JP5109771B2 - Circuit module and manufacturing method thereof - Google Patents

Description

  The present invention relates to a circuit module used for a power supply circuit of an OA device such as a copying machine or a scanner, and a manufacturing method thereof.

  In recent years, office equipment such as copiers and scanners are required to be further reduced in size and speeded up in response to demands for improving office efficiency. In order to meet this need for higher speed, the power supply circuit itself is required to have higher power.

  As a result, it is required to reduce the size and increase the heat dissipation of the circuit module used for the power supply circuit.

  13A and 13B are cross-sectional views illustrating an example of a conventional circuit module.

  13A and 13B, a lead frame 3 is fixed on an aluminum base plate 1 via an insulating adhesive 2 to form a kind of heat dissipation structure. A power semiconductor 4 is mounted on the lead frame 3. On the other hand, the general electronic components 6 and the like that control the power semiconductor 4 are supported by the exterior portion 7 while being mounted on the plurality of circuit boards 5 a and 5 b, and are connected to a part of the lead frame 3 by the solder 8. .

  FIG. 13A shows a state in which the second circuit board 5b is further set on the first circuit board 5a fixed to the lead frame 3 with the solder 8 in advance. FIG. 13B shows a state where the second circuit board 5 b and the lead frame 3 are connected by lead-free solder 8. As shown in FIG. 13B, when the second circuit board 5b and the lead frame 3 are to be connected by the lead-free solder 8, the lead-free soldering heat is transmitted through the lead frame 3 to The lead-free soldering portion (for example, the portion indicated by the dotted line 9) between the circuit board 5a and the lead frame 3 is remelted (may be written as remelting), and the solder floats (or This causes problems such as solder cracking. Since this solder float occurs not on the circuit board 5b installed in a place where it can be seen with the naked eye, but on the circuit board 5a which is shadowed and hidden under the circuit board 5b, whether or not solder float has occurred Confirmation of this becomes extremely difficult.

  On the other hand, the market demands further reduction in the thickness of the circuit module, and the gap between the plurality of circuit boards 5a and 5b needs to be further narrowed. As a result, the lead of the upper circuit board (for example, the circuit board 5b) is required. During free soldering, solder floating tends to occur in the lower layer (or the inner layer, for example, the circuit board 5a).

  Such solder floating is particularly likely to occur with hand-free solder, especially lead-free solder (soldering using a machine or robot is also a kind of hand solder).

  Next, the problem in the case of using lead-free solder will be described with reference to FIGS. FIGS. 14A to 14C are cross-sectional views for schematically explaining the problems that occur specifically in lead-free solder.

  FIG. 14A is a cross-sectional view for explaining a problem portion generated at an interface with a land (not shown) of the circuit board 5a. In FIG. 14A, the problem portion 10a is sometimes called solder floating (or fillet peeling, lift-off).

  FIG. 14B is a cross-sectional view for explaining the problem portion 10 b generated at the interface with the lead frame 3. In FIG. 14B, the problem portion 10b may be called a crack or a crack other than the solder floating.

  FIG. 14C is a cross-sectional view illustrating a problem portion 10c generated near the center of the soldering portion. In FIG. 14 (C), the problem portion 10c is called “shrinkage nest” and is likely to occur, for example, in Sn—Ag-based lead-free solder. It is a phenomenon where a surface is exposed or a gap is formed at the interface.

  14A and 14B, the solder floating such as the problem portions 10a and 10b generated in the circuit board 5a and the shrinkage nest of the problem 10c are soldered to a circuit board (not shown) installed in the upper layer. It tends to occur sometimes.

  For example, the solder floating described in the problem portions 10a and 10b is a decrease in peeling at the interface between the solder fillet and the circuit board land, which is also called lift-off or fillet peeling, and has been pointed out as a problem peculiar to lead-free solder. Yes.

  The solder floating described in the problem parts 10a and 10b and the shrinkage nest described in the problem part 10c are likely to occur when the part once soldered is reheated and the lead-free solder is remelted. This is one of the issues affecting reliability and the like.

  Further, as described in FIGS. 14A to 14C, the first circuit board 5a in which the problem portions 10a to 10c are likely to occur is hidden behind the second board 5b. It is extremely difficult to optically (or inspect by visual inspection or the like) the presence or absence of the problem portions 10a to 10c.

For example, Patent Document 1 and Non-Patent Document 1 are known as prior art document information relating to the invention of this application.
Japanese Patent No. 3547333 Matsushita Electric Works Technical Report (Feb. 2003), pages 23-29

  However, as shown in FIGS. 14A to 14C, when a plurality of circuit boards are stacked on the heat dissipation board and electrically connected to each other, the soldering is already performed when the upper circuit board 5b is soldered. In the lower circuit board 5a, there is a possibility that problem portions 10a, 10b, 10c, etc. peculiar to lead-free solder due to remelting of the solder 8 or the like may occur.

  Therefore, in order to solve the above problems, the present invention provides a metal plate, a heat transfer layer including a sheet-like thermosetting resin and an inorganic filler provided thereon, and a lead frame fixed to the heat transfer layer. A plurality of connection terminals formed by bending a part of the lead frame from the heat transfer layer substantially perpendicularly, and the heat dissipation board is disposed substantially parallel to the one or more connection terminals. A circuit comprising: a first circuit board connected by a first circuit board; a heat radiating board; and a second circuit board installed between the first circuit board and the remaining one of the connection terminals. The module is a circuit module in which the second circuit board and the first circuit board are connected by mounting an inter-board connection terminal having a folded portion with lead-free solder.

  As described above, according to the present invention, by connecting connections between a plurality of circuit boards with inter-board connection terminals having folded portions, when soldering the upper circuit board, the lower layer part that has been soldered The lead-free solder in the soldered portion of the circuit board is not re-melted, and problems such as solder floating do not occur in the lower circuit board.

  Note that some of the manufacturing steps shown in the embodiment of the present invention are performed using a molding die or the like. However, the molding die is not shown unless it is necessary for explanation. Further, the drawings are schematic views and do not show the positional relations in terms of dimensions.

(Embodiment 1)
Hereinafter, as a first embodiment of the present invention, a structure of a circuit module in which the occurrence of solder floating is suppressed will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view illustrating a circuit module attached to a chassis. In FIG. 1, reference numeral 101 denotes a chassis, and the chassis 101 includes a housing and the like. Reference numeral 102 denotes a circuit module. By fixing the circuit module 102 to the chassis 101 with screws or the like (not shown), heat generated in the circuit module 102 is radiated to the chassis 101 or the like.

  Reference numeral 103 denotes a metal plate, 104 denotes a heat transfer layer, and 105 a and 105 b denote connection terminals. A part of a lead frame (not shown) embedded in the sheet-like heat transfer layer 104 is substantially perpendicular to the heat transfer layer 104. It is bent.

  Reference numeral 106 denotes a first circuit board, and 107 denotes a second circuit board. As the first and second circuit boards 106 and 107, printed wiring boards obtained by impregnating commercially available glass fibers with an epoxy resin can be used. Reference numeral 108 denotes lead-free solder, 109 denotes an inter-substrate connection terminal, and a heat dissipation structure is provided in a part or more of the inter-substrate connection terminal 109. By providing a heat dissipation structure (for example, a U-shaped portion in FIG. 1 or a U-shaped portion shown in FIG. 8 described later) over a part of the inter-substrate connecting terminal 109, the inter-substrate connecting terminal is provided in advance on the second circuit board 107. Even after one end of 109 is fixed by lead-free solder 108, the remaining one end of this inter-board connection terminal 109 can be soldered to the first circuit board 106, and in this soldering, the second circuit No solder floating occurs between the substrate 107 and the inter-substrate connection terminal 109. This is because by providing a folded portion (for example, the folded portion 121 shown in FIG. 8 to be described later) over a part of the inter-substrate connection terminal 109, the amount of heat that causes solder floating is not transmitted.

  The connection terminal 105 a is connected to the first circuit board 106, and the connection terminal 105 b is connected to the second circuit board 107 separately. The same connection terminal 105a, 105b does not electrically connect the first circuit board 106 and the second circuit board 107. This is to prevent solder floating (for example, FIGS. 14A and 14B).

  Reference numeral 110 denotes an odd-shaped part such as a transformer or a choke coil. Reference numeral 111 denotes a dotted line, and 112 denotes an opening. For example, by providing the opening 112 as shown by the dotted line 111 in the first circuit board 106, low profile mounting of the odd-shaped component 110 is realized.

  Further, in the circuit module 102 shown in FIG. 1, instead of a single large circuit board, a plurality of circuit boards such as the first and second circuit boards 106 and 107 are provided with inter-substrate connection terminals 109 in the thickness direction. Used to laminate and connect. This is because, as shown in FIG. 1, a plurality of circuit boards are stacked and connected in the thickness direction using inter-substrate connection terminals 109 to reduce the size of the circuit module 102 and to take measures against noise.

  As shown in FIG. 1, mounting positions of various electronic components (for example, signal processing semiconductor elements and chip components, both not shown in FIG. 1) mounted on the first and second circuit boards 106 and 107. To optimize. For example, in the case of an electronic component for which ESL (equivalent series inductance) is a problem, mounting on the second circuit board 107 side provides a lower inductance than when mounting on the first circuit board 106, so that Stabilization (for example, the cleanliness of the electric signal) becomes possible.

  Further, an electronic component or the like whose temperature rise is a problem is mounted on the first circuit board 106 side, so that a thermal effect from a heat generating component (not shown) directly fixed to the lead frame on the heat transfer layer 104 is obtained. Can be suppressed. In addition, the influence of noise on the first circuit board 106 is suppressed by using the second circuit board 107 as a kind of noise blocking wall.

  As described above, the metal plate 103, the heat transfer layer 104 including the sheet-like thermosetting resin and the inorganic filler provided on the metal plate 103, and the lead frame (not shown) fixed to the heat transfer layer 104 A heat radiating board (for example, a heat radiating board 113 in FIG. 2 described later) having a plurality of connection terminals 105a and 105b formed by bending a part of the lead frame substantially vertically from the heat transfer layer 104. The first circuit board 106, which is installed substantially parallel to the heat dissipation board and connected by a part of the connection terminals 105a (for example, one or more), the heat dissipation board, and the first circuit board 106 A circuit module 102 comprising a second circuit board 107 installed in between and connected by a connection terminal 105b (for example, a connection terminal 105b not connected to the first circuit board 106), The circuit module 102 is connected between the second circuit board 107 and the first circuit board 106 by mounting an inter-board connection terminal 109 having a folded portion with lead-free solder 108. Thus, a highly reliable circuit module 102 that can suppress the occurrence of solder floating or the like is provided.

  As described above, in FIG. 1, the first circuit board 106 (for example, the circuit board exposed to the outside on the surface layer side) and the second circuit board 107 (for example, the circuit board hidden on the shadow on the inner layer side) are provided. By using the inter-substrate connection terminal 109 having a heat dissipation structure at a part thereof, the heat of soldering of the first circuit board 106 is turned back (for example, described later) provided on the inter-substrate connection terminal 109. Therefore, the lead-free solder 108 in the second circuit board 107 is not remelted and the occurrence of solder floating can be prevented. As a result, the distance between the first circuit board 106 and the second circuit board 107 can be further reduced, and the circuit module 102 can be reduced in size, thickness, and height.

(Embodiment 2)
In the second embodiment, an example of an assembly method of the circuit module 102 described in the first embodiment will be described with reference to FIGS. 2 to 7, and by using the inter-substrate connection terminal 109, the remelting of solder is performed. A mechanism for preventing solder floating (or solder cracking) will be described.

  FIG. 2 is a cross-sectional view for explaining how the heat dissipation board is attached to the chassis 101 with screws or the like. In FIG. 2, 113 is a heat dissipation board, 114 is an arrow, and 115 is a screw.

  In FIG. 2, the heat dissipation substrate 113 includes a metal plate 103, a heat transfer layer 104 including a sheet-like thermosetting resin and an inorganic filler provided on the metal plate 103, and leads embedded in the heat transfer layer 104. A frame (not shown) and a part of the lead frame are constituted by connection terminals 105a and 105b which are bent substantially vertically from the heat transfer layer 104.

  A heat generating component (not shown) such as a deformed component 110 or a power semiconductor is mounted on the surface of the heat dissipation substrate 113. Thereafter, as shown by an arrow 114 in FIG. 2, the screw 115 or the like is used to fix the chassis 101 or the like. In FIG. 2, holes for inserting screws 115 are not shown in the metal plate 103 and the chassis 101.

  In FIG. 2, the screw 115 is illustrated as being inserted from the heat dissipation board 113 side, but the insertion direction is not limited to this, and the reverse direction of the arrow 114 in FIG. 2 (from the chassis 101 side), A screw 115 may be inserted.

  FIG. 3 is a cross-sectional view illustrating the heat dissipation board 113 attached on the chassis 101. In FIG. 3, 116 is a hole. Further, the mounting screw 115 and the like are not shown.

  As shown in FIG. 3, the second circuit board 107 is set on the connection terminals 105a and 105b (in the second circuit board 107, through holes into which the connection terminals 105a and 105b and the like are inserted are not shown). A dotted line 111 in FIG. 3 indicates a set position of the second circuit board 107. After the second circuit board 107 is inserted as indicated by an arrow 114a, the inter-board connection further having a folded portion thereon. The terminal 109 is inserted into the hole 116 as shown by an arrow 114b (note that the hole 116 is not shown in FIGS. 1, 2, 4, 5, etc.), and these are soldered by lead-free solder 108.

  Furthermore, the inter-substrate connection terminal 109 can be mounted on the second circuit board 107 with lead-free solder 108 after the second circuit board 107 is fixed and then soldered by hand solder (or robot solder, etc.). (For example, FIG. 1 corresponds to after soldering), and it is possible to cope with the inter-substrate connecting terminals having a complicated shape. Further, since the soldering surface is the upper surface, it is easy to inspect the appearance of the soldered portion.

  FIG. 4 is a cross-sectional view for explaining the state after the second circuit board 107 and the inter-substrate connection terminal 109 are fixed on the heat dissipation board 113 with lead-free solder 108. In FIG. 4, the second circuit board 107 and the connection terminal 105 b are connected by lead-free solder 108. Thus, by soldering both the inter-substrate connection terminal 109 and the connection terminal 105b at the same time (exposed surface) of the second circuit board 107, the workability is improved and the appearance of the soldered portion is improved. Inspection is also easy.

  Thereafter, the second circuit board 107 is set on the heat dissipation board 113 as shown by an arrow 114 and soldered.

  FIG. 5 is a cross-sectional view for explaining a state in which the second circuit board 107 is mounted on the heat dissipation board 113 with lead-free solder 108 and the first circuit board 106 is set. In FIG. 5, the connection terminal 105 a and the inter-substrate connection terminal 109 are inserted into through holes (not shown) provided in the second circuit board 107. Thereafter, these are connected to each other by lead-free solder 108, and the state shown in FIG. 1 is obtained. Since the inter-substrate connection terminal 109 is provided with a heat dissipation structure (the elastic portion 120 will be described with reference to FIG. 8 described later), the inter-substrate connection terminal 109 and the second circuit board 107 are soldered. However, since the lead-free solder 108 that connects the second circuit board 107 and the inter-substrate connection terminal 109 is not remelted by the heating temperature of the soldering, solder floating or the like does not occur.

  Next, an example of a method for manufacturing the heat dissipation substrate 113 will be described with reference to FIGS. 6 (A), 6 (B), and 7 (A), 7 (B).

  FIGS. 6A and 6B are cross-sectional views illustrating an example of a method for manufacturing the heat dissipation substrate 113.

  6A and 6B, 117 is a lead frame, and 118 is a heat transfer material.

  As the lead frame 117, it is desirable to use a member made of a metal plate having high thermal conductivity such as copper or aluminum. The thickness of the lead frame 117 is desirably 0.2 mm or more (preferably 0.3 mm or more). When the thickness of the lead frame 117 is less than 0.2 mm, the strength of the connection terminals 105a, 105b and the like is lowered, and there is a possibility that the lead frame 117 is bent or deformed during the operation.

  The thickness of the lead frame 117 is desirably 5.0 mm or less (preferably 3.0 mm or less). If the thickness of the lead frame 117 exceeds 5.0 mm, there is a possibility of affecting the fine patterning of the connection terminals 105a and 105b and the lead frame 117.

  In addition, even when a thick lead frame 117 is used (for example, 0.2 mm or more, preferably 0.3 mm or more) by embedding a part or more of the lead frame 117 in the heat transfer layer 104, the thickness is radiated. It does not appear as a step on the surface of the substrate 113.

  By preventing the occurrence of a step on the surface in this way, the solderability of the surface mount component can be improved. It can also be expected to suppress the generation of stress inside the solder caused by the step.

  Further, by preventing the occurrence of a level difference on the surface, the printability of a solder resist (not shown) on the lead frame 117 can be improved (the presence or absence of formation of the solder resist can be selected according to the application). Therefore, depending on the application, the formation of a solder resist may be unnecessary).

  Next, the heat transfer material 118 will be described. The heat transfer material 118 is made of, for example, a resin and a filler, so that the thermal conductivity can be increased. And the reliability is improved by using a thermosetting resin as resin.

  Here, as the inorganic filler, for example, it has a substantially spherical shape, and its diameter is suitably 0.1 μm or more and 100 μm or less (if it is less than 0.1 μm, it becomes difficult to disperse in the resin. 104 becomes thick and affects the thermal diffusivity). In this embodiment, the inorganic filler is a mixture of two types of alumina having an average particle diameter of 3 μm and an average particle diameter of 12 μm. By using alumina having two kinds of large and small particle diameters, it is possible to fill the gaps between the large particle diameters of alumina with small particle diameters, so that alumina can be filled at a high concentration to nearly 90% by weight. As a result, the thermal conductivity of these heat transfer layers 104 is about 5 W / (m · K).

  The inorganic filler is at least one selected from the group consisting of alumina, magnesium oxide, boron nitride, silicon oxide, silicon carbide, silicon nitride, and aluminum nitride, zinc oxide, silica, titanium oxide, tin oxide, and zircon silicate. It is desirable from the viewpoint of thermal conductivity and cost.

  In addition, when using a thermosetting resin, what contains at least 1 type of thermosetting resin chosen from the group of an epoxy resin, a phenol resin, cyanate resin, a polyimide resin, an aramid resin, and PEEK resin is desirable. This is because these resins are excellent in heat resistance and electrical insulation.

  The particle size of the inorganic filler such as alumina powder and the thermosetting resin are not necessarily limited to these, and those having high thermal conductivity may be selected.

  First, as shown in FIG. 6 (A), a heat transfer material 118 and a lead frame 117 are set on a metal plate 103 and indicated by an arrow 114 using a press or a die (both not shown). Thus, these are heated under pressure and integrated. Thus, the heat transfer material 118 is formed into a sheet-like heat transfer layer 104.

  Thus, as shown in FIG. 6B, a metal plate 103, a heat transfer layer 104 including a sheet-like thermosetting resin and an inorganic filler provided on the metal plate 103, and the heat transfer layer 104 A heat radiating substrate 113 including a fixed lead frame 117 is prepared.

  7A and 7B are cross-sectional views illustrating a state in which a part of the lead frame 117 is bent from the heat transfer layer 104 to form the connection terminal 105.

  As shown in FIG. 7A, a part of the lead frame 117 is bent so as to be substantially perpendicular to the heat transfer layer 104 to form the connection terminal 105. In this case, if necessary, a part of the lead frame 117 is peeled off from the heat transfer layer 104 to form the connection terminal 105, whereby the creepage distance between the metal plate 103 and the connection terminal 105 (in FIG. 7A). , The opening 112 is shown). In particular, it is effective to secure such a creepage distance for the primary circuit.

  In this way, a heat dissipation substrate 113 as shown in FIG. A dotted line 111 in FIG. 7B indicates the position of the step provided on each of the connection terminals 105a and 105b, and the first and second circuit boards 106 and 107 fixed on this by the step. Distinguish differences such as (not shown). Note that it is not desirable to connect the first circuit board 106 and the second circuit board 107 in a state where they are adjacent to each other by using the same connection terminal 105a in common. This is because there is a possibility that solder floating or the like as shown by the dotted line 9 in FIG. 13B or the problems 10a to 10c in FIGS. 14A to 14C may occur. Even if the connection terminals 105a and 105b are not adjacent to each other (for example, even if one lead frame pattern is raised at different positions), problems such as solder floating do not occur. . This is because heat at the time of soldering is dissipated by the intermediate heat transfer layer 103 or the like.

  Further, as shown in FIG. 1 and the like, it is desirable to connect the first circuit board 106 and the second circuit board 107 with an inter-substrate connection terminal 109 having a heat dissipation structure. This is because the second circuit board 107 and the inter-substrate connection terminal 109 are mounted with lead-free solder 108 in advance, and the second circuit board 107 is further mounted with lead-free solder 108. This is because the portion soldered first does not remelt. This is because the heat dissipation structure provided in the inter-substrate connection terminal 109 cools the soldering heat while it is transmitted to the previously soldered portion even when soldering is performed later.

(Embodiment 3)
In Embodiment 3, an example of the inter-substrate connection terminal 109 will be described. 8A and 8B show examples of cross-sectional views of the inter-substrate connection terminal 109. FIG. 8A and 8B, reference numerals 119a and 119b are both insertion portions, and are insertion portions into holes 116 (for example, the holes 116 in FIG. 3) formed in the circuit boards 106 and 107. Reference numeral 120 denotes an elastic portion, and 121 denotes a folded portion.

  By using the insertion portions 119a and 119b and the folded portion 121 as a portion (or mounting portion) to be soldered with lead-free solder 108, stress relaxation or heat dissipation by the inter-substrate connection terminal 109 can be achieved.

  Further, a part of the inter-board connection terminal 109 is inserted into the circuit boards 106 and 107 (not shown) (or the elastic portion 120 is directly pressed against the circuit board as shown in FIG. 9B described later). By doing so, the influence of external force on the circuit boards 106 and 107 (for example, prevention of peeling of the copper foil on the surface) is suppressed. In this case, the folded portion 121 and the elastic portion 120 both exhibit both effects of stress relaxation and heat dissipation.

  8A shows a part of a metal piece constituting the inter-substrate connection terminal 109 having a U-shape (or a shape in which the U-shape lies sideways), and FIG. 8B shows the inter-substrate connection terminal. A slit is formed in a part of a metal piece constituting 109, and both sides of the slit are opened (for example, a Chinese character “human character”).

  8A and 8B, an arrow 114a indicates that the inter-substrate connection terminal 109 (for example, the folded portion 121 and the elastic portion 120) can be elastically deformed, and an arrow 114b indicates the inter-substrate connection terminal 109 (for example, The elastic portion 120) has heat dissipation (including air cooling, thermal radiation, etc.).

  As shown in FIGS. 8A and 8B, it is desirable to provide an elastic portion 120 having an elastic structure over a part of the inter-substrate connection terminal 109. For example, in FIGS. 8A and 8B, the heat dissipating structure is U-shaped (or human-shaped) to form the elastic portion 120. Thus, the stress between the plurality of circuit boards 106 and 107 (for example, the generation of stress due to distortion between the circuit boards 106 and 107 and variations in parallelism) is also absorbed by the elastic portion.

  8A and 8B, the insertion portions 119a and 119b are provided on a lower circuit board (for example, the second circuit board 107 in FIG. 1) or an upper circuit board (for example, the first circuit board in FIG. 1). 1 may be an insertion portion into a hole formed in the circuit board 106). By doing so, the positioning accuracy of the inter-substrate connection terminal 109 is increased.

  It is desirable to use a metal spring material (or a contact material or a metal thin plate) having elasticity such as phosphor bronze for the inter-substrate connection terminal 109. This is because stress generated between a plurality of substrates can be absorbed by the inter-substrate connection terminal 109, and the lead-free solder 108 portion between the inter-substrate connection terminal 109 and the first and second circuit substrates 106 and 107. This is to reduce the stress generated in.

  Note that if the elasticity of the inter-substrate connection terminal 109 is too low, the insertability to the circuit boards 106 and 107 may be affected. Further, if the elasticity is too high, there is a possibility of causing stress on the circuit boards 106 and 107. In the experiments by the inventors, when the distance between the circuit boards 106 and 107 is 3 mm, the force when the distance is reduced by 0.3 mm (that is, deformation of 10% of the distance) is 1 gf (1 gram force, force is force) or more. , 250 gf or less (preferably 100 gf or less). If the spring is stronger than that, the circuit board may be affected. When the spring strength is less than 1 gf, the inter-substrate connection terminal 109 may be easily deformed. Here, 1 gf is a unit of force of a weight system based on a mass of 1 g.

  Needless to say, the strength of these springs can be optimized by the number and position of the springs.

  FIGS. 9A to 9C are a front view, a side view, and a cross-sectional view after mounting, respectively, of an inter-substrate connection terminal having a folded portion 121 at one or more ends. As shown in FIGS. 9A to 9C, by providing a folded portion 121 at one or more ends of the inter-substrate connection terminal 109, the folded portion can be a heat radiating portion or an elastic portion. .

  As shown by an arrow 114a in FIG. 9A, by making the insertion portion 119b thinner than other portions, the insertion property into the hole 116 is improved, and heat conduction (or heat transfer) through the insertion portion 119b is further improved. Reduce.

  FIG. 9B is a side view showing a state in which the folded portion 121 is provided at one or more ends of the inter-substrate connection terminal 109. As shown by an arrow 114b in FIG. 9B, the insertion portion 119b is shifted to the outside (for example, the elastic portion 120 side) from the center of the insertion portion 119a on the folded-back portion 121 side, so that FIG. As shown, the external force applied to the insertion portion 119b can be released to the circuit board 107 side via the elastic portion 120.

  FIG. 9C is a cross-sectional view illustrating a state in which the inter-substrate connection terminal 109 is used for connection between the first and second circuit boards 106 and 107. As shown in FIG. 9C, by using only one surface (or one direction) of the folded portion 121 and selectively mounting with lead-free solder 108, not only the elastic portion 120 but also the folded portion 121 It can function as an elastic structure part or a heat dissipation structure part. The external force can be directly transmitted to the circuit board 107 and the like via the elastic portion 120, and the influence on the wiring pattern (not shown) of the circuit board 107 is suppressed.

  FIGS. 10A to 10E are perspective views showing how the shape of the inter-substrate connection terminal 109 is devised. 10A to 10E, the folded portion 121 is not shown for easy explanation of the structure. As shown in FIG. 10A, the elastic portion 120 may be three-dimensional. And it is good also as the insertion parts 119a and 119b from which width differs on the upper and lower ends of the elastic part 120. FIG. By doing so, the insertability into the circuit boards 106 and 107 is improved.

  Note that the width of the insertion portion 119 into the circuit board on the upper layer side of the inter-substrate connection terminal 109 is narrowed (for example, narrowed by the amount indicated by the arrow 114a shown in FIG. 9A), or the tip is sharpened (or rounded). ) And the like are performed, so that the insertability is improved and the heat conduction between the insertion portion 119a and the insertion portion 119b is suppressed. This is because heat conduction is prevented by narrowing a part of the inter-substrate connection terminal 109.

  10B to 10E, the elastic portion 120 is deformed so that the inter-substrate connection terminal 109 absorbs external force (for example, twist, inclination, angle variation, etc. between the plurality of circuit boards 106 and 107). It is a perspective view explaining a mode to do. An arrow 114 shown in FIGS. 10B to 10E is an external force generated due to a shift of the circuit boards 106 and 107 or the like. The inter-board connection terminal 109 can absorb the external force indicated by the arrow 114 by deforming itself.

  FIGS. 11A to 11C are perspective views each showing a deviation or the like of the plurality of circuit boards 106 and 107. FIG. In FIGS. 11A to 11C, an arrow 114a indicates a twist (for example, an angle twist) between the plurality of circuit boards 106 and 107, and an arrow 114b indicates an interval variation. Such a dimensional variation is absorbed by the inter-substrate connection terminal 109 inserted at the location of the dotted line 111 or the like (it is not necessary to be limited to one location, and the inter-substrate connection terminal 109 may be mounted at a plurality of locations). It shows how it is done.

  Next, the reduction of solder floating by the heat dissipation structure of the inter-substrate connection terminal 109 will be described with reference to FIG.

  12A to 12C are cross-sectional views illustrating the effect of suppressing the occurrence of solder floating by the inter-substrate connection terminal 109 having the elastic portion 120. 12A to 12C, the arrow 114b indicates that the soldering heat is caused by the elastic part 120 (the elastic part 120 is shown in FIGS. 8 to 10 and the like) and the folding part 121 (the folding part 121 is shown in FIGS. 9 shows that the folded portion 121 is dissipated (or includes cooling and cooling) by being omitted in FIGS. As a result, in the lead-free solder 108, problems such as solder floating are suppressed.

  As described above, the inter-substrate connection terminal 109 is a circuit module 102 having an elastic structure (which can be reduced in size by being also used as the elastic portion 120) in a part or more thereof, thereby heating the device ( For example, power strain can be absorbed at the time of cooling (for example, the power is turned off) and at ambient temperature or the like, and the reliability of the device can be improved.

  Further, by using one or more materials such as a plate-like metal spring material or phosphor bronze for the inter-substrate connection terminal 109, the inter-substrate connection terminal 109 can be made highly accurate and reliable, and the circuit module. The reliability of 102 can be improved.

  The lead frame 117 can be a thick lead frame 117 by using the circuit module 102 embedded in the heat transfer layer 104 so that a part of the lead frame 117 is exposed to the outside.

  The circuit module 102 includes, for example, a metal plate 103, a heat transfer layer 104 including a sheet-like thermosetting resin and an inorganic filler provided thereon, a lead frame 117 fixed to the heat transfer layer 104, At least in the step of preparing the heat dissipation substrate 113, the step of installing a plurality of circuit boards 106, 107 substantially parallel to the heat dissipation substrate 113, and the electrical connection between the plurality of circuit boards 106, 107. One or more circuit board connecting terminals 109 may be connected (or mounted) by lead-free solder 108 to one or more circuit board connections.

  The lead-free solder 108 can be selected from, for example, Sn—Ag lead-free solder, Sn—Ag—Cu lead free solder, Sn—Ag—Cu—Bi lead free solder, and the like. Other lead-free solders may be used. This is because the present invention can prevent the occurrence of problems caused by solder floating and shrinkage nest solder.

  Further, by providing the folded portion 121 with an appropriate elasticity (or spring property), an effect of preventing a drop when inserted into the hole 116 formed in the second circuit board 107 can be obtained. In this way, by providing the folded portion 121 with a suitable elasticity (designing by computer simulation is useful for this purpose), etc., a drop prevention structure can be used to reduce the soldering cost of the inter-board connection terminal 109. Can be reduced.

  In addition, as a fall prevention structure, it is a folded portion 121 with appropriate elasticity, and a structure portion such as a bent portion of the tip of the fishing hook (sometimes called “aggu” or “chin”) if necessary. It may be provided.

  In this way, the folded portion 121 has a fall prevention structure, so that a surface-mounted component (various chip components or SMD components) mounted on the opposite surface with the surface where the inter-substrate connection terminal 109 is inserted facing down is provided. Then, the inter-substrate connection terminal 109 can be soldered at once with reflow soldering, and the effect of reducing the number of times of soldering can be obtained.

  As described above, various methods such as reflow soldering and flow soldering can be selected for soldering the inter-substrate connection terminal 109 to the circuit boards 106 and 107 as well as manual soldering (including robot soldering). Can meet your needs.

  As described above, the circuit module according to the present invention, the manufacturing method thereof, and the inter-substrate connection terminal used for the circuit module can increase the strength of the heat dissipation board. Therefore, a plurality of circuit boards are substantially parallel on the heat dissipation board. Thus, it is possible to prevent the occurrence of solder floating or the like when the layers are stacked while being spaced apart from each other by a certain distance, and it is possible to reduce the size and reliability of various devices.

Sectional drawing explaining the circuit module attached to the chassis Sectional drawing explaining a heat sink board being attached to a chassis with a screw etc. Sectional drawing explaining the heat sink mounted on the chassis Sectional drawing explaining the state after fixing the 2nd circuit board on the heat sink with solder Sectional drawing explaining a mode that the 1st circuit board was set, after mounting the 2nd circuit board with lead free solder on the heat dissipation board (A) (B) is sectional drawing explaining an example of the manufacturing method of a heat sink. (A) (B) is sectional drawing explaining a mode that a part of lead frame is bent from a heat-transfer layer, and it is set as a connection terminal. (A) and (B) are cross-sectional views of the inter-board connection terminals. (A)-(C) is a front view, a side view, and a cross-sectional view after mounting of inter-substrate connection terminals each having a folded portion at one or more ends. (A)-(E) are perspective views which show a mode that the shape of the connection terminal between board | substrates was devised together. (A) and (B) are perspective views showing misalignment of a plurality of circuit boards, and (C) is a top view. (A)-(C) is sectional drawing explaining the effect which suppresses generation | occurrence | production of solder floating by the board | substrate connection terminal which has a thermal radiation structure part together. (A) (B) is sectional drawing explaining an example of the conventional circuit module together FIGS. 4A to 4C are cross-sectional views schematically explaining problems that are peculiar to lead-free solder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Chassis 102 Circuit module 103 Metal plate 104 Heat-transfer layer 105a, 105b Connection terminal 106 1st circuit board 107 2nd circuit board 108 Lead-free solder 109 Inter-board connection terminal 110 Deformed part 111 Dotted line 112 Opening 113 Heat dissipation board 114 Arrow 115 Screw 116 Hole 117 Lead frame 118 Heat transfer material 119a, 119b Insertion part 120 Elastic part 121 Folding part

Claims (5)

A metal plate, a heat transfer layer including a sheet-like thermosetting resin and an inorganic filler provided thereon, a lead frame fixed to the heat transfer layer, and a part of the lead frame from the heat transfer layer A plurality of connection terminals bent substantially vertically, and a heat dissipation board,
A first circuit board that is installed substantially parallel to the heat dissipation board and connected by one or more of the connection terminals;
A circuit module comprising: a second circuit board installed between the heat dissipation board and the first circuit board and connected by one or more remaining connection terminals;
The circuit module which connects between the said 2nd circuit board and the said 1st circuit board by mounting the board | substrate connection terminal which has a folding | turning part with lead-free solder. The circuit module according to claim 1, wherein the inter-substrate connection terminal has an elastic structure in a part or more thereof. 2. The circuit module according to claim 1, wherein at least one of a plate-shaped metal spring material and phosphor bronze is used for the inter-substrate connection terminal. The circuit module according to claim 1, wherein at least one of the inter-board connection terminals is mounted on the circuit board via at least one or more folded portions. Preparing a heat radiating substrate comprising a metal plate, a heat transfer layer including a sheet-like thermosetting resin and an inorganic filler provided thereon, and a lead frame fixed to the heat transfer layer;
Installing a plurality of circuit boards substantially parallel to the heat dissipation board;
In the electrical connection between the plurality of circuit boards, a step of connecting one or more folded portions of the inter-board connection terminals with lead-free solder to the connection of at least one of the circuit boards;
A method for manufacturing a circuit module.

Images