopting the above-mentioned further technical solution are that baking the tube shell and cover plate before packaging controls the moisture content inside the product and improves welding quality.

[0051] Furthermore, the steps for cleaning the cover plate include: ultrasonically cleaning the cover plate using a cleaning solution and ethanol; the steps for wiping the outer casing sealing area on the tube shell include: wiping the outer casing sealing area with acetone.

[0052] The beneficial effects of adopting the above-mentioned further technical solutions are that the cover plate is ultrasonically cleaned using environmentally friendly cleaning fluid and ethanol; and the sealing area of ​​the outer shell is wiped with acetone. This removes dirt from the welding positions and improves the welding quality.

[0053] Further steps to check the integrity of the gold solder include: confirming that the pre-applied gold solder has not fallen off or been damaged.

[0054] The beneficial effect of adopting the above-mentioned further technical solution is that it can check the integrity of the solder, confirm that the pre-placed gold-tin solder has not fallen off or been damaged, and improve product quality.

[0055] Furthermore, the steps for positioning and assembling the cover plate and the tube shell include: aligning and assembling the cover plate and the tube shell using a suction nozzle to avoid scratching or damaging the gold solder.

[0056] The beneficial effects of adopting the above-mentioned further technical solution are that aligning and assembling the cover plate and the tube shell using a special suction nozzle avoids scratching or damaging the solder, thus improving stability and reliability.

[0057] Furthermore, after step S2, the following steps are performed: fine leak testing and rough leak testing are carried out on the finished product in sequence to ensure that the seal is qualified.

[0058] The beneficial effect of adopting the above-mentioned further technical solution is that, in accordance with relevant standard requirements, the finished product is subjected to fine leak inspection and rough leak inspection in sequence to ensure that the sealing is qualified.

[0059] Furthermore, in step S1, the cover plate is pre-filled with a 4J42 Kovar alloy cover plate with a gold-tin solder thickness of 0.05mm; the tube shell is a metal shell or a ceramic shell; the cover plate has a cubic structure with a side length of 9.8mm and a thickness of 0.3mm.

[0060] The beneficial effect of adopting the above-mentioned further technical solutions is that they are applicable to parallel sealing and encapsulation of various metal and ceramic shells, thus improving applicability.

[0061] This invention aims to solve the problems of stress concentration, cover plate warping, and high void ratio in gold-tin solder caused by single-point pre-fixation in existing parallel sealing processes. It provides an ultra-low void ratio parallel sealing process suitable for pre-placed gold-tin solder cover plates, which can be a bilateral pre-fixed parallel sealing process capable of achieving ultra-low solder void ratio. Its core lies in changing the cover plate pre-fixation method from single-sided single-point to bilateral multi-point pre-fixation, followed by continuous sealing.

[0062] By setting multiple pre-fixing points on two pairs of parallel edges, the stress state and constraint conditions of the cover plate during the sealing process are changed. The pre-fixing points around the perimeter are similar to "anchor points," stably "anchoring" the cover plate to the shell, forming a symmetrical constraint system. During the sealing of the first pair of parallel edges, the electrode wheel pressure and welding thermal stress are shared and buffered by the pre-fixing points around the perimeter (4-6 on each side, depending on the shell and cover plate structure), effectively preventing stress accumulation at local locations on the second pair of parallel edges, which could lead to cover plate warping and solder voids. Actual measurements showed that for a 4J42 Kovar alloy cover plate with a side length of 9.8mm*9.8mm, a thickness of 0.3mm, and a pre-applied gold-tin solder thickness of 0.05mm, after adopting this process, the cover plate warping height was reduced from 10um to 3.5um (a 65% decrease), and the average void rate of the gold-tin solder was only 5%. After relevant environmental tests, mechanical tests, and aging tests, the seal passed.

[0063] This process requires no modification to existing equipment and has advantages such as good process compatibility, simple implementation, and no additional costs. It is suitable for parallel sealing and encapsulation of various metal and ceramic shells.

[0064] The following example illustrates the process steps using a 4J42 Kovar alloy cover plate (pre-filled with 0.05mm gold-tin solder) with sides of 9.8mm*9.8mm*0.3mm and a ceramic shell: 1. Pre-treatment: Use environmentally friendly cleaning solution and ethanol to ultrasonically clean the cover plate; wipe the sealing area of ​​the outer shell with acetone; bake the tube shell and cover plate before packaging to control the moisture content inside the product.

[0065] 2. Check the integrity of the solder: Confirm that the pre-placed gold solder has not fallen off or been damaged.

[0066] 3. Positioning and assembly: Align the cover plate with the tube shell using a special suction nozzle to avoid scratching or damaging the solder.

[0067] 4. Design pre-fixed points: Set 5 pre-fixed points on the first opposite side and 6 pre-fixed points on the second opposite side.

[0068] 5. Bilateral pre-fixation: Using appropriate parallel sealing welding parameters, weld the above 11 pre-fixing points to anchor the cover plate to the pipe shell.

[0069] 6. Continuous parallel sealing: Using appropriate parallel sealing parameters, first weld a pair of sides with 5 pre-fixed points, and then weld another pair of sides with 6 pre-fixed points.

[0070] 7. Sealing test: In accordance with relevant standards, the finished product is subjected to fine leak testing and rough leak testing in sequence to ensure that the sealing is qualified.

[0071] Figures 2 to 4 In the diagram, the gray part is the shell 1, the yellow part is the metallized area (sealing area 2), the blue part is the cover plate 3, the middle part of the shell 1 is the cavity interior 4, the sealing area 2 is located on the shell 1, and the serial number indicates the operating sequence.

[0072] Figure 2 and Figure 3 This is a schematic diagram of the structure of the shell 1 and the cover plate 3.

[0073] Figure 4 The process of double-sided multi-point pre-fixed parallel sealing is shown: 1. First side multi-point pre-fixing, 2. Second side multi-point pre-fixing, 3. Sealing the first pair of parallel sides (green dashed lines), 4. Sealing the second pair of parallel sides (red dashed lines).

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A parallel sealing process for ultra-low void ratio suitable for pre-placed gold-tin solder cover plates, characterized in that, include: S1. Multiple pre-fixing points are set on the first and second opposite sides of the cover plate to pre-fix the cover plate to the tube shell by means of double-sided multi-point pre-fixing. S2. Seal weld continuously on the first and second opposite sides of the cover plate.

2. The ultra-low void ratio parallel sealing process for pre-placed gold-tin solder cover plates according to claim 1, characterized in that, In step S1, the first pair of sides and the second pair of sides are two pairs of parallel sides; the number of pre-fixed points on each of the first pair of sides and the second pair of sides ranges from 4 to 6.

3. The ultra-low void ratio parallel sealing process for pre-placed gold-tin solder cover plates according to claim 2, characterized in that, Step S1 includes: S11. Set 5 pre-fixed points on the first opposite side and 6 pre-fixed points on the second opposite side; S12. Using the first preset parallel sealing welding parameters, weld the pre-fixed point to anchor the cover plate to the pipe shell; Step S2 includes: using the first preset parallel sealing welding parameters, first welding the first pair of sides with 5 pre-fixed points, and then welding the second pair of sides with 6 pre-fixed points.

4. The ultra-low void ratio parallel sealing process for pre-placed gold-tin solder cover plates according to claim 1, characterized in that, Before step S1, the following are included: Pre-treatment of the cover plate and pipe shell; Check the integrity of the gold-tin solder; Position and assemble the cover plate and the tube shell.

5. The ultra-low void ratio parallel sealing process for pre-placed gold-tin solder cover plates according to claim 4, characterized in that, The pretreatment steps for the cover plate and the casing include: Clean the cover plate; Wipe the outer sealing area on the tube shell; Before packaging, the tube shell and cover are baked to control the moisture content inside the product.

6. The ultra-low void ratio parallel sealing process for pre-placed gold-tin solder cover plates according to claim 5, characterized in that, The steps for cleaning the cover plate include: ultrasonically cleaning the cover plate with cleaning solution and ethanol; the steps for wiping the outer casing sealing area on the tube shell include: wiping the outer casing sealing area with acetone.

7. The ultra-low void ratio parallel sealing process for pre-placed gold-tin solder cover plates according to claim 4, characterized in that, The steps for checking the integrity of the gold solder include: confirming that the pre-applied gold solder has not fallen off or been damaged.

8. The ultra-low void ratio parallel sealing process for pre-placed gold-tin solder cover plates according to claim 4, characterized in that, The steps for positioning and assembling the cover plate and the tube shell include: aligning and assembling the cover plate and the tube shell using a suction nozzle to avoid scratching or damaging the gold solder.

9. The ultra-low void ratio parallel sealing process for pre-placed gold-tin solder cover plates according to claim 1, characterized in that, Step S2 is followed by: performing fine leak checks and rough leak checks on the finished product in sequence to ensure that the seal is qualified.

10. The ultra-low void ratio parallel sealing process for pre-placed gold-tin solder cover plates according to claim 1, characterized in that, In step S1, a 4J42 Kovar alloy cover plate with a gold-tin solder thickness of 0.05mm is pre-placed on the cover plate; The casing can be made of metal or ceramic. The cover plate has a cube structure, with a side length of 9.8 mm and a thickness of 0.3 mm.

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