Integrally-formed inductor packaging process for preventing coil deformation

Abstract

The invention relates to the technical field of electronic component manufacturing and semiconductor packaging, and discloses an integrally-formed inductor packaging process for preventing coil deformation. According to the process, a composition containing magnetic powder, crystalline epoxy resin, an epoxy-terminated hyperbranched polymer and a urea-based thixotropic agent is adopted, and transfer molding is carried out under the low pressure of 5-15 MPa by utilizing a semiconductor injection molding machine. According to the invention, through synergistic viscosity reduction of resin phase change and hyperbranched molecular lubrication and cooperation of the thixotropic agent to prevent magnetic powder sedimentation, the bottleneck that a high filling material is difficult to flow under low pressure is solved. According to the process, traditional dry powder high-pressure pressing is replaced, the risks of coil disordering and deformation are thoroughly eliminated, single-mode multi-cavity high-flux precision manufacturing is achieved, and it is ensured that product resistors are stably arranged and the magnetic performance is highly consistent.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic component manufacturing and semiconductor packaging, in particular to a one-piece forming inductance packaging process for preventing coil deformation. BACKGROUND

[0002] One-piece forming power inductance has become an indispensable core passive component in smart phones, automotive electronics and high-performance servers due to its high saturation current, low direct current resistance and excellent electromagnetic shielding characteristics. The typical structure of such components is to completely bury the wound hollow copper coil in a magnetic powder matrix to form an integrated structure through solidification forming process.

[0003] Currently, the mainstream manufacturing process in the industry usually adopts dry powder high-pressure pressing technology, that is, after filling the magnetic powder in the mold, the powder is compacted by mechanical stamping to apply a pressure of hundreds of megapascals or even several tons to pursue high density and high magnetic permeability. However, this process which relies on external mechanical force to form has a significant congenital defect. Since the internal hollow copper coil is relatively soft compared to the hard magnetic powder, it is prone to geometric deformation, flattening, and even causes the coil to be misaligned during high-strength extrusion. This uncontrollable deformation not only causes the coil insulating paint film to be damaged, causing turn-to-turn short circuit or poor voltage resistance, but also causes serious dispersion in key electrical parameters such as direct current resistance and inductance of batch products, making it difficult to meet the stringent requirements of high-end electronic devices for precision components.

[0004] In order to solve the problem of coil damage caused by high-pressure pressing, the industry has begun to try to use the low-pressure transfer molding process in the field of semiconductor chip packaging to encapsulate the coil by injecting molten material into the mold at a lower injection pressure using a semiconductor injection molding machine. The pressure of this process is usually only a few tenths of the traditional pressing process, which can theoretically protect the coil shape to the greatest extent. However, directly transplanting this process into high-performance inductance manufacturing faces great technical challenges. In order to ensure the magnetic saturation performance of the inductance, a high proportion of magnetic powder must be filled in the molding material, which results in a very high viscosity of the material melt, making it difficult to flow under the low-pressure forming conditions of the semiconductor injection molding machine, and unable to effectively fill the mold cavity. If the resin viscosity is simply reduced or the powder content is reduced to improve flowability, it will cause serious gravity settling and solid-liquid separation of the magnetic powder in the flow channel, resulting in uneven magnetic performance in the product. SUMMARY

[0005] In view of the shortcomings of the prior art, the present application provides a one-piece forming inductance packaging process for preventing coil deformation, which solves the problems of coil deformation, turn-to-turn misalignment and unstable resistance arrangement caused by traditional dry powder high-pressure pressing process, and solves the problems of poor flowability of super-high filled magnetic material and easy settling of magnetic powder in the semiconductor low-pressure injection molding process.

[0006] In a first aspect, the present application provides a one-piece inductance packaging process for preventing coil deformation, which adopts the following technical solution:

[0007] A one-piece inductance packaging process for preventing coil deformation, comprising the following steps:

[0008] S1: preparing a magnetic molding composition cake: mixing raw materials including magnetic powder, crystalline epoxy resin, curing agent, epoxy-terminated hyperbranched polymer, and thixotropic rheological modifier, and then performing melt mixing, cooling, and crushing to press a solid cake;

[0009] S2: arranging coils: arranging a coil array wound on a lead frame into a mold with multiple cavities;

[0010] S3: low-pressure transfer molding: heating and melting the cake prepared in step S1, and injecting the mold cavity under the condition that the injection transfer pressure is 5-15 MPa to wrap the coil;

[0011] S4: curing: after pressure maintaining and preliminary curing in the mold, the product is taken out of the mold, and post-curing treatment is performed;

[0012] The epoxy-terminated hyperbranched polymer has a weight average molecular weight of 1500-5000 g / mol; and the thixotropic rheological modifier is a urea-based compound.

[0013] By adopting the above technical solution, the present application uses specific material rheological properties to adapt to the low-pressure molding process, fundamentally solves the coil displacement and deformation problem caused by high-pressure injection molding, and overcomes the contradiction between insufficient filling and magnetic powder sedimentation under low pressure. The specific innovation mechanism is as follows:

[0014] 1. Low-pressure molding and coil protection mechanism: by controlling the injection transfer pressure in the extremely low range of 5-15 MPa, the mechanical impact force of the melt flow front on the suspended coil is significantly reduced. Compared with the pressure of 80-120 MPa usually required by the traditional process, the low-pressure environment of the present application greatly reduces the risk of elastic deformation or plastic displacement of the coil, ensuring that the coil always maintains the geometric center of the magnet.

[0015] 2. Phase change viscosity reduction mechanism of crystalline resin: in order to achieve effective delivery of high-filled magnetic powder under low pressure, the system selects a crystalline epoxy resin. The resin is in a solid crystalline state below the melting point, which is convenient for operation; once heated above the melting point, the crystal lattice collapses rapidly, and the viscosity decreases by an order of magnitude. This sharp temperature-dependent viscosity feature provides the basic carrier fluidity for low-pressure filling.

[0016] 3. Internal lubrication and topological effect of hyperbranched polymer: The epoxy-terminated hyperbranched polymer has a highly branched three-dimensional spherical topological structure. Compared with linear polymers, there is no entanglement between molecular chains, and the hydrodynamic volume is small. During the melt flow process, the spherical molecules play a role similar to microscopic balls between magnetic powder particles and between resin macromolecules, reducing the internal friction coefficient and melt viscosity of the system, so that high-viscosity composites can flow smoothly under low shear force and fill the micro-cavity.

[0017] 4. Rheological control mechanism of urea-based thixotropic agent: Simple low viscosity can cause the magnetic powder to settle quickly when at rest, resulting in uneven magnetic properties of the product. The scheme introduces urea-based compounds as thixotropic rheological modifiers. The compound builds a physical network structure in the resin matrix through intermolecular hydrogen bonding:

[0018] Shear thinning stage (when injection molding): During the high shear rate injection molding process of S3, the physical hydrogen bond network is destroyed, and the material exhibits low viscosity, which is beneficial for flow filling;

[0019] Thixotropy recovery stage (when pressure holding): When the melt fills the mold and the shear stops, the hydrogen bond network quickly reorganizes and recovers, and the system viscosity rises sharply, preventing gravity settlement before the resin solidifies and ensuring the uniformity of the overall density of the product.

[0020] Preferably, in S3, the injection transfer pressure is 8-12 MPa, the injection transfer time is 10-20 seconds, and the mold temperature is controlled at 165-180°C.

[0021] By adopting the above technical scheme, the process window is further narrowed to the optimal range. The pressure range of 8-12 MPa realizes the best balance between filling integrity and coil position stability, and the mold temperature of 165-180°C cooperates with the transfer time of 10-20 seconds to ensure that the crystalline resin is fully melted without premature crosslinking, and at the same time, the hydrogen bond network of the thixotropic agent can play a role under the appropriate thermal history.

[0022] Preferably, in S1, the minimum melt viscosity of the magnetic molding composition at 150°C is 4.0-16.0 Pa·s, and the thixotropy index after curing is 9.0-15.0, the thixotropy index is the ratio of the viscosity at a shear rate of 0.5 s -1 to the viscosity at 500 s -1 .

[0023] By adopting the technical scheme, the rheology index of the material is quantitatively limited, the extremely low viscosity of 4.0-16.0 Pa·s is a physical prerequisite for realizing long-distance low-pressure flow, and the thixotropic index of 9.0-15.0 indicates that the material has extremely strong structural rheological characteristics. The high thixotropic index value means that the material has extremely high structural strength in a static state, can effectively resist phase separation under the action of gravity, and ensures that the large-area packaging products of 1200 cavities or even more cavities have high consistency.

[0024] Preferably, in S1, the magnetic molding composition comprises the following components by weight percentage: 86.0wt%-92.0wt% of magnetic powder; 3.0wt%-6.0wt% of crystalline epoxy resin; 1.5wt%-4.0wt% of curing agent; 0.5wt%-2.5wt% of epoxy-terminated hyperbranched polymer; 0.2wt%-0.8wt% of thixotropic rheology modifier; and the balance of auxiliary additives.

[0025] By adopting the technical scheme, the solid-liquid ratio of the formula system is optimized. A high content of magnetic powder ensures high saturation current and high inductance of the inductor; and appropriate amount of resin and hyperbranched polymer ensures insulation and bonding strength while providing necessary flow carrier.

[0026] Preferably, the crystalline epoxy resin is a biphenyl type epoxy resin, and the melting point thereof is 95℃-115℃, and the melt viscosity thereof at 150℃ is less than 0.1 Pa·s.

[0027] By adopting the technical scheme, the rigidity of the biphenyl structure and the low molecular weight characteristics are utilized to realize the effect of clear melting point and extremely low viscosity after melting. The biphenyl structure also endows the cured product with excellent heat resistance and low hygroscopicity, improving the reliability of the inductor.

[0028] Preferably, the epoxy-terminated hyperbranched polymer is prepared by modifying the hyperbranched polyester formed by condensation of a core molecule and ABx type monomer with terminal epoxy groups, the core molecule is selected from trimethylolpropane or pentaerythritol, and the ABx type monomer is 2,2-bis(hydroxymethyl)propionic acid.

[0029] By adopting the technical scheme, the structure source of the hyperbranched polymer is clarified.

[0030] 1. Skeleton construction: trimethylolpropane is used as the core, and 2,2-bis(hydroxymethyl)propionic acid is used as the AB2 type monomer for condensation to form a spherical polyester skeleton with a large number of terminal hydroxyl groups. The skeleton not only provides support, but also ensures good solubility and dispersibility.

[0031] 2. End group modification: By subsequent epoxidation modification, the inert hydroxyl groups are converted into highly reactive glycidyl ether groups. This makes the hyperbranched polymer not only as a physical lubricant, but also as a crosslinking point to participate in the curing network of epoxy resin, avoiding surface defects caused by migration and precipitation of small molecule lubricants, while improving the crosslinking density and mechanical strength of the cured product.

[0032] Preferably, in S1, the thixotropic rheology modifier is a precipitate prepared by reacting a diisocyanate with a monoamine compound; preferably, the diisocyanate is diphenylmethane diisocyanate, and the monoamine compound is n-butylamine.

[0033] By adopting the above technical solution, organic micro-powder containing high-density urea-based structures is synthesized in situ or in stages. Compared with inorganic thixotropic agents, this organic urea-based compound has better compatibility with the epoxy resin matrix. The urea groups on its molecular chain can form a stronger and more reversible hydrogen bond network with the polar groups in the resin and between themselves, thereby maintaining excellent anti-settling thixotropic performance at high temperatures.

[0034] Preferably, in S1, the temperature of the melt mixing is controlled at 85-100℃, and in S3, the cake is preheated in the injection molding machine barrel for 3-8 seconds before injection.

[0035] By adopting the above technical solution, the temperature is controlled to be lower than the melting point of the crystalline resin but higher than the softening point of the resin during the preparation of the cake. This allows the epoxy-terminated hyperbranched polymer to preferentially spread on the surface of the magnetic powder to form a pre-wetting layer, while the crystalline resin remains relatively intact. This dispersion state is conducive to the staged release of viscosity during subsequent injection molding. The short-term preheating before injection causes the surface of the cake to soften initially, reducing the pressure loss when entering the flow channel.

[0036] In a second aspect, the present application provides an integrally formed inductor prepared by the above process, which adopts the following technical solution:

[0037] An integrally formed inductor prepared by the anti-coil deformation integrally formed inductor packaging process of the first aspect, the displacement rate of the internal coil of the inductor is less than 1.5% by X-ray perspective measurement, and the displacement rate is the ratio of the maximum offset distance of the coil center axis relative to the magnet center axis to the average diameter of the coil.

[0038] By adopting the above technical solution, the integrally formed inductor obtained has extremely high geometric symmetry. A coil displacement rate of less than 1.5% means that the coil is accurately fixed at the center of the magnet, which brings the following technical effects:

[0039] 1. Preventing short circuit breakdown: maximizes the insulation distance between the coil and the surface of the inductor, reducing the risk of poor voltage resistance.

[0040] 2. Magnetic circuit symmetry: The coil is centered to ensure uniform distribution of the magnetic flux path, avoiding local magnetic saturation and improving the DC superposition characteristics.

[0041] 3. Electrical consistency: Precise geometric position ensures high consistency of batch products in terms of parasitic capacitance, leakage inductance, and other parameters.

[0042] Preferably, the inductance is an array-type batch packaging product, and the inductance position deviation at the beginning and end of the whole product is less than 2.0%.

[0043] By adopting the above technical scheme, the superiority of thixotropic control in the process is embodied. The inductance deviation of less than 2.0% indicates that even at the farthest end of the mold flow channel, the concentration of magnetic powder in the material remains consistent with the near end, without significant solid-liquid separation or sedimentation. This solves the technical problem of large performance difference between the beginning and end of the large-size mold mass production, and improves the production yield.

[0044] The present application provides an integrated inductance packaging process for preventing coil deformation. It has the following beneficial effects:

[0045] 1. The present application replaces the traditional dry powder high-pressure pressing process with a semiconductor transfer molding process, fundamentally solving the problems of coil disorder and deformation. By using a specially designed low-viscosity magnetic composition, the packaging can be completed using a semiconductor injection molding machine in a low-pressure environment. This fluid filling method eliminates the extrusion of internal hollow copper coils by large mechanical pressure, effectively preventing coil geometric collapse, turn-to-turn misplacement, or insulation layer damage, and improving the voltage resistance yield and structural integrity of the inductance.

[0046] 2. The present application realizes single-injection multi-hole high-throughput array manufacturing and resistance arrangement stability by introducing urea-based thixotropic rheological modifiers in combination with crystalline resins. In the realization of large-scale production of single-mode multiple units, the melt propulsion is smooth and the pressure distribution is uniform, ensuring that the coils in each unit do not displace or stretch, thereby stabilizing the DC resistance value distribution of the whole product and overcoming the defects of poor product performance consistency caused by pressure gradient in traditional processes.

[0047] 3. The present application utilizes the temperature-sensitive phase change characteristics of crystalline resins and the molecular ball lubrication effect of hyperbranched polymers to significantly reduce the internal friction of high-magnetic-powder-content composites, enabling high-magnetic-permeability materials to smoothly fill micro-cavities under low-pressure parameters of semiconductor injection molding machines. The semiconductor packaging technology is successfully grafted to inductance manufacturing, ensuring excellent magnetic performance while achieving non-destructive packaging of precision coils. DETAILED DESCRIPTION

[0048] The technical solutions in the embodiments of the present application will be clearly and completely described below, obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present application.

[0049] The main raw materials and reagents used in the following examples and comparative examples are as follows, and the reagents not specifically described are commercially available analytical pure or higher grade products.

[0050] Magnetic powder A1: phosphating treated iron-silicon-chromium alloy powder. The chemical composition is as follows in terms of weight percentage: Fe balance, Si: 3.5-6.5%, Cr: 2.5-5.5%. The powder morphology is spherical, the median particle size D50 is 25 μm, and the tap density is 4.5 g / cm 3 . The particle surface has an in-situ generated phosphate insulating layer with an average thickness of 50 nm.

[0051] Magnetic powder A2: phosphating treated iron-silicon-aluminum alloy powder. The chemical composition is as follows in terms of weight percentage: Fe balance, Si: 9.0-10.0%, Al: 5.0-6.0%. The powder morphology is spherical, the median particle size D50 is 15 μm, and the tap density is 4.2 g / cm 3 . The particle surface has an in-situ generated phosphate insulating layer with an average thickness of 40 nm.

[0052] Matrix resin B1: 3,3',5,5'-tetramethyl-4,4'-diphenylol diglycidyl ether. The CAS number is 85954-11-6. The resin is a crystalline epoxy resin, the appearance is white crystalline powder, the melting point is 105℃, the epoxy equivalent weight is 186 g / eq, and the melt viscosity at 150℃ is 0.05 Pa·s.

[0053] Matrix resin B2: o-cresol formaldehyde epoxy resin. The CAS number is 29690-82-2. The resin is a non-crystalline solid resin, the softening point is 75℃, the epoxy equivalent weight is 200 g / eq, and the melt viscosity at 150℃ is 3.5 Pa·s.

[0054] Curing agent C1: phenol aralkyl resin. The chemical structure is a polymer with phenol and p-xylene groups alternately connected, and the CAS number is 26834-32-2. The softening point is 80℃, and the hydroxyl equivalent weight is 175 g / eq.

[0055] Thixotropic rheology modifier E1: 4,4'-diphenylmethane diisourea. The substance is not a conventional product on the market, and is prepared according to the method of Preparation Example 3 below. The substance is a micron-sized white powder with a melting point of 240℃.

[0056] Curing accelerator F1 : triphenylphosphine. CAS No. 603-35-0. White flaky crystals, melting point 80°C.

[0057] Coupling agent F2: isopropyl tri(dioctylpyrophosphato) titanate. CAS No. 65345-34-8. Yellow viscous liquid.

[0058] Release agent F3: montan wax. CAS No. 8002-53-7. Main component is long chain fatty acid ester, drop melting point 82°C, acid value 15-20 mg KOH / g.

[0059] Colorant F4: carbon black. CAS No. 1333-86-4. Average particle size 20 nm, oil absorption value 110 ml / 100 g.

[0060] Epoxy-terminated hyperbranched polymer D1 : not a commercially available conventional product, prepared according to the method of Preparation Example 1 below. This polymer is a hyperbranched polyester with trimethylolpropane as the core and 2,2-bis(hydroxymethyl)propionic acid as the branching monomer, and the terminal hydroxyl groups are modified with epichlorohydrin to glycidyl ether groups. The weight average molecular weight (Mw) of this polymer is 2500 g / mol, the polydispersity index (PDI) is 1.5, the epoxy equivalent weight is 320 g / eq, and the degree of branching (DB) is 0.55.

[0061] Epoxy-terminated hyperbranched polymer D2: not a commercially available conventional product, prepared according to the method of Preparation Example 2 below. The chemical composition of this polymer is the same as D1, but the difference lies in the degree of polymerization and molecular weight. The weight average molecular weight (Mw) of this polymer is 4500 g / mol, the polydispersity index (PDI) is 1.8, the epoxy equivalent weight is 350 g / eq, and the degree of branching (DB) is 0.60.

[0062] Preparation Example 1 : This preparation example provides a method for preparing epoxy-terminated hyperbranched polymer D1.

[0063] Into a four-necked flask equipped with mechanical stirring, nitrogen inlet tube and water separator, 13.4 g of trimethylolpropane (TMP, 0.1 mol) and 134.1 g of 2,2-bis(hydroxymethyl)propionic acid (DMPA, 1.0 mol) were added. The flask was protected by nitrogen and heated to 140 °C to melt the raw materials. 1.5 g of p-toluenesulfonic acid was added as catalyst and the melt polycondensation reaction was carried out at 140 °C. The generated water was removed by the water separator and the reaction progress was monitored by acid value titration. The reaction was stopped when the acid value dropped below 10 mgKOH / g to obtain the hydroxyl-terminated hyperbranched polyester intermediate. The obtained intermediate was cooled to 60 °C and dissolved in 300 mL of tetrahydrofuran. Subsequently, 277.5 g of epichlorohydrin (3.0 mol) and 4.8 g of tetrabutylammonium bromide (phase transfer catalyst) were added to the solution and the reaction was carried out at 60 °C with stirring. During the reaction, 48 g of powdered sodium hydroxide (1.2 mol) was added in portions. After the addition was completed, the reaction was continued at 60 °C for 5 hours. After the reaction was completed, the generated sodium chloride salt was removed by filtration and the filtrate was subjected to rotary evaporation to remove the unreacted epichlorohydrin and solvent. The obtained product was washed with ether three times to remove impurities and finally dried in a vacuum drying oven at 50 °C for 24 hours to obtain a light yellow viscous liquid of epoxy-terminated hyperbranched polymer D1. The weight average molecular weight was 2500 g / mol and the polydispersity index was 1.5 as determined by gel permeation chromatography (GPC). The epoxy equivalent weight was 320 g / eq as determined by the hydrochloric acid-acetone method.

[0064] Preparation Example 2: This preparation example provides a method for preparing an epoxy-terminated hyperbranched polymer D2.

[0065] The preparation process was basically the same as that of Preparation Example 1, with the main difference being the adjustment of the raw material ratio and reaction time. Specifically, 13.4 g of trimethylolpropane (TMP, 0.1 mol) and 201.2 g of 2,2-bis(hydroxymethyl)propionic acid (DMPA, 1.5 mol) were added to the reaction flask, the amount of catalyst p-toluenesulfonic acid was increased to 2.0 g, the melt polycondensation reaction time was extended until the acid value dropped below 8 mgKOH / g, and in the subsequent end group modification step, the amount of epichlorohydrin was increased to 416.3 g (4.5 mol) and the amount of sodium hydroxide was increased to 72 g (1.8 mol). The final treatment obtained the epoxy-terminated hyperbranched polymer D2. The weight average molecular weight was 4500 g / mol, the polydispersity index was 1.8, and the epoxy equivalent weight was 350 g / eq.

[0066] Preparation Example 3: This preparation example provides a method for preparing a thixotropic rheology modifier E1 (modified urea).

[0067] In a reaction flask equipped with a stirrer, a thermometer and a dropping funnel, 250 g of 4,4'-diphenylmethane diisocyanate (MDI, 1.0 mol) was added and dissolved in 1000 mL of N-methylpyrrolidone (NMP). The temperature of the solution was controlled at 10°C under stirring. 146.3 g of n-butylamine (2.0 mol) was dissolved in 200 mL of N-methylpyrrolidone, and then slowly added dropwise into the reaction flask through the dropping funnel, controlling the dropping speed so that the reaction temperature did not exceed 40°C. After the addition was completed, the temperature was raised to 60°C and the reaction was continued for 1 hour under stirring. After the reaction was completed, the reaction solution was poured into a large amount of deionized water to precipitate a white precipitate, which was collected by filtration and washed with ethanol and water alternately for three times. The washed product was dried in a vacuum drying oven at 80°C for 12 hours, and finally crushed by an air flow crusher to obtain 4,4'-diphenylmethane diisourea powder E1 with an average particle size of 5 μm.

[0068] Example 1:

[0069] The present embodiment provides a method for manufacturing an integrally formed inductor based on a low-pressure transfer molding process, comprising the following steps:

[0070] (1) Preparation of a magnetic molding compound:

[0071] The raw materials were weighed according to the following weight ratio: magnetic powder A1: 890 g (89.0 wt%), matrix resin B1: 50 g (5.0 wt%), curing agent C1: 25 g (2.5 wt%), epoxy-terminated hyperbranched polymer D1: 15 g (1.5 wt%), thixotropic rheology modifier E1: 5 g (0.5 wt%), curing accelerator F1: 2 g (0.2 wt%), coupling agent F2: 5 g (0.5 wt%), release agent F3: 5 g (0.5 wt%), colorant F4: 3 g (0.3 wt%).

[0072] The above raw materials were put into a high-speed mixer and pre-mixed at 25°C for 5 minutes at a speed of 800 rpm. The mixed powder was sent to a twin-screw extruder for melt mixing, with the temperature of the feeding section set at 65°C, the temperature of the mixing section set at 90°C, the screw speed set at 60 rpm, and the residence time of the material set at 45 seconds. After the extrudate was cooled to room temperature by a water-cooled steel belt, a crusher was used to crush it into particles with a particle size of less than 1 mm. Finally, a rotary tablet press was used to press the particles into a cylindrical cake with a diameter of 40 mm and a height of 30 mm under a pressure of 20 MPa.

[0073] (2) Arrangement of coil array:

[0074] A copper alloy lead frame was selected, which was arranged with 40 rows x 30 columns, i.e. 1200 unit areas. In each unit area, a hollow copper coil was placed and welded on the pad of the unit area by an automatic wire placement machine.

[0075] (3) Low pressure transfer molding:

[0076] The lead frame was placed into the transfer molding machine mold and the mold was closed. The mold temperature was set to 175°C. The pellets prepared in step (1) were placed into the injection molding machine cylinder and preheated for 5 seconds. The injection transfer pressure was set to 10 MPa and the transfer time was set to 15 seconds. The plunger was activated and the molten magnetic molding material was injected into the mold cavity until it was filled. The holding pressure was set to 15 MPa and the holding time was set to 10 seconds. The mold was then kept closed for 90 seconds for curing inside the mold.

[0077] (4) Post-processing:

[0078] The mold was opened and the injection molded finished panel product was removed. After removing the runner waste, the product was placed into an oven and post-cured for 3 hours at 175°C. Finally, the cutting machine was used to separate along the cutting path to obtain 1200 one-piece inductor finished products.

[0079] Example 2:

[0080] The present embodiment provides a method for manufacturing a one-piece inductor with a high magnetic powder filling amount, comprising the following steps:

[0081] (1) Preparation of magnetic molding pellets:

[0082] The raw materials were weighed according to the following proportions: magnetic powder A1: 920g (92.0wt%), base resin B1: 30g (3.0wt%), curing agent C1: 15g (1.5wt%), epoxy-terminated hyperbranched polymer D1: 25g (2.5wt%), thixotropic rheology modifier E1: 3g (0.3wt%), curing accelerator F1: 1g (0.1wt%), coupling agent F2: 3g (0.3wt%), release agent F3: 2g (0.2wt%), colorant F4: 1g (0.1wt%).

[0083] The preparation process was the same as in Example 1, except that the mixing temperature during melting was adjusted to 95°C to accommodate the dispersion requirements under high filling amount.

[0084] (2) Coil array arrangement:

[0085] The same as in Example 1.

[0086] (3) Low pressure transfer molding:

[0087] The mold temperature was set to 180°C. The preheating time was 6 seconds. Due to the high content of magnetic powder, the injection transfer pressure was set to 15 MPa and the transfer time was set to 20 seconds. The holding pressure was set to 20 MPa and the holding time was set to 12 seconds. The in-mold curing time was extended to 120 seconds.

[0088] (4) Post-processing:

[0089] The post-curing baking temperature is adjusted to 180°C, and the time is 4 hours, which is the same as in Example 1.

[0090] Example 4:

[0091] The present embodiment provides a method for manufacturing an integrally formed inductor by adjusting the proportion of rheological components, comprising the following steps:

[0092] (1) Preparation of a magnetic molding compound:

[0093] The raw materials are weighed according to the following weight ratio: magnetic powder A1: 900g (90.0wt%), base resin B1: 45g (4.5wt%), curing agent C1: 22g (2.2wt%), epoxy-terminated hyperbranched polymer D1: 8g (0.8wt%), thixotropic rheology modifier E1: 8g (0.8wt%), curing accelerator F1: 2g (0.2wt%), coupling agent F2: 8g (0.8wt%), release agent F3: 5g (0.5wt%), colorant F4: 2g (0.2wt%).

[0094] The preparation process is exactly the same as in Example 1.

[0095] (2) Arrangement of coil array:

[0096] The same as in Example 1.

[0097] (3) Low-pressure transfer molding:

[0098] The mold temperature is set to 175°C. The injection transfer pressure is set to 12MPa, and the transfer time is 18 seconds. The holding pressure is set to 18MPa, and the holding time is 10 seconds. The in-mold curing time is 90 seconds.

[0099] (4) Post-processing:

[0100] The same as in Example 1.

[0101] Comparative Example 1:

[0102] Compared with Example 1, the difference is that an equal amount of base resin B2 (non-crystalline o-cresol formaldehyde epoxy resin) is used instead of base resin B1 (crystalline biphenyl epoxy resin); and due to the higher viscosity of B2 resin, in order to fill the mold, the injection transfer pressure is adjusted to 120MPa, and the rest is the same.

[0103] Comparative Example 2:

[0104] Compared with Example 1, the difference is that the epoxy-terminated hyperbranched polymer D1 is not included in the formula, and is replaced by an equal amount of base resin B1. The rest of the formula composition and process parameters are the same.

[0105] Comparative Example 3:

[0106] The difference compared with Example 1 is that the thixotropic rheology modifier E1 is not included in the formulation, which is replaced by an equivalent amount of base resin B1. The rest of the formulation composition and process parameters are the same.

[0107] Comparative Example 4:

[0108] The difference compared with Example 1 is that the epoxy-terminated hyperbranched polymer D1 is replaced by an equivalent amount of commercially available conventional lubricant Montan wax (same as the component of release agent F3, here added additionally). The rest of the formulation composition and process parameters are the same.

[0109] Comparative Example 5:

[0110] The difference compared with Example 1 is that the thixotropic rheology modifier E1 is replaced by an equivalent amount of conventional fumed silica (specific surface area 200 m 2 / g). The rest of the formulation composition and process parameters are the same.

[0111] Comparative Example 6:

[0112] The difference compared with Example 3 is that the injection transfer pressure is increased to 100 MPa. The rest are the same.

[0113] Test Example 1: Rheological properties and process adaptability evaluation of molded materials

[0114] This test example aims to evaluate the rheological behavior and solidification characteristics of the magnetic molded materials prepared in the above examples and comparative examples in the molten state, to verify their feasibility in the low-pressure transfer molding process.

[0115] 1. Test items and methods

[0116] (1) Spiral flow length

[0117] According to the EMMI-1-66 standard, the test is carried out using a standard Archimedes spiral mold. The mold flow channel cross section is semicircular with a radius of 1.75 mm. The test conditions are as follows:

[0118] Mold temperature: 175℃;

[0119] Injection transfer pressure: 8 MPa;

[0120] Injection amount: 15 g.

[0121] Record the length of the material after complete solidification and stop flowing in the spiral flow channel, in centimeters (cm). This index directly reflects the filling capacity of the material under low pressure.

[0122] (2) Minimum melt viscosity

[0123] The test was conducted using a rotational rheometer.

[0124] Test mode: Oscillating shear mode;

[0125] Heating rate: 5℃ / min (from 40℃ to 200℃);

[0126] Cutting frequency: 1Hz;

[0127] Strain: 1%.

[0128] Record the lowest viscosity value in the viscosity-temperature curve, in Pascal-seconds (Pa·s).

[0129] (3) Thixotropic index

[0130] The test was conducted using a rotational rheometer at a constant temperature of 175°C.

[0131] Test procedure: First, at a low shear rate (0.5s) -1 Shear for 30 seconds and record the viscosity η1; then quickly switch to a high shear rate (500 s). -1 Shear for 30 seconds and record the viscosity η2 after stabilization; finally, quickly switch back to a low shear rate (0.5 s). -1 Record the recovered viscosity η3.

[0132] Calculate the thixotropic index TI = η1 / η2. The larger the thixotropic index value, the higher the degree of shear thinning of the material, and the stronger its resistance to settlement in a static state.

[0133] (4) Gelatinization time

[0134] The test was conducted on a hot plate at 175°C, following the JIS-K-6910 standard. The time from when the sample first touched the hot plate until it could no longer be drawn into a thread was recorded in seconds (s).

[0135] 2. Test Results

[0136] Table 1. Rheological properties and process adaptability tests of the materials in each embodiment and comparative example.

[0137]

[0138] 3. Conclusion

[0139] (1) High viscosity non-crystalline resin is used, with a minimum melt viscosity of up to 320.5 Pa·s. It cannot flow under low pressure of 8 MPa (spiral length 18 cm). However, by using crystalline resin in combination with hyperbranched polymer, the minimum viscosity is reduced to 4.2-15.3 Pa·s, which enables long-distance flow of more than 110 cm and establishes the material basis for low-pressure filling.

[0140] (2) In Comparative Example 2, the viscosity increased and the thixotropic index decreased after removing the hyperbranched polymer. In Comparative Example 4, the thixotropic index was only 4.8 when conventional Montan wax was used as a substitute. This confirms that the hyperbranched polymer has the dual functions of physical lubrication and thixotropic network enhancement, which is superior to conventional small molecule lubricants.

[0141] (3) In Comparative Example 3, the thixotropic index was only 1.1 after the removal of the thixotropic agent. Although it had good flowability, it lacked anti-settling ability. Examples 1-4 maintained the thixotropic index above 9.0, achieving a balance between flowability and anti-settling. Comparative Example 5 shows that the compatibility and network effect of organic urea thixotropic agents with this system are better than those of fumed silica.

[0142] Test Example 2: Evaluation of the Physical and Electrical Performance of Molded Inductors

[0143] This test case focuses on the 1200-hole integrally molded inductor products prepared in the embodiments and comparative examples. It examines the filling integrity, magnetic performance consistency, and internal coil shape retention in the actual mass production process to verify the actual effectiveness of the technical solution in solving the problems of coil deformation and magnetic powder sedimentation.

[0144] 1. Test Items and Methods

[0145] (1) Effective filling rate

[0146] The number of qualified products with complete appearance, no missing glue, and no air holes was counted out of 1200 products in the whole sheet.

[0147] Calculation formula: Effective filling rate = (Number of qualified products / 1200) × 100%.

[0148] (2) Inductance position deviation (ΔL)

[0149] To assess whether magnetic powder sedimentation or separation occurs during long-distance flow, 20 samples were randomly selected from the glue inlet area (near end, holes 1-20) and the flow channel end area (far end, holes 1180-1200) of the entire product.

[0150] The inductance (L value) was tested using an LCR meter at 100 kHz and 1.0 V.

[0151] Calculate the percentage difference in average inductance between the two groups of samples:

[0152] ΔL = |(L distal mean - L proximal mean) / L proximal mean| × 100%;

[0153] The smaller the ΔL value, the more uniform the distribution of magnetic powder in the resin, and the stronger the resistance to sedimentation / separation.

[0154] (3) Coil displacement rate

[0155] Thirty samples were randomly selected from the finished products of each set of examples and comparative examples, and fluoroscopic images were taken using industrial X-ray inspection equipment.

[0156] Measure the maximum offset distance (d) of the coil's central axis relative to the magnet's central axis, and the coil's average diameter (D).

[0157] The coil displacement rate is calculated as (d / D) × 100%. This indicator reflects the effect of fluid impact on the coil position during the injection molding process.

[0158] (4) DC superposition characteristics

[0159] The inductance of the test inductor was reduced under a rated DC bias current. The current value at which the inductance decreased by 30% was recorded. The average value of 20 samples was taken. This indicator reflects the density and uniformity of the magnetic powder filling.

[0160] 2. Test Results

[0161] Table 2. Physical and electrical performance test data of the molded inductor product

[0162]

[0163]

[0164] 3. Conclusion

[0165] (1) The low filling rate of Comparative Example 1 confirms that high viscosity resin cannot meet the requirements of low-pressure filling of 1200 cells. The high filling rates of Examples 1-4 and Comparative Examples 3 and 6 indicate that low viscosity is a prerequisite for high-throughput filling.

[0166] (2) Although Comparative Example 3 was completely filled, the lack of thixotropic agent led to severe phase separation, with an inductance position deviation as high as 61.2%. Example 1 used a strong thixotropic network to control the inductance position deviation to 0.9%, ensuring the uniformity of magnetic powder distribution.

[0167] (3) Comparative Example 6 was formed under high pressure, and the coil displacement rate was as high as 18.5%; while Example 3 had a coil displacement rate of only 0.8% under low pressure of 5MPa, which proved the protective effect of low pressure process on fine coils.

[0168] (4) Comparative Example 2 lacks hyperbranched polymers, resulting in low filling rate, large deviation and obvious coil displacement.

Claims

1. An integrated inductance package process for preventing coil deformation, characterized in that, The method comprises the following steps: S1: preparing a magnetic molding composition cake: mixing raw materials including magnetic powder, crystalline epoxy resin, curing agent, epoxy-terminated hyperbranched polymer, and thixotropic rheology modifier, melt mixing, cooling, crushing, and then pressing into a solid cake; S2: arranging coils: arranging the wound coil array on a lead frame and placing it into a mold with multiple cavities; S3: low-pressure transfer molding: heating and melting the cake prepared in step S1, and injecting the mold cavity under the condition that the injection transfer pressure is 5-15 MPa to wrap the coil; S4: curing: after pressure maintaining and preliminary curing in the mold, the product is taken out of the mold, and post-curing treatment is performed; The weight average molecular weight of the epoxy-terminated hyperbranched polymer is 1500-5000 g / mol, and the thixotropic rheology modifier is a urea-based compound.

2. The process of claim 1, wherein, In S1, the temperature of melt mixing is controlled at 85-100°C; in S3, the cake is preheated in the injection molding machine barrel for 3-8 seconds before injection, the injection transfer pressure is 8-12 MPa, the injection transfer time is 10-20 seconds, and the mold temperature is controlled at 165-180°C.

3. The process of claim 1, wherein the process is integrated into a process of manufacturing an inductor package. In S1 the magnetic molding composition has a minimum melt viscosity at 150 °C of 4.0 to 16.0 Pa-s and a thixotropic index after curing of 9.0 to 15.0, the thixotropic index being the ratio of the viscosity at a shear rate of 0.5 s -1 to 500 s -1 .

4. The process of claim 1, wherein, In S1, the magnetic molding composition comprises the following components by weight percentage: In S1, the magnetic molding composition comprises the following components by weight percentage: 86.0wt%-92.0wt% of magnetic powder; 3.0wt%-6.0wt% of crystalline epoxy resin; 1.5wt%-4.0wt% of curing agent; 0.5wt%-2.5wt% of epoxy-terminated hyperbranched polymer; 0.2wt%-0.8wt% of thixotropic rheology modifier; The balance of auxiliary additives.

5. The process of claim 4, wherein the process is an integral inductance package process for preventing coil deformation. The magnetic powder is selected from amorphous alloy powder, nanocrystalline alloy powder, or a mixture thereof.

6. The process of claim 4, wherein the process is an integral inductance package process for preventing coil deformation. The crystalline epoxy resin is a biphenyl type epoxy resin with a melting point of 95-115°C and a melt viscosity of less than 0.1 Pa·s at 150°C.

7. The process of claim 1, wherein the process is integrated into a process of manufacturing an inductor package. The epoxy-terminated hyperbranched polymer is prepared by modifying the hyperbranched polyester formed by the polycondensation of a core molecule and ABx type monomers with terminal epoxy groups, wherein the core molecule is selected from trimethylolpropane or pentaerythritol, and the ABx type monomer is 2,2-bis(hydroxymethyl)propionic acid.

8. The process of claim 1, wherein, In S1, the thixotropic rheology modifier is a precipitated product prepared by reacting diisocyanate with monoamine compound, wherein the diisocyanate is diphenylmethane diisocyanate, and the monoamine compound is n-butylamine.

9. The integrated inductor with anti-coil-deformation is applied to the integrated inductor packaging process with anti-coil-deformation of any one of claims 1-8, wherein, The displacement rate of the inductance internal coil is less than 1.5% by X-ray perspective measurement, and the displacement rate is the ratio of the maximum offset distance of the coil center axis relative to the magnet center axis to the average diameter of the coil.

10. The one-piece inductor of claim 9, wherein, The inductance is an array type batch packaging product, and the position deviation of the inductance at the beginning and end of the whole product is less than 2.0%.

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