JP2008066741A - Electronic equipment and method of packaging electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent island lifting at low cost even if unleaded solder is used. <P>SOLUTION: The tip of the lead 22 of an electronic component 20 protruded from the surface of a wiring board 110A has a length that is a half of the radius of the island 15 of the wiring board 110A. The tip of the lead 22 needs not to be protruded from the surface of the wiring board 110A. In this case, the length of the tip of the lead 22 protruded therefrom is zero or a negative value. When the lead 22 is inserted into a through hole 14 of the wiring board 110A, the length of the tip of the lead 22 protruded therefrom is made a half that of the radius of the land 15. The through hole 14 and the lead 22 are bonded with unleaded solder 32 in this state. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to an electronic device using a wiring board, and particularly to an electronic device using a wiring board for mounting an electronic component using lead-free solder.
The present invention also relates to an electronic component mounting method, and more particularly, to an electronic component mounting method for mounting an electronic component using lead-free solder on a wiring board.

A configuration example of a conventional wiring board will be described with reference to FIG. A copper-clad laminate 11 is used for the conventional wiring board 110A shown in FIG. The copper-clad laminate 11 is formed by impregnating a paper base material, a glass base material or a polyester fiber base material with an epoxy resin, a phenol resin or the like to form an insulating sheet, and a copper foil is formed on the surface of the insulating sheet. It is affixed by pressure and heat treatment.
A through hole 12 is formed at a predetermined location of the copper-clad laminate 11. The inner surface of the through hole 12 is covered with a conductive film (first conductive film) 13 connected to the copper foil on the surface of the copper-clad laminate 11. The conductive film 13 is formed, for example, by applying a catalyst to the inner surface of the through-hole 12, performing base plating by electroless copper plating, and electrolytic copper plating thereon. Hereinafter, the through hole 12 covered with the conductive film 13 is referred to as a through hole 14.

The copper foil on the surface of the copper-clad laminate 11 is etched, and a circular land (second conductive film) 15 and circuit wiring 16 connected to the land 15 are formed around the opening of the through hole 14. The land 15 and the circuit wiring 16 are formed on both surfaces of the substrate 11, but may be formed on one surface of the substrate 11. The land 15 is formed as small as possible within a range in which a minimum bonding strength can be secured in accordance with recent high-density mounting.
Portions other than the lands 15 such as the circuit wiring 16 on the surface of the copper-clad laminate 11 are covered with a solder resist 17. This solder resist 17 acts as a protective film that protects portions other than the lands 15 to be soldered from the tin-lead solder 31, and is formed by printing and applying a paste and then exposing it. Here, the solder resist 17 is formed so as not to cover the land 15 so as to prevent the formation of the fillet 31A of the tin-lead solder 31 as much as possible.

  A lead (conductive member) 22 drawn from the casing 21 of the electronic component 20 is inserted into the through hole 14 of the wiring board 110A having such a configuration, and the lead 22 is inserted into the through hole via the tin-lead solder 31 in this state. 14 is joined. At present, tin-lead eutectic solder (Sn63 wt%, remaining Pb, hereinafter referred to as Pb-63Sn) is most frequently used as the tin-lead solder 31. Since the tin-lead solder 31 plays a role of relieving the thermal expansion mismatch caused by the bonding of different substances, no connection failure particularly occurred at the bonding portion between the electronic component 20 and the wiring board 110A.

  However, in recent years, environmental pollution due to lead has become a problem due to an increase in environmental awareness, and the conversion from tin-lead solder 31 to lead-free solder containing no lead is progressing. This lead-free solder is a solder mainly composed of tin and made of silver, copper, zinc, bismuth, indium, antimony, nickel, germanium, or the like. The melting temperature of lead-free solder is 190 ° C. to 230 ° C., which is higher than the melting temperature of Pb-63Sn described above. Since the glass transition temperature of the epoxy-based material that is the main material of the wiring board 110A is 125 to 140 ° C., when Pb-63Sn that has been used in the past is converted to lead-free solder, the difference in solidification shrinkage temperature is widened and soldering is performed. The stress generated by the contraction of the substrate of the wiring board 110A that is sometimes expanded increases. In addition, lead-free solder has metal characteristics such as higher metal tensile strength and creep strength and less elongation compared to Pb-63Sn, so that stress relaxation at the soldered portion is less likely to occur. For these reasons, it has been clarified that when the electronic component 20 is mounted on the conventional wiring board 110 </ b> A using lead-free solder, land peeling that hardly occurs in the tin-lead solder 31 occurs frequently.

  When the conventional wiring board 110A is soldered using the lead-free solder 32, as shown in the photograph of FIG. 20A, the land 15 is peeled off from the substrate of the wiring board 110A, and the land 15 is lifted. At this time, the circuit wiring 16 connected to the land 15 is also lifted and pulled together, and thus receives excessive stress. After that, when a temperature cycle test that repeats overheating and cooling is performed for 200 cyc and the thermal stress is continuously applied, the boundary between the end of the land 15 and the circuit wiring 16 becomes large as shown in the photograph of FIG. Deforms and breaks. As can be seen from this verification experiment, when an electronic device is manufactured using the conventional wiring board 110A in which land peeling occurs as it is, the reliability of the electronic device is significantly reduced.

  On the other hand, Patent Document 1 describes one method for suppressing land separation. In the conventional wiring board 110B described in this publication, as shown in FIG. 21, the outer peripheral edge of the land 15 is covered with the extending portion 117A of the solder resist 117 so as to suppress the land peeling. is there.

JP 2001-332851 A

  However, for the existing off-the-shelf products that are not new products and have already been shipped, a wiring board that is not provided with a land stripping countermeasure, such as the conventional wiring board 110A shown in FIG. 19, is often used. ing. In the case where the electronic component of such a product breaks down and is repaired by replacing it with a new electronic component 21, if the new electronic component 21 is mounted on the wiring board 110A using the lead-free solder 32, land peeling occurs and the reliability is increased. It becomes a sexual problem.

Therefore, in order to suppress land peeling, it is also possible to discard the wiring board 110A that has not been subjected to land countermeasures and replace it with the conventional wiring board 110B shown in FIG. It is done. However, in order to newly manufacture the wiring board 110B, it is necessary to design a jig for printing and applying the paste to be the solder resist 117 in a predetermined pattern, and to actually form the solder resist 117 using this jig. It must be expensive. In addition, since the non-failed wiring board 110A is discarded, the waste is increased.
The problem of high cost in manufacturing the conventional wiring board 110B is a problem that occurs not only when repairing an existing product but also when manufacturing a new product.

  The present invention has been made to solve such problems, and an object of the present invention is to prevent land peeling at low cost even when lead-free solder is used.

In order to achieve such an object, in the electronic device of the present invention, the length of the tip of the conductive member of the electronic component that protrudes outward from the surface of the substrate of the wiring board is formed on the substrate of the wiring board. It is characterized by being 1/2 or less of the land radius.
The land portion is subjected to a force W that shrinks the substrate that has expanded during soldering and a vertical component Tsinθ of the tension T that accompanies the solidification shrinkage of the lead-free solder (θ is the fillet forming angle that is the angle between the fillet and the land). ,
Adhesion between land and substrate <W + Tsinθ
In this case, land peeling occurs. Since Tsinθ decreases as the fillet forming angle θ decreases, the length of the conductive member of the electronic component that protrudes outward from the substrate surface is set to ½ or less of the land radius, and the height of the fillet is reduced. Becomes difficult to peel from the substrate.
Further, the adjustment of the length of the conductive member protruding from the substrate surface can be adjusted at a lower cost than newly forming the solder resist 117 in FIG. 21, and therefore, land stripping can be suppressed at a low cost.

Here, the tip of the conductive member may not protrude outward from the surface of the substrate.
In these electronic devices, a spacer may be provided between the wiring board and the electronic component. Since the position of the casing of the electronic component is increased by the height of the spacer, the length that the conductive member of the electronic component protrudes outward from the substrate surface is shortened.
Here, the spacer may cover at least a part of the outer peripheral edge of the land facing the electronic component. This makes it difficult for the land facing the electronic component to peel from the substrate.

In the electronic device of the present invention, when the conductive member of the electronic component is inserted into the through hole of the wiring board, at least one of the tip side and the base side is covered with a coating film as viewed from the portion facing the inner surface of the through hole. In other words, the coating film is formed of a material that is less reactive with lead-free solder than the material of the conductive member.
By inserting such a conductive member into the through-hole and taking out the part covered with the coating film from the substrate surface to the outside, lead-free solder does not wet and spread in the part covered with the coating film, A lead-free solder fillet is not formed between the conductive member and the land, and land peeling is suppressed.
Further, since the coating film can be formed at a lower cost than the new formation of the solder resist 117 in FIG. 21, the land peeling can be suppressed at a low cost.

In these electronic devices, the cross-sectional shape perpendicular to the longitudinal direction of the conductive member may be a circle, an oval, a square, a rectangle, a polygon, a cross, a star, or a deformation thereof.
Further, the lead-free solder may include tin-zinc solder, tin-silver solder, or tin-copper solder.

The electronic component mounting method according to the present invention allows the length of the tip of the conductive member protruding from the substrate surface of the wiring board to pass through when inserting the conductive member of the electronic component into the through hole of the wiring board. The first step of setting the radius of the land formed around the opening of the hole to be ½ or less, and in this state, the first conductive film and the conductive member in the through hole are joined via lead-free solder. And 2 steps.
In this electronic component mounting method, the first step may include a step of inserting a conductive member into the through hole in a state where a spacer is sandwiched between the wiring board and the electronic component.
Or you may further provide the process of shortening the length of an electroconductive member before a 1st process.

  In the electronic component mounting method of the present invention, the first covering the at least one of the leading end side and the base side of the conductive member with a coating film made of a material having a lower reactivity with lead-free solder than the conductive member material of the electronic component is provided. And a step of inserting the conductive member into the through hole of the wiring board and joining the first conductive film in the through hole and the portion not covered with the coating film by the conductive member via lead-free solder. And a process.

  As described above, in the present invention, the height of the fillet is reduced by making the length of the conductive member of the electronic component protruding outward from the substrate surface to be ½ or less of the land radius. Since T sin θ is also small, the land is difficult to peel off from the substrate. In addition, since it is only necessary to adjust the length of the conductive member protruding outward from the substrate surface, land stripping can be suppressed at a low cost.

  Further, in the present invention, at least one of the tip and base of the conductive member of the electronic component is covered with a coating film, and the portion covered with the coating film is exposed outside from the substrate surface, thereby covering with the coating film. Lead-free solder does not get wet and spread in the areas that are broken. Thereby, a fillet is not formed between a conductive member and a land, and land peeling is suppressed. In addition, since it is only necessary to form a coating film on the conductive member, land peeling can be suppressed at a low cost.

By suppressing land separation in this way, it is possible to improve the reliability of an electronic device including a configuration in which an electronic component is mounted on a wiring board at a low cost.
In particular, even in the case of repairs that replace existing electronic products that have already been shipped with existing non-new products, but are replaced with new electronic components, it is possible to perform repairs at low cost using lead-free solder. it can. In addition, it is possible to reuse a wiring board that has not failed without being discarded.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is an enlarged cross-sectional view illustrating a wiring board according to a first embodiment of the present invention and a partial structure of an electronic device configured by mounting electronic components on the wiring board. FIG. 2 is a plan view of the wiring board shown in FIG. 1 as viewed from the II-II ′ line direction. In these drawings, the same members as those shown in FIG. 19 are denoted by the same reference numerals as those in FIG.

As shown in FIGS. 1A and 2, the wiring board 10 includes a covering member 18 that covers the outer peripheral edge 15A of the circular land 15 formed on the surface of the wiring board 110A shown in FIG. is there. The length from the central axis of the through hole 14 to the inner peripheral edge of the covering member 18 is the opening radius of the covering member 18, and the length from the central axis of the through hole 14 to the outer peripheral edge of the land 15 is the radius of the land 15. The opening radius of the member 18 is slightly smaller than the radius of the land 15.
The covering member 18 is made of a material having heat resistance against the melting point of the lead-free solder 32 (for example, 216 to 217 ° C. in the case of Sn—Ag—Cu solder), for example, heat-resistant resin such as epoxy, heat-resistant silicone rubber, etc. Can be used. The wiring board 110A may be either a double-sided board or a multilayer board.

Next, the principle that land separation is suppressed when the electronic component 20 is mounted on the wiring board 10 using the lead-free solder 32 will be described.
As shown in FIG. 1 (b), when lead 22 pulled out from housing 21 of electronic component 20 is inserted into through hole 14 of wiring board 10 and soldered using lead-free solder 32, molten lead-free The solder 32 is blocked by the covering member 18 and does not spread over the land 15 to the outer peripheral edge 15A.

  Thereafter, when the molten lead-free solder 32 is cooled and solidified and contracted, for example, as shown in FIG. 3, a tension T is generated in a diagonally downward direction along the fillet 32A. Assuming that the angle formed between the fillet 32A and the land 15 is the fillet forming angle θ, a force of Tsin θ acts on the interface between the land 15 and the copper-clad laminated substrate 11, and a contraction force W of the substrate 11 acts on the upper direction. work. As described above, the molten lead-free solder 32 does not wet and spread on the land 15 to the outer peripheral edge 15 </ b> A, and Tsin θ works at a point P inside the outer peripheral edge 15 </ b> A of the land 15. The adhesion between the surface of the substrate 11 and the land 15 is the weakest at the outer peripheral edge 15A of the land 15, but since Tsinθ is not applied here, the land 15 is difficult to peel off from the substrate 11.

Further, since the peripheral edge portion 15A of the land 15 is not fixed by the lead-free solder 32, the land 15 can easily follow the thermal expansion and contraction of the substrate 11, and the land peeling hardly occurs.
Thus, by covering the outer peripheral edge 15A of the land 15 with the covering member 18, the land peeling that frequently occurs when the electronic component 20 is mounted using the lead-free solder 32 is suppressed, and the electronic device has a long life and high reliability. Can be manufactured. In addition, by using the covering member 18 that can be manufactured at a lower cost than newly forming the solder resist 117 in FIG. 21, it is possible to suppress the land peeling, and thus to manufacture a highly reliable electronic device with a long lifetime. .

  The mounting method of the electronic component 20 described above can be applied not only when a new product is manufactured, but also with a conventional off-the-shelf product that is not a new product, but the electronic component that has already been shipped breaks down, and the new electronic component The present invention can also be applied to repairs that are replaced with 20. In the latter case, when the wiring board 110A that does not have the covering member 18 is used as an off-the-shelf product, the new electronic component 20 may be mounted after the covering member 18 is newly added to the wiring board 110A. As a result, the wiring board 110 </ b> A used in the ready-made product can be repaired using the lead-free solder 32 without being discarded.

Next, the configuration of the covering member 18 will be further described.
The covering member 18 may cover at least a part of the outer peripheral edge of the land 15. Here, the covering member 18 may cover the entire outer periphery of the land 15, or covers only the portion of the outer periphery of the land 15 that is susceptible to solidification shrinkage of the lead-free solder 32. You may do it. For example, by covering only the portion of the outer peripheral edge of the land 15 that is connected to the circuit wiring 16, peeling at this portion can be suppressed, and cutting between the land 15 and the circuit wiring 16 can be prevented. The same effect can be obtained by covering only the portion of the outer peripheral edge of the land 15 that faces the portion connected to the circuit wiring 16. In addition, you may cover both the part connected to the circuit wiring 16 among the outer periphery of the land 15, and the part which opposes it.

  FIG. 2 shows an example in which the opening radius of the covering member 18 is slightly smaller than the radius of the land 15, but there is no upper limit on the overlapping width of the covering member 18 and the land 15. The covering member 18A may be configured to cover the entire area of the land 15 like the wiring board 10A. In addition, the state which mounted the electronic component 20 on the wiring board 10A using the lead-free solder 32 is shown in FIG.4 (b).

  Further, like the wiring board 10 </ b> B shown in FIG. 5A, the covering member 18 </ b> B may cover not only the entire area of the land 15 but also all the openings of the through holes 14. In this case, if the covering member 18 </ b> B is formed on the substrate 11 including the land 15 with a material capable of making a hole relatively easily, such as a heat-resistant adhesive tape, the covering member 18 </ b> B is formed by the leads 22 of the electronic component 20. The lead 22 can be inserted into the through hole 14 as it is. Thereafter, if soldering is performed, as shown in FIG. 5B, the fillet 32A is not formed on the side where the covering member 18B is formed (the upper side in FIG. 5B), and land peeling is suppressed. The

The reliability of the electronic device in which the electronic component 20 is mounted on the wiring board 10B shown in FIG. Here, a temperature cycle test was performed for 200 cyc under the same conditions as those of the conventional wiring board 110A described above. As a result, as shown in the photograph of FIG. 6, the lead-free solder 32 does not contact the land 15 and the fillet 32 </ b> A is not formed. Therefore, the occurrence of land peeling is not recognized, and the configuration shown in FIG. It was confirmed that there was an effect.
As shown in FIG. 5, when the opening of the through hole 14 is closed, the vaporized flux used for soldering may not easily come out of the through hole 14. A gap may be provided between the two.
The covering members 18, 18A and 18B in FIGS. 1, 4 and 5 may be left on the substrate 11 after soldering, or may be removed.

  The planar shape of the land 15 is not limited to a circle, and may be any of an oval, a polygon, a cross, a star, or a deformation thereof. Further, as shown in FIG. 7, a semicircular sub-brand 19 may be provided at a connection portion between the land 15 and the circuit wiring 16. By providing the sub-brand 19 to reduce the change in the width from the land 15 to the circuit wiring 16, the connection between the land 15 and the circuit wiring 16 can be further strengthened. Note that a subland may be formed on a land that is not circular, and the planar shape of the subland is not limited to a semicircular shape.

  As the lead-free solder 32, any of tin-zinc based solder, tin silver based solder, and tin copper based solder may be used. Here, the tin-zinc-based solder is a generic name of the ones whose characteristics are improved by changing the amount of zinc or adding other elements, centering on Sn-9.0 wt% Zn which is a eutectic composition of tin zinc. is there. A typical example is Sn-8.0Zn-3.0Bi. Tin-silver-based solder is a generic name for those whose characteristics are improved by changing the amount of silver or adding other elements, centering on Sn-3.5 wt% Ag, which is a eutectic composition of tin silver. Typical examples are Sn-3.0Ag-0.5Cu and Sn-3.5Ag-0.75Cu. The tin-copper-based solder is a generic name for improving characteristics by changing the amount of copper or adding other elements with Sn-0.7 wt% Cu being the eutectic composition of tin-copper. A typical example is Sn-0.7Cu-0.3Ag. The lead-free solder 32 may contain lead as an impurity to the extent that its properties do not change.

[Second Embodiment]
FIG. 8 is an enlarged cross-sectional view illustrating a wiring board according to a second embodiment of the present invention and a partial structure of an electronic device configured by mounting electronic components on the wiring board.
The thickness of the covering member is not particularly limited. As shown in FIG. 8, the thickness of the covering member 18C is set to be equal to the distance between the wiring board 10C and the casing 21 of the electronic component 20, and the wiring board 10C and the casing are formed. The space between the body 21 may be filled with the covering member 18C without a gap.
In this case, the stress acting between the lead 22 and the lead-free solder 32 of the electronic component 20 or between the lead-free solder 32 and the through hole 14 is reduced by using an elastic body such as heat-resistant silicone rubber for the covering member 18C. In addition, it is possible to prevent the lead-free solder 32 from peeling from the lead 22 or the through hole 14.

[Third Embodiment]
FIG. 9 is an enlarged sectional view showing a part of the structure of an electronic apparatus according to the third embodiment of the present invention. In this figure, the same members as those shown in FIG. 19 are denoted by the same reference numerals as those in FIG.
In the electronic device shown in FIG. 9A, the length of the leading end of the lead 22 of the electronic component 20 protruding from the surface of the wiring board 110A (hereinafter referred to as the protruding length) is the radius of the land 15 of the wiring board 110A. Or less than 1/2. As shown in FIG. 9B, the tip of the lead 22 may not protrude from the surface of the wiring board 110A. In this case, the protruding length of the lead 22 is 0 or a negative value.

In order to form such an electronic device, when the lead 22 is inserted into the through hole 14 of the wiring board 110A, the protruding length of the lead 22 is set to ½ or less of the radius of the land 15, and in this state, The lead 22 is joined via a lead-free solder 32.
When the molten lead-free solder 32 is cooled and solidified and contracted, as shown in FIG. 10, a tension T is generated obliquely downward along the fillet 32A. At this time, at the interface between the land 15 and the copper-clad laminate 11, a force of Tsinθ acts in the downward direction and a contraction force W of the substrate 11 acts in the upward direction. Tsin θ decreases as the fillet forming angle θ decreases, and the fillet forming angle θ decreases as the height h of the fillet 32B decreases. Therefore, by setting the protruding length of the lead 22 to ½ or less of the radius of the land 15 and reducing the height h of the fillet 32B, Tsinθ is reduced and the land 15 is difficult to peel from the substrate 11.

  The reliability of the electronic device shown in FIG. 9 was verified. Here, a temperature cycle test was performed for 200 cyc under the same conditions as those of the conventional wiring board 110A described above. As a result, as shown in the photograph of FIG. 11, the lead-free solder 32 comes into contact with the land 15 and the solder fillet 32B is formed, but the fillet forming angle θ is small as compared with FIGS. 20 (a) and (b). No land peeling is observed. Therefore, it was confirmed that the configuration shown in FIG. 9 is effective for land peeling.

Thus, by making the protrusion length of the lead 22 less than or equal to ½ of the radius of the land 15, land peeling that frequently occurs when the electronic component 20 is mounted using the lead-free solder 32 is suppressed, and the life is long and reliable. It becomes possible to manufacture an electronic device with high performance. Further, since the protrusion length of the lead 22 can be adjusted at a lower cost than newly forming the solder resist 117 in FIG. 21, it is possible to reduce the land peeling and to manufacture a highly reliable electronic device with a long lifetime at a low cost. realizable.
The mounting method of the electronic component 20 described above can be applied not only when a new product is manufactured, but also with a conventional off-the-shelf product that is not a new product, but the electronic component that has already been shipped breaks down, and the new electronic component The present invention can also be applied to repairs that are replaced with 20. As a result, the wiring board 110 </ b> A used in the off-the-shelf product can be repaired using the lead-free solder 32 without being discarded.

The cross-sectional shape perpendicular to the longitudinal direction of the lead 22 is not particularly limited, and may be any of a circle, an oval, a square, a rectangle, a polygon, a cross, a star, or a deformation thereof.
As the lead-free solder 32, any of tin-zinc based solder, tin silver based solder, and tin copper based solder may be used.
The protruding length of the lead 22 may be 1 mm or less.

[Fourth Embodiment]
FIG. 12 is an enlarged cross-sectional view showing a part of the structure of an electronic apparatus according to the fourth embodiment of the present invention.
In the electronic device shown in FIG. 12, a spacer 41 that is in contact with the entire surface of the housing 21 is sandwiched between the wiring board 110 </ b> A and the housing 21 of the electronic component 20. In order to form such an electronic device, first, a spacer 41 is arranged on the surface of the wiring board 110A, and the leads 22 of the electronic component 20 are inserted into the through holes 14 of the wiring board 110A via the spacer 41, and the leads What is necessary is just to join 22 and the through hole 14 via the lead-free solder 32.

  As can be seen from FIGS. 13A and 13B, by arranging the casing 21 of the electronic component 20 on the spacer 41, the position of the casing 21 is increased by the height of the spacer 41. The protruding length of the lead 22 is shortened. Therefore, by using the spacer 41 having a predetermined height, it is easy to adjust the protruding length of the lead 22 to be ½ or less of the radius of the land 15. As a result, it is the same as in the third embodiment that the effects of suppressing land separation and producing an electronic device having a long life and high reliability can be obtained.

Further, by providing the spacer 41 with the function of the covering member 18 described above and covering at least a part of the outer peripheral edge of the land 15 facing the housing 21, peeling of the land 15 facing the housing 21 can be suppressed. An effect is also obtained.
Note that the spacer 41 may be disposed so as to contact the entire surface of the housing 21 as shown in FIG. 12, or the spacer 42 may be disposed along the outer periphery of the housing 21 as shown in FIG. Good. In this case, it is necessary to separately provide the covering members 18, 18A to 18C in FIGS.
The material of the spacers 41 and 42 only needs to have heat resistance against the substrate surface temperature during soldering. For example, a heat resistant resin such as epoxy, heat resistant silicone rubber, or the like can be used.

[Fifth Embodiment]
FIG. 15 is an enlarged cross-sectional view showing a part of the structure of an electronic apparatus according to the fifth embodiment of the present invention.
In the electronic device shown in FIG. 15, as shown in FIGS. 16 (a) and 16 (b), the length of the lead 22 of the electronic component 20 is reduced, and the lead 23 of the electronic component 20A thus created is shown in FIG. As shown in c), it is inserted into the through hole 14 of the wiring board 110A and mounted. Alternatively, an electronic component 20A in which the length of the lead 23 is short may be used in advance. This facilitates the adjustment of the protrusion length of the lead 23 to be ½ or less of the radius of the land 15. As a result, it is the same as in the third embodiment that the effects of suppressing land separation and producing an electronic device having a long life and high reliability can be obtained.

  When the electronic component 20A is mounted on the wiring board 110A, the casing 21 of the electronic component 20A is brought into contact with the surface of the wiring board 110A so that the casing 21 acts in the same manner as the covering member 18 described above. Separation of the opposing land 15 is suppressed. However, when the housing 21 cannot be brought into contact with the surface of the wiring board 110A, such as when the housing 21 does not have heat resistance against the substrate surface temperature during soldering, the land 15 facing the housing 21 As a measure against peeling, for example, as shown in FIG. 17, it is necessary to separately provide a covering member 18B. In addition, you may provide the covering members 18, 18A, and 18C in FIG.

[Sixth Embodiment]
FIG. 18 is an enlarged cross-sectional view showing a part of the structure of an electronic apparatus according to the sixth embodiment of the present invention.
In the electronic device shown in FIG. 18, both the front end side and the base side are covered with the coating film 25 except for the central portion in the longitudinal direction of the lead 24 of the electronic component 20B. The central portion of the lead 24 corresponds to a portion facing the inner surface of the through hole 14 when the lead 24 is inserted into the through hole 14 of the wiring board 110A. The length of the central portion of the lead 24 is the length of the through hole 14. Same as the length.
The coating film 25 has heat resistance against the melting point of the lead-free solder 32 (for example, 216 to 217 ° C. in the case of Sn—Ag—Cu solder), and the reactivity with the molten solder is higher than the material of the lead 24. For example, a heat-resistant resin such as epoxy, a heat-resistant silicone rubber, or the like can be used. A heat-resistant adhesive tape may be wound around the lead 24 as the coating film 25.

The lead 24 on which the coating film 25 is formed is inserted into the through hole 14 of the wiring board 110A, and only the portion covered with the coating film 25 by the lead 24 is brought out of the wiring board 110A. In this state, the exposed portion that is not covered with the coating film 25 by the lead 24 and the conductive film 13 of the through hole 14 are joined via the lead-free solder 32. Thereby, the electronic device shown in FIG. 18 is completed.
In this electronic device, the surface of the lead 24 protruding outward from the surface of the wiring board 110A is covered with the coating film 25, and the lead-free solder 32 does not wet and spread in the portion covered with the coating film 25. Therefore, the fillet 32 </ b> A of the lead-free solder 32 is not formed between the lead 24 and the land 15. Accordingly, it is possible to manufacture an electronic device that suppresses land peeling and has a long life and high reliability. Further, since the coating film 25 can be formed at a lower cost than when the solder resist 117 shown in FIG. 21 is newly formed, it is possible to reduce the land peeling and to manufacture a highly reliable electronic device with a long lifetime at a low cost. it can.

The mounting method of the electronic component 20B described above can be applied not only when a new product is manufactured, but also with a conventional off-the-shelf product that is not a new product, but the electronic component that has already been shipped fails, and the new electronic component The present invention can also be applied to repairs that are replaced with 20B. As a result, the wiring board 110 </ b> A used in the off-the-shelf product can be repaired using the lead-free solder 32 without being discarded.
18 shows an example in which the coating film 25 is formed on both the distal end side and the base side of the lead 24. However, the coating film 25 is formed only on the distal end side or the proximal side of the lead 24. May be. In this case, it is necessary to take the land stripping countermeasures shown in the first to fifth embodiments in the direction where the coating film 25 is not formed.
Further, when the lead 24 is inserted into the through hole 14 of the wiring board 110A, only the boundary part between the part facing the inner surface of the through hole 14 and the part coming out of the wiring board 110A is covered with the coating film. Also good.

Examples of electronic devices to which the present invention can be applied include printers, facsimiles, LCD monitors, personal computers, large computers (including servers and supercomputers), exchanges, transmission devices, and base station devices.
In addition, the 1st-6th embodiment mentioned above may each be implemented independently, and may be implemented in combination with another form. Further, the present invention is not limited to the first to sixth embodiments, and it goes without saying that each embodiment can be appropriately changed within the scope of the technical idea of the present invention.

(A) is sectional drawing which expands and shows a part of structure of the wiring board which is the 1st Embodiment of this invention, (b) is comprised by mounting an electronic component in the said wiring board. It is sectional drawing which expands and shows the structure of some electronic devices. It is the top view which looked at the wiring board shown in FIG. 1 from the II-II 'line direction. It is a figure for demonstrating the principle by which land peeling is suppressed by the wiring board shown in FIG. 1, and has shown conceptually the III section in FIG. (A) is sectional drawing which shows the modification of the wiring board shown in FIG. 1, (b) is sectional drawing which shows the modification of the electronic device shown in FIG. (A) is sectional drawing which shows the other modification of the wiring board shown in FIG. 1, (b) is sectional drawing which shows the other modification of the electronic device shown in FIG. It is a cross-sectional photograph after implementing a temperature cycle test with respect to the wiring board and electronic device which were shown in FIG. It is a top view of the wiring board which has a sub-brand. (A) is sectional drawing which expands and shows a part of structure of the wiring board which is the 2nd Embodiment of this invention, (b) is comprised by mounting an electronic component in the said wiring board. It is sectional drawing which expands and shows the structure of some electronic devices. It is sectional drawing which expands and shows a part of structure of the electronic device which is the 3rd Embodiment of this invention, (a) shows the state from which the lead has come out from the surface of a wiring board, (b) It shows a state where no lead comes out from the surface of the wiring board. FIG. 10 is a diagram for explaining a principle that land peeling is suppressed by the electronic device illustrated in FIG. 9, and conceptually illustrates a portion X in FIG. 9. 10 is a cross-sectional photograph after performing a temperature cycle test on the electronic device shown in FIG. 9. It is sectional drawing which expands and shows a part of structure of the electronic device which is the 4th Embodiment of this invention. It is a figure for demonstrating the adjustment principle of the protrusion length of a lead, (a) shows the state where the spacer is not arrange | positioned between a wiring board and the housing | casing of an electronic component, (b) is a spacer arranged. It shows the state. FIG. 13 is a cross-sectional view illustrating a modification of the electronic device illustrated in FIG. 12, where (a) illustrates the entire structure, and (b) illustrates an enlarged part of the structure. It is sectional drawing which expands and shows a part of structure of the electronic device which is the 5th Embodiment of this invention. FIG. 16 is a cross-sectional view showing each manufacturing step of the electronic device shown in FIG. 15. FIG. 16 is a cross-sectional view illustrating a modified example of the electronic device illustrated in FIG. 15. It is sectional drawing which expands and shows a part of structure of the electronic device which is the 6th Embodiment of this invention. (A) is sectional drawing which expands and shows a part of structure of the conventional wiring board, (b) is sectional drawing which expands and shows a part of structure where the electronic component was mounted in the said wiring board. It is. It is the cross-sectional photograph of the land peeling confirmed by verification experiment, (a) shows an initial state, (b) has shown the state after a temperature cycle test. It is sectional drawing which expands and shows a part of structure of the conventional wiring board described in Unexamined-Japanese-Patent No. 2001-332851.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10,10A-10C, 110A ... Wiring board, 11 ... Copper-clad laminated board, 12 ... Through-hole, 13 ... Conductive film, 14 ... Through-hole, 15 ... Land, 15A ... Perimeter of land, 16 ... Circuit wiring, 17 ... Solder resist, 18 ... Coating member, 19 ... Subland, 20, 20A, 20B ... Electronic component, 21 ... Electronic component housing, 22-24 ... Lead, 25 ... Coating film, 32 ... Lead-free solder, 32A ... Lead-free solder fillet, 41 ... spacer.

Claims (11)

A substrate having a through hole, a first conductive film covering the inner surface of the through hole, and a second conductive layer formed around the opening of the through hole on the surface of the substrate and connected to the first conductive film A wiring board having a land made of the conductive film, a circuit wiring formed on the surface of the substrate and connected to the land, and the first conductive material inserted into the through hole of the wiring board. In an electronic device including an electronic component having a conductive member joined to a film via lead-free solder,
The length of the front-end | tip of the said electrically-conductive member protruded outside from the surface of the said board | substrate is 1/2 or less of the radius of the said land, The electronic device characterized by the above-mentioned. The electronic device according to claim 1,
The electronic device according to claim 1, wherein a leading end of the conductive member does not protrude outward from a surface of the substrate. The electronic device according to claim 1 or 2,
An electronic apparatus comprising a spacer disposed between the wiring board and the electronic component. The electronic device according to claim 3,
The said spacer covers at least one part of the outer periphery of the land facing the said electronic component, The electronic device characterized by the above-mentioned. A substrate having a through hole, a first conductive film covering the inner surface of the through hole, and a second conductive layer formed around the opening of the through hole on the surface of the substrate and connected to the first conductive film A wiring board having a land made of the conductive film, a circuit wiring formed on the surface of the substrate and connected to the land, and the first conductive material inserted into the through hole of the wiring board. In an electronic device including an electronic component having a conductive member joined to a film via lead-free solder,
When the conductive member is inserted into the through hole, at least one of the distal end side and the base side as viewed from the portion facing the inner surface of the through hole is covered with a coating film,
The coating film is formed of a material that is less reactive with the lead-free solder than the material of the conductive member. In the electronic device according to any one of claims 1 to 5,
The cross-sectional shape perpendicular to the longitudinal direction of the conductive member is a circular shape, an oval shape, a square shape, a rectangular shape, a polygonal shape, a cross shape, a star shape, or a deformation thereof. In the electronic device according to any one of claims 1 to 6,
The lead-free solder includes tin-zinc solder, tin-silver solder, or tin-copper solder. A substrate having a through hole, a first conductive film covering the inner surface of the through hole, and a second conductive layer formed around the opening of the through hole on the surface of the substrate and connected to the first conductive film In an electronic component mounting method for mounting an electronic component having a conductive member on a wiring board having a land made of a conductive film and a circuit wiring formed on the surface of the substrate and connected to the land,
A first step in which when inserting the conductive member into the through hole, the length of the tip of the conductive member protruding outward from the surface of the substrate is ½ or less of the radius of the land;
In this state, the electronic component mounting method comprising: a second step of joining the first conductive film in the through hole and the conductive member via lead-free solder. The electronic component mounting method according to claim 8,
The electronic component mounting method, wherein the first step includes a step of inserting the conductive member into the through hole in a state where a spacer is sandwiched between the wiring board and the electronic component. The electronic component mounting method according to claim 8,
An electronic component mounting method, further comprising a step of shortening the length of the conductive member before the first step. A substrate having a through hole, a first conductive film covering the inner surface of the through hole, and a second conductive layer formed around the opening of the through hole on the surface of the substrate and connected to the first conductive film In an electronic component mounting method for mounting an electronic component having a conductive member on a wiring board having a land made of a conductive film and a circuit wiring formed on the surface of the substrate and connected to the land,
A first step of covering at least one of the leading end side and the base side of the conductive member with a coating film made of a material whose reactivity with lead-free solder is lower than that of the conductive member;
The conductive member is inserted into the through hole, and the first conductive film in the through hole is joined to the portion not covered by the coating film with the conductive member via the lead-free solder. An electronic component mounting method comprising the steps of:

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