Preparation method of package substrate
By setting photosensitive patterns on the bonding pads of the packaging substrate and etching to adjust bonding pads with inconsistent heights, the problem of uneven copper thickness was solved, achieving flatness of the packaging substrate and precise placement of electronic components, thus reducing production costs.
Patent Information
- Application Number
- CN202410513075.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-25
- Publication Date
- 2025-10-31
AI Technical Summary
Uneven copper thickness distribution in high-end packaging substrates leads to poor product performance. Connection points not being on the same plane may cause open circuit problems, substandard resistance, and interlayer micro-short circuits. Existing methods are difficult to achieve uniform copper thickness in high-end products.
By setting photosensitive patterns on connector pads of varying heights on the packaging substrate, and using optical exposure development and etching techniques, the connector pad with the larger height is exposed through a window. After etching, it is made flush with the other connector pad to ensure flatness.
It improves the flatness of the packaging substrate, reduces warpage, improves the placement accuracy of electronic components, and reduces production costs and equipment complexity.
Smart Images
Figure CN120882086A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of packaging substrate manufacturing, and more particularly to a method for preparing a packaging substrate. Background Technology
[0002] In packaging substrates, especially for high-end products, uneven copper thickness distribution has become common due to the precision of the circuitry. Excessive differences in copper thickness between densely packed circuit areas and large, open copper areas lead to poor product performance. Specifically, this manifests as: surface unevenness, causing connection points to be off-plane when connecting to chips due to thickness differences, potentially resulting in open circuits; substandard resistance and impedance; interlayer micro-short circuits; and sparking.
[0003] In general, copper plating stations employ techniques such as prolonged low current, adding plating masks, and auxiliary anodes to improve copper thickness uniformity. However, in high-end products, due to equipment or product design limitations, these methods often fail to achieve consistent copper thickness uniformity. Summary of the Invention
[0004] To address the above technical problems, this application provides a method for preparing a packaging substrate.
[0005] A method for fabricating a packaging substrate includes the following steps: providing a packaging substrate, the packaging substrate including a substrate, a first connecting pad, and a second connecting pad, the first connecting pad and the second connecting pad being located on opposite sides of the substrate, the first connecting pad having a first surface, the second connecting pad having a second surface, the packaging substrate having a thickness direction, and the first surface and the second surface being offset along the thickness direction; depositing a photosensitive film on the packaging substrate, the photosensitive film covering the first connecting pad and the second connecting pad; developing the photosensitive film using optical exposure to form a photosensitive pattern, the wavelength of the light used for optical exposure being 570-590 nanometers, the photosensitive pattern having a window, a portion of the first surface or a portion of the second surface being exposed through the window; etching the first surface to form a third surface, the third surface being flush with the second surface, or etching the second surface to form a fourth surface, the fourth surface being flush with the first surface; and removing the photosensitive pattern.
[0006] In some possible implementations, the step of "depositing a photosensitive film on the packaging substrate" further includes the step of: obtaining offset height information between the first surface and the second surface. The step of "etching the first surface to form a third surface" or "etching the second surface to form a fourth surface" includes the step of: etching the first surface to form the third surface based on the height information, or etching the second surface to form the fourth surface based on the height information.
[0007] In some possible implementations, the step "exposing and developing the photosensitive film to form a photosensitive pattern" includes: creating a photolithographic pattern based on the height information and loading the photolithographic pattern into an exposure machine. The exposure machine exposes the photosensitive film based on the photolithographic pattern. The exposed photosensitive film is then placed in a developing solution, such that a portion of the exposed area of the photosensitive film is dissolved by the developing solution, thereby forming the photosensitive pattern.
[0008] In some possible implementations, the third surface is flush with the second surface, and the fabrication method further includes the step of: setting electronic components on the third surface and the second surface.
[0009] In some possible implementations, the fourth surface is flush with the first surface, and the fabrication method further includes the step of: setting electronic components on the fourth surface and the first surface.
[0010] In some possible implementations, the photosensitive film includes a photosensitive layer, a protective layer, and a separable layer, wherein the photosensitive layer is connected between the protective layer and the separable layer, the separable layer is connected between the encapsulation substrate and the photosensitive layer, and the protective layer is disposed on the side of the photosensitive layer opposite to the separable layer.
[0011] In some possible implementations, the photosensitive layer includes a photoresist and a photosensitive polymer, the protective layer includes polyethylene or polypropylene, and the removable layer includes release paper.
[0012] In some possible implementations, the method for preparing the packaging substrate includes the steps of: fabricating the first connecting pad and / or the second connecting pad by an additive or subtractive method.
[0013] In some possible implementations, the packaging substrate further includes a core plate, side plates, and a plurality of interlayer conductors. The side plates are disposed on opposite sides of the core plate. The first connecting pad and the second connecting pad are respectively disposed on the side of the side plate away from the core plate. The plurality of interlayer conductors are embedded in the side plates and the core plate. One end of each interlayer conductor is connected to the first connecting pad and the second connecting pad, and the other end is connected to the side plate and / or the core plate.
[0014] In some possible implementations, the height at which the first surface is offset from the second surface is 3 to 9 micrometers.
[0015] The packaging substrate fabrication method provided in this application sets photosensitive patterns on first and second connecting pads of different heights, and exposes the first or second connecting pad with a larger height through a window in the photosensitive pattern. Finally, a portion of the first or second connecting pad with a larger height is removed by etching, so that the heights of the first and second connecting pads are finally consistent. This helps to maintain the flatness of the packaging substrate, reduce warpage, and improve the placement accuracy of electronic components. Attached Figure Description
[0016] Figure 1 This is a cross-sectional schematic diagram of a packaging substrate provided in an embodiment of this application.
[0017] Figure 2 for Figure 1 The diagram shows a cross-sectional view of the encapsulation substrate after the photosensitive film has been applied.
[0018] Figure 3 for Figure 2 The diagram shows an enlarged cross-sectional view of the photosensitive film.
[0019] Figure 4 For exposure Figure 2 The diagram shows a cross-section of the photosensitive film.
[0020] Figure 5 For development Figure 4 The diagram shown is a cross-sectional view of the photosensitive film after it has formed a photosensitive pattern.
[0021] Figure 6 For etching Figure 5 The diagram shows a cross-sectional view of the second connecting pad.
[0022] Figure 7 To remove Figure 6 A schematic diagram of the cross-section after the photosensitive pattern is shown.
[0023] Figure 8 for Figure 7 The diagram shows a cross-sectional view of the first and second connecting pads after electronic components have been installed.
[0024] Explanation of main component symbols
[0025] Packaging substrate 100
[0026] Substrate 10
[0027] Core board 101
[0028] Side panel 102
[0029] Interlayer conductor 103
[0030] First connecting pad 11
[0031] First surface 111
[0032] Second connecting pad 12
[0033] Second surface 121
[0034] Third surface 131
[0035] Photosensitive film 20
[0036] Photosensitive pattern 24
[0037] Photosensitive layer 21
[0038] Open window 211
[0039] Protective layer 22
[0040] Separable layer 23
[0041] First welding ball 31
[0042] First opening 321
[0043] First weld resist layer 32
[0044] Packing 301
[0045] Second weld shielding layer 33
[0046] Second opening 331
[0047] Second solder ball 34
[0048] Thickness direction A Detailed Implementation
[0049] The preferred embodiments of this application are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit this application.
[0050] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and does not specifically refer to any order or sequence, nor is it intended to limit this application. They are merely used to distinguish components or operations described using the same technical terms and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions and features of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application.
[0051] One embodiment of this application provides a method for preparing a packaging substrate 100 to improve the flatness of the packaging substrate 100. See also: Figure 1 The encapsulation substrate 100 includes a substrate 10, a plurality of first connecting pads 11, and a plurality of second connecting pads 12. The plurality of first connecting pads 11 and the plurality of second connecting pads 12 are alternately connected to opposite sides of the substrate 10. Each first connecting pad 11 has a first surface 111 facing away from the substrate 10. Each second connecting pad 12 has a second surface 121 facing away from the substrate 10. The encapsulation substrate 100 has a thickness direction A, and both the first surface 111 and the second surface 121 are generally perpendicular to the thickness direction A. Along the thickness direction A, the height at which the first surface 111 and the second surface 121 are offset is 3–9 micrometers. The fabrication method is used to reduce the height difference between the first connecting pads 11 and the second connecting pads 12, thereby improving flatness and reducing warpage.
[0052] The preparation method includes the following steps:
[0053] S1: Obtain a photolithography pattern based on the thickness data of the plurality of first connecting pads 11 and the plurality of second connecting pads 12, and import the photolithography pattern into the exposure machine.
[0054] In this embodiment, step S1 specifically includes:
[0055] S11: Measure the thickness data of the plurality of first connecting pads 11 and the plurality of second connecting pads 12 of the packaging substrate 100 using a copper thickness gauge, with a range between 1 μm and 1000 μm. That is, obtain the offset height information between the first surface 111 and the second surface 121. The copper thickness gauge is either an electromagnetic induction copper thickness gauge or an X-ray copper thickness gauge.
[0056] S12: Design the circuit diagram using CAD software based on the thickness data. That is, create a photolithography file based on the height information.
[0057] S13: Convert the circuit pattern into a Gerber format photolithography file. The Gerber format photolithography file is a standard format for storing graphic information. The Gerber format photolithography file contains a series of instructions for controlling the light beam of the exposure machine.
[0058] S14: After inspecting and editing the Gerber format photolithography file, output the Gerber format photolithography file to the exposure machine.
[0059] S2: Please see Figure 2A photosensitive film 20 is disposed on the packaging substrate 100, and the photosensitive film 20 covers a plurality of first connecting pads 11 and a plurality of second connecting pads 12.
[0060] Please see below. Figure 3 The photosensitive film 20 includes a photosensitive layer 21, a protective layer 22, and a separable layer 23. The photosensitive layer 21 is connected between the protective layer 22 and the separable layer 23. The separable layer 23 is connected between the encapsulation substrate 100 and the photosensitive layer 21. The protective layer 22 is disposed on the side of the photosensitive layer 21 opposite to the separable layer 23.
[0061] The photosensitive layer 21 includes photoresist, photosensitive polymer, etc., and is used for photosensitive exposure to form a photolithographic pattern. The protective layer 22 is made of a transparent material and is used to protect the photosensitive layer 21 from external damage. The material of the protective layer 22 includes polyethylene, polypropylene, etc. The removable layer 23 is made of an easily peelable material and is used to separate from the photosensitive layer 21. The removable layer 23 includes release paper.
[0062] In this embodiment, step S2 specifically includes:
[0063] S21: Select a suitable photosensitive material, and cut the photosensitive film 20 to the appropriate size according to the size of the encapsulation substrate 100 and the area to be covered, and ensure that the photosensitive film 20 is of good quality and free from impurities, bubbles and other defects.
[0064] S22: Using appropriate tools or equipment, apply the photosensitive film 20 flatly onto the encapsulation substrate 100, ensuring that the photosensitive film 20 completely covers the plurality of first connecting pads 11 and the plurality of second connecting pads 12, and that there are no bubbles or wrinkles.
[0065] S23: After covering the photosensitive film 20, perform pretreatment operations, such as heating, pressurizing or vacuum adsorption, to ensure a tight fit between the photosensitive film 20 and the encapsulation substrate 199, and to avoid displacement or detachment in subsequent steps.
[0066] Through steps S21 to S23 above, the photosensitive film 20 is disposed on the packaging substrate 100, preparing it for subsequent exposure and development steps. The precise execution of these steps is crucial to ensuring the quality and performance of the packaging substrate 100.
[0067] S3: Please see Figure 4 and Figure 5The photosensitive film 20 is optically exposed to light with a wavelength of 570-590 nanometers, and then developed to form a photosensitive pattern 24, which has a window 211. The thickness of the second connecting pad 12 is greater than that of the first connecting pad 11, and the second surface 121 of the second connecting pad 12 is exposed at the bottom of the window 211.
[0068] In other embodiments of this application, the thickness of the second connecting pad 12 is less than the thickness of the first connecting pad 11, and the first surface 111 of the first connecting pad 11 is exposed at the bottom of the window 211.
[0069] In this embodiment, step S3 specifically includes:
[0070] S31: Place the photosensitive film 20 and the encapsulation substrate 100 in an exposure machine. The light source used in the exposure machine is a UV / mercury lamp light source.
[0071] S32: The exposure machine selects an appropriate exposure time and light intensity to expose the photosensitive film 20 according to the photolithography pattern.
[0072] S33: Please see Figure 5 The exposed photosensitive film 20 is placed in a developing solution, causing a portion of the exposed area of the film 20 to dissolve, leaving the unexposed portion to form the photosensitive pattern 24. The developing solution includes an alkaline developer, which effectively reacts with specific chemical substances produced by the photosensitive film 20, dissolving it in the solution. Examples of alkaline developers include sodium carbonate. Furthermore, the developing solution may contain an appropriate amount of surfactant to improve the developing effect and ensure the clarity and accuracy of the pattern. Simultaneously, to maintain the stability of the developing solution and extend its lifespan, buffers, inhibitors, and other additives may be added. During the developing process, parameters such as the temperature, concentration, and developing time of the developing solution need to be controlled to ensure that the photosensitive film 20 is correctly developed, forming the desired photosensitive pattern 24.
[0073] S4: Please see Figure 6 The second connecting pad 12 exposed in the window 211 is etched so that the etched second connecting pad 12 is approximately flush with the first connecting pad 11.
[0074] In this embodiment, step S4 includes: etching the second surface 121 of the second connecting pad 12 to form a third surface 131. The third surface 131 is flush with the first surface 111.
[0075] In other embodiments of this application, step S4 includes: etching the first surface 111 of the first connecting pad 11 to form a fourth surface (not shown). The fourth surface is flush with the second surface 121.
[0076] S5: Please see Figure 7 The photosensitive pattern 24 is removed. Specifically, the separable layer 23 is removed by etching with sodium hydroxide solution, so that the photosensitive pattern 24 is separated from the packaging substrate 100, and the first surface 111 of the first connecting pad 11 is exposed.
[0077] In this embodiment, the packaging substrate 100 is a multilayer laminated structure. The substrate 10 includes a core plate 101, side plates 102, and a plurality of interlayer conductors 103. The side plates 102 are disposed on opposite sides of the core plate 101. The first connecting pad 11 and the second connecting pad 12 are respectively disposed on the side of the side plate 102 away from the core plate 101. The plurality of interlayer conductors 103 are embedded in the side plates 102 and the core plate 101. One end of each interlayer conductor 103 communicates with the first connecting pad 11 and the second connecting pad 12. The other end communicates with the side plate 102 and / or the core plate 101.
[0078] In this embodiment, the packaging substrate 100 is fabricated using a subtractive method. That is, the first connection pad 11 and the second connection pad 12 are formed by selectively removing a portion of the copper layer. In other embodiments of this application, the packaging substrate 100 is fabricated using an additive method, that is, conductive patterns are formed by deposition or electroplating. However, neither the additive nor the subtractive method can guarantee that the first connection pad 11 and the second connection pad 12 are at the same height.
[0079] In this embodiment, the method for fabricating the packaging substrate 100 further includes the step of: setting electronic components 30 and a plurality of first solder balls 31 on the third surface 131 and the first surface 111. The electronic components 30 include chips. It can be understood that in other embodiments of this application, the method for fabricating the packaging substrate 100 further includes the step of: setting electronic components 30 on the fourth surface 112 and the second surface 121.
[0080] In this embodiment, the step of "setting electronic components 30 and a plurality of first solder balls 31 on the third surface 131 and the first surface 111" includes:
[0081] A first solder resist layer 32 is provided on one side of the third surface 131 or the first surface 111. The first solder resist layer 32 has a first opening 321, through which a portion of the first surface 111 or a portion of the third surface 131 is exposed at the bottom of the first opening 321. The first solder resist layer 32 is used to protect the circuit from oxidation. A first solder ball 31 is disposed within the first opening 321, and one end of the first solder ball 31 is electrically connected to the first surface 111 or the third surface 131.
[0082] The electronic component 30 is disposed on the first solder resist layer 32. The electronic component 30 is connected to the other end of the first solder ball 31. The height of the first solder ball 31 is greater than the thickness of the first solder resist layer 32, so that there is a gap (not shown) between the electronic component 30 and the first solder resist layer 32.
[0083] A filler 301 is provided in the gap, and the filler 301 fixes the electronic component 30 and the first solder resist layer 32.
[0084] In this embodiment, the method for preparing the packaging substrate 100 further includes the following steps:
[0085] A second solder resist layer 33 and a plurality of second solder balls 34 are disposed on the third surface 131 or the first surface 111 on the other side. The second solder resist layer 33 is provided with a plurality of second openings 331, and one end of the plurality of second solder balls 34 is disposed in the second opening 331 and electrically connected to the third surface 131 or the first surface 111. The other end of the second solder balls 34 is used to connect to a chip carrier board (not shown).
[0086] Compared to existing technologies, the method for fabricating the packaging substrate 100 provided in this application involves setting photosensitive patterns 24 on first connecting pads 11 and second connecting pads 12 with different heights, and exposing the first connecting pad 11 or second connecting pad 12 with a larger height through the opening 211 of the photosensitive pattern 24. Finally, a portion of the first connecting pad 11 or second connecting pad 12 with a larger height is removed by etching, so that the heights of the first connecting pad 11 and the second connecting pad 12 are finally consistent. This helps to maintain the flatness of the packaging substrate 100, reduce warpage, and improve the placement accuracy of the electronic components 30.
[0087] In addition, the method for fabricating the packaging substrate 100 provided in this application has the following advantages:
[0088] (i) Since the optical exposure process is performed in batches, multiple packaging substrates 100 or wafers can be processed simultaneously, improving production efficiency. Furthermore, the equipment required by the above-mentioned preparation method is relatively simple, eliminating the need for expensive instruments and equipment, thus reducing production costs.
[0089] (II) Widely used in the semiconductor and display industries, specifically, the packaged substrate 100 is widely used in the semiconductor industry and flat panel display production. In the semiconductor industry, the packaged substrate 100 is used to fabricate micro / nano structures such as integrated circuits, sensors, and MEMS. In flat panel display production, the packaged substrate 100 is used to fabricate key components such as liquid crystal panels and organic light-emitting diodes (OLEDs).
[0090] The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.
Claims
1. A method for preparing a packaging substrate, characterized in that, Including the following steps: A packaging substrate is provided, the packaging substrate including a substrate, a first connecting pad and a second connecting pad, the first connecting pad and the second connecting pad being located on both sides of the substrate, the first connecting pad having a first surface and the second connecting pad having a second surface, the packaging substrate having a thickness direction, and the first surface and the second surface being offset along the thickness direction; A photosensitive film is disposed on the packaging substrate, the photosensitive film covering the first connecting pad and the second connecting pad; The photosensitive film is developed by optical exposure to form a photosensitive pattern, wherein the wavelength of the light used for optical exposure is 570-590 nanometers, and the photosensitive pattern has a window through which a portion of the first surface or a portion of the second surface is exposed. Etching the first surface to form a third surface, the third surface being flush with the second surface, or etching the second surface to form a fourth surface, the fourth surface being flush with the first surface, and Remove the photosensitive pattern.
2. The preparation method according to claim 1, characterized in that, The step preceding the step "depositing a photosensitive film on the encapsulation substrate" also includes the following step: Obtain the offset height information between the first surface and the second surface; The step "etching the first surface to form the third surface" or "etching the second surface to form the fourth surface" includes the following steps: Based on the height information, the first surface is etched to form the third surface, or based on the height information, the second surface is etched to form the fourth surface.
3. The preparation method according to claim 2, characterized in that, The step "exposing and developing the photosensitive film to form a photosensitive pattern" includes: A photolithography pattern is created based on the height information, and the photolithography pattern is loaded into the exposure machine; The exposure machine exposes the photosensitive film according to the photolithography pattern; The exposed photosensitive film is placed in a developing solution, so that a portion of the exposed area of the photosensitive film is dissolved by the developing solution, thereby obtaining the photosensitive pattern.
4. The preparation method according to claim 1, characterized in that, The third surface is flush with the second surface, and the preparation method further includes the step of: setting electronic components on the third surface and the second surface.
5. The preparation method according to claim 1, characterized in that, The fourth surface is flush with the first surface, and the preparation method further includes the step of: setting electronic components on the fourth surface and the first surface.
6. The preparation method according to claim 1, characterized in that, The photosensitive film includes a photosensitive layer, a protective layer, and a separable layer. The photosensitive layer is connected between the protective layer and the separable layer. The separable layer is connected between the encapsulation substrate and the photosensitive layer. The protective layer is disposed on the side of the photosensitive layer opposite to the separable layer.
7. The preparation method according to claim 6, characterized in that, The photosensitive layer includes a photoresist and a photosensitive polymer, the protective layer includes polyethylene or polypropylene, and the separable layer includes release paper.
8. The preparation method according to claim 1, characterized in that, The method for preparing the packaging substrate includes the steps of: preparing the first connecting pad and / or the second connecting pad by an additive or subtractive method.
9. The preparation method according to claim 1, characterized in that, The packaging substrate further includes a core plate, side plates, and multiple interlayer conductors. The side plates are disposed on opposite sides of the core plate. The first connecting pad and the second connecting pad are respectively disposed on the side of the side plate away from the core plate. The multiple interlayer conductors are embedded in the side plates and the core plate. One end of each interlayer conductor is connected to the first connecting pad and the second connecting pad, and the other end is connected to the side plate and / or the core plate.
10. The preparation method according to claim 1, characterized in that, The height at which the first surface and the second surface are offset is 3 to 9 micrometers.