JP2007220915A - Pin connecting structure of printed board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pin connecting structure of a printed board which can maintain a good reliability in vibration and heat-cycle environments. <P>SOLUTION: In the pin connecting structure, there is provided a via 7 for connecting a lead terminal 1 inserted into a through-hole 3 with an inner layer 42 present in a printed board 2. Consequently, the connection can be secured even when a joining interface 6a is damaged between the through-hole 3 and the inner layer 42 due to vibrations and heat cycles. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pin connection structure of a printed circuit board, and more particularly, to an improvement in a structure for connecting a pin standing in a through hole of the printed circuit board to an inner layer conductor pattern of the printed circuit board.

  A printed circuit board (hereinafter referred to as a printed circuit board) is provided with a pin fixing through hole (referred to as a through hole), and a conductor pattern is formed on the inner peripheral surface thereof. It is widely used in printed circuit board technology to fix a pin). Hereinafter, this structure is called a printed circuit board pin connection structure. Examples of this type of pin include a DIP type IPM lead terminal described in Patent Document 1.

  When a multilayer printed board is used for high-density mounting, it is necessary to mix a case where this pin is connected to the surface conductor pattern of the multilayer printed board and a case where this pin is connected to the inner layer conductor pattern. The multilayer printed board having a structure for connecting the latter pin and the inner layer conductor pattern is referred to as an inner layer / pin connection type multilayer printed board.

  A conventional connection structure between pins of a multilayer printed circuit board (hereinafter also simply referred to as a printed circuit board) and an inner layer conductor pattern will be briefly described with reference to FIGS.

  In FIG. 6, the printed circuit board 2 has surface layer conductor patterns (hereinafter also referred to as surface layers) 41 and 44, inner layer conductor patterns (hereinafter also referred to as inner layers) 42 and 43, and through holes 3. However, the through-hole 3 referred to here means a pin insertion through-hole penetrating the printed circuit board 2 and also means a through-hole conductor layer formed on the inner peripheral surface of the pin insertion through-hole. To do. The through hole 3 and the inner layer 42 are joined at the joining interface 6. The lead terminal 1 of the IPM is inserted into the through hole 3 and fixed by the solder 5, and is thereby connected to the inner layer 42 through the through hole 3, more precisely, the through hole conductor layer formed in the through hole.

FIG. 7 shows a structure for increasing the current capacity of the connection path between the lead terminal 1 and the conductor layer pattern of the printed circuit board 2, and is preferably a printed circuit board used for connecting a large current lead terminal such as an IPM main electrode terminal. 1 shows a pin connection structure (hereinafter also referred to as a large current connection structure). In FIG. 7, the lead terminal 1 is connected to all of the surface layers 41 and 44 and the inner layers 42 and 43 through the solder 5 and the through holes 3. The through hole 3 is connected to the inner layer 42 through the bonding interface 6 and to the inner layer 43 through the bonding interface 60.
JP 2005-183463 A

  However, when the above-described inner layer / pin connection type multilayer printed circuit board is used for a vehicle, the present inventors need to consider an increase in electrical resistance or occurrence of disconnection at a connection portion between the pin and the inner layer conductor pattern. I found out. Hereinafter, this problem found by the present inventors will be described in more detail.

  In the inner layer / pin connection type multilayer printed board described above, the pins are connected to a mass body such as an IPM. In most cases, the mass body is mounted and fixed to the multilayer printed board by solder or the like, but may be fixed to a separate member from the multilayer printed board such as a heat sink or a base plate.

  First, it is assumed that a strong excitation force is applied to the circuit device when the mass body is fixed to the printed circuit board. When the mass, the multilayer printed circuit board, and the extended part of the pin vibrate at the same acceleration, no force is generated between the pin and the multilayer printed circuit board, and this force is formed in the through hole to form the inner layer conductor pattern. There is no adverse effect on the connection between the through-hole conductor layer and the inner-layer conductor pattern interposed between the solder and the solder in the through-hole.

  However, since the multilayer printed circuit board has a particularly small bending rigidity in the thickness direction, the multilayer printed circuit board is bent by an external excitation force, and therefore has a different acceleration with respect to the mass body. Therefore, in this case, the pin whose one end is fixed to the mass body gives a force to the solder in the through hole. This force is applied to the joint between the inner layer conductor pattern and the through hole conductor layer through the solder in the through hole. More simply, between the through-hole conductor layer fixed to the solder or pin in the through-hole and the inner-layer conductor pattern that is extended in the multilayer printed circuit board and more strongly affected by bending deformation of the multilayer printed circuit board. There is a possibility that the joint state of the joint part deteriorates due to the external excitation force.

  The above problem becomes more serious when the IPM pins are fixed to the through holes of the multilayer printed board, but the IPM itself is fixed to another member such as a heat sink and not directly fixed to the multilayer printed board. To explain further, considering a case in which the heat sink with the IPM fixed is fixed to the case together with the multilayer printed circuit board, for example, the external excitation force acts on the case etc. to elastically deform them, and the same as described above. It is necessary to consider the case where the above-described force is applied to the solder in the through hole. In addition, it is necessary to consider the case where the change in the thermal expansion amount of the pin due to the high temperature / low temperature thermal cycle of the IPM pin gives the same force to the solder in the through hole.

  In any case, in a thermal cycle environment or vibration environment, a large stress is generated in the small area joint between the through-hole conductor layer and the inner layer conductor pattern, and it is assumed that an increase in electrical resistance or disconnection occurs at this part. It will be appreciated that it is important, for example, in vehicle applications.

  The above problem will be described more specifically in the printed circuit board pin connection structure shown in FIGS. When vibration is applied to the entire board, an IPM package (not shown) located above the lead terminal 1 and arranged separately from the printed board 2 is displaced relative to the printed board 2. Then, the joining of the lead terminal 1, the solder 5, the through-hole (through-hole conductor layer) 3 and the inner layer 42 is pulled in the changing direction. As a result, there is a possibility that an adverse effect may occur on the bonding of the bonding interface 6 that is most susceptible to stress.

  Further, the above problem becomes more serious in the large current connection structure shown in FIG. That is, in FIG. 7, when a large current flows through the path, when one of the two bonding interfaces 6 and 60 breaks and the resistance increases, the current concentrates on the other bonding interface and the deterioration of the remaining bonding interface is promoted. It is necessary to consider the possibility of being burned out.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a pin connection structure of a printed circuit board that can maintain good reliability in a vibration environment and a heat cycle environment.

  The printed circuit board pin connection structure of the present invention that solves the above problems includes a multilayer printed circuit board having a surface conductor pattern on the surface and an inner conductor pattern inside, and a pin insertion through-hole, and the pin insertion Terminal pins inserted into through holes for use and fixed with solder, wherein the terminal pins are formed on the multilayer printed board in the pin connection structure of the printed board connected to the inner layer conductor pattern, and the inner layer conductors It has a via conductor reaching a pattern, and a pin connection conductor extending on the surface of the multilayer printed board and connecting the terminal pin and the via conductor.

  In addition, the through-hole said above means the through-hole conductor layer which is the hole for inserting the lead terminal of an electrical component, or the conductor layer formed in the inner peripheral surface of this hole, and a via conductor is A conductor formed in a via hole which is a hole into which a lead terminal is not inserted shall be said.

  That is, the present invention is characterized in that pins such as IPM lead terminals soldered to the through holes of the multilayer printed board are electrically connected to the inner conductor pattern of the multilayer printed board through via conductors.

  According to the present invention, the stress applied to the junction between the through hole conductor layer of the pin insertion through hole and the inner layer conductor pattern due to the vehicle vibration or thermal cycle described above can be greatly reduced. The connection reliability between the pins such as lead terminals and the inner layer conductor pattern can be greatly improved as compared with the conventional case.

  In a preferred aspect, the via conductor is formed close to the pin insertion through hole. In this way, the connection resistance between the via conductor and the pin insertion through hole can be reduced, and the arrangement of the conductor layer pattern on the surface of the multilayer printed board can be facilitated.

  In a preferred aspect, the terminal pins are respectively connected to the plurality of via conductors formed at different positions. If it does in this way, the reliability of the said connection part can be improved and the electrical resistance between a via conductor and a pin insertion through-hole can also be reduced.

  In a preferred aspect, the pin connection conductor comprises the surface layer conductor pattern. Thereby, an extra connection process does not increase.

  In a preferred aspect, the via conductor is configured by a predetermined connection through hole that is penetrated through the multilayer printed board, and solder disposed in the connection through hole. Thereby, the electrical resistance from the inner layer conductor pattern to the pin can be reduced.

  In a preferred aspect, the pin connection conductor is formed by connecting the solder disposed in the pin insertion through hole and the solder forming the via conductor. Thereby, the electrical resistance from the inner layer conductor pattern to the pin can be further reduced.

  A preferred embodiment of the printed circuit board pin connection structure of the present invention will be described below. However, the present invention should not be construed as being limited to this embodiment, and it goes without saying that the technical idea of the present invention may be realized by a combination of other techniques.

(Embodiment 1)
The pin connection structure of the printed circuit board according to the first embodiment will be described with reference to FIG. 1 which is a schematic vertical sectional view. FIG. 1 is a longitudinal sectional view of a printed circuit board.

  In FIG. 1, the printed circuit board 2 has surface layers 41 a and 44 a, inner layers 42 and 43, a through hole 3 and a via 7. Reference numeral 1 denotes an IPM lead terminal (not shown), and a lead terminal (pin referred to in the present specification) 1 fixed by solder 5 is inserted and fixed in the through hole 3.

  However, the via 7 referred to here is a via hole that is a hole that is penetrated through the printed circuit board 2 but into which the lead terminal is not inserted and fixed. A via hole conductor that is a conductor layer formed on the inner peripheral surface of the via hole. It may also mean a layer (via conductor). Similarly, the through hole 3 refers to a through hole for inserting a pin penetrating the printed board 2 and also means a through hole conductor layer formed on the inner peripheral surface of the through hole for inserting a pin.

  6a is an interface of a portion of the through-hole 3 that is a through-hole conductor layer that is closest to the inner layer 42, but is not joined to the inner layer 42 in this embodiment.

  The via 7 is formed relatively close to the through hole 3, and the via 7 as a via hole conductor is joined to the inner layer 42 at the joining interface 6 b. The via 7 as a via-hole conductor and the through-hole 3 as a through-hole conductor layer are connected through surface layers (pin connection conductors) 41b and 44b.

  Thus, the electrical path from the lead terminal 1 to the inner layer 42 is as follows: lead terminal 1 → solder 5 → surface layer 41b, 44b → via 7 → bonding interface 6b → inner layer 42. The connection interface 6b between the via 7 and the inner layer 42 is not directly subjected to the excitation force or thermal stress from the lead terminal 1 because the lead terminal 1 is not inserted into the via 7, and the connection without via shown in FIG. Compared to the structure, it is possible to join significantly more resistant to thermal cycling and vibration.

  In addition, although the positions of the vias 7 are arbitrary, it is preferable to arrange a plurality of vias near the through hole 3. However, in the case where the lead terminal 1 does not require a current capacity like the control terminal of the IPM, it is preferable to use a single via 7 and make the diameter smaller than the through hole 3 in order to increase the mounting area. . Of course, in FIG. 1, only one of the surface layers 41 b and 44 b may be connected to the through hole 3 and the via 7.

(Embodiment 2)
A second embodiment will be described below with reference to FIG. The feature of this embodiment is that the interface 6a separated from the inner layer 42 in the first embodiment is joined in the same manner as in FIG. In this way, since the electrical conduction paths are in parallel, the connection reliability can be further improved. However, it should be noted that the current path is different before and after the fracture of the interface 6a, and it is unavoidable to affect the signal voltage and signal current to be transmitted (see FIG. 3). Of course, also in this embodiment, it is desirable that the via 7 be installed in the vicinity of the through hole 3, and the via 7 may be connected by either one of the surface layers 41b and 44b.

(Embodiment 3)
A third embodiment will be described below with reference to FIG. This embodiment is a large current connection structure, and is characterized in that a plurality of vias are provided and the thickness of each conductor layer pattern is increased in the second embodiment shown in FIG. In FIG. 4, two vias 7 a and 7 b are formed, and these vias 7 a and 7 b are connected to the inner layer 42. The inner layer 42 is also connected to the through hole 3 through the bonding interface 6a. Furthermore, the vias 7 a and 7 b are connected to the solder 5 through surface layers (pin connection conductors) 41 and 44. Reference numeral 6b denotes a bonding interface between the via 7a and the inner layer 42, and reference numeral 6c denotes a bonding interface between the via 7b and the inner layer 42. Eventually, the lead terminal 1 is connected in parallel by the three bonding interfaces 6a, 6b and 6c.

  Of course, the number of vias is not limited to two. For example, a larger number of vias may be provided around the through hole 3. For example, if a single via has a current capacity of 3 A, it is sufficient to provide 10 or more vias if a 30 A current is desired to flow. At this time, the via diameter is not particularly relevant as long as the current capacity is concerned. Arranging the via close to the through hole 3 is also preferable from the viewpoint of reducing inductance and wiring resistance.

(Embodiment 4)
Another embodiment will be described below with reference to FIG. This embodiment is a large current connection structure, and the feature thereof is that, in the third embodiment shown in FIG. 4, one via is provided and the via 7 is filled with the solder 5b. With this configuration, the current capacity between the via 7 and the through hole 3 can be greatly improved. It is better to make the diameter of the via 7 equal to that of the through hole 3.

  In this embodiment, as shown in FIG. 4, the solder 5a of the through hole 3 and the solder 5b of the via 7 are in contact with each other on the upper surfaces of the surface layers 41 and 44 to constitute the pin connection conductor referred to in the present invention. ing. That is, the through hole 3 and the via 7 are disposed at a distance that allows the solder 5 a and the solder 5 b to directly contact with each other on the surface of the printed board 2. Thereby, the electrical resistance between the solder 5b of the via 7 and the solder 5a can be further reduced. Of course, when direct contact between the solder 5a and the solder 5b is not required, the distance between the through hole 3 and the via 7 is free. Also in this embodiment, a plurality of vias 7 may be provided.

3 is a schematic vertical sectional view showing a pin connection structure of the printed circuit board according to Embodiment 1. FIG. It is a model vertical sectional view which shows 2nd Embodiment. It is a model vertical sectional view which shows the problem in 2nd Embodiment. It is a model vertical sectional view which shows 3rd Embodiment. It is a model vertical sectional view which shows 4th Embodiment. It is a model vertical sectional view which shows the conventional form (at the time of a small electric current). It is a model vertical sectional view which shows a conventional form (at the time of a large current).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lead terminal 2 Printed circuit board 3 Through hole 5 Solder 5a Solder 5b Solder 6 Bonding interface 6a Interface (bonding interface)
6b Bonding interface 7 Via 7a Via 7b Via 41 Surface layer 41a Surface layer 41b Surface layer 42 Inner layer 43 Inner layer 44 Surface layer 60 Bonding interface

Claims (6)

A multilayer printed circuit board having a surface conductor pattern on the surface and an inner layer conductor pattern inside, and through-holes for pin insertion, and terminal pins inserted through the pin insertion through-holes and fixed with solder The terminal pin is a pin connection structure of a printed circuit board connected to the inner layer conductor pattern,
A via conductor formed on the multilayer printed circuit board and reaching the inner layer conductor pattern;
A pin connection conductor extending on the surface of the multilayer printed circuit board and connecting the terminal pin and the via conductor;
A printed circuit board pin connection structure characterized by comprising: In the printed circuit board pin connection structure according to claim 1,
The via conductor is a pin connection structure of a printed circuit board formed close to the pin insertion through hole. In the printed circuit board pin connection structure according to claim 1,
The terminal pin is a pin connection structure of a printed circuit board connected to the plurality of via conductors formed at different positions. In the printed circuit board pin connection structure according to claim 1,
The pin connection conductor is a printed circuit board pin connection structure comprising the surface conductor pattern. In the printed circuit board pin connection structure according to claim 1,
The via conductor is a pin connection structure of a printed circuit board constituted by a predetermined connection through hole penetrating the multilayer printed circuit board and solder disposed in the connection through hole. The printed circuit board pin connection structure according to claim 5,
The pin connection conductor is a pin connection structure of a printed circuit board in which the solder disposed in the pin insertion through hole and the solder forming the via conductor are connected.

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