JP4794397B2 - Wiring board connection structure - Google Patents

Description

  The present invention relates to a wiring board connection structure in which a first wiring board and a second wiring board are directly connected to each other, and a repair work that can be removed and reconnected after the connection is made.

  As a connection structure of a conventional wiring board, there is one disclosed in Patent Document 1. In this connection structure, a plurality of connection terminal portions exposed at the connection portion of the first wiring board are provided, and a plurality of connection terminal portions exposed at the connection portion of the second wiring board are provided, which correspond to each other. The connection portions where the connection terminal portions are brought into contact with each other are connected using a thermoplastic adhesive or a thermoplastic anisotropic conductive adhesive.

  According to this conventional example, after both the connecting portions are connected, if the adhesive is heated to a certain temperature or more, the adhesive is melted and the connected state can be released, so that a repair operation is possible.

  By the way, as a connection characteristic (physical characteristic) required in the structure in which both the connection parts of the first and second wiring boards are directly connected, good electrical connectivity between both the conductor parts, and both connections are provided. There is strong connection strength between parts and good insulation between adjacent conductor parts. And it is necessary to satisfy such connection characteristics even in a repairable connection structure.

  The connection characteristics of the conventional example will be examined individually. First, regarding the electrical connectivity between the two connection terminal portions, the connection terminals between the two connection terminals are electrically connected by surface contact, and partial contact is made only by minute irregularities on the connection terminal portions. Therefore, there is a possibility that good electrical connectivity cannot be obtained. However, when an anisotropic conductive adhesive is used, the electrical characteristics are improved, but the electrical characteristics are inferior compared to those in which the connection terminal portions are metal-bonded.

  Next, as for the connection strength between the two connection portions, since the connection portions between the two connection portions are connected only by the adhesive force of the adhesive, there is a possibility that a strong connection strength cannot be obtained. In particular, when the contact area of the adhesive is small, there is a high possibility that a desired connection strength cannot be obtained.

  Finally, the insulation between adjacent connection terminal portions is basically determined by the distance between the connection terminal portions, but the gap between adjacent connection terminal portions is filled with a thermoplastic adhesive. Insulating properties are improved, and conversely, insulating properties are lowered when a thermoplastic anisotropic conductive resin is filled.

As described above, in the connection structure of the conventional example, the repair work of removing and reconnecting after connection is possible, but it is not satisfactory in terms of connection characteristics.
JP 2005-327892 A

  The present invention enables a repair work to be removed and reconnected after connection, and has good electrical connectivity between conductor parts, strong connection strength between both connection parts, and good insulation between adjacent conductor parts. An object of the present invention is to provide a wiring board connection structure.

  According to one aspect of the present invention, a plurality of connection terminal portions exposed at the connection portion of the first wiring board are provided, and a plurality of connection terminal portions exposed at the connection portion of the second wiring board are provided. In the connection structure of the wiring board in which the corresponding connection terminal portions are directly connected to each other, both the connection terminal portions are connected to each other by soldering, and a thermoplastic resin is filled between both the connection portions, Assuming that the heat resistance temperature of the first and second wiring boards is Ttp, the soldering temperature is Tss, the glass transition temperature of the thermoplastic resin is Tgr, and the melting point of the thermoplastic resin is Tmr, Ttp> Tss> Tgr as Condition 1 The gist of the present invention is a connection structure for a wiring board formed of a material that simultaneously satisfies the relationship of Ttp> Tmr> Tss as Condition 2.

  By satisfying the condition 1 and the condition 2 at the same time by making such an aspect of the invention, it is possible to carry out a repair work in which the connection portion is reinforced with a thermoplastic resin to increase the connection strength and is removed and reconnected after connection. And a connection structure that can withstand the soldering process by reflow.

  In the connection structure of the wiring board according to the present invention, the thermoplastic resin may be spot-filled in two partial regions along the tip portions of both connection portions.

  In the connection structure of the wiring board according to the present invention, the thermoplastic resin may be spot-filled in four partial regions corresponding to both corners of the front end portions of both connection portions.

  In the wiring board connection structure of the present invention, the thermoplastic resin is spotted in one partial region along the tip of one of the connection portions and in two partial regions corresponding to both corners of the tip of the other connection portion. It may also be filled.

  According to the present invention, regarding the electrical connectivity between the two connection terminal portions, both the connection terminal portions are connected by metal bonding using solder, and therefore, good electrical connectivity can be obtained. With respect to the connection strength between the two connection portions, both connection terminal portions are metal bonded by solder and the connection portions are connected by the adhesive force of the thermoplastic resin, so that a strong connection strength can be obtained. The insulation between the adjacent connection terminal portions is basically determined by the distance between the conductor portions, but if the gap between the adjacent conductor portions is filled with a thermoplastic resin that does not contain a conductive filler. Even so-called fine pitch (both the width of the conductor portion and the distance between the conductor portions is about 20 μm) can ensure good insulation.

  In addition, in order to release the connection of both the connection parts, both the connection parts are heated to a temperature equal to or higher than the glass transition temperature of the thermoplastic resin and lower than the soldering temperature to remove the softened thermoplastic resin. Then, the solder is heated to a temperature equal to or higher than the soldering temperature and lower than the heat resistance temperature of the wiring board, and the melted solder is removed. Since the wiring board from which the thermoplastic resin and the solder have been removed is heated only below its heat-resistant temperature, thermal damage does not remain and reconnection using the wiring board is possible.

  As described above, it is possible to perform repair work by removing and reconnecting after connection, and it has good electrical connectivity between conductor parts, strong connection strength between both connection parts, and good insulation between adjacent conductor parts. A connection structure for a wiring board can be provided.

  Hereinafter, details of a connection structure between wiring boards according to an embodiment of the present invention will be described with reference to the drawings. However, it should be noted that the drawings are schematic, and the thicknesses and ratios of the material layers are different from actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, the part from which the relationship and ratio of a mutual dimension differ also in between drawings is contained.

(First embodiment)
1 and 2 show a first embodiment of the present invention. FIG. 1A is a plan view of a wiring board connection structure, and FIG. 1B is a cross-sectional view taken along line AA in FIG. FIG. 1 (c) is a cross-sectional view taken along line BB of FIG. 1 (a), and FIG. 2 is a plan view showing the start of application of a thermoplastic resin.

  As shown in FIGS. 1A, 1B, and 1C, the wiring board connection structure includes a rigid wiring board 10 that is a first wiring board and a flexible wiring board 20 that is a second wiring board. Are directly connected in a state in which the connecting portions 14 and 24 are abutted.

  The rigid wiring board 10 is disposed on the insulating substrate 11, a plurality of conductor portions 12 arranged in a predetermined circuit pattern on the insulating substrate 11, and the plurality of conductor portions 12 covering the plurality of conductor portions 12. It has a three-layer structure composed of a transparent insulating resist layer 13 formed. In the connection part 14 of the rigid wiring substrate 10, the resist layer 13 is peeled off, and a plurality of connection terminal parts 12 </ b> A formed from a part of the plurality of conductor parts 12 are exposed. The plurality of exposed connection terminal portions 12A are arranged in a predetermined width dimension and at a predetermined interval from each other.

  The flexible wiring board 20 is disposed on the insulating film 21 so as to cover the insulating film 21, the plurality of conductor portions 22 disposed on the insulating film 21 at intervals, and the plurality of conductor portions 22. It has a three-layer structure including a transparent insulating coverlay layer 23. In the connection portion 24 of the flexible wiring board 20, the coverlay layer 23 is peeled off, and a plurality of connection terminal portions 22 </ b> A formed respectively from a part of the plurality of conductor portions 22 are exposed. The plurality of exposed connection terminal portions 22A are arranged in a predetermined width dimension and at a predetermined interval from each other.

  The connection portions 14 and 24 of both the rigid wiring substrate 10 and the flexible wiring substrate 20 are metal-bonded by the solder 30 in a state where the corresponding connection terminal portions 12A and 22A are aligned with each other. Further, a thermoplastic resin 31 containing no conductive filler is filled between the connection portions 14 and 24 and around the connection terminal portions 12A and 22A where the connection portions 14 and 24 are exposed. Yes. That is, the thermoplastic resin 31 is filled so as to seal both the connection terminal portions 12A and 22A in all regions.

  In the connection structure between the wiring boards according to the embodiment, the heat-resistant temperature of the rigid wiring board 10 and the flexible wiring board 20 is Ttp, the soldering temperature is Tss, the glass transition temperature of the thermoplastic resin 31 is Tgr, and the thermoplastic resin When the melting point is Tmr, it is formed of a material that simultaneously satisfies the relationship of Ttp> Tss> Tgr as Condition 1 and the relationship of Ttp> Tmr> Tss as Condition 2. In the case where the heat resistant temperatures of the rigid wiring board 10 and the flexible wiring board 20 are different, the heat resistant temperature on the lower heat resistant temperature side is defined as Ttp.

  Next, specific materials having such conditions 1 and 2 will be described. For the rigid wiring board 10 and the flexible wiring board 20, a material having a heat resistance of about 300 ° C. corresponding to a lead-free high temperature solder (about 270 ° C.), for example, a general glass epoxy or polyimide such as FR-4 Or aramid.

  In addition, in both the rigid wiring board 10 and the flexible wiring board 20, products having a high glass transition temperature have been developed, and there are those having a glass transition temperature of 370 ° C. for glass epoxy and 310 ° C. for aramid. Here, the heat-resistant temperature and the glass transition temperature of the wiring board are different concepts, and in this embodiment, any material that can clear even the heat-resistant temperature condition that can maintain the characteristics as the wiring board may be used.

  As the thermoplastic resin 31, an underfill resin for sealing a semiconductor chip or NCP (Non-Conductive Paste) having a glass transition temperature of about 200 ° C. is used. These are both epoxy-based and have a glass transition temperature Tgr in the range of 70 ° C to 270 ° C.

  Regarding the solder 30, there are lead-containing ones having a melting point Tmr of 183 ° C. and lead-free ones having a melting point Tmr of 200 ° C. to 220 ° C., which are used. The soldering temperature Tss is about 250 ° C. when lead-containing solder is used, and about 260 ° C. to 270 ° C. when lead-free solder is used.

  Next, the connection procedure of the wiring board will be described. The resist layer 13 of the connection portion 14 of the rigid wiring board 10 is peeled off from the cover lay layer 23 of the connection portion 24 of the flexible wiring board 20 so that both connection terminal portions 12A and 22A are exposed.

  Solder plating or solder paste is applied to at least one of the connection terminal portions 12A and 22A of the rigid wiring board 10 and the flexible wiring board 20. Next, the connection terminal portions 12A and 22A corresponding to each other of the connection portions 14 and 24 of both the rigid wiring substrate 10 and the flexible wiring substrate 20 are aligned and overlapped. Next, both the connection parts 14 and 24 are heated with a heater chip etc., the solder 30 is melted, and the connection terminal parts 12A and 22A are metal-joined.

  Next, as shown in FIG. 2, a thermoplastic resin 31 is applied along the exposed surface of the connection portion 14 of the rigid wiring board 10 and along the tip of the connection portion 24 of the flexible wiring board 20. A thermoplastic resin 31 is applied on the exposed surface of the connection portion 24 of the flexible wiring board 20 and along the distal end portion of the connection portion 14 of the rigid wiring board 10. Then, the two applied thermoplastic resins 31 flow into the gaps (spaces) between the two connection terminal portions 12A and 22A by a capillary phenomenon. As a result, the thermoplastic resin 31 is filled in the vicinity of the exposed connection terminal portions 12A and 22A of both the connection portions 14 and 24 and in the entire gap between the connection terminal portions 12A and 22A. After this filling, the thermoplastic resin 31 is heated to a curing temperature in an oven or the like, and the thermoplastic resin 31 is cured to complete. The thermoplastic resin 31 used here is a material that satisfies a relationship of Ttp> Tmr> Tss (condition 2).

  Next, an operation for releasing the connection between the connection portions 14 and 24 will be described. Both the connecting portions 14 and 24 are heated to a temperature equal to or higher than the glass transition temperature of the thermoplastic resin 31 and lower than the soldering temperature, and the thermoplastic resin 31 that has become soft like a gel is removed from the connecting portions 14 and 24. Next, the solder 30 is heated to a temperature equal to or higher than the soldering temperature and lower than the heat resistance temperature of both the wiring boards 10 and 20, and the molten solder 30 is removed from the connection portions 14 and 24.

  As described above, in the present embodiment, the connection terminal portions 12A and 22A of both the rigid wiring substrate 10 and the flexible wiring substrate 20 are connected by soldering, and the thermoplastic resin is provided between the connection portions 14 and 24. When the heat resistance temperature of the rigid wiring board 10 and the flexible wiring board 20 is Ttp, the soldering temperature is Tss, the glass transition temperature of the thermoplastic resin 31 is Tgr, and the melting point of the thermoplastic resin is Tmr, the condition 1 is satisfied. As well as the relationship of Ttp> Tss> Tgr as condition 2 and the relationship of Ttp> Tmr> Tss as condition 2.

  Therefore, as for the electrical connectivity between the two connection terminal portions 12A and 22A, since both the connection terminal portions 12A and 22A are connected by metal bonding with the solder 30, good electrical connectivity can be obtained. With respect to the connection strength between the two connection portions 14 and 24, both the connection terminal portions 12A and 22A are metal-bonded by the solder 30, and the connection portions 14 and 24 are connected by the adhesive force of the thermoplastic resin 31. Therefore, strong connection strength can be obtained. The insulation between the adjacent connection terminal portions 12A and 22A is basically determined by the distance of the gap between the connection terminal portions 12A and 22A, but is electrically conductive in the gap between the adjacent connection terminal portions 12A and 22A. Since a thermoplastic resin that does not contain a filler is filled, good insulation can be ensured even with a so-called fine pitch (both the width of the connection terminal portion and the distance between the connection terminal portions are about 20 μm).

  Further, when removing the connection structure of the wiring board, it can be removed by heating as described above, and the rigid wiring board 10 and the flexible wiring board 20 from which the thermoplastic resin 31 and the solder 30 are removed have the heat resistant temperature. Since it is heated only to less than that, thermal damage does not remain, and the wiring boards 10 and 20 can be used for reconnection.

  Furthermore, according to the structure formed of a material satisfying the relationship of Ttp> Tmr> Tss (condition 2), the thermoplastic resin 31 is cured between the connecting portions 14 and 24 of the rigid wiring board 10 and the flexible wiring board 20. After the connection, when heated to a temperature higher than the soldering temperature Tss and lower than the melting temperature Tmr of the thermoplastic resin 31, the thermoplastic resin 31 becomes softer than the glass transition temperature Tgr but is not melted to some extent. Since it has viscosity, it retains adhesive properties, and the strength of both connecting portions 14 and 24 is maintained. Therefore, after the rigid wiring board 10 and the flexible wiring board 20 are connected, it can be passed through a reflow furnace, and component mounting by soldering is possible.

  In particular, there is a rigid flexible wiring board in which a rigid wiring board is laminated on a flexible wiring board, and this rigid flexible wiring board has a flexible wiring board and a rigid wiring board connected thereto arranged in a sheet form. The electronic component is mounted on the mounting process line. A rigid flexible wiring board to which the wiring board connection structure according to the present modification is applied can be placed on the mounting process line of the rigid flexible wiring board and soldered.

  As described above, according to the connection structure of the wiring board of the present invention, it is possible to perform a repair work by removing and reconnecting after connection, good electrical connectivity between conductor portions, strong connection strength between both connection portions, It has good insulation between the matching conductor parts.

  In the present embodiment, the thermoplastic resin 31 that does not include a conductive filler is used. However, if the insulation between the adjacent connection terminal portions 12A and 22A can be sufficiently ensured, a conductive filler is included. Thermoplastic resins may be used.

(Second Embodiment)
FIG. 3 is a plan view of a wiring board connection structure according to the second embodiment of the present invention. As shown in FIG. 3, in the second embodiment, the thermoplastic resins 31 </ b> A and 31 </ b> B are spot-filled in two partial regions along the leading end portions of the rigid wiring board 10 and the flexible wiring board 20. Yes. The reason why the thermoplastic resins 31A and 31B are filled only in a spot manner is as follows. That is, the thermoplastic resins 31A and 31B are used for ensuring insulation between the connection terminal portions 12A and 22A and ensuring strength between the connection portions 14 and 24. Therefore, when the distance between the connection terminal portions 12A and 22A of the connection portions 14 and 24 is a sufficient distance to ensure insulation, it is necessary to use the thermoplastic resins 31A and 31B for ensuring insulation. However, it may be used to the extent necessary to ensure the strength of the connecting portions 14 and 24. For this reason, the thermoplastic resin 31 is spot-filled in the second embodiment.

  Since other configurations are all the same as those of the first embodiment, description thereof will be omitted to avoid redundant description. In FIG. 3, the same components as those in the first embodiment are denoted by the same reference numerals for clarification.

  In the second embodiment, since the thermoplastic resins 31A and 31B are filled only along the vicinity of the distal ends of both the rigid wiring board 10 and the flexible wiring board 20, the thermoplastic resin is used during repair work. It is easy to remove 31A and 31B. Further, since the thermoplastic resins 31A and 31B are not filled in almost the entire area between the connecting portions 14 and 24, the material cost of the thermoplastic resins 31A and 31B can be reduced.

(Third embodiment)
FIG. 4 is a plan view of a wiring board connection structure according to the third embodiment of the present invention. As shown in FIG. 4, in the third embodiment, the thermoplastic resins 31 </ b> C and 31 </ b> D are spot-filled in four partial areas corresponding to both corners of the tip portions of both connection portions 14 and 24. The reason why the thermoplastic resins 31C and 31D are filled only in a spot manner is the same as in the second embodiment.

  Since other configurations are all the same as those of the first embodiment, description thereof will be omitted to avoid redundant description. In FIG. 4, the same components as those of the first embodiment are denoted by the same reference numerals for clarification.

  Also in the third embodiment, since the thermoplastic resins 31C and 31D are filled only in the vicinity of the periphery of the connecting portions 14 and 24, the thermoplastic resins 31C and 31D can be easily recovered during the repair work. . In addition, when the thermoplastic resins 31C and 31D are applied, the thermoplastic resins 31C and 31D are applied only from the rigid wiring board 10 side, and when the thermoplastic resins 31C and 31D are recovered, the thermoplastic resins 31C and 31C are applied only from the rigid wiring board 10 side. Since 31D can be removed, it is easy to apply and remove the thermoplastic resins 31C and 31D. Further, since the thermoplastic resin 31 is not filled in the entire area between the connecting portions 14 and 24, the material cost of the thermoplastic resins 31C and 31D can be reduced.

(Fourth embodiment)
FIG. 5 is a plan view of a wiring board connection structure according to a fourth embodiment of the present invention. As shown in FIG. 5, in the fourth embodiment, the thermoplastic resins 31 </ b> A and 31 </ b> D are formed between the partial region along the distal end portion of the connection portion 14 of the flexible wiring substrate 10 and the distal end portion of the rigid wiring substrate 20. It is filled in three spots with two partial areas hitting both corners. The reason for filling the thermoplastic resins 31A and 31D only in a spot manner is the same as that in the second embodiment.

  Since other configurations are all the same as those of the first embodiment, description thereof will be omitted to avoid redundant description. In FIG. 5, the same components as those in the first embodiment are denoted by the same reference numerals for clarification.

  Also in the fourth embodiment, since the thermoplastic resins 31A and 31D are filled only in the vicinity of the periphery of both the connecting portions 14 and 24, the thermoplastic resins 31A and 31D can be easily recovered during the repair work. . In addition, when the thermoplastic resins 31A and 31D are applied, the thermoplastic resins 31A and 31D are applied only from the rigid wiring board 10 side, and when the thermoplastic resins 31A and 31D are recovered, the thermoplastic resins 31A and 31A are applied only from the rigid wiring board 10 side. Since 31D can be removed, the operation of applying and removing the thermoplastic resin 31 is easy. In addition, since the thermoplastic resins 31A and 31D are not filled in the entire area between the connecting portions 14 and 24, the material cost of the thermoplastic resins 31A and 31D can be reduced.

  In the connection structure of the wiring board according to each of the above embodiments, the first wiring board is the rigid wiring board 10 and the second wiring board is the flexible wiring board 20. Of course, the present invention can be applied even if both of the wiring boards are a flexible wiring board or a rigid wiring board.

FIG. 1A is a plan view of a wiring board connection structure according to the first embodiment of the present invention, FIG. 1B is a cross-sectional view taken along line AA in FIG. FIG.1 (c) is the BB sectional drawing of Fig.1 (a). It is a top view which shows the time of the start of application | coating of the thermoplastic resin which concerns on the 1st Embodiment of this invention. It is a top view of the connection structure of the wiring board which concerns on the 2nd Embodiment of this invention. It is a top view of the connection structure of the wiring board which concerns on the 3rd Embodiment of this invention. It is a top view of the connection structure of the wiring board which concerns on the 4th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,20 ... Wiring board 11 ... Insulating substrate 12 ... Conductor part 12A ... Connection terminal part 13 ... Resist layer 14 ... Connection part 21 ... Insulating film 22 ... Conductor part 22A ... Connection terminal part 23 ... Coverlay layer 24 ... Connection part 30 ... Solder 31, 31A, 31B, 31C, 31D ... Thermoplastic resin

Claims (4)

A plurality of connection terminal portions exposed at the connection portion of the first wiring board are provided, a plurality of connection terminal portions exposed at the connection portion of the second wiring board are provided, and the connection terminal portions corresponding to each other are provided. In the connection structure of the wiring board that is directly connected,
Both the connection terminal portions are connected by soldering, and between both the connection portions is filled with a thermoplastic resin,
If the heat resistance temperature of the first and second wiring boards is Ttp, the soldering temperature is Tss, the glass transition temperature of the thermoplastic resin is Tgr, and the melting point of the thermoplastic resin is Tmr, then Ttp as Condition 1> A wiring board connection structure characterized by being formed of a material that simultaneously satisfies the relationship of Tss> Tgr and Ttp>Tmr> Tss as Condition 2.   2. The wiring board connection structure according to claim 1, wherein the thermoplastic resin is spot-filled in two partial regions along the front end portions of both of the connection portions.   The wiring board connection structure according to claim 1, wherein the thermoplastic resin is spot-filled in four partial regions corresponding to both corners of the tip portions of both the connection portions.   The thermoplastic resin is spot-filled in one partial region along the tip of one of the connection portions and two partial regions corresponding to both corners of the tip of the other connection portion. The connection structure of a wiring board according to claim 1, wherein

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