Lead frame manufacturing method

Abstract

The invention discloses a manufacturing method of a lead frame, which improves the reliability of the lead frame in a packaging process so as to stably achieve a high reliability level, so that a packaged integrated circuit does not have a layering phenomenon in an application process, and the service life of the integrated circuit is ensured. According to the method, electrolytic degreasing, copper plating, single-face crude copper plating, silver pre-plating, silver plating, silver stripping, water washing, drying and forming treatment are sequentially carried out, and finally the lead frame is obtained, single-face crude copper plating is carried out through single-face crude copper plating equipment, one face of the stamped lead frame makes contact with coarsening liquid medicine for copper material coarsening, and the other face of the lead frame does not make contact with the liquid medicine.

Description

Technical Field

[0001] The invention relates to the field of integrated circuit packaging, and in particular to a method for manufacturing a lead frame. Background Art

[0002] In the process of integrated circuit packaging, its reliability depends to a great extent on the bonding strength between the plastic packaging material and the lead frame. In order to meet the needs of high heat dissipation and high reliability, the packaging form of exposed heat sinks is gradually pursuing high reliability. However, the existing technology generally implements double-sided roughening treatment. For packaging, the overflow on the exposed heat sink is extremely difficult to remove, which not only affects the appearance, but also has an adverse effect on the heat dissipation effect of the exposed heat sink. Therefore, it is urgent to develop a lead frame manufacturing method that can perform single-sided roughening. Summary of the invention

[0003] In view of the above problems, the present invention provides a lead frame manufacturing method, which improves the reliability of the lead frame during the packaging process, thereby stably achieving a high reliability level, so that the packaged integrated circuit will not delaminate during use, thereby ensuring the service life of the integrated circuit.

[0004] A method for manufacturing a lead frame, characterized in that: electrolytic degreasing, copper plating, single-sided rough copper plating, pre-silver plating, silver plating, silver stripping, water washing, drying and molding are sequentially performed to finally obtain a lead frame:

[0005] The single-sided rough copper plating is performed using a single-sided rough copper plating device. One side of the stamped lead frame contacts with a roughening solution to roughen the copper material, while the other side of the lead frame does not contact with the solution.

[0006] It is further characterized by:

[0007] The single-sided rough copper plating equipment comprises an outer frame, the two side plates of the outer frame are connected by a plurality of transverse fixed brackets, a liquid medicine tank body is formed in the central area in the length direction of the outer frame, lead frame guide mechanisms are respectively provided at both ends in the length direction of the outer frame, upper water holes arranged in an array are provided on the bottom plate of the liquid medicine tank body, the liquid medicine tank body is provided with an electrode plate, a partition is provided between the liquid medicine tank body and the lead frame guide mechanisms at both ends, an overflow hole groove is provided on the partition, the width and height of the overflow hole groove enable the lead frame to pass reliably, and the overflow hole groove enables only the lower surface of the lead frame to be located below the liquid surface of the liquid medicine, and the upper surface of the lead frame is located above the liquid surface of the liquid medicine;

[0008] The potion is obtained by mixing copper sulfate solution, hydrochloric acid, copper additive PPR, and copper auxiliary agent PPR-H;

[0009] The solubility of each component in the potion is: the copper sulfate solution is copper sulfate with a concentration of 200±50g / L, sulfuric acid with a concentration of 10±2%, and water at a temperature of 35°C±2°C;

[0010] The concentration of hydrochloric acid solution is 100PPM;

[0011] Copper additive PPR concentration of 3 ± 0.2 ml / l, and water;

[0012] The concentration of copper adjuvant PPR-H is 203±10 ml / l, and water.

[0013] It is further characterized by:

[0014] The liquid medicine enters the liquid medicine tank through the upper water hole. When the lead frame moves along the lead frame guide mechanism through the liquid medicine tank, its running speed is precisely controlled within the range of 2.5±0.2 m / min. When the liquid medicine is supplied through the upper water hole, its pressure range is strictly controlled within 3.5-5 kg / cm 2 It effectively solves the problem of water ripple height without generating bubbles, and firmly controls the water ripple height within 0.08mm. The solution will not infiltrate the upper surface of the lead frame, thus achieving a single-sided roughening effect.

[0015] It is further characterized in that:

[0016] The liquid medicine tank body is provided with two product support rods on the upper surface corresponding to the bottom plate, and the width between the product support rods is used to guide the lead frame to move linearly;

[0017] An inwardly concave guiding groove is provided between the facing surfaces of the two product support bars, and the inwardly concave guiding groove is used for guiding the lead frame, and the bottom height of the inwardly concave guiding groove is used for determining the height of the lower surface of the lead frame;

[0018] Each product support rod is provided with an upper convex mounting column at the position corresponding to the horizontal fixing bracket. The adjusting bolt passes through the mounting hole of the horizontal fixing bracket and is fixedly connected to the upper convex mounting column. The upper convex mounting column is provided with a vertical screw hole. The height of the product support rod is reasonably adjusted according to the thickness of the lead frame and the height of the liquid in the upper water hole to ensure that only the bottom surface of the lead frame can be roughened.

[0019] The mounting hole of the horizontal fixing bracket is a horizontal long slot hole, which enables the width between the two product support rods to be quickly adjusted according to the width of the lead frame, thereby ensuring the versatility of the equipment;

[0020] The bottom of the electrode plate in the liquid medicine tank is connected to the corresponding position of the bottom plate, and the upper parts of several electrode plates are respectively fixed to the electrode support plate, and the electrode support plate is a closed rectangular frame, which makes the assembly of the electrode plates on both sides quick and convenient;

[0021] Each group of the lead frame guide mechanism comprises a group of product limiting wheels and a plurality of guide rollers. The lead frame is formed along the width direction at a spacing between the product limiting wheels and is introduced into the medicine tank body or leaves the medicine tank body through the plurality of guide rollers, so as to ensure that the lead frame is transported reliably and stably.

[0022] A reflux hole is provided on the bottom plate of each set of lead frame guide mechanisms, and the medicine flowing out along the overflow hole groove flows back to the medicine box at the bottom through the reflux hole. The medicine box at the bottom then inputs the medicine into the medicine tank body through the upper water hole through the pump body and the pipeline.

[0023] After adopting the structure of the present invention, one side of the stamped lead frame contacts with the roughening solution to roughen the copper material, while the other side does not contact with the solution. The roughness of one side of the stamped lead frame is increased, thereby increasing the bonding force between the silver layer and the plastic packaging material during the packaging process, so that the bonding force between the copper layer and the silver layer of the lead frame and the plastic packaging material is increased during the packaging process, thereby improving the reliability of the lead frame during the packaging process, thereby stably reaching a high reliability level, so that the packaged integrated circuit will not be delaminated during use, and the service life of the integrated circuit can be guaranteed. The film surface of the copper material maintains the original copper material state and is not roughened. The overflow after packaging can be easily removed without affecting the aesthetics and heat dissipation requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A flow chart for preparing a lead frame of the present invention;

[0025] Figure 2 This is a front view of the copper surface of the lead frame manufactured according to the present invention after the front surface is roughened under a 45x microscope;

[0026] Figure 3 This is a copper surface back view of the back of the lead frame manufactured according to the present invention under a 45x microscope;

[0027] Figure 4 A three-dimensional diagram of a single-sided rough copper plating device used in the present invention;

[0028] Figure 5 A top view of a single-sided rough copper plating device used in the present invention;

[0029] Figure 6 Scanning diagram of reliability test of eLQFP128(218X218)(C)-2P lead frame after being processed by the method of the present invention Figure 1 ;

[0030] Figure 7 Scanning diagram of reliability test of eLQFP128(218X218)(C)-2P lead frame after being processed by the method of the present invention Figure 2 ;

[0031] The names corresponding to the serial numbers in the figure are as follows:

[0032] Peripheral frame 100, transverse fixing bracket 101, transverse long slot hole 102;

[0033] The medicine tank body 10 includes a bottom plate 11, a water hole 12, an electrode plate 13, a partition plate 14, an overflow hole groove 15, a product support rod 16, a concave guide groove 161, an upper convex mounting column 162, an electrode support plate 17, a lead frame guide mechanism 20, a product limiting wheel 21, a guide roller 22, and a reflux hole 23. DETAILED DESCRIPTION

[0034] A method for manufacturing a lead frame, see Figure 1 : It sequentially performs electrolytic degreasing, copper plating, single-sided rough copper plating, pre-silver plating, silver plating, silver stripping, water washing, drying and molding to finally obtain a lead frame:

[0035] Single-sided rough copper plating is carried out using single-sided rough copper plating equipment. One side of the stamped lead frame is in contact with the roughening solution for copper roughening, while the other side of the lead frame is not in contact with the solution.

[0036] See Figure 4-5 The single-sided rough copper plating equipment includes an outer frame 100, and the two side plates of the outer frame 100 are connected by a plurality of transverse fixing brackets 101. The central area of ​​the outer frame 100 in the length direction forms a liquid medicine tank body 10, and the two ends of the outer frame 100 in the length direction are respectively provided with lead frame guide mechanisms 20, and the bottom plate 11 of the liquid medicine tank body 10 is provided with array-arranged upper water holes 12, and the liquid medicine tank body 10 is provided with an electrode plate 13. A partition 14 is provided between the liquid medicine tank body 10 and the lead frame guide mechanisms 20 at both ends, and an overflow hole groove 15 is provided on the partition 14. The width and height of the overflow hole groove 15 allow the lead frame to pass reliably, and the overflow hole groove 15 allows only the lower surface of the lead frame to be located below the liquid surface of the liquid medicine, and the upper surface of the lead frame is located above the liquid surface of the liquid medicine;

[0037] Two product support rods 16 are provided on the upper surface of the medicine tank body 10 corresponding to the bottom plate 11, and the width between the product support rods 16 is used to guide the lead frame to move linearly;

[0038] An indented guide groove 161 is provided between the facing surfaces of the two product support rods 16. The indented guide groove 161 is used for guiding the lead frame. Meanwhile, the bottom height of the indented guide groove 161 is used for determining the height of the lower surface of the lead frame.

[0039] Each product support rod 16 is provided with an upper convex mounting column 162 at a position corresponding to the horizontal fixing bracket 101. An adjusting bolt (not shown in the figure, belonging to an existing mature connecting bolt structure) passes through the mounting hole of the horizontal fixing bracket 101 and is fixedly connected to the upper convex mounting column 162. A vertical screw hole is provided on the upper convex mounting column 162. The height of the product support rod 16 is reasonably adjusted according to the thickness of the lead frame and the height of the liquid in the upper water hole 12 to ensure that only the bottom surface of the lead frame can be roughened.

[0040] The mounting hole of the horizontal fixing bracket 101 is a horizontal long slot hole 102, which enables the width between the two product support rods 16 to be quickly adjusted according to the width of the lead frame, ensuring the versatility of the device;

[0041] The bottom of the electrode plate 13 in the liquid medicine tank 10 is connected to the corresponding position of the bottom plate 11, and the upper parts of the electrode plates 13 are respectively fixed to the electrode support plates 17, which are closed rectangular frames, making the assembly of the electrode plates 13 on both sides quick and convenient;

[0042] Each set of lead frame guide mechanisms 20 includes a set of product limiting wheels 21 and a plurality of guide rollers 22. The lead frame moves along the spacing between the product limiting wheels 21 set at a certain spacing in the width direction, and is introduced into the liquid medicine tank body 10 or leaves the liquid medicine tank body 10 through the plurality of guide rollers 22, so as to ensure that the lead frame is transported reliably and stably.

[0043] A reflux hole 23 is provided on the bottom plate of each set of lead frame guide mechanisms 20. The medicine flowing out along the overflow hole groove 15 flows back to the medicine box at the bottom through the reflux hole 23. The medicine box at the bottom then inputs the medicine into the medicine tank body through the upper water hole through the pump body and the pipeline.

[0044] In specific implementation, the potion is obtained by mixing copper sulfate solution, hydrochloric acid, copper additive PPR, and copper auxiliary agent PPR-H;

[0045] The solubility of each component in the medicine solution is: the copper sulfate solution is copper sulfate with a concentration of 200±50g / L, sulfuric acid with a concentration of 10±2%, and water at a temperature of 35℃±2℃;

[0046] The concentration of hydrochloric acid solution is 100PPM;

[0047] Copper additive PPR concentration of 3 ± 0.2 ml / l, and water;

[0048] The concentration of copper adjuvant PPR-H is 203±10 ml / l, and water.

[0049] In a specific embodiment, the stamped eLQFP128 (218X218) (C) -2P lead frame is obtained by performing electrolytic degreasing, copper plating, single-sided rough copper plating, pre-silver plating, silver plating, silver stripping, water washing, drying and forming processes;

[0050] When single-sided rough copper plating is performed, the stamped lead frame is set as the cathode, the electrolytic plate is used as the anode, a 55°C solution is used, the current is set to 5A, and the line speed is controlled to 2.5m / min;

[0051] Single-sided rough copper plating is carried out in single-sided rough copper plating equipment and potion, the composition of the potion is as follows: copper sulfate (CUSO4) concentration is 220g / L, temperature is 35°C; hydrochloric acid (HCL) concentration is 100PPM; copper additive (PPR) concentration is 3ml / l; copper auxiliary agent (PPR-H) concentration is 210ml / l.

[0052] The lead frame is fed into the medicine tank body 10 by a set of product limiting wheels 21 and a plurality of guide rollers 22. The medicine overflows into the medicine tank body 10 through the upper water hole 12, and is electrically conductive by the electrode plate 13. The medicine is applied through the upper water hole 12. The lead frame is supported by the product support rod 16 and has a gap with the bottom plate 11 to ensure that the wave of the liquid does not exceed 0.08 mm during the flow of the medicine. Both sides of the lead frame are embedded in the concave guide groove 161 of the product support rod 16. The height of the concave guide groove 161 is equal to or slightly greater than the thickness of the lead frame, which ensures that the shaking of the lead frame during operation does not exceed 0.08 mm. Therefore, the medicine will not soak through the upper surface of the lead frame, but only slightly adhere to the use surface of the lead frame, thereby achieving the effect of single-sided roughening of the product. The average SA value of the single-sided roughening is 500 nanometers.

[0053] In a specific implementation, the front side of the lead frame is the side that needs to be roughened, and the back side of the lead frame does not need to be roughened. Then, before the operation starts, the lead frame is turned over and sent into a single-sided rough copper plating device.

[0054] A high reliability lead frame roughening process for eLQFP128(218X218)(C)-2P: Figure 1 As shown, the stamped lead frame is subjected to electrolytic degreasing, copper plating, single-sided rough copper plating, pre-silver plating, silver plating, silver stripping, water washing, and drying.

[0055] The front and back images of the eLQFP128(218X218)(C)-2P lead frame sample obtained in Example 1 under a 45x microscope are as follows: Figure 2 and Figure 3 shown.

[0056] The reliability scan image of the eLQFP128(218X218)(C)-2P lead frame sample obtained in Example 1 after high reliability experiment is as follows: Figure 6 , Figure 7 There is no delamination, indicating that the product processed by the process of this embodiment can pass the industry's high reliability assessment.

[0057] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0058] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A lead frame manufacturing method, characterized in that: The process is followed by electrolytic degreasing, copper plating, single-sided rough copper plating, pre-silver plating, silver plating, silver stripping, water washing, drying and forming to finally obtain the lead frame: The single-sided rough copper plating is performed using a single-sided rough copper plating device. One side of the stamped lead frame contacts with a roughening solution to roughen the copper material, while the other side of the lead frame does not contact with the solution.

2. A lead frame manufacturing method according to claim 1, characterized in that: The single-sided rough copper plating equipment includes an outer frame, and the two side plates of the outer frame are connected by a plurality of transverse fixed brackets. The central area of ​​the outer frame in the length direction forms a medicine tank body, and the two ends of the outer frame in the length direction are respectively provided with lead frame guiding mechanisms, and the bottom plate of the medicine tank body is provided with array-arranged water holes, and the medicine tank body is provided with an electrode plate. A partition is provided between the medicine tank body and the lead frame guiding mechanisms at both ends, and an overflow hole groove is provided on the partition. The width and height of the overflow hole groove allow the lead frame to pass reliably, and the overflow hole groove allows only the lower surface of the lead frame to be located below the liquid level of the medicine, and the upper surface of the lead frame is located above the liquid level of the medicine.

3. A lead frame manufacturing method according to claim 2, characterized in that: The potion is obtained by mixing copper sulfate solution, hydrochloric acid, copper additive PPR, and copper auxiliary agent PPR-H.

4. A lead frame manufacturing method according to claim 3, characterized in that: The solubility of each component in the potion is: the copper sulfate solution is copper sulfate with a concentration of 200±50g / L, sulfuric acid with a concentration of 10±2%, and water at a temperature of 35°C±2°C; The concentration of hydrochloric acid solution is 100PPM; Copper additive PPR concentration of 3 ± 0.2 ml / l, and water; The concentration of copper adjuvant PPR-H is 203±10 ml / l, and water.

5. A lead frame manufacturing method according to claim 2, characterized in that: The liquid medicine enters the liquid medicine tank through the upper water hole. When the lead frame moves along the lead frame guide mechanism through the liquid medicine tank, its running speed is precisely controlled within the range of 2.5±0.2 m / min. When the liquid medicine is supplied through the upper water hole, its pressure range is strictly controlled within 3.5-5 kg / cm 2 It effectively solves the problem of water ripple height without generating bubbles, and firmly controls the water ripple height within 0.08mm. The solution will not infiltrate the upper surface of the lead frame, thus achieving a single-sided roughening effect.

6. A lead frame manufacturing method according to claim 2, characterized in that: The medicine tank body is provided with two product support rods on the upper surface corresponding to the bottom plate, and the width between the product support rods is used to guide the lead frame to move linearly.

7. A lead frame manufacturing method according to claim 6, characterized in that: An inwardly concave guiding groove is arranged between the facing surfaces of the two product supporting bars, and the inwardly concave guiding groove is used for guiding the lead frame, and the bottom height of the inwardly concave guiding groove is used for determining the height of the lower surface of the lead frame.

8. A lead frame manufacturing method according to claim 7, characterized in that: Each product support rod is provided with an upper convex mounting column at the position corresponding to the horizontal fixing bracket. The adjusting bolt passes through the mounting hole of the horizontal fixing bracket and is fixedly connected to the upper convex mounting column. The upper convex mounting column is provided with a vertical screw hole. The height of the product support rod can be reasonably adjusted according to the thickness of the lead frame and the height of the medicine outlet in the upper water hole.

9. A lead frame manufacturing method according to claim 8, characterized in that: The mounting hole of the transverse fixing bracket is a transverse long slot hole.

10. The lead frame manufacturing method according to claim 2, characterized in that: A reflux hole is provided on the bottom plate of each set of lead frame guide mechanisms, and the medicine flowing out along the overflow hole groove flows back to the medicine box at the bottom through the reflux hole. The medicine box at the bottom then inputs the medicine into the medicine tank body through the upper water hole through the pump body and the pipeline.

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