CN116437567A - Printed circuit board - Google Patents

Abstract

The invention discloses a printed circuit board which comprises a substrate, a bonding pad and a first copper layer, wherein the bonding pad is arranged on the upper surface of the substrate, the first copper layer is arranged on the upper surface of the substrate and surrounds the bonding pad, a space is arranged between the bonding pad and the first copper layer to form a solder resist groove between the bonding pad and the first copper layer, the upper surface of the first copper layer is provided with a first ink layer, the upper surface of the first ink layer is higher than the upper surface of the bonding pad, one side of the upper surface of the solder resist groove adjacent to the first copper layer is provided with a second ink layer, and the first ink layer is connected with the second ink layer. The printed circuit board can realize the purpose of preventing the bonding pad from being connected with tin by arranging the second ink layer with a certain width in the solder resist groove, and the solder resist groove has the advantages of wider width, low processing difficulty, low cost and good tin connection preventing effect.

Description

Printed circuit board

Technical Field

The invention relates to the technical field of printed circuit boards, in particular to a printed circuit board.

Background

A printed circuit board (Printed Circuit Board, abbreviated as PCB), also called a printed circuit board, is an important electronic component, is a support for electronic components, and is a carrier for electrical connection of the electronic components. When the components are welded, two or more welding spots are connected together by solder, so that the functions and the appearance of the product are poor.

Along with the speed of updating modern electronic products, the design thought of a designer of a printed circuit board is more preferred to the modularized design, wherein the appearance of a multifunctional large-size module (the size of the module is larger than 50mm multiplied by 50 mm) is not lack, the SMT (surface mount technology, the abbreviation of Surface Mounting Technology) welding technology of the module is a technical difficulty in the current industry, due to the improvement of the integration level of the module, the size of the module is larger, bubbles are difficult to be discharged in the SMT welding process, the weight of the module is unprecedented, the supporting capacity of solder paste on the module in the SMT welding process is limited, and the solder paste on a PCB pad is extremely easy to be flattened by the module and overflowed to an area outside the pad to lead to tin connection.

Disclosure of Invention

The present invention aims to solve at least one of the technical problems in the related art to some extent.

Therefore, the embodiment of the invention provides a printed circuit board with low processing difficulty and good tin connection prevention effect.

The printed circuit board comprises a substrate, a bonding pad and a first copper-plated layer, wherein the bonding pad is arranged on the upper surface of the substrate, the first copper-plated layer is arranged on the upper surface of the substrate and surrounds the bonding pad, a space is formed between the bonding pad and the first copper-plated layer to form a solder resist groove therebetween, the upper surface of the first copper-plated layer is provided with a first ink layer, the upper surface of the first ink layer is higher than the upper surface of the bonding pad, one side, adjacent to the first copper-plated layer, of the upper surface of the solder resist groove is provided with a second ink layer, and the first ink layer is connected with the second ink layer.

According to the printed circuit board provided by the embodiment of the invention, the solder resist groove is arranged and the second ink layer with a certain width is arranged in the solder resist groove, so that the space for storing tin overflow is increased, and tin in the solder resist groove can form a good wetting angle, thereby achieving the purpose of preventing solder connection of a solder pad, and the solder resist groove is wider in width, low in processing difficulty and low in cost.

In some embodiments, the second ink layer includes a transition portion and a horizontal portion, one end of the transition portion is connected to the first ink layer, the other end of the transition portion is connected to the horizontal portion, a thickness of the transition portion gradually decreases in a direction from the first ink layer to the horizontal portion, and a thickness of the horizontal portion remains unchanged in a horizontal direction.

In some embodiments, the plurality of solder pads are provided, and the solder resist grooves on the peripheral sides of the plurality of solder pads are not communicated with each other.

In some embodiments, the second ink layer has a space between the second ink layer and the peripheral wall of the pad.

In some embodiments, the solder mask slot has a width of 0.3 to 0.4mm and the second ink layer has a width of 0.2 to 0.3mm.

In some embodiments, the solder resist groove surrounds the bond pad for one revolution.

In some embodiments, the solder resist groove surrounds a portion of the outer perimeter of the solder pad.

In some embodiments, the thickness of both the first ink layer and the second ink layer is greater than 0.4mil.

In some embodiments, the bonding pad includes a second copper-clad layer and a plating layer disposed on an upper surface of the second copper-clad layer.

In some embodiments, the pads are circular pads, square pads, or rectangular pads.

Drawings

Fig. 1 is a schematic diagram of a printed circuit board according to an embodiment of the present invention.

Fig. 2 is a schematic diagram of a printed circuit board according to an embodiment of the present invention after being connected to a module.

Fig. 3 is a top view of a printed circuit board according to an embodiment of the present invention.

Fig. 4 is a top view of a printed circuit board according to another embodiment of the present invention.

Reference numerals:

1. a substrate; 11. a solder resist groove; 2. a bonding pad; 21. a second copper layer is paved; 22. plating; 3. a first copper layer is paved; 4. a first ink layer; 5. a second ink layer; 51. a transition section; 52. a horizontal portion; 61. a first tin portion; 62. a second tin portion; 63. a third tin portion; 7. and (5) a module.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.

A printed circuit board according to an embodiment of the present invention is described below with reference to the accompanying drawings.

As shown in fig. 1 to 4, the printed circuit board according to the embodiment of the present invention includes a substrate 1, a bonding pad 2 and a first copper layer 3, wherein the substrate 1 may be made of any common PCB substrate, such as fiberglass, ceramic, aluminum, copper, etc., the bonding pad 2 and the first copper layer 3 are disposed on the upper surface of the substrate 1, the first copper layer 3 is formed by laying copper foil on the substrate 1, the bonding pad 2 may be connected to a module 7 by tin, and a plurality of bonding pads 2 are typically disposed on a printed circuit board.

Specifically, the first copper layer 3 is disposed on the upper surface of the substrate 1 and surrounds the bonding pad 2, and a space is provided between the bonding pad 2 and the first copper layer 3 to form a solder resist groove 11 therebetween, the bottom of the solder resist groove 11 is a bare substrate 1, and the solder resist groove 11 is generally annular and surrounds the periphery of the bonding pad 2. The upper surface of the first copper layer 3 is provided with a first ink layer 4, one side of the upper surface of the solder mask groove 11 adjacent to the first copper layer 3 is provided with a second ink layer 5, the first ink layer 4 is formed by ink coated on the first copper layer 3, the second ink layer 5 is formed by ink coated on the substrate 1, the upper surface of the first ink layer 4 is higher than the upper surface of the bonding pad 2, and the materials of the first ink layer 4 and the second ink layer 5 are solder mask ink, such as green oil. The first ink layer 4 and the second ink layer 5 are connected, and the first ink layer 4 and the second ink layer 5 may be simultaneously coated and formed, so that the ink layers on different structures are separated into the first ink layer 4 and the second ink layer 5 for convenience. It should be noted that, the present application describes a single-sided PCB board as an example, and the structure may be applied to a double-sided PCB board.

It will be appreciated that the shape of the second ink layer 5 is annular, the width of the second ink layer 5 means its annular width, and the second ink layer 5 is located on the side of the first copper layer 3, and there is a space between the second ink layer 5 and the pad 2, and there is no direct contact between the two. The width of the second ink layer 5 is 0.2-0.3 mm, for example 0.2mm, 0.23mm, 0.25mm and 0.3mm, and in this range, the solder resist groove 11 can store overflowed liquid tin, so that the overflow of the liquid tin onto the first ink layer 4 and even the overflow of the liquid tin onto other peripheral bonding pads 2 can be effectively prevented, and tin connection is caused. The solder resist groove 11 of the printed circuit board has the advantages of wide width, low processing difficulty, low cost and good tin connection prevention effect.

As shown in fig. 2, after the module 7 is soldered to the PCB board by the solder paste, the tin includes tin located between the module 7 and the pad 2 and tin located in the solder resist tank 11, and the tin located in the solder resist tank 11 includes tin located above the second ink layer 5 and tin located above the substrate, and the tin located between the module 7 and the pad 2 is defined as a first tin portion 61, the tin located above the bare substrate 1 is defined as a second tin portion 62, and the tin located above the second ink layer 5 is defined as a third tin portion 63.

Wherein, first tin portion 61 is the main carrier of joint strength, when first tin portion 61 is extruded by the weight of module 7, spill over to in the solder mask groove 11, a part tin spills over to base plate 1 top and forms second tin portion 62 with here regional profile modeling, another part tin continues to spill over to second printing ink layer 5 top, and form third tin portion 63 with here regional profile modeling, second tin portion 62 links to each other with third tin portion 63 and forms better wetting angle, from this, can avoid the unlimited spreading of tin to form the wetting angle that is close 180, and then cause stress concentration, lead to the problem of solder joint fracture.

The following describes the defects in the related art and the design concept of the printed circuit according to the embodiment of the present invention.

In the related art, the most common solution to the problem of tin connection is to provide a solder mask window (corresponding to the solder mask groove 11 in the application) of 0.07mm on the PCB board, but this approach is difficult to solve the problem of tin connection of large-sized modules. Therefore, to the large-size module even tin problem, the practitioner has proposed to increase the solder mask ring on the copper laying area (corresponding to the first copper laying layer 3 in this application) outside the solder mask windowing and to circle the bonding pad 2, and the mode of digging the recess on the PCB substrate (corresponding to the substrate 1 in this application) below the solder mask ring position stops solder paste to melt and overflow to other positions or other bonding pads 2, and this scheme can solve even tin problem, but the processing degree of difficulty is big and the cost is higher, and the solder paste printing degree of difficulty also improves thereupon, influences production speed and production quality.

Through the understanding to industry PCB conventional design, the welding jumbo size module all has even tin risk, even tin roughly falls into three kinds of situations: the first type is that a bonding pad and a copper layer coated with printing ink are connected into a whole, no solder mask window is arranged between the bonding pad and a copper layer region, the design is designed as an SMD (surface mounted device), after tin on the bonding pad is extruded, the tin directly diffuses into the copper layer region, and when the overflow tin quantity is enough, the tin is connected with the peripheral bonding pad; the second type is that only a very narrow solder mask window is arranged between the bonding pad and the copper laying area, the design is NSMD, after tin on the bonding pad is extruded, the narrow solder mask window cannot contain too much tin, the tin can continuously spread to the copper laying area beyond the solder mask window, and when the spreading distance is long enough, the tin can be connected with the adjacent bonding pad; the third type is that the periphery of the bonding pad is not covered with copper area, and the printing ink directly covers the PCB substrate, in such a case, the height of the printing ink is lower than that of the bonding pad, and the tin on the bonding pad is extruded, is easy to flow obliquely downwards and extends, and can be connected with the periphery bonding pad when the tin extends to a certain length.

Through the analysis, when the SMT is welded, the solder paste is molten and is in a liquid state after passing through the furnace, and the solder paste is solidified to have a certain shrinkage force so as to enable the solder paste to be pulled back to the bonding pad, but even if the solder paste is pulled back to the bonding pad after solidification, when the size of the module is too large and the weight is also large, the shrinkage force of the solder cannot resist the gravity of the module, and then the solder cannot be pulled back to the bonding pad completely, so that enough space is needed to store overflowed solder. Of course, people also put forward that the amount of solder paste is small, no extra tin is extruded out of the solder pad, and it is necessary to remind that the module and the PCB are plane-to-plane, the larger the size of the module is, the more difficult the parallel relation is to control, the reaction is that the gap between the solder pad of the module and the solder pad of the PCB is small in the welding process, the amount of solder paste is too small, the solder pad of the module and the solder pad of the PCB are difficult to be connected by tin, and the problem of false welding (or false welding) occurs when the solder pad of the module is not contacted with the solder paste, so that the amount of tin cannot be infinitely reduced. So the space between the bonding pad of the module and the bonding pad of the PCB is smaller or the module is heavier, the solder paste of the bonding pad can be extruded, the overflowed tin must be stored in space and needs to be connected with the tin on the bonding pad into a whole, so that the problem of tin beads cannot occur (the risk of the tin beads is higher, the tin beads are unfixed on the surface of the board, the tin beads are uncertain in what position, and when the product is used, the tin beads move to the periphery of a closely-spaced pin chip and are clamped between pins, so that the product is short-circuited). Therefore, the design of the storage space of overflowed tin is the key point of the application, and the space design is low in cost, simple and easy to operate, and the production quality can be ensured.

The solder resist groove 11 in the printed circuit board of the embodiment of the invention is a space for storing overflowed tin, when tin flows into the solder resist groove 11, the tin can be subjected to two forces in the tin solidification process, one force is a traction force applied in the tin solidification process, the other force is a shielding thrust force caused by the fact that the height of the first ink layer 4 is higher than that of the bonding pad 2, and the directions of the traction force and the shielding thrust force are both towards the bonding pad 2, so that the tin is brought back to the bonding pad 2 or is left in the solder resist groove 11, so that the tin cannot easily overflow above the first ink layer 4 and cannot be connected with the peripheral bonding pads 2, and the problem of tin connection in large-module SMT soldering is solved. In addition, as long as the width dimension of the second ink layer 5 is properly controlled, the application is also applicable to SMT soldering technology of package products such as LGA modules and QFN with any dimension.

It should be noted that the width of the second ink layer 5 may not be too small or too large, and if the width is too small, there is not enough space to store tin; if the width is too large, the tin is spread out, a certain welding wetting angle cannot be formed, the welding strength is reduced, and the inventor finds that when the width of the second printing ink layer 5 is controlled within the range of 0.2-0.3 mm, the space requirement for storing tin can be met, and a better wetting angle can be formed, so that the use effect is good.

As shown in fig. 1, in some embodiments, the second ink layer 5 includes a transition portion 51 and a horizontal portion 52, the upper surface of the pad 2 is higher than the upper surface of the horizontal portion 52, one end of the transition portion 51 is connected to the first ink layer 4, and the other end of the transition portion 51 is connected to the horizontal portion 52, so that the first ink layer 4 and the second ink layer 5 are connected into a whole, and thus the problem of copper exposure of the PCB board can be avoided, which results in short circuit and corrosion of the PCB board.

The thickness of the transition portion 51 gradually decreases in the direction of the first ink layer 4 toward the horizontal portion 52, in other words, the thickness of the transition portion 51 gradually decreases from the outside to the inside in the radial direction of the pad 2 until the thickness coincides with the thickness of the horizontal portion 52, and the thickness of the horizontal portion 52 remains unchanged in the horizontal direction. It should be noted that, in fig. 1, the corners at the connection of the first ink layer 4 and the second ink layer 5 and the connection of the horizontal portion 52 and the transition portion 51 are all in a zigzag shape, which is for convenience of drawing, and each corner may be smoothly transited during actual production.

As shown in fig. 3 and 4, in some embodiments, the solder resist groove 11 surrounds the pad 2 for one revolution, or the solder resist groove 11 surrounds a portion of the outer circumference of the pad 2. During the preparation of the printed circuit board, the solder resist groove 11 may be placed around the solder pad 2 for one week if the module 7 has no signal connection, the solder resist groove 11 may need to be broken, around a part of the outer circumference of the solder pad 2 if the module 7 has a signal connection,

in some embodiments, the number of the solder resist grooves 11 on the peripheral sides of the plurality of solder resist grooves 2 is plural, so that the solder of two or more solder resist grooves 2 is prevented from flowing along the solder resist grooves 11, resulting in occurrence of a solder connection.

In some embodiments, a space is formed between the second ink layer 5 and the peripheral wall of the bonding pad 2, in other words, a region uncovered by ink is formed between the second ink layer 5 and the bonding pad 2, and the substrate 1 at the region is exposed, so that the tin storage space of the solder mask groove 11 can be increased, more tin can be contained in the tin storage space, a certain processing allowance can be provided when the second ink layer 5 is paved, the second ink layer 5 is prevented from contacting the upper surface of the bonding pad 2, the welding spot is prevented from cracking when the solder paste is printed, and the processing difficulty and the production cost of the printed circuit board are reduced.

In some embodiments, the width of the solder resist groove 11 is 0.3 to 0.4mm, for example, 0.3mm, 0.33mm, 0.35mm, 0.4mm, etc., and since the width of the second ink layer 5 is 0.2 to 0.3mm, the width of the substrate 1 not covered by the second ink layer 5 is 0 to 0.1mm, and this width should be greater than 0, the substrate 1 not covered by the second ink layer 5 is annular, this width is annular.

Since the substrate 1 is directly exposed, the smaller the width of the substrate 1 not covered by the second ink layer 5 is, the better, and thus, is set to 0 to 0.1mm for the protection of the substrate 1.

In some embodiments, the thickness of the first ink layer 4 and the second ink layer 5 is greater than 0.4mil (about 10 um), thereby ensuring that the first ink layer 4 and the second ink layer 5 are both thick enough to achieve good solder resist.

In some embodiments, the pad 2 includes a second copper-clad layer 21 and a plating layer 22 disposed on an upper surface of the second copper-clad layer 21. The second copper-clad layer 21 is formed by copper foil being clad on the substrate 1, and the thickness of the second copper-clad layer 21 may be equal to that of the first copper-clad layer 3, but it should be ensured that the total thickness of the second copper-clad layer 21 and the plating layer 22 is smaller than that of the first copper-clad layer 3 and the first ink layer 4.

Further, the plating layer 22 is a metal plating layer 22 or an oxide film plating layer 22, such as a gold plating layer 22, a silver plating layer 22, a tin plating layer 22, or the like.

In some embodiments, the pads 2 are circular pads 2, square pads 2 or rectangular pads 2, the circular pads 2 refer to the projection shape of the pads 2 on the substrate 1 in the thickness direction of the substrate 1 being circular, the square pads 2 and the rectangular pads 2 are the same, the number of the pads 2 may be plural on the same substrate 1, and the shapes of the plural pads 2 may be the same or different, or may be partially the same or partially different.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.

In the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; may be mechanically connected, may be electrically connected or may be in communication with each other; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.

In the present invention, unless expressly stated or limited otherwise, a first feature "up" or "down" a second feature may be the first and second features in direct contact, or the first and second features in indirect contact via an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.

For purposes of this disclosure, the terms "one embodiment," "some embodiments," "example," "a particular example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.

While the above embodiments have been shown and described, it should be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives, and variations of the above embodiments may be made by those of ordinary skill in the art without departing from the scope of the invention.

Claims (10)

1. A printed circuit board, comprising:

a substrate (1);

a bonding pad (2), wherein the bonding pad (2) is arranged on the upper surface of the substrate (1);

the first copper layer (3) of spreading, first copper layer (3) of spreading sets up the upper surface of base plate (1) just encircles pad (2) set up, just pad (2) with have the interval between the first copper layer (3) of spreading in order to form solder mask groove (11) between the two, the upper surface of first copper layer (3) of spreading is provided with first printing ink layer (4), the upper surface of first printing ink layer (4) is higher than the upper surface of pad (2), the upper surface of solder mask groove (11) is adjacent one side of first copper layer (3) of spreading is provided with second printing ink layer (5), first printing ink layer (4) with second printing ink layer (5) link to each other.

2. The printed circuit board according to claim 1, characterized in that the second ink layer (5) comprises a transition portion (51) and a horizontal portion (52), one end of the transition portion (51) is connected to the first ink layer (4), the other end of the transition portion (51) is connected to the horizontal portion (52), the thickness of the transition portion (51) gradually decreases in the direction of the first ink layer (4) toward the horizontal portion (52), and the thickness of the horizontal portion (52) remains unchanged in the horizontal direction.

3. The printed circuit board according to claim 1, wherein the number of the pads (2) is plural, and the solder resist grooves (11) on the peripheral sides of the plurality of pads (2) are not communicated with each other.

4. Printed circuit board according to claim 1, characterized in that the second ink layer (5) is spaced from the peripheral wall of the solder pad (2).

5. The printed circuit board according to claim 4, characterized in that the solder resist groove (11) has a width of 0.3-0.4 mm and the second ink layer (5) has a width of 0.2-0.3 mm.

6. The printed circuit board according to claim 1, characterized in that the solder resist groove (11) surrounds the solder pad (2) for one week.

7. The printed circuit board according to claim 1, characterized in that the solder resist groove (11) surrounds a portion of the outer periphery of the solder pad (2).

8. The printed circuit board of claim 7, wherein the thickness of both the first ink layer (4) and the second ink layer (5) is greater than 0.4mil.

9. The printed circuit board according to claim 1, characterized in that the bonding pad (2) comprises a second copper-clad layer (21) and a plating layer (22) provided on an upper surface of the second copper-clad layer (21).

10. The printed circuit board according to any of claims 1-9, characterized in that the pads (2) are circular pads, square pads or rectangular pads.

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