TW202333176A - Packaging of roll-type solid electrolytic capacitor elements - Google Patents

Abstract

This invention describes a packaging structure for roll-type (wound-type) aluminum conductive polymer capacitor element. Two protective substrates are applied to sandwich a roll-type capacitor element in between with an insulating material surrounding the capacitor element also in between the protective substrates. The protective substrates comprise electrically separated anodic conductive pad and cathodic conductive pad on their surfaces and through holes that pass through the conductive pads. The capacitor element is oriented with its axis perpendicular to the two substrates. The anodic and cathodic leads of the capacitor element pass through the through holes. An anodic external terminal is plated over the anodic conductive pad and a cathodic external terminal is plated over the cathodic conductive pad so that the anodic external terminal is electrically connected to the anodic lead and the cathodic external terminal is electrically connected to the cathodic lead.

Description

Packaging of wound solid electrolytic capacitor cores

Cross-Reference to Related Applications: Through the present inventor, this application claims the benefit of U.S. Provisional Application No. 63/283,222, filed on November 25, 2021, the entire contents of which are incorporated by reference into this application.

The present invention relates to a packaging structure and method for a capacitor core, in particular to a packaging structure and method for a wound capacitor core.

Existing packaging methods for wound-type solid electrolytic capacitors have shortcomings in component size and shock resistance, and therefore have limitations in specific application areas. Figure 1 shows several common roll-type or wound-type solid electrolytic capacitor cores manufactured from existing commercial equipment and parts. Among them, 10F and 10G are the most typical types. A typical wound type (winding type) solid electrolytic capacitor core includes a cylindrical capacitor core body 13, an anode lead 11 and a cathode lead 12. The capacitor core body is rolled into a cylindrical shape by etched aluminum foil strips and spacer layers, and then filled with polymer-based solid electrolyte. The lead is usually a three-section structure composed of three materials: the root section (11D, 12D) is an aluminum tab or aluminum wire and end welded directly to the anode or cathode aluminum foil tape in the capacitor core body. The sections (11DC, 12DC) are copper-clad steel core leads, and the connecting sections (11W, 12W) that weld the root section and the end section to each other. For convenience of explanation, this is called a standard lead. In addition, capacitor cores using only aluminum wires as leads are also available, as shown in Figure 1 as 11D and 12D in types 10D and 10E. The two leads of types 10F and 10D are on the same end of the body, while the leads of types 10G and 10E are on opposite ends of the body. The existing packaging method of wound solid electrolytic capacitors is to use a can-shaped aluminum shell to accommodate the capacitor core body, and seal it by clamping a sealing material (such as plastic or rubber) with the aluminum shell at one or both ends. Existing packaging methods include multiple separate parts, which must be manufactured separately on special machines, and usually must be done one by one, without parallel processing. In many packaged capacitors, the sealing material accounts for a significant portion of the total component volume. In addition, this can-type packaging method allows the capacitor core to be supported only by aluminum leads at one or both ends, and the core body does not have any mechanical support. Therefore, in applications in the automotive and transportation industries, reliability issues can arise due to aluminum lead material fatigue caused by frequent vibrations.

Because the core of solid electrolytic capacitors is fragile, some common electronic packaging processes are difficult to apply. Traditional packaging processes, such as transfer molding of molding compounds, require high-viscosity materials to flow under high pressure. In order to create a thin insulating layer to reduce component size, the distance between the mold wall and the capacitor core needs to be reduced, resulting in increased viscous stress on the capacitor core while maintaining the same flow rate. Compression molding can reduce pressure flow but does not eliminate it completely. Sheet molding compound involves high pressure. Therefore, an improved packaging structure and method would be beneficial.

The present invention describes a packaging structure for a roll-type or wound-type aluminum conductive polymer capacitor element. A wound capacitor core is surrounded by insulating material and sandwiched between two protective substrates. The axis of the capacitor core is perpendicular to the two protective substrates. After the anode lead and cathode lead of the capacitor core are cut short, they pass through the through holes to the outside of the protective substrate and are electrically connected to the anode and cathode external terminals on the outer surface of the protective substrate. For capacitor cores with only aluminum leads, the external terminals and the electrical connection from the terminals to the aluminum leads of the capacitor core are usually accomplished through a multi-step electroplating process that includes a zinc substitution step. Aluminum leads can be receive plating. For capacitor cores with standard leads, that is, capacitor cores with the aforementioned typical three-material three-section structure and copper-clad lead end sections, the electrical conductive connection between the leads and the external terminals is basically through soldering and then electroplating. Finish. The aluminum sheet portion (root section) in the lead is bent to rotate the connecting section approximately 90 degrees, which brings the body of the capacitor core closer to the surface of the protective substrate or package, thereby reducing the overall component size. The copper-clad portions (end sections) of the leads are also bent to facilitate connection to external terminals. The electrical conductive connection between the external terminals and the copper-clad end sections from the terminals to the capacitor core leads is essentially accomplished by soldering, surface treatment and electroplating.

The filling of insulation material can be carried out through a capillary filling process or a simple pouring and flooding process. Typically, a low to medium viscosity liquid insulating material is used and the flow rate is kept low to avoid damaging the capacitor core. After filling, the insulation material hardens during the curing process and bonds the assembly into a single unit.

The details of the present invention will be described in detail through the following examples:

[example 1]

A wound type capacitor core package in which the aluminum leads are located at the same end of the core body uses a protective substrate with a conductive pad on the non-conductive surface.

Figure 2(a) is an exploded view of the packaging structure of a wound capacitor core with the anode lead and cathode lead at the same end, showing the main parts. The capacitor core 10D is placed between the upper protection substrate 20U and the lower protection substrate 20L in an axial direction perpendicular to the protection substrate. The leads on the capacitor core have been cut short in advance, so that the remaining anode lead 11D and cathode lead 12D are both aluminum wires. The upper protective substrate 20U is composed of an electrically insulating substrate body 21 and conductive pads (22A, 22C) on its outer surface. Two through holes (28A, 28C) penetrate the substrate body and the conductive pad. During assembly, the anode lead 11D passes through the through hole 28A, and the cathode lead 12D passes through the through hole 28C, as shown in the cross-sectional view of FIG. 2(b) and FIG. 3 . During assembly, the capacitor core is fixed on the upper protective substrate with adhesive 52 . There is a metal pad 22T on the inside of the lower protective substrate 20L, which serves as an anti-moisture shield during packaging.

The protective substrate can be made using a copper-clad printed circuit board (PCB copper clad board). The copper-clad printed circuit board usually consists of an electrically insulating substrate body 21 made of glass fiber reinforced epoxy resin, and a copper-clad layer on one or both sides. Copper conductive pads can be made by printing a copper clad layer using standard circuit board printing processes. Through-hole plating can also be processed through standard circuit board printing processes.

Figure 2(b) shows the main components after assembly. The space 60S surrounding the capacitor core between the two protective substrates is filled with insulating material 60, as shown in the perspective view of the packaged capacitor core in Figure 2(c). The insulating material fills the through hole and wraps the leads and the entire capacitor core, as shown in the cross-section in Figure 3. The protruding parts of the two leads on the upper surface are first cut and then coated or electroplated with conductive material to form external terminals. The perspective view of the packaged capacitor core in Figure 2(c) shows that external terminals 40A (anode) and 40C (cathode) are located on the top of the insulating body 42. The outer conductive pads (22A, 22C) are covered with electroplated conductive material. This brings the external anode terminal 40A and the cathode terminal 40C into conduction with the anode lead 11D and cathode lead 12D of the capacitor core.

Next, the formation method of the external terminals and their electrical connection with the conductive pads on the protective substrate will be further explained. After the insulating material 60 is filled and cured and before the external terminals 40A and 40C are plated, the tips of the leads (11D, 12D) that slightly protrude from the conductive pads (22A, 22C) are processed so that the surfaces are flat and the tip surfaces of the leads ( 11DA, 12DA) exposed. Then, a layer of first conductive material is deposited on the tip surface. For example, a layer of nickel is deposited on the tip surface through a zinc substitution process and an electroless nickel strike process. In this example, electroless nickel strike is generally not plated on the exposed surface of the electrically insulating substrate body 21 or the insulating material 60, nor is it plated on the copper pads (22A, 22C), because copper It has no catalytic effect on electroless nickel. Next, electroless copper plating and electrolytic plating are performed to increase the thickness to form external terminals 40A and 40C. Use appropriate masks during the process to protect areas that need to remain non-conductive. The zinc substitution process (also known as the zinc activation process (zincate process) or the zinc-nickel process (zinc-nickel process)) is an electroplating process that covers aluminum with electroplating. An example of this process can be found in the article "Effect of Zincate Treatment on Adhesion of Electroless Nickel-Phosphorus Coating for Commercial Pure Aluminum" by K. Murakami et al., Materials Transactions, Vol. 47, No. 10 (2006) pp. 2518 -2523, or found in S. Court's article "Monitoring of zincate pre-treatment of aluminum prior to electroless nickel plating", Transactions of the Institute of Metal Finishing 95(2): 97-105, which is incorporated by reference in its entirety. .

[Example 2]

A wound capacitor core with the anode lead at the same end as the cathode lead is packaged with an accompanying component.

It is more convenient in some applications to package one or more accompanying components and the wound capacitor core in the same package, that is, to combine the two into a circuit and package them together.

For example, the power supply system of a circuit board will require a set of capacitors containing various capacitance specifications in order to stabilize the supply voltage at the power connections of each component. These include main capacitors (bulk capacitors) close to the power connection part of the circuit board, with specifications ranging from a few microfarads to hundreds of microfarads, as well as local filtering and bypass (by-pass) capacitors, whose specifications are generally 0.01 to 0.1 microfarad. The existing method is to assemble individual capacitors of different types and capacity specifications onto a circuit board one by one. For mass-produced circuit boards, it is more convenient to package a combination of several capacitors in one package to reduce the total footprint and assembly time. For example, aluminum solid electrolytic capacitors of several hundred microfarads paired with tantalum capacitors of hundreds to tens of microfarads are often used close to the power connector. Smaller capacitors, such as film type or multilayer ceramic capacitors (MLCC), are used locally. Therefore, for tighter layout designs, these capacitors can be packaged together. Since aluminum solid electrolytic capacitors are the largest in size, it makes sense to package a wound aluminum solid electrolytic capacitor with one or more smaller capacitors.

Figure 4(a) shows an exploded view of an exemplary package structure, including a wound solid electrolytic capacitor core 10D and a small capacitor 70. The packaging, connection methods and parts of the wound solid electrolytic capacitor are basically the same as those in Figure 2(a). However, the upper substrate additionally adds a second set of outer conductive pads 23C and 23A and inner conductive pads 23CI and 23AI. 20UL shows the inner structure of the upper substrate from a lower view. The inner conductive pad and the outer conductive pad are connected through vias 29C and 29A, that is, plated through holes. The small capacitor is electrically connected to the second set of conductive pads from the inside through soldering or conductive paste 54 . The vias and their connections to the small capacitors can be made in advance in a separate process. After the parts are assembled, insulating material is filled in to wrap the two capacitors, as shown in Figure 4(b). Figure 5 is a cross-sectional view of Figure 4(b) at section A-A, showing the connection of small capacitors. Therefore, this package contains two separate capacitors with separate external terminals (40C, 40A and 41C, 41A) plated on corresponding conductive pads (22C, 22A and 23C, 23A). When used, these two capacitors can be used as two independent components, with external terminals connected to the power/ground plane/node of the circuit board as needed.

[Example 3]

A wound capacitor core (10E) package with anode and cathode leads at both ends.

The package structure and process are basically similar to Figure 2, the only difference is that via 28A, anode conductive pad 22A and terminal 40A will be located on the upper substrate 20U, while via 29A and cathode conductive pad 22C and terminal 40C will be located on the lower substrate 20L superior. Figure 6 shows the capacitor packaged in this case. Figure 6(a) shows the anode side of the package, while Figure 6(b) shows the cathode side. 28A and 28C mark where the leads connect to the terminals.

[Example 4]

Batch manufacturing using parallel processing.

One of the advantages of this new packaging structure and process is that large numbers of capacitor cores can be mass-produced simultaneously through parallel manufacturing. Although the construction shown in Figures 2 to 5 is a single package component, this construction can be extended to a two-dimensional matrix. Figure 7(a)(b) depicts this idea. Initially, the protective substrates were two large full-size substrates (20UF, 20LF), and preprocessing of conductive pads and holes had been completed at the corresponding positions of multiple components. Several capacitor cores are then placed (glued) to these locations and assembled onto the substrate.

The insulating material 60 may be filled together as a whole between the two full-size substrates. The filling of insulation material can be carried out through a capillary filling process or a simple pouring and flooding process. Typically low to medium viscosity insulating materials are used and flow rates are kept low to avoid damaging the capacitor core. After filling, the insulation material hardens during the curing process and bonds the assembly into a single unit. The curing/hardening process inevitably causes uneven expansion and contraction between the insulation material and the protective substrate. By sandwiching the insulating material between two protective substrates, bending deformation after hardening of the assembly can be minimized.

The plating of external terminals of all components (such as 40A, 40C) can also be performed simultaneously. Finally, cutting is performed along cutting lines CLH and CLV to separate individual components.

[Example 5]

The standard wound capacitor core (10F) package with the leads located at the same end of the capacitor core body uses a protective substrate with a conductive pad on the non-conductive surface.

Standard lead extensions are covered with copper to make connection to external terminals easier. Because it can be directly welded, zinc replacement is not required. Figure 8 shows the packaging structure and flow. Figures 8(a) and 8(b) show the assembly process of the main parts. The process is similar to Figures 2(a) and 2(b) except that the leads of the capacitor core are bent or folded. The aluminum sheet part (11D, 12D) (root section) in the lead is bent, causing the connecting section (11W, 12W) to rotate 90 degrees. This allows the body of the capacitor core to be assembled close to the protective substrate, thus reducing the overall component size. The copper-clad portions (11DC, 12DC) (end sections) of the leads are also bent so that they point upward to protect the corresponding holes in the substrate 20U. The bending of the leads can be completed in a separate process using a forming mold before assembly with the protective substrate.

The protective substrate can be made using a copper-clad printed circuit board (PCB copper clad board). In Figure 8(b), the capacitor core is glued to the bottom surface of the upper protective substrate 20U, and its leads pass through two vias or plated through-holes (29A, 29C). Plated through-holes connect the external conductive pads (22A, 22C) and internal conductive pads (22AI, 22CI) of the anode and cathode respectively. In other words, the inside surface of the via, the top and bottom outsides, and the leads that pass through the hole are all copper. A spot welder can therefore be used to solder the leads to the conductive pads on the upper side of the upper substrate. With proper use of flux, solder 55 can flow into the plated through hole and solder the leads to the through hole and conductive pad, as shown in Figure 8(c).

Then the insulating material 60 is filled in and solidified, so that the assembly hardens into a complete solid. Next, trim the protruding leads and sand away the residue. Figure 8(d) depicts this idea. A layer of copper is then electroplated onto the copper pads (22A, 22C) and the remaining solder 55 on the copper pads to form external terminals (40A, 40C), as shown in Figure 8(e). Figure 9 shows a cross-section of the completed structure.

It is best to use high temperature solder to ensure that the external terminals of the packaged capacitor do not melt during the reflow soldering process.

[Example 6]

The standard lead is located at the same end of the capacitor core body as a wound capacitor core (10F) package, using an all-conductor to protect the substrate.

The protective substrate may also only have a conductive substrate and conductive pads, without an insulating substrate body. For example, an all-conductor substrate can be made of thin copper sheets. This packaging further reduces overall component thickness. Taking the construction of a printed circuit board (PCB) as an example, a typical printed circuit board (PCB) may contain an insulating core made of fiberglass-reinforced epoxy resin that is 4 to 8 inches thick (or 0.1 to 0.2 millimeters) , and the 1 ounce or even half ounce copper clad layer (copper clad) covered on both sides, the corresponding thickness is 1.4 to 0.7 inches (or 0.035 to 0.018 mm). The total thickness of the two protective substrates made of printed circuit board (PCB) is about 0.27 to 0.54 mm. On the other hand, if 0.1 mm copper foil is used, the total thickness of the two substrates can be reduced to 0.2 mm. If only copper clad sheets are used, the total thickness of the two substrates can be further reduced to 0.035 to 0.07 mm.

Figure 10 shows a cross-sectional view of the packaging structure based on an all-conductor protective substrate. This structure is basically similar to Figure 9, with the only difference being that the PCB copper clad board is replaced by an upper metal (copper) substrate 20UM and a lower copper substrate 20LM. The through holes (28A, 28C) may be direct through holes. The packaging process is also similar to Figure 8. The only difference is that the copper pads 22A and 22C need to be made by an etching process after the wires are soldered and the insulating material is cured, and a gap 20G is opened to separate the two electrodes.

[Example 7]

The standard leads are located at both ends of the capacitor core body in a wound capacitor core (10G) package.

This example is similar to Example 5 or Example 6, with the only difference being that the anode lead and the cathode lead are connected to external terminals on the upper and lower substrates on opposite sides of the package component, respectively. The final component looks similar to the one shown in Figure 6.

The invention disclosed herein has been described above through multiple specific embodiments and multiple process steps. However, many modifications, changes and improvements can be made by those skilled in the art without departing from the spirit and scope of the disclosure as set forth in the claims.

[prior art] 10D, 10E, 10F, 10G: different types of wound capacitor cores 13: Cylindrical capacitor core body 11:Anode lead 12:Cathode lead 11D, 12D: root segment 11DC, 12DC: terminal section 11W, 12W: connecting section [Embodiment] 10D: Single capacitor core (wound type solid electrolytic capacitor core) 20U: Upper protection substrate (upper substrate) 20L: Lower protection substrate (lower substrate) 11D: Anode lead (anode, lead) 12D: Cathode lead (cathode, lead) 21:Electrically insulating substrate body 22A: External surface (external conductive pad, copper pad, conductive pad, anode conductive pad) 22C: External surface (external conductive pad, copper pad, conductive pad, cathode conductive pad) 28A, 28C:Through hole 52:Viscose 22T: metal pad 60S: Gap 60:Insulating materials 40A: External terminal (anode terminal, terminal) 40C: External terminal (cathode terminal) 42: Insulating body 11DA, 12DA: tip surface 13: Cylindrical capacitor core body 70:Small capacitor 23C, 23A: External conductive pad (conductive pad) 23CI, 23AI: Internal conductive pad 29C: Via hole (plated through hole) 29A: Via hole (plated through hole) 54:Conductive glue 41C, 41A: External terminals 10E: Body (capacitor core body) 20UF, 20LF: Large full-size substrate D1-D5: components CLH, CLV: cutting line 11W, 12W: connecting section 11DC, 12DC: Lead wire 22AI, 22CI: Internal conductive pad 55: Solder (welding material) 20UM: Upper metal (copper) substrate 20LM: Lower copper substrate 20G: Gap

Figure 1 shows several common wound solid electrolytic capacitor cores manufactured from existing commercial equipment and parts.

Figure 2 (a), (b) and (c) show one of the packaging structures and packaging processes of the wound solid electrolytic capacitor core proposed by the present invention. The aluminum leads are located at the same end of the capacitor core body.

FIG. 3 is a cross-sectional view of the package structure of FIG. 2 .

Figures 4 (a) and (b) show an exemplary packaging structure proposed by the present invention, including a wound solid electrolytic capacitor core and a small capacitor.

FIG. 5 is a cross-sectional view of the package structure of FIG. 4 .

Figures 6 (a) and (b) show the package of a wound solid electrolytic capacitor core in which the aluminum leads proposed by the present invention are respectively located at both ends of the capacitor core body.

Figures 7 (a) and (b) illustrate a method for batch manufacturing a plurality of capacitor elements proposed by the present invention.

Figure 8 (a), (b), (c), (d) and (e) show one of the packaging structures and packaging processes of the wound solid electrolytic capacitor core proposed by the present invention. Its standard leads are located at The same end as the capacitor core body.

Figure 9 is a cross-sectional view of the package structure of Figure 8.

FIG. 10 shows a cross-sectional view of the packaging structure based on an all-conductor protective substrate proposed by the present invention.

11D: Anode lead (anode, lead)

12D: Cathode lead (cathode, lead)

21:Electrically insulating substrate body

22A: External surface (external conductive pad, copper pad, conductive pad, anode conductive pad)

22C: External surface (external conductive pad, copper pad, conductive pad, cathode conductive pad)

28A, 28C:Through hole

52:Viscose

60:Insulating materials

40A: External terminal (anode terminal)

40C: External terminal (cathode terminal)

11DA, 12DA: tip surface

13: Cylindrical capacitor core body

Claims (10)

A packaging structure of a wound solid electrolytic capacitor, which includes: Two protective substrates include a lower substrate and an upper substrate. The substrate has an anode conductive pad and a cathode conductive pad at a predetermined position on its surface. The two conductive pads are not conductive to each other. The protective substrate also includes a through multiple through holes of the conductive pad; A wound solid electrolytic capacitor core, the winding axis of which is perpendicular to the protective substrate, is arranged between the upper and lower substrates, the capacitor core includes an anode lead and a cathode lead, the anode lead Passing through the through hole on the anode conductive pad, and the cathode lead passing through the through hole on the cathode conductive pad; An insulating material fills the space between the substrates and surrounds the capacitor core, so that the protective substrate, the capacitor core, and the insulating material form an integrated solid; An anode external terminal plated on the anode conductive pad and a cathode external terminal plated on the cathode conductive pad, the anode external terminal is electrically connected to the anode lead, and the cathode external terminal is electrically An electrical conduction is connected to the cathode lead. The packaging structure of claim 1, wherein the external terminal is copper plated, the anode lead and the cathode lead are aluminum leads, and the leads are electrically connected to the corresponding ones through an internal nickel layer. the external terminals. The packaging structure of claim 1, wherein the anode lead and the cathode lead are standard leads with copper-clad end sections, the through holes are copper-plated through holes, and the copper-clad end sections of the leads It is electrically connected to the corresponding conductive pad through a solder, and the external terminal is copper plated on the conductive pad and the solder. The packaging structure of claim 3, wherein the anode lead and the cathode lead are bent to reduce the distance between the capacitor core and the protective substrate. The packaging structure of claim 1, wherein the protective substrate is a fully conductive substrate including a thin copper sheet, and the conductive pad is a portion of the thin copper sheet separated into mutually non-conductive parts by selective etching. The package structure of claim 1 further includes at least one accompanying component located in the same package. The package structure of claim 1, wherein the accompanying component is another capacitor for voltage stabilizing applications. A mass production method for the packaging structure of wound solid electrolytic capacitors, which includes: (a) Provide a first substrate as the upper substrate, the surface of which includes a plurality of conductive pads and a plurality of through holes at predetermined positions; (b) Arrange a plurality of wound solid electrolytic capacitor cores on the lower surface of the upper substrate, and the electrode leads of the capacitor cores pass through the through holes; (c) Provide a second substrate as the lower substrate, clamp the plurality of capacitor cores between the lower substrate and the upper substrate, and fill a liquid insulating material between the two substrates space, and then harden the insulating material so that the upper substrate, the lower substrate, and the plurality of capacitor cores are combined into an integrated component; (d) Plating copper on the plurality of conductive pads to form a plurality of external terminals, and electrically connecting the plurality of external terminals to the electrode leads of the plurality of capacitor cores. According to the method described in claim 8, the electrical conduction connecting the plurality of external terminals and the electrode lead uses an aluminum wire as the electrode lead, and a zinc replacement process is used to first plate a tip of the aluminum wire. The nickel layer is then copper plated to become the external terminals. As claimed in claim 8, the method of electrically connecting the plurality of external terminals and the electrode lead includes: Plating copper on the plurality of through-holes to form a plurality of copper-plated through-holes; A lead with a copper-clad end section is used as the electrode lead; The copper-clad end section of the electrode lead is soldered to the conductive pad and the copper-plated through hole.