JP4639353B2 - Electronic component mounting substrate, mounting method and apparatus - Google Patents

Description

  The present invention relates to an electronic component mounting board, a mounting method, and an apparatus for mounting electronic components on a printed circuit board.

As a defect related to solder joining that occurs in the flow soldering method or the local flow soldering method, there is a solder wetting failure to the lead of the electronic component with lead in the through hole.
This phenomenon occurs when the heated and melted solder supplied from the leading end side of the lead portion is cooled and becomes the solidification temperature of the solder before it is sufficiently wetted and filled in the through hole.
In particular, the melting point of lead-containing solder that has been generally used in the past is 183 ° C. However, when switching to lead-free solder, which has been rapidly applied to electrical products in recent years for environmental reasons, However, in a typical example, the temperature rises to about 220 ° C. and 40 ° C. Therefore, the lead-free solder is more prominent in solder wetting than the conventional lead-containing solder.

In addition to this lead-free solder, other factors that worsen solder wettability include the area (volume) of the conductive layer made of copper foil connected to the through hole and the heat capacity of electronic components with leads. When they are large, the cooling of the solder is promoted (heat sink), and the wettability of the solder is deteriorated.
This poor solder wetting is caused by insufficient amount of solder filled in the through-holes, so that in the environment where it is used as a product, the printed circuit board and leaded electronic components are expanded and contracted due to temperature changes. When a crack occurs in the solder in the through hole due to repetition, there is a problem that it is easy to cause a disconnection failure of an electric circuit of the product.

In the following Patent Document 1, after the lead of the electronic component with lead is inserted into the through hole provided in the printed circuit board, it is immersed in the solder heated and melted from the front end side of the lead using the flow soldering method. After that, an electronic component mounting board is described in which the electronic component with leads is connected to the printed circuit board by separating from the solder and cooling and solidifying the solder.
In this technology, as a measure to improve solder wetting failure, a through hole that is to be electrically connected by soldering by the flow soldering method and a via hole for heat transfer around the electronic component with leads is provided. Connect with a solid pattern. Then, when the flow soldering is performed, the via hole is filled with solder at the same time, so that heat is transmitted from the via hole and supplied to improve the solder wettability.

JP 2003-69202 A

However, in the above-described conventional method, as described above, solder is filled in the heat transfer via hole, and heat is transferred from the via hole through the solid pattern to improve the solder wetting failure. Therefore, when the solder is filled, solder balls may be generated on the solder non-flow surface of the printed circuit board, causing a short circuit between terminals.
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems of the prior art, and to improve the solder wetting of the lead on the electronic component without generating solder balls. Is to provide.

In order to solve the above problems, the present invention provides a through hole for mounting an electronic component provided on a substrate, a via hole for heat transfer provided in the substrate and transferring heat to the through hole, and the heat A heat transfer layer provided on an inner wall of the via hole for transmission and along both sides of the substrate, and the heat transfer provided on the solder flow surface side of the substrate in the heat transfer layer A layer is provided from the inner wall to the vicinity of the opening of the heat transfer via hole;
The heat transfer layer provided on the solder non-flow surface side of the substrate is configured to extend closer to the through hole than the heat transfer layer provided on the solder flow surface side. Yes.

  ADVANTAGE OF THE INVENTION According to this invention, the board | substrate for electronic component mounting, the mounting method, and apparatus which can improve the wetting of the solder to the lead | read | reed of an electronic component can be provided, without generating a solder ball.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings described below, components having the same function are denoted by the same reference numerals, and repeated description thereof is omitted.
Embodiment 1
FIG. 1A is a cross-sectional view of a printed circuit board before soldering according to the first embodiment of the present invention, and FIG. 1B is a view of the printed circuit board as viewed from the solder non-flow surface. 1A is a cross-sectional view taken along the line AA ′ in FIG. 1B (the same applies to FIGS. 2 and 4 to 6).

  In the figure, 10 is a printed circuit board which is a substrate for mounting electronic components, 1 is a substrate made of, for example, glass epoxy resin, 2 is a lead of electronic components with leads, 3 is a through hole, 4 is a via hole for heat transfer, For example, a conductive layer for an electric circuit made of copper foil, 6 is a heat transfer layer made of, for example, copper foil, 7 is a solder resist layer, 11 is a solder flow surface of the printed circuit board 10, and 12 is a non-flow of solder of the printed circuit board 10. Surface.

  The substrate 1 of the printed circuit board 10 of the present embodiment is made of, for example, glass epoxy resin, and penetrates through the solder non-flow surface 12 that is the upper surface of the printed circuit board 10 (substrate 1) and the flow surface 11 that is the lower surface. Then, the lead 2 of the electronic component with lead (not shown) is inserted, and the through hole 3 that is an electrical connection target, and the lead 2 of the electronic component with lead is not inserted, and the electrical connection is not performed. The heat transfer via hole 4 is provided for the purpose of heat transfer.

On the inner wall of the through-hole 3 and the non-flow surface 12 and the flow surface 11 in the vicinity of the opening of the through-hole 3, an electric circuit conductive layer 5 made of, for example, steel foil is formed. Further, a heat transfer layer 6 made of, for example, copper foil is similarly formed on the inner wall of the heat transfer via hole 4 and the non-flow surface 12 and the flow surface 11 near the opening. The electric circuit conductive layer 5 provided in the vicinity of the inner wall of the through-hole 3 and the opening is further extended from the opening, and constitutes an electric circuit by being connected to other electronic components. On the other hand, the heat transfer layer 6 provided in the vicinity of the inner wall and opening of the heat transfer via hole 4 is not connected to other electric circuits and is separated. The heat transfer layer 6 extends from the opening only on the non-flow surface 12 side, and is provided so as to surround the vicinity of the through-hole 3 that is a target for transferring heat, as shown in FIG. . Further, the electric circuit conductive layer 5 in the vicinity of the inner wall of the through hole 3 and the opening is left in an annular shape (the electric circuit conductive layer 5 in the vicinity of the opening left in the annular shape is called “land”), The other portions are coated with a solder resist layer 7 made of a resin called a solder resist, and have a structure in which the solder does not adhere to prevent a defect such as a short circuit in a portion where soldering is unnecessary.
On the other hand, all the heat transfer layers 6 of the heat transfer via holes 4 are coated with a solder resist layer 7 as shown in FIG.

  Next, a method for connecting the printed circuit board 10 and the leaded electronic component by the flow soldering method will be described. In general, after mounting electronic components with leads on the printed circuit board 10, the printed circuit board 10 is conveyed by a conveyor, a chemical called flux is applied to the entire flow surface 11 of the printed circuit board 10, and heated by a flow soldering device. The molten solder is brought into contact with the entire flow surface 11 of the printed circuit board 10 to fill the through hole 3 with the solder, and then cooled and solidified to connect the lead 2 of the electronic component with lead to the through hole 3. . The solder enters the through hole 3 and gets wet and filled from the flow surface 11 toward the non-flow surface 12, but the heat is taken away by the conductive layer 5 for electric circuit and the electronic components with leads, and the temperature of the solder is descend. When the temperature of the solder is lower than the melting point, the solder is solidified before the through hole 3 is filled with 100% of the solder, resulting in poor solder wetting.

  However, in the printed circuit board 10 of the present embodiment, heat is transferred to the non-flow surface 12 side near the through hole 3 through the heat transfer layer 6 provided in the heat transfer via hole 4, and the through hole 3 is cooled. It is possible to prevent solder solidification, that is, poor solder wetting. In particular, when the printed circuit board 10 is conveyed on the conveyor, a structure in which the heat transfer via hole 4 is provided on the upstream side with respect to the transfer direction of the printed board 10, that is, the heat transfer via hole 4 is more than the through hole 3. If the structure is such that the solder contacts the solder first, the solder will first contact the heat transfer via hole 4 and the heat will be effectively transferred to the through hole 3 in the passage of time through the flow soldering device. Can do.

  Further, even if the solder is immersed in the heat transfer via hole 4 for a relatively long time until the heat is conducted to the through hole 3, the heat transfer via hole 4 is covered with the solder resist layer 7, so that No solder jumps out of the flow surface 12 or solder balls are generated. As described above, the electronic component mounting board (printed circuit board 10) of the present embodiment is provided in the board 1, the through hole 3 for mounting electronic parts provided in the board 1, and the through hole 3 provided in the board 1. A heat transfer via hole 4 for transferring heat to the hole 3 and a heat transfer layer 6 provided from the inner wall of the heat transfer via hole 4 to the surface of the substrate 1. The heat transfer layer 6 is extended to the vicinity of the through hole 3. With such a configuration, heat is transferred to the through hole 3 on the non-flow surface 12 side through the heat transfer layer 6 extended to the vicinity of the through hole 3, and the heat is transferred well to the through hole 3. Cooling can be prevented and poor solder wetting can be prevented.

  A heat transfer layer 6 provided from the inner wall of the heat transfer via hole 4 to the surface of the substrate 1 is covered with a solder resist layer 7. Since the heat transfer via hole 4 is covered with the solder resist layer 7 as described above, heat is not transferred by directly filling the heat transfer via hole with solder as in the above-described prior art, but heated. By bringing the molten solder into contact with the heat transfer via hole 4, heat is transferred to the heat transfer layer 6, so that the solder does not wet the heat transfer via hole 4 toward the non-flow surface 12 side. Therefore, the through-hole 3 that is an object to be electrically connected to the lead 2 of the electronic component with lead can be heated without generating a solder ball, and good solder wettability of the through-hole 3 can be obtained.

  Further, a heat transfer via hole 4 is provided on the upstream side of the through hole 3 with respect to the transport direction of the substrate 1. Thus, heat can be effectively transferred to the through-hole 3 by the solder first contacting the heat transfer via hole 4 during the passage of time through the flow solder apparatus.

<< Embodiment 2 >>
2A is a cross-sectional view of the printed circuit board 10 before soldering according to the second embodiment of the present invention, FIG. 2B is a view of the printed circuit board 10 viewed from the non-flow surface 12, and FIG. ) Is a perspective view of the flow surface 11 viewed from the non-flow surface 12.

The present embodiment differs from the first embodiment in that only the flow surface 11 of the printed circuit board 10 extends the electric circuit conductive layer 5 to route the electric circuit. Further, the heat transfer layer 6 provided in the vicinity of the inner wall and the opening of the heat transfer via hole 4 is not connected to other electric circuits and is separated. And it is extended from the opening part of the via hole 4 for heat transfer only in the non-flow surface 12 side, and as shown in FIG.2 (b), it is provided so that the perimeter of the through hole 3 may be surrounded. Unlike the first embodiment, the structure in which the electric circuit conductive layer 5 of the present embodiment is extended only by the flow surface 11 can freely dispose the heat transfer layer 6 on the non-flow surface 12, and the through It becomes possible to surround the entire circumference of the hole 3.
The other configurations / actions / effects and the mechanism for filling the solder by the flow soldering method are the same as those in the first embodiment, and a description thereof will be omitted.

  Thus, in the present embodiment, the heat transfer layer 6 is arranged so as to surround the entire periphery of the through hole 3 on the non-flow surface 12. Thereby, the heat transfer effect to the through hole 3 which is an object to which the electronic component with leads is electrically connected can be further enhanced.

  Further, the electric circuit conductive layer 5 connected to the conductive layer provided on the inner wall of the through hole 3 is formed only on the flow surface 11 of the substrate 1. Thereby, the freedom degree which arrange | positions the heat-transfer layer 6 in the non-flow surface 12 increases. That is, when the electric circuit conductive layer 5 is extended on the non-flow surface 12, it is difficult to surround the entire circumference of the through hole 3 with the heat transfer layer 6 due to layout restrictions. Since the effect is insufficient, the heat transfer effect can be maximized by limiting the conductive layer for electric circuit to the flow surface 11 and the heat transfer layer 6 to the non-flow surface 12. In addition, the degree of freedom of arrangement of the heat transfer via holes 4 can be improved, and the above-described conventional layout restrictions when the heat transfer via holes 4 are provided in the vicinity of the through holes 3 can be eliminated.

<< Embodiment 3 >>
4A is a cross-sectional view of the printed circuit board 10 before soldering according to the third embodiment of the present invention, and FIG. 4B is a view of the printed circuit board 10 viewed from the non-flow surface 12.
The present embodiment differs from the first embodiment in that the heat transfer layer 6 provided on the inner wall and the opening of the heat transfer via hole 4 is different from the electric circuit conductive layer 5 on the non-flow surface 12. It is connected and constitutes an electric circuit.

  The other configurations / actions / effects and the mechanism for filling the solder by the flow soldering method are the same as those in the first embodiment, and a description thereof will be omitted. As an effect of the configuration in which the through hole 3 and the heat transfer via hole 4 of the present embodiment are connected, the heat transfer layer 6 is used to directly transfer the heat of the solder to the through hole 3. The temperature drop from the hole 4 to the through hole 3 is small, the through hole 3 can be heated more effectively, and the solder wet-up failure can be improved.

  Thus, in the present embodiment, the heat transfer layer 6 is connected to the conductive layer provided on at least the inner wall of the through hole 3 on the non-flow surface 12. Thus, by directly connecting the through hole 3 for connecting the lead 2 of the electronic component with lead and the via hole 4 for heat transfer with the heat transfer layer 6, the heat of the solder is further reduced and the effect on the through hole 3 is further reduced. The heat transfer effect to the through hole 3 can be enhanced.

  Further, the heat transfer layer 6 is covered with the solder resist layer 7, leaving a part of the conductive layer provided on the non-flow surface 12 near the opening of the through hole 3 in an annular shape. As a result, the solder does not wet the heat transfer via hole 4 toward the non-flow surface 12 side, and the through hole 3 can be heated without generating a solder ball, thereby obtaining good solder wettability. Can do.

<< Embodiment 4 >>
5A is a cross-sectional view of the printed circuit board 10 before soldering according to the fourth embodiment of the present invention, and FIG. 5B is a view of the printed circuit board 10 as seen from the non-flow surface 12.
This embodiment differs from the first embodiment in that the heat transfer layer 6 provided on the inner wall of the heat transfer via hole 4 and the flow surface 11 and the non-flow surface 12 of the printed circuit board 10 is a solder resist layer. 7 is not covered. That is, in the present embodiment, the electric circuit conductive layer 5 in the vicinity of the inner wall of the through hole 3 and the opening is left in an annular shape, and the portions other than the heat transfer layer 6 of the heat transfer via hole 4 are solder resist layers. 7 coated.

  The other configurations / actions / effects and the mechanism for filling the solder by the flow soldering method are the same as those in the first embodiment, and a description thereof will be omitted. In the present embodiment, even if the solder wets the heat transfer via hole 4 and the solder jumps to the non-flow surface 12, the solder is trapped by the solder getting wet to the heat transfer layer 6 of the heat transfer via hole 4. Therefore, the generation of solder balls can be prevented (the solder balls are not generated by joining with the heat transfer layer 6).

  As described above, in the present embodiment, the heat transfer layer 6 provided from the inner wall of the heat transfer via hole 4 to the surface of the substrate 1 is not covered with the solder resist layer 7, and the solder wets up. . In this structure, even if the solder wets the heat transfer via hole 4 and jumps out to the non-flow surface 12, it is trapped by the solder getting wet on the heat transfer layer 6 around the heat transfer via hole 4 (heat transfer). Therefore, the generation of solder balls can be prevented.

<< Embodiment 5 >>
6A is a cross-sectional view of the printed circuit board 10 before soldering according to the fifth embodiment of the present invention, and FIG. 6B is a view of the printed circuit board 10 viewed from the non-flow surface 12.
The present embodiment is different from the first embodiment in that the electric circuit conductive layer 5 on the non-flow surface 12 in the vicinity of the opening of the through hole 3 is covered with the solder resist layer 7.

  The other configurations / actions / effects and the mechanism for filling the solder by the flow soldering method are the same as those in the first embodiment, and a description thereof will be omitted. In the present embodiment, the solder resist layer 7 is applied to the non-flow surface 12 of the through hole 3, so that no solder fillet is formed on the non-flow surface 12 of the through hole 3. It is possible to prevent certain lift-off, that is, solder fillet peeling and land peeling.

  Thus, in the present embodiment, the conductive layer on the non-flow surface 12 near the opening of the through hole 3 is covered with the solder resist layer 7. In this way, the solder resist layer 7 is also formed on the conductive layer (land) of the opening on the non-flow surface 12 side of the through hole 3 to be electrically connected to the lead 2 of the electronic component with lead, thereby preventing non-flow. The solder fillet is not formed on the surface 12, and the occurrence of poor soldering quality such as lift-off (solder fillet peeling) and land peeling when lead-free solder is used for the solder can be prevented.

<< Embodiment 6 >>
FIGS. 7A and 7C are cross-sectional views of the printed circuit board 10 before soldering according to the sixth embodiment of the present invention, and FIG. 7B is a diagram showing a preheating plate used in the preheating process. (D) is a figure which shows the plate for soldering used for a soldering process.
In (b), 21 is a preheating plate made of, for example, stainless steel, 23 is a nozzle for solder jet, 25 is solder that has been heated and melted, and in FIG. Nozzle for use.

  In this embodiment, a local flow soldering method is used. Two plates are used, and a preheating plate 21 and a soldering plate 22 are used. The preheating plate 21 shown in FIG. 7B is provided with a nozzle 23 through which molten solder 25 is jetted at a position corresponding to the heat transfer via hole 4, and is used for soldering as shown in FIG. The plate 22 is provided with a nozzle 24 for jetting molten solder 25 at a position corresponding to the through hole 3.

Next, the soldering procedure will be described.
After mounting electronic components with leads on the printed circuit board 10, a chemical called flux is applied to the non-flow surface 12 of the printed circuit board 10 and heated using a halogen heater or the like. Next, the printed circuit board 10 is conveyed onto the preheating plate 21, and the molten solder 25 jetted from the nozzle 23 is brought into contact with the heat transfer via hole 4. Then, the through hole 3 can be preheated through the heat transfer layer 6.

  Thereafter, the printed circuit board 10 is conveyed onto the soldering plate 22, the molten solder 25 jetted from the nozzle 24 is brought into contact with the through hole 3, the solder 25 is filled in the through hole 3, and then cooled and solidified. At this time, since the through hole 3 is sufficiently heated, it is possible to obtain an effective rigid solder wettability.

  When such a method (sequence) is used, the time for the molten solder 25 to contact the via hole 4 for heat transfer and the through hole 3 can be determined by a program, so that the preheating time can be freely controlled. The target effective solder wet-up property can be ensured.

  Further, since the positions of the nozzles 23 and 24 through which the molten solder 25 for heating the heat transfer via holes 4 and the through holes 3 are jetted can be freely arranged, the heat transfer via holes 4 are arranged at appropriate positions. The layout restriction of the above-described prior art in which the heat transfer via hole 4 is provided in the vicinity of the through hole 3 can be eliminated.

  As described above, in the electronic component mounting method of the present embodiment, the substrate 1 (printed circuit board 10) is transferred onto the preheating plate 21 of the heat transfer via hole 4, and the solder melted in the heat transfer via hole 4 is used. And a step of bringing the substrate 1 onto the soldering plate 22 of the through hole 3 and bringing the molten solder 25 into contact with the through hole 3. Before soldering the through hole 3 that is the electrical connection target in the second procedure, the heat transfer layer 6 including the heat transfer via hole 4 is preheated in the first procedure in advance, so that the through hole 3 is formed. It can effectively preheat. In addition, since the preheating is performed on the heat transfer via hole 4 covered with the solder resist layer 7 and the through hole 3 provided with the conductive layer for trapping the solder, the solder is brought into contact with a relatively long time for the preheating. However, since there is no solder ball or solder jump-out, the preheating time can be set longer and the degree of freedom in the preheating time can be improved. In addition, it is possible to eliminate the limitations of the prior art processes that would not be effective unless the heat transfer via hole 4 and the through hole 3 are heated simultaneously in a short time of soldering.

  The electronic component mounting apparatus (solder flow apparatus) used in the present embodiment includes a preheating plate 21 for the heat transfer via hole 4 and a soldering plate 22 for the through hole 3. The above mounting method can be easily implemented by such a mounting apparatus.

The preheating plate 21 is provided with a nozzle 23 through which molten solder 25 is jetted at a position corresponding to the heat transfer via hole 4, and the soldering plate 22 is melted at a position corresponding to the through hole 3. A nozzle 24 through which the solder 25 is jetted is provided. Since the positions of the nozzles 23 and 24 through which the solder for heating the heat transfer via holes 4 and the through-holes 3 flow can be freely arranged, the heat transfer via holes 4 can be arranged at arbitrary positions and the layout can be freely set. The degree can be improved.
In addition, since the preheating time can be freely controlled in the program of the mounting apparatus according to the present embodiment, it is possible to ensure the effective solder wet-up property of the target through hole 3.

  Next, effects of the printed circuit board 10 and the mounting method of the first embodiment will be described. FIG. 8 shows a temperature profile a in which the heat transfer via hole 4 is heated by the preheating plate 21 of the sixth embodiment using the printed circuit board 10 of the first embodiment, and heat transfer without using the present invention. It is a figure which compares and shows the temperature profile b which is not heating the via hole 4 for an object. The temperature measurement point is an opening on the non-flow surface 12 side of the through hole 3.

  FIG. 9 is a diagram showing a comparison of the filling rate of the solder 25 in the through hole 3 when 3 seconds have elapsed after the soldering of the lead. (A) When the heat transfer via hole 4 is preheated and then soldered (in the case of temperature profile a in FIG. 8), (b) is when the heat transfer via hole 4 is soldered without preheating ( (Temperature profile b in FIG. 8).

  As shown in FIG. 8, the temperature profile a reaches 200 ° C. in 3 seconds. Here, 200 ° C. is generally a temperature necessary for the solder 25 to be 100% filled in the through hole 3 as shown in FIG. That is, if the opening on the non-flow surface 12 side of the through hole 3 does not reach 200 ° C., the solder 25 is not 100% filled. On the other hand, since the temperature profile b reaches only 180 ° C. in 3 seconds, the filling rate into the through hole 3 is about 67% as shown in FIG. 9B. Therefore, the solder wet-up effect in the through-hole 3 by this sequence is + 50%. Moreover, since it takes 4.5 seconds to reach 200 ° C., the difference is 1.5 seconds, which also shows that the effect of this sequence is great.

  The embodiment described above is described in order to facilitate understanding of the present invention, and is not described in order to limit the present invention. Therefore, each element disclosed in the above embodiment includes all design changes and equivalents belonging to the technical scope of the present invention.

(A) is sectional drawing of the printed circuit board before soldering of Embodiment 1 of this invention, (b) is the figure which looked at the printed circuit board from the non-flow surface of the solder. (A) is sectional drawing of the printed circuit board before soldering of Embodiment 2 of this invention, (b) is the figure which looked at the printed circuit board from the non-flow surface of the solder. (C) is the perspective view which looked at the flow surface of Embodiment 2 of this invention from the non-flow surface. (A) is sectional drawing of the printed circuit board before soldering of Embodiment 3 of this invention, (b) is the figure which looked at the printed circuit board from the non-flow surface of the solder. (A) is sectional drawing of the printed circuit board before soldering of Embodiment 4 of this invention, (b) is the figure which looked at the printed circuit board from the non-flow surface of solder. (A) is sectional drawing of the printed circuit board before soldering of Embodiment 5 of this invention, (b) is the figure which looked at the printed circuit board from the non-flow surface of the solder. (A), (c) is sectional drawing of the printed circuit board before soldering of Embodiment 6 of this invention, (b) is a figure which shows the plate for preheating used for a preheating process, (d) is It is a figure which shows the plate for soldering used for a soldering process. Using the printed circuit board of the first embodiment of the present invention, the temperature profile a in which the heat transfer via hole is heated by the preheating plate of the sixth embodiment, and the heat transfer via hole is heated without using the present invention. It is a figure which compares and shows the temperature profile b which has not been performed. FIG. 5 is a diagram showing a comparison of the filling rate of solder in the through-hole when 3 seconds have elapsed after the soldering of the lead, in which (a) shows a case in which the heat transfer via hole is preheated and then soldered (of the temperature profile a). Case), (b) shows the case of soldering (temperature profile b) without preheating the via hole for heat transfer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Board | substrate 2 ... Lead 3 ... Through-hole 4 ... Heat transfer via hole 5 ... Electric circuit conductive layer 6 ... Heat transfer layer 7 ... Solder resist layer 10 ... Printed circuit board 11 ... Flow surface 12 ... Non-flow surface 21 ... Residual heat plate 22 ... Soldering plates 23, 24 ... Nozzle 25 ... Solder

Claims (11)

A substrate,
A through hole for mounting an electronic component provided on the substrate;
A heat transfer via hole provided in the substrate for transferring heat to the through hole;
A heat transfer layer provided on an inner wall of the via hole for heat transfer and provided along both sides of the substrate;
Of the heat transfer layer, the heat transfer layer provided on the solder flow surface side of the substrate is provided from the inner wall to the vicinity of the opening of the heat transfer via hole,
The heat transfer layer provided on the solder non-flow surface side of the substrate is extended closer to the through hole than the heat transfer layer provided on the solder flow surface side. PCB for component mounting.   2. The electronic component mounting substrate according to claim 1, wherein a heat transfer layer provided along both surfaces of the substrate from an inner wall of the heat transfer via hole is covered with a solder resist layer.   3. The electronic component mounting board according to claim 1, wherein the heat transfer layer is disposed so as to surround the entire periphery of the through hole on the non-flow surface.   4. The electronic component mounting board according to claim 1, wherein the heat transfer layer is connected to a conductive layer provided on at least an inner wall of the through hole on the non-flow surface.   5. The electron according to claim 4, wherein the heat transfer layer is covered with a solder resist layer, leaving a part of the conductive layer provided on the non-flow surface near the opening of the through hole in an annular shape. PCB for component mounting.   2. The electronic component mounting substrate according to claim 1, wherein a heat transfer layer provided along both surfaces of the substrate from an inner wall of the heat transfer via hole is not covered with a solder resist layer.   7. The electronic component mounting substrate according to claim 1, wherein the conductive layer on the non-flow surface in the vicinity of the opening of the through hole is covered with a solder resist layer.   8. The electronic component mounting board according to claim 1, wherein the heat transfer via hole is provided upstream of the through hole with respect to the transport direction of the board. In the electronic component mounting method of the electronic component mounting substrate according to any one of claims 1 to 8,
Transporting the substrate onto a preheating plate for the heat transfer via hole, bringing the molten solder into contact with the heat transfer via hole, and transporting the substrate onto the through hole soldering plate; And a step of bringing the molten solder into contact with the through hole. In the electronic component mounting apparatus used for the electronic component mounting method according to claim 9,
An electronic component mounting apparatus comprising: a preheating plate for the heat transfer via hole; and a soldering plate for the through hole. The preheating plate is provided with a nozzle through which molten solder is jetted at a position corresponding to the heat transfer via hole,
11. The electronic component mounting apparatus according to claim 10, wherein the soldering plate is provided with a nozzle for jetting molten solder at a position corresponding to the through hole.

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