JP2010161205A - Substrate for bga mounting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent molten solder which overflows from a via from being connected to other lands and vias of non-equal potential. <P>SOLUTION: On one surface 2a of a substrate body 2, many lands 3 and vias 5 electrically connected to the lands 3 by potential equalizing conductor patterns 4 to be at the same potential are formed. At a one-surface 2a part of the via 5, a conductor pattern 6 for guidance is formed. The conductor pattern 6 for guidance is exposed on the one surface 2a of the substrate body 2 at the via 5, and formed such that a triangle is joined to a circle in plane view, and only one apex 6a of the triangle protrudes from the circle and faces a land 3 of the same potential with the via 5. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a BGA mounting substrate on which a BGA is mounted.

  Conventionally, a substrate on which a BGA (Ball Grid Array) is mounted has a land on one surface of the substrate body and a via that is electrically connected by the same potential conductor pattern to form the same potential. A plurality of sets of lands and vias are arranged in an aligned state. In this arrangement state, a land having the same potential as that of the via and a land having a different potential are arranged so as to surround the specific via. The via penetrates from one surface of the substrate body to the other surface on the opposite side.

  After mounting (mounting) the BGA on one side of this board, if the other side is flow soldered, the solder on the one side melts due to the heat of the flow solder and overflows from the via or land, or there is a through hole in the via From there, flow solder may climb to one side and overflow from the via. Even if flow soldering is performed on the other surface before mounting the BGA on the one surface, if the via has a through hole, the flow solder may also climb from the first surface to overflow from the via.

  Patent Document 1 describes a technique that serves as a reference for improving such a problem. This Patent Document 1 describes a technique for specifying the flowing direction of molten solder away from other lands by solder resist clearance.

JP-A-10-294554

  Therefore, in the BGA mounting substrate, it is necessary to prevent molten solder generated in the via from flowing to other vias and lands. However, in the BGA mounting substrate, the vias and lands are formed extremely densely. For this reason, the method of taking a distance as in Patent Document 1 cannot be adopted because it unnecessarily increases the size of the BGA.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a BGA mounting substrate capable of preventing molten solder overflowing from a via from being connected to other lands and vias having a non-equal potential. There is.

  In the invention of claim 1, the via is exposed on the one surface side portion of the substrate main body in the via, and a triangle is joined to the circle in a plan view, and only one vertex of the triangle protrudes from the circle. The guide conductor pattern is formed such that the apex faces the land having the same potential as the via.

  In the above configuration, when the molten solder overflows on the via, it is transmitted from the via onto the guiding conductor pattern. The melt (liquid) solder pressure is maximized at the apex portion of the guide conductor pattern. Therefore, it is the apex portion of the guide conductor pattern that first exceeds the limit of the surface tension. Since this apex portion faces the direction of the land of the same potential, the overflowing molten solder goes to the land of the same potential. As a result, the land where the molten solder ends up becomes a land of the same potential.

  In addition, the molten solder that has reached the land has a circular phenomenon that causes the molten solder to have a capillary phenomenon at the outer peripheral portion of the circular land (capillary phenomenon due to a slight step or gap between the land and the substrate surface). ) To expand around the outer periphery of the land. When the molten solder pressure is weakened at the time of overflow, it does not escape from the capillary action on the outer periphery of the land, and eventually remains at the same potential land. As a result, even if the molten solder overflowing from the via is connected to the land, it is connected to the land having the same potential, and can be prevented from being connected to other lands and vias having the same potential.

  According to a second aspect of the present invention, the center of the triangular portion of the guide conductor pattern has a land having the same potential as the via rather than the distance from the center of each non-equal potential land surrounding the via. It is characterized by being set so that the distance from the center is closer. According to the second aspect of the present invention, the molten solder overflowing from the via easily reaches the land having the same potential, and the molten solder is more reliably prevented from connecting to another land and via having the same potential. it can.

  According to a third aspect of the present invention, the apex of the acute angle portion projecting from the triangular circle of the guide conductor pattern is a land whose virtual line in the apex side direction extended from two sides constituting the apex has the same potential. It is characterized in that it is disposed on the substrate body so as to be in contact with the outer periphery of the substrate or overlap with the land plane.

  Since the molten solder overflowing from the apex of the triangle of the guide conductor pattern is pushed out by the force converging in the direction of the apex of the triangle, a force in the same direction is applied. As a result, the molten solder moves toward the apex direction. In this case, in the above configuration, the imaginary line extending in the apex direction extending from the two sides constituting the apex is arranged on the substrate body so that the outer periphery of the land having the same potential is in contact with or overlaps the land plane. Therefore, the directing direction of the apex is the land direction of the same potential, and therefore, it is easy to surely reach the land of the same potential, and the molten solder overflowing from the via is transferred to other lands and vias with non-equal potential. It can prevent more reliably connecting to.

  According to a fourth aspect of the present invention, there is provided an auxiliary guide having a shape projecting substantially in a V shape in a plan view on a part of the outer peripheral portion of the land and having the V-shaped apex facing the direction of the same potential via. It is characterized in that a conductive pattern is formed. The land with the same potential as that of the via approaches the apex of the triangular shape of the via conductor pattern for the via, so that the molten solder overflowing from the via is reliably connected to the land with the same potential. As a result, it is possible to more reliably prevent connection to other lands and vias having non-equal potentials.

The top view of the board | substrate for BGA mounting which shows 1st Example of this invention Sectional drawing which follows the arrow QQ line of FIG. (A) is a figure for demonstrating the reflow soldering process in the one surface of a board | substrate, (b) is a figure which shows after the reflow soldering process completion | finish. The partial top view of the board | substrate for BGA mounting which shows the 2nd Example of this invention FIG. 4 equivalent view showing a third embodiment of the present invention. FIG. 1 equivalent view showing a fourth embodiment of the present invention. FIG. 4 equivalent diagram showing a fifth embodiment of the present invention.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows the substrate 1 in plan view, and FIG. 2 shows a cross section of the substrate 1 along the arrow Q-Q line. On one surface 2a of the substrate body 2 of the substrate 1, a number of lands 3 and vias 5 that are electrically connected to the lands 3 by the same potential conductor pattern 4 and have the same potential are formed. The lands 3 and vias 5 having the same potential relationship in the equipotential conductor pattern 4 are set as a set, and a plurality of sets of lands 3 and vias 5 and equipotential conductor patterns 4 are arranged in an aligned state. The via 5 is made of a via conductor, and the via 5 is attached to the inner surface of a through hole 5a formed in the substrate body 2 so that the substrate body 2 penetrates from the one surface 2a to the other surface 2b side. Is provided.

In this case, with respect to a specific via 5 (a via 5 located outside the peripheral edge of the substrate body 2), a land 3 having the same potential as the via 5 and a land 3 having a different potential surround the specific via 5. It is an arranged form.
A guide conductor pattern 6 is formed on the surface 2 a of the via 5. The guide conductor pattern 6 is exposed on the one surface 2a of the substrate body 2 in the via 5, and has a shape in which a triangle is joined to a circle in a plan view and only one vertex of the triangle projects from the circle. Further, the apex 6a is formed so as to face the land 3 having the same potential as the via 5.

  Furthermore, in this case, the center 6g (see FIG. 1) of the triangular portion of the guide conductor pattern 6 in the via 5 is each non-equal potential land 3 surrounding the via 5 (the land not connected by the equipotential conductor pattern 4). ) Is set such that the distance Lh from the center 3p of the land 3 having the same potential as the via 5 is closer than the distances L1, L2, and L3 from each center 3p. Here, the “center 6g of the triangular portion” is a triangle formed by two sides that form one vertex of the triangle and a virtual line that connects the ends of the two sides that are in contact with the circle. The center of the part.

  The land 3 and the equipotential conductor pattern 4 are formed in advance by, for example, printing a conductor pattern on the one surface 2 a of the substrate body 2. Then, the land 3 is masked, the guide conductor pattern 6 formation region in the equipotential conductor pattern 4 is masked, the insulating layer 7 is applied to the one surface 2a, and the mask 3 is removed to remove the land 3 and The guide conductor pattern 6 is exposed on the upper surface of the substrate 1, and the equipotential conductor pattern 4 is covered with the insulating layer 7. Therefore, the guiding conductor pattern 6 is constituted by a portion where the insulating layer 7 is removed from the equipotential conductor pattern 4. Note that the insulating layer 7 is shown by hatching in FIG.

  A BGA is mounted on the substrate 1. First, as shown in FIG. 3A, a BGA 8 is disposed on one surface 2 a of the substrate 1. In this case, the ball solder 8a of the BGA 8 is arranged so as to be positioned on the appropriate land 3. And the reflow soldering process of BGA8 is performed in a warming state. Thereby, the ball solder 8a is melted, whereby the BGA 8 and the substrate 1 are electrically connected. FIG. 3B shows a state after the reflow solder process.

Further, in the state of FIG. 3B, the other surface 2b of the substrate 1 is subjected to a flow solder process.
In FIG. 3B, when the other surface 2b is flow-soldered, the solder on the one surface 2a side is melted by the heat of the flow solder and overflows from the via 5 or the land 3, or through the via 5 as in this embodiment. When there is the hole 5a, the flow solder may climb to the side 2a and overflow from the via 5. Even if the other surface 2b is flow soldered before the BGA 8 is mounted on the one surface, in the present embodiment, the via 5 has the through hole 5a. Sometimes.

  In this case, in the above configuration, the climbing molten solder is transmitted from the via 5 to the guide conductor pattern 6. The pressure of the molten solder is maximized at the apex portion of the guide conductor pattern 6. Therefore, it is the apex 6a portion of the guiding conductor pattern 6 that first exceeds the limit of the surface tension. Since the apex 6a is directed to the land 3 having the same potential, the overflowing molten solder is directed to the land 3 having the same potential. As a result, the land where the molten solder ends up becomes a land of the same potential.

  In addition, the molten solder that has reached the land 3 is formed into a circular shape, so that the molten solder has a capillary phenomenon (between the land 3 and the surface of the BGA mounting substrate 1 between the outer periphery of the circular land 3). It develops around the outer periphery of the land 3 due to a capillary step due to a slight step or gap. When the molten solder pressure is weakened at the time of overflow, it does not escape from the capillary action on the outer periphery of the land 3, and eventually remains at the land 3 having the same potential. As a result, even if the molten solder overflowing from the via 5 is connected to the land 3, it is connected to the land 3 having the same potential and connected to the other land 3 and via 5 having the same potential. Can be prevented.

  In addition, according to the present embodiment, the center 6g of the triangular portion of the guide conductor pattern 6 is closer to the via 5 than the distances L1 to L3 from the centers of the non-equal potential lands 3 surrounding the via 5. Since the distance Lh from the center of the land 3 having the same potential as that of the land 3 is set closer, the molten solder overflowing from the via 5 easily reaches the land 3 having the same potential, and the molten solder Can be more reliably prevented from being connected to other lands 3 and vias 5 having the same potential.

  FIG. 4 shows a second embodiment of the present invention. In this embodiment, the vertices 6a in the direction of the apex 6a extending from the two sides constituting the apex 6a are the apexes 6a of the acute angle portion projecting from the triangular circle of the guide conductor pattern 6. It is characterized in that it is disposed on the substrate body 2 so as to overlap with the land 3 plane of the same potential. In this embodiment, when the molten solder overflows from the vertex 6a of the triangle, the molten solder is pushed out by the force converged in the direction of the vertex 6a of the triangle. It depends. As a result, the molten solder moves in the direction of the apex 6a. In this case, in the above configuration, the virtual lines R1 and R2 extending in the direction of the vertex 6a extending from the two sides constituting the vertex 6a are in contact with the outer periphery of the land 3 having the same potential or overlapping the land 3 plane. Thus, since it is arranged on the substrate body 2, the direction of the apex 6 a is the direction of the land 3 having the same potential, and therefore, it is easy to reliably reach the land 3 having the same potential and overflowed from the via 5. It is possible to more reliably prevent the molten solder from connecting to other lands 3 and vias 5 having non-equal potential.

  In this case, as shown in FIG. 5 showing the third embodiment of the present invention, the vertices 6a have virtual lines R1 and R2 extending in the direction of the vertex 6a extending from two sides constituting the vertex 6a. You may make it arrange | position to the board | substrate body 2 so that it may become a position which contacts the outer periphery of the land 3 of the same electric potential. Even if it does in this way, the effect similar to a 2nd Example can be acquired.

  FIG. 6 shows a fourth embodiment of the present invention. In this embodiment, a part of the outer peripheral portion of the land 3 has a substantially V-shaped shape in plan view and the V-shaped apex 3b. Is characterized in that the auxiliary guiding conductor pattern 3a is formed so as to face the via 5 having the same potential. With respect to the triangular vertex 6a of the guide conductor pattern 6 of the via 5, the land 3 having the same potential as the via 5 is close to the V-shaped vertex 3b, so that the molten solder overflowing from the via 5 has the same potential. Thus, it is possible to more reliably prevent connection to other lands 3 and vias 5 having the same potential.

  FIG. 7 shows a fifth embodiment of the present invention. In the fourth embodiment, the planar shape of the equipotential conductor pattern 11 that electrically connects the land 3 and the via 5 is the same as that of the first embodiment. Different from the example (FIG. 1). That is, the equipotential conductor pattern 4 of the first embodiment is configured to connect the land 3 and the via 5 to be equipotentially almost linearly. The conductor pattern 11 is connected in a substantially U shape. In this case, the guide conductor pattern 12 is formed on the one surface 2a side of the via 5 by a conductor pattern different from the equipotential conductor pattern 11 without using the equipotential conductor pattern 11. Also in this case, the guide conductor pattern 12 has a shape in which the apex 12 a faces the land 3 having the same potential as the via 5. In the fifth embodiment, the same effect as in the first embodiment can be obtained.

  In the drawings, 1 is a substrate, 2 is a substrate body, 2a is one surface, 2b is the other surface, 3 is a land, 3a is an auxiliary guide conductor pattern, 4 is an equipotential conductor pattern, 5 is a via, and 6 is a guide conductor. Pattern, 7 is an insulating layer, 8 is BGA, 8a is ball solder, 11 is an equipotential conductor pattern, and 12 is a guide conductor pattern.

Claims (4)

A BGA is mounted on one surface of the substrate body, and a circular land is provided on the one surface, and vias that penetrate the substrate body from the one surface to the other surface on the opposite side are provided, and the land and the via are on the one surface. A plurality of sets of lands and vias are provided, and the other surface is soldered, with the lands and the vias having the same potential set by the same set potential conductor pattern as a set. A substrate to be attached,
The via is exposed on the one surface side portion of the substrate body in the via, is joined to a circle in a plan view, and only one vertex of the triangle protrudes from the circle, and the vertex is A BGA mounting substrate, characterized in that a guide conductor pattern having a shape facing a land having the same potential as the via is formed.   The distance between the center of the triangular portion of the guide conductor pattern and the center of the land having the same potential as the via is greater than the distance from the center of each non-equal potential land surrounding the via. The BGA mounting substrate according to claim 1, wherein the BGA mounting substrate is set so as to be close to each other.   The apex of the acute angle portion protruding from the triangular circle of the guide conductor pattern is such that the virtual line extending in the apex direction extending from two sides constituting the apex is in contact with the outer periphery of the land of the same potential. The BGA mounting substrate according to claim 1, wherein the BGA mounting substrate is disposed on the substrate body so as to overlap with the substrate. An auxiliary guide conductor pattern is formed on a part of the outer peripheral portion of the land so as to project in a substantially V shape in a plan view and the apex of the V shape faces the direction of the via having the same potential. The BGA mounting substrate according to any one of claims 1 to 3.

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