Printed circuit board design

Abstract

The invention relates to a printed circuit board (10) or conductor film for attaching THT components, comprising an upper face (20), also referred to as the populating face; a lower face (30), also referred to as the soldering face; at least one via (40) for attaching wired components; a metallized sleeve (50) in the at least one via (40); conductor tracks (70); and pad regions (60) on the upper face (80), the pad regions being provided in the region of the vias (40). The invention is characterized in that the pad regions (60) are divided into two or more sub-regions.

Description

[0001] 202301534

[0002] 1

[0003] Description

[0004] Printed circuit board design

[0005] The present invention relates to a printed circuit board or circuit foil for mounting through-hole components, comprising a top side (component side) and a bottom side (solder side), at least one via for mounting wired components, a metallized sleeve in the at least one via, conductive traces, and pad areas on the top side, which are arranged in the area of ​​the vias. The invention further relates to a method for testing the solder penetration of such a printed circuit board.

[0006] The technical solutions for creating solder joints of through-hole components on a printed circuit board are diverse. They include reflow soldering processes (e.g., pin-in-paste) or vapor phase soldering, as well as automated soldering with a soldering iron, laser soldering, wave soldering or mini-wave soldering, and dip soldering.

[0007] On a printed circuit board (PCB) with copper cladding on both sides, the hole for mounting through-hole components contains a metallized sleeve. The same applies if the PCB has more than two copper layers. When a through-hole component is soldered to the solder side of this board, the copper ring on the solder side is wetted by the molten solder. Furthermore, the molten solder fills the metallized sleeve of the PCB. The fill level of the sleeve with solder is called the solder penetration. Solder penetration is a measure of the fill level of a through-hole component when soldering a through-hole component into a two- or multi-layer PCB. It is a crucial criterion for the quality of a solder joint.

[0008] Soldering methods for through-hole components most commonly include wave soldering, selective soldering, dip soldering, hand soldering, and robotic soldering with a soldering iron. The IPC A 610 Class 3 requirement for through-hole technology (THT) solder joints specifies >75% penetration through the printed circuit board in the vertical direction.

[0009] Some OEMs require a full THT hole penetration of 100% of the total PCB thickness, which is even higher quality than IPC A Class 3.

[0010] To ensure this, a complex process control system is necessary, including partial X-ray inspection of the soldered through-hole components. 202301534

[0011] 2

[0012] In automated X-ray inspection of electronic assemblies or components, the test object is illuminated by a usually cone-shaped X-ray beam inside a radiation-tight housing. The magnified X-ray image is then captured on a detector located below.

[0013] X-ray inspection systems can be used as part of production lines (inline) or as a separately installed inspection station (offline). The main task of an X-ray system is the detection of soldering defects in partially or fully concealed, as well as visible, solder joints.

[0014] However, the non-destructive evaluation of a complete solder penetration by optical or X-ray inspection in the case of concealed, overlapping, shadowed components, inaccessible or non- / hardly radiolucent plated-through-hole (PTH) solder joints is technically complex and complicated or severely impaired by design due to overlapping or partially / completely concealed test zones in known printed circuit boards.

[0015] It is therefore an object of the present invention to provide a printed circuit board or conductive film for mounting through-hole technology (THT) components, in which the solder penetration can be reliably verified by means of simple process controls. Furthermore, it is an object of the present invention to provide a testing method for such printed circuit boards or conductive films.

[0016] This problem can be solved by a printed circuit board or conductive film according to independent claim 1 and the method according to independent claims 10 and 11. Preferred embodiments are described in the dependent claims.

[0017] PCB pads, also known as solder pads, are areas on a printed circuit board (PCB) specifically designed for mounting electronic components. These pads are typically circular or rectangular and made of copper or another conductive material. PCB pads serve as connection points between the electronic components and the traces on the PCB. They provide a surface onto which the components' leads or connections are soldered or mounted. The pads are usually located at the ends of the traces where components are to be placed. The design and placement of the pads can directly affect the solderability, reliability, and thermal conductivity of components.

[0018] 3

[0019] A special printed circuit board or substrate design (ceramic) on the component side (here referred to as the top side) enables electrical verification of complete solder penetration of hidden, shaded components, inaccessible, or non-transmissible PTH solder joints. This is achieved by using a specific pad design on the printed circuit board. According to a first aspect of the invention, the pad design is divided into two or more pad sub-areas. The at least two sub-areas are not electrically connected in their initial state and therefore represent an electrical isolation or a very high resistance. When an applied solder connects these separate sub-areas during the soldering process, a typical standardized electrical test (e.g.,

[0020] Resistance measurement is possible, and a very low resistance is achieved (electrically conductive continuity test). Therefore, 100% solder penetration is always present and verifiable when the resulting contact resistance is very low.

[0021] According to one embodiment, a test point is arranged on one or each of the sub-areas of the respective pad area. This ensures good accessibility for the contacting test probes of the testing device.

[0022] According to one embodiment, the sub-areas of the respective pad area are in close proximity. The solder applied during the soldering process can wet these closely adjacent pad areas and thus also electrically connect them.

[0023] According to one embodiment, the sub-areas comprise an inner PTH sub-area and an outer sub-area, wherein the outer sub-area completely or partially encloses the inner sub-area. This represents a design variant.

[0024] According to one embodiment, the inner PTH section is electrically connected to the metallized sleeve. When solder penetrates the inner PTH section, the electrical connection is established via the solder to the outer section, which were electrically isolated before the soldering process.

[0025] According to one embodiment, the inner PTH sub-area is annular in shape, and the outer sub-area surrounds the inner PTH sub-area in a circular shape and is designed as an open annulus. 202301534

[0026] 4

[0027] According to one embodiment, the PTH sub-areas consist of nearly identical partial circular rings.

[0028] According to one embodiment, the PTH sub-areas consist of a circular ring that is subdivided along a tangent to the inner circumference of the circular ring.

[0029] According to one embodiment, the PTH sub-areas consist of meandering shapes arranged close to one another. These are just a few examples of pad design and placement. Other arrangements are also conceivable, depending on the requirements of the specific printed circuit board.

[0030] According to a further aspect of the invention, a method for testing the solder penetration of a printed circuit board is described, comprising the application of a leaded component to the top side of the circuit board. It further comprises soldering the component to the underside of the circuit board, applying a voltage to the test points of the pad area of ​​the respective via, and finally testing the applied voltage.

[0031] According to a further aspect, the invention comprises a method for testing the solder penetration of a printed circuit board, which includes applying a wired component to the top side of the printed circuit board. It further comprises soldering the component to the underside of the printed circuit board, applying a voltage to a test point of the pad area of ​​the respective via and to the soldered through-hole component, and subsequently testing the applied voltage.

[0032] This method allows for reliable inspection of solder penetration and thus the quality of solder joints in complex or massive assemblies. Furthermore, it also improves the inspection of B2B (board-to-board) connections, where two adjacent, stacked, or nested printed circuit boards are joined, as well as multi-layered printed circuit board stacks, where boards are connected layer by layer. 202301534

[0033] 5

[0034] Complex inspection methods, such as X-ray inspection, are no longer necessary. Furthermore, these types of circuit boards and testing procedures provide a clear criterion for the solder penetration of PTH solder joints. In addition, solid metal THT components can be mounted, and design options for improved product testability become available. Even B2B connections of circuit boards with multiple layers (hidden solder joints) can still be inspected for complete solder penetration.

[0035] Further embodiments of the present invention will become apparent from the detailed description provided below. It is understood that the detailed description and examples, although they represent the preferred embodiment of the invention, are intended solely for illustrative purposes and are not meant to limit the scope of protection of the invention.

[0036] Embodiments of the invention are described below by way of example with reference to schematic drawings, which show:

[0037] Fig. 1 is a schematic, perspective view of a printed circuit board;

[0038] Fig. 2 shows a first schematic embodiment of a pad arrangement;

[0039] Fig. 3 shows a second schematic embodiment of a pad arrangement;

[0040] Fig. 4 shows a third schematic embodiment of a pad arrangement, and

[0041] Fig. 5 a, b and c show further schematic embodiments of pad arrangements.

[0042] Figure 1 shows a sectional perspective view of a printed circuit board 10 according to the invention for mounting through-hole components. The printed circuit board 10 has a top surface 20, also referred to as the component side, and a bottom surface 30, also referred to as the solder side, as well as vias 40 for mounting through-hole components. A metallized sleeve 50 is arranged in each via 40, extending from the top surface 20 to the bottom surface 30 of the printed circuit board 10. Furthermore, pad areas 60 are provided on the top surface 20 of the printed circuit board 10 in the area of ​​the via 40, which are only indicated by their position in Figure 1 and are described in the following figures in the corresponding embodiments.

[0043] 6 will be. Furthermore, 10 conductor tracks 70 are arranged on the top side 20 of the circuit board.

[0044] To attach wired components, they are first placed at the designated locations on the printed circuit board 10, the component leads are inserted into the via 40, and then soldered from the underside 30 (solder side) of the printed circuit board 10. The solder then flows from the underside 30 of the printed circuit board 10 through the via 40 towards the top side 20 of the printed circuit board 10, a process known as solder penetration. Ideally, the solder flows completely through the via 40 and over the top side 20 of the printed circuit board 10.

[0045] Figure 2 schematically illustrates a first arrangement of pad areas 60A according to the invention. The arrangement has an inner PTH sub-area 80A, which is designed as a closed circular ring. At its central inner circumference, the inner PTH sub-area 80A is electrically connected to the metallized sleeve 50A. A pin 50A of an inserted component is indicated inside the sleeve 50A.

[0046] An outer PTH section 100A, designed as an open circular ring, is arranged around the inner PTH section 80A. The two PTH sections 80A and 100A are spaced apart from each other in such a way that there is no electrical connection between them. Test points 110A are provided on both the inner PTH section 80A and the outer PTH section 100A, at which, for example, a resistance measurement can be carried out in a known manner.

[0047] Another arrangement of pad areas 60B according to the invention is shown in Figure 3. This arrangement consists of two PTH sub-areas 120B, 130B, each comprising two graduated circular rings spaced apart from one another such that there is no electrical connection between them. One of the PTH graduated circular rings 130B is electrically connected to the metallized sleeve (50B) at its inner circumference. A test point 110B is provided on each of the PTH graduated circular rings 120B, 130B. A pin 90B of the component is arranged centrally in a metallized sleeve 50B. In general, the openings between the two PTH graduated circular rings 120B, 130B can be arranged at different positions. In Figure 2, the distances are located at 12 and 6 o'clock. However, any other variant is also conceivable, e.g., 10 o'clock and 4 o'clock or the like. 202301534

[0048] 7

[0049] Referring to Figure 4, a pad area 60D can be seen, consisting of two PTH sub-areas 120D and 130D. These PTH sub-areas 120D and 130D are formed by an annulus subdivided along a tangent to the inner circumference of the annulus. The two PTH sub-areas 120D and 130D are also separated along this tangent, so that no electrical connection exists. At its central inner circumference, the PTH sub-area 130D is electrically connected to a metallized sleeve 50D. Test points 110D are provided on both PTH sub-areas 120D and 130D.

[0050] Figures 5 a, b, c show further pad areas 60E, 60F, 60G, each with two PTH sub-areas 120E, 130E; 120F, 130F; 120G, 130G, which are arranged close to each other, so that there is no electrical connection between the respective PTH sub-areas 120E, 130E; 120F, 130F; 120G, 130G.

[0051] Figure 5a shows a meandering arrangement consisting of an outer circular PTH section 120E and an inner PTH section 130E enclosed by it. The two PTH sections 120E and 130E have extensions 140E with which they interlock in a meandering pattern without establishing an electrical connection. The radially inner PTH section 130E is electrically connected to the metallized sleeve 50E. A test point 110E is provided on the outer PTH section 120E. In this embodiment, the resistance measurement is performed between the test point 110E and the component inserted via pin 90E.

[0052] Figures 5b and 5c show further meandering arrangements of the PTH sub-areas 120F, 130F; 120G, 130G according to the invention. These each comprise an inner PTH sub-area 120F, 120G, which is in electrical contact with a metallized sleeve 50F, 50G, and each comprises an outer PTH sub-area 130F, 130G, which surrounds the respective inner PTH sub-area 120F, 120G without being electrically connected to it. Extensions 140F, 150F; 140G, 150G project from the outer sub-area to the inner sub-area 130F, 130G and vice versa. Test points 110F, 110G can be provided in various ways, e.g., B. as in Figure 5c, one at the outer pad area 130G and the component to be inserted later, which is indicated by pin 90G. 202301534

[0053] 8

[0054] Other pad arrangements are also conceivable. In any case, for electrical testing and checking the solder joint for complete continuity, it is possible to contact only a portion of the test contour with a test point and to select the soldered component itself as the second contact point. Thus, the metal pin in the through-hole connection would be the first contact, and a test point or the contour (e.g., outer ring) from the top / component side would be the second contact.

Claims

202301534 9 Patent claims 1. Printed circuit board (10) or conductive film for mounting THT components comprising a top side (20) and a bottom side (30), at least one via for mounting wired components, a metallized sleeve (50A) in the at least one via (40), conductor tracks (70), Pad areas (60) on the top surface (20), which are arranged in the area of ​​the vias (40), characterized in that the pad areas (60) are divided into two or more sub-areas (80A, 100A).

2. Printed circuit board (10) or conductive foil according to claim 1, characterized in that a test point (110A) is arranged on one or each of the sub-areas (80A, 100A) of the respective pad area (60A).

3. Printed circuit board (10) or conductive foil according to one of claims 1 or 2, characterized in that the partial areas (80A, 100A) of the respective pad area (60A) are positionally close together.

4. Printed circuit board (10) or conductive foil according to one of claims 1 to 3, characterized in that the sub-areas (80A,100A) comprise an inner PTH sub-area (80A) and an outer sub-area (100A), wherein the outer sub-area (100A) partially or completely encloses the inner PTH sub-area (80A).

5. Printed circuit board (10) or conductive foil according to claim 4, characterized in that the inner PTH sub-area (80A) is in electrical connection with the metallized sleeve (50A).

6. Printed circuit board (10) or conductive foil according to one of claims 3 or 5, characterized in that the inner PTH sub-area (80A) is formed in an annular shape and the outer sub-area (100A9) surrounds the inner PTH sub-area (80A) in a circular shape and is formed as an open annular shape. 202301534 10 7. Printed circuit board (10) or conductive foil according to one of claims 1 to 3, characterized in that the sub-areas consist of nearly identical partial circular rings (120B,130B).

8. Printed circuit board (10) or conductive foil according to one of claims 1 to 3, characterized in that the sub-areas (120D,130D) consist of an annulus which is subdivided along a tangent to the inner circumference of the annulus.

9. Printed circuit board (10) or conductive foil according to one of claims 1 to 2, characterized in that the sub-areas (120E,130E;120F;130F;120G,130G) consist of a meander shape and are closely adjacent to each other.

10. Method for testing the solder penetration of a printed circuit board (10) or conductive foil according to one of claims 1 to 9, characterized by the steps: - Applying a wired component to the top side (20) of the printed circuit board, - Soldering the component on the underside (30) of the circuit board (10), applying a voltage to the test points (110A, 110B, 110D) of the pad area (60A, 60B, 60D) of the respective via (40), - Checking the applied voltage.

11. Method for testing the solder penetration of a printed circuit board (10) or conductive foil according to one of claims 1 to 9, characterized by the steps: - Applying a wired component to the top side (20) of the printed circuit board (10), - Soldering the component on the underside (30) of the printed circuit board (10), applying a voltage to a test point (110E, 110F, 110G) of the pad area (60E, 60F, 60G) of the respective via (40) and to the soldered THT component (90E, 90F, 90G), - Checking the applied voltage.

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