JP2001177038A - Wiring board with lead pin and electronic component with lead pin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide wiring board and electronic component with lead pins, with which a lead pin can be bonded with a favorable strength even to a wiring board using an insulating substrate with unfavorable heat resistance. SOLUTION: This electronic component is equipped with an insulating substrate, a plurality of wiring conductors 9, 10 formed on a surface of the insulating substrate and/or inside thereof, a land 12 formed on a lower surface of the insulating substrate and a lead pin 5 whose head portion 5a is soldered to the land 12. The lead pin 5 is provided with a C surface and an R surface in the periphery 5c of the head portion 5a on the head top side. The Young's modulus of a shaft portion 5b is 30-80 GPa. Even when a brazing filler material 14 having a low melting point is used for the wiring board 4 having unfavorable heat resistance, a favorable bonding strength equal to a stretch in a perpendicular direction is obtained for a stretch of the lead pin 5 in an oblique direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an input / output device suitably used for an electronic component storage package or an electronic device for mounting or housing a semiconductor device such as a semiconductor integrated circuit device or an electronic component such as a hybrid integrated circuit. A so-called pin grid array (Pin
The present invention relates to a grid board (hereinafter abbreviated as PGA) type wiring board with lead pins and an electronic component with lead pins using the same.

[0002]

2. Description of the Related Art Conventionally, in a PGA type wiring board with lead pins, input / output terminals can be taken out in a planar arrangement by arranging the lead pins in, for example, a grid-like arrangement. Since a relatively sufficient pitch between terminals can be secured without increasing the external dimensions of the substrate, electronic components such as various semiconductor devices such as semiconductor integrated circuit devices such as MPU (Micro Processing Unit) are mounted and accommodated. It is widely used as an electronic component storage package, or an electronic component or electronic device on which such electronic components are mounted.

[0003] Alumina ceramics and the like are generally used as insulating substrates constituting such wiring boards and electronic parts.
An inorganic material based on an inorganic material composed of various ceramics such as aluminum nitride ceramics as a main component of the insulating layer, an organic resin such as epoxy resin or BT (dismaleide-triazine) resin, or a glass-epoxy resin composite base material; Alternatively, it is roughly classified into an organic material-based material containing an organic material such as a composite base material in which an inorganic material filler of various ceramics is bonded with a thermosetting resin such as an epoxy resin as a main component of the insulating layer.

[0004] Among them, the wiring board with lead pins of an inorganic material system can easily form a multi-layered insulating layer constituting an insulating board, and electrically connects a wiring conductor layer between insulating layers and a wiring conductor layer between different layers as a wiring conductor. A through-hole conductor such as a via-hole conductor connected to the substrate can be easily formed, and a so-called nail head type lead pin head is formed on a lead pin bonding land formed by being electrically connected to a wiring conductor on the lower surface of the substrate. By abutting the top of the head and brazing with a bonding material having a large yield stress, such as a silver-copper alloy brazing material, it has a feature that bonding can be performed easily and with high strength.

[0005] However, this inorganic material-based wiring board has a large specific gravity because a sintered body such as alumina ceramics fired at a high temperature of about 1500 to 1600 ° C is used as a main component of the insulating layer. However, since the weight of the electronic component tends to increase, it is difficult to say that the electronic component is suitable for the recent demand for weight reduction. When the insulating substrate is made thinner for weight reduction, chipping, cracking and the like occur, and the wiring conductor tends to be easily broken.

On the other hand, a wiring board made of an organic material containing an organic material as a main component of the insulating layer can meet the market demand for a reduction in the weight of electronic equipment. On the other hand, since the dielectric constant of the insulating layer is small and copper, which is a low electric resistance material, can be used for the wiring conductor, attention has recently been paid to development as being more suitable than inorganic materials, and development has been promoted.

[0007] Such an organic material-based wiring board with lead pins is formed by a photolithography method such as resist coating or etching on a copper-clad resin plate made of a glass-epoxy resin composite base material having copper foil adhered to one or both surfaces. A copper wiring pattern is formed by processing, and a plurality of layers are laminated and bonded with an epoxy adhesive to form a multilayer substrate. Then, a desired through hole is provided by drilling or the like, and a wall surface of the through hole is formed. A structure is adopted in which a copper conductor is formed by plating or the like, the copper wiring patterns of each layer are connected, then a lead pin is pressed into a through hole, and the lead pin is connected and fixed to an external electric circuit board using solder. Was.

[0008]

However, in an organic material-based wiring board having such a lead pin connection / fixing structure, a large number of through holes for fixing the lead pins to an external electric circuit board penetrate the insulating board. Since the wiring conductors are formed, high integration of the wiring conductor cannot be achieved, and there is a problem that the wiring density is reduced.

In particular, a wiring board formed by a build-up method in which an insulating layer and a wiring conductor layer are sequentially laminated on the surface of a core substrate to form a multilayer structure has a feature that high-density wiring can be easily formed. Nevertheless, by providing through holes for fixing lead pins to the insulating substrate through the insulating substrate, the degree of freedom of wiring is greatly impaired, and it becomes difficult to form high-density wiring. It had problems.

Therefore, it is possible to increase the wiring density without providing a through-hole penetrating the insulating substrate, and solder such as solder is attached to a land for lead pin bonding formed on one surface of the wiring substrate, usually on the lower surface. The material is applied, and the resin substrate having the through holes for pin fixing, in which the lead pins are inserted in advance, is bonded so that the corresponding lead pins abut on the lands of the wiring board, and heated. There has been proposed an organic material-based PGA-type wiring board with lead pins that achieves both freedom of wiring and bonding strength of the lead pins, such as brazing the lead pins to lands.

However, according to this conventional wiring board with organic material-based lead pins, the resin substrate having the through holes for pin fixing is soldered to the heads of all the lead pins to be brazed, that is, the nail head. Since it is bonded and fixed so as to hold the wiring board, the thickness of the wiring board as a whole increases by the amount of the resin board, so that the wiring board or an electronic component using the wiring board can be connected to an external electric circuit such as a motherboard. When mounted on a board, the mounting height increases and the overall dimensions of the device increase, making it difficult to satisfy the recent demand for smaller and lighter electronic devices. There was a point.

Further, since the resin substrate for fixing the lead pins is bonded only to one surface of the wiring board, the upper and lower layer structures of the wiring board itself constituting the electronic component are different. When a thermal load is applied, the entire electronic component is greatly warped, and there is a problem that mounting reliability is impaired.

Therefore, following a wiring board with lead pins made of an inorganic material such as alumina ceramics fired at a high temperature,
Instead of using the resin substrate for fixing the lead pins, the head of the nail head type lead pin, that is, the nail head is abutted against the lead pin bonding lands formed on the lower surface of the wiring board, and the nail head is made of various brazing materials. Brazing structures have been attempted.

FIG. 6 is a sectional view showing an example of this conventional wiring board with organic material-based lead pins and an electronic component using the same. In FIG. 6, an electronic component 31 is configured by mounting a semiconductor element 33 as an individual electronic component on a wiring board 32 with lead pins. The wiring board with lead pins 32 is configured by joining lead pins 35 to a wiring board 34 by brazing.

Numeral 36 denotes a core substrate constituting the wiring substrate 34, and numeral 37 denotes an insulating layer laminated on the surface of the core substrate 36. These core substrate 36 and the insulating layer 37 constitute an insulating substrate of the wiring substrate 34. I have. 38 is a through-hole conductor as a through conductor formed inside the core substrate 36, 39 is a wiring conductor layer of a predetermined pattern formed on the surface or between the core substrate 36 and the insulating layer 37, and 40 is a wiring conductor between different layers. This is a via conductor as a through conductor for electrically connecting the layers 39 to each other. The through-hole conductor 38 electrically connects the wiring conductor layers 39 formed on the upper and lower surfaces of the core substrate 36 to each other. These through-hole conductors 38, wiring conductor layers 39, and via conductors 40 form a plurality of wiring conductors on the surface and / or inside the insulating substrate. 41 is formed on the upper surface of the wiring board 34,
Semiconductor element that is electrically connected to and mounted on 39
Reference numeral 33 denotes a pad to which the electrodes are electrically connected. Reference numeral 42 denotes a land formed on the lower surface of the wiring board 34 by being electrically connected to the wiring conductor layer 39. Are brazed by a brazing material 44 such as solder.

Reference numeral 43 denotes a solder resist layer formed on the outermost layer of the wiring board 34. Openings are formed in portions corresponding to the pads 41 and the lands 42. The electrodes of the semiconductor element 33 are connected to the pads 41 via, for example, the conductor bumps 45, whereby the semiconductor element 33 is electrically connected to the wiring conductors of the wiring board.

However, in such conventional wiring board 32 with lead pins and electronic component 31,
When the insulating layer 37 is made of an organic resin material, the glass transition temperature of the organic resin material is as low as about 100 to 150 ° C., so there is a problem in heat resistance to heat when brazing the lead pin 35. There was a problem that there is.

On the other hand, in the case of an inorganic material-based wiring board with lead pins and an electronic component, even if a glass-ceramic material which is advantageous in electric characteristics such as a dielectric constant and can be fired at a low temperature is used for the insulating layer, it can be used at a high temperature. Since the sintering temperature is about 600 to 800 ° C lower than that of inorganic materials such as alumina ceramics produced by sintering, the yield stress of the lead pins is large following the wiring board made of high-temperature sintering materials such as alumina ceramics Even if an attempt is made to join with a silver-copper-based brazing material having excellent strength, the silver-copper-based brazing material has a high melting point of about 500 ° C. or higher, so that there is still a problem in that heat resistance is difficult and it cannot be used. there were.

Therefore, the wiring board 34 having poor heat resistance is used.
In order to manufacture the wiring board 32 with lead pins and the electronic component 31 by brazing and joining the lead pins 35 by using a material having a low melting point by a brazing material 44, for example, a lead-tin solder or the like. .

However, according to such a conventional wiring board 32 with lead pins and the electronic component 31 with lead pins using the same, the reduction in mounting reliability due to the warpage of the board as in the case of using the above-mentioned resin board does not occur. Although it can be avoided, the yield stress of the lead-tin solder used for the brazing material 44 for joining the lead pin 35 is small, and the corner of the head 35a of the lead pin 35, that is, the peripheral edge 35c on the top of the head is usually sharp. In addition, since the Young's modulus of the shaft portion 35b of the lead pin 35 is large and rigid, in a practical use situation in which the lead pin 35 is inserted into and removed from the socket of the external electric circuit board, the tip portion of the shaft portion 35b is added. The oblique external force acts as a large moment on the top edge 35c of the head 35a, and the brazing material 44
In the vertical pull test on the lead pin 35, the bonding strength per pin is about 30
Even if it is enough to be 50 N, for example, in a tensile test in a diagonal direction of 20 °, only a very weak bonding strength of about 10 to 20 N can be obtained, and when an external force is applied to the lead pin 35, the brazing material 44 becomes easy. However, there has been a problem that the bonding strength cannot be obtained for practical use.

The present invention has been made in view of the problems of the prior art described above. In the case of a wiring board made of an organic material, high-density low-resistance wiring is possible, and a low dielectric constant and high frequency While making use of excellent characteristics such as excellent electrical characteristics and low cost, low resistance wiring is also possible in the case of a wiring board made of glass ceramic material.
Utilizing characteristics such as low dielectric constant, excellent electrical characteristics at high frequencies and easy multi-layering, and furthermore, taking advantage of the original high reliability even in the case of high-temperature fired ceramic material wiring boards, Lead pins can be brazed with extremely high bonding strength and bonding reliability against diagonal tensile loads, and the density of wiring conductors formed in a wiring board can be increased and the demand for more pins is increased. It is an object of the present invention to provide a wiring board with lead pins and an electronic component with lead pins using the same.

[0022]

In order to achieve the above object, the present inventors have conducted intensive studies on the bonding state between the lands on the wiring board and the nail head type lead pins. By setting the shape of the corner part of the peripheral edge of the top of the head of the lead pin and the physical properties of the shaft of the lead pin in an appropriate state, it has been found that the joining strength in the oblique pull test of the lead pin is greatly improved, The present invention has been completed.

That is, a wiring board with lead pins according to the present invention comprises an insulating substrate, a plurality of wiring conductors formed on the surface and / or inside the insulating substrate, and a lower surface of the insulating substrate. It comprises a land electrically connected and a lead pin whose head is brazed to the land, and a semiconductor element is mounted on the upper surface of the insulating substrate and electrically connected to the wiring conductor. A wiring board with lead pins, wherein the lead pins are provided with a C-plane or an R-plane on the periphery of the top of the head,
In addition, the Young's modulus of the shaft portion is 30 to 80 GPa.

Further, in the wiring board with lead pins according to the present invention, in the above-mentioned configuration, the C surface has a size within 2/3 of a thickness of the head portion and 50% with respect to a direction of the shaft portion.
It has an angle of up to 80 °.

Further, in the wiring board with lead pins according to the present invention, in the above structure, the R surface has a thickness of the head.
It has a radius of curvature of 25 to 150%.

Further, in the wiring board with lead pins according to the present invention, in the above structure, an R surface having a radius of curvature of 100 to 130% of the thickness of the head is provided on the periphery of the top of the head. An R surface having a radius of curvature of 25 to 35% of the thickness of the head portion is provided on the periphery of the shaft portion side of the portion.

According to the electronic component with lead pins of the present invention, a semiconductor element is mounted on the upper surface of the insulating substrate and the electrodes and the wiring conductors are electrically connected to the wiring substrate with lead pins of the above-described configurations. It consists of

According to the wiring board with lead pins and the electronic component with lead pins of the present invention, the head of the lead pin is
At least a C-plane or a radius is provided at the corner of the peripheral edge of the head so that the stress applied to the brazing material at the joint is dispersed from the moment generated by a 15-35 ° oblique pulling force applied to the shaft. By providing the surface, the concentration of stress on the brazing material caused by the moment applied to the corner portion is reduced, the volume of the brazing material around the head is increased, and the Young's modulus of the shaft portion is reduced by 30 to 80 GPa. As a result, the fulcrum of the moment shifts from the joint of the lead pin head with the brazing material to the shaft of the lead pin, and the moment itself acting on the joint with the brazing material becomes small. Effectively disperse the stress applied to the joint between the lead pin and brazing material, even if a diagonal pull of 15 to 35 mm is applied when inserting or removing the circuit from the socket. Can, prevents the breaking the joint occurs, it is possible to obtain a practically sufficient bonding strength bonding strength becomes equal to the strength in the tensile vertical in the tensile diagonal lead pin. As a result, the number of pins can be increased without compromising the degree of freedom of the wiring and without causing the substrate to be warped, and it is possible to cope with a higher wiring density.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a wiring board with lead pins and an electronic component with lead pins according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing an example of an embodiment of a wiring board with lead pins and an electronic component with lead pins according to the present invention, taking a PGA type wiring board of an organic material as an example. 2 to 5 are side views showing the shapes of the lead pins used in the wiring board with lead pins and the electronic component with lead pins of the present invention, respectively.

In these figures, an electronic component 1 with lead pins is constituted by mounting a semiconductor element 3 as an individual electronic component on a wiring board 2 with lead pins. As the semiconductor element 3, a semiconductor integrated circuit element or a hybrid integrated circuit is mounted. The wiring board 2 with lead pins is configured such that a lead pin 5 of a nail head type is brazed to the wiring board 4.

Reference numeral 6 denotes a core substrate constituting the wiring board 4, and 7 denotes an insulating layer laminated on the surface of the core substrate 6. The core substrate 6 and the insulating layer 7 constitute an insulating substrate of the wiring board 4. I have. 8 is a through-hole conductor as a through conductor formed inside the core substrate 6, 9 is a wiring conductor layer of a predetermined pattern formed on the surface or between the core substrate 6 and the insulating layer 7, and 10 is a wiring conductor between different layers. The via conductor is a through conductor that electrically connects the layers 9 to each other. The through-hole conductors 8 electrically connect the wiring conductor layers 9 formed on the upper and lower surfaces of the core substrate 6 to each other. These through-hole conductors 8, wiring conductor layers 9, and via conductors 10 form a plurality of wiring conductors on the surface and / or inside of the insulating substrate.

Reference numeral 11 denotes a pad formed on the upper surface of the wiring board 4 and electrically connected to the wiring conductor layer 9 and electrically connected to the electrode of the semiconductor element 3 mounted thereon. A land formed on the lower surface of the lead wire 5 by being electrically connected to the wiring conductor layer 9. The head of the lead pin 5 is brazed to the land 12 with a brazing material 14 such as solder.

Reference numeral 13 denotes a solder resist layer formed on the outermost layer of the wiring board 4, and an opening is formed in a portion corresponding to the pad 11 and the land 12. The pads 11 are connected to the electrodes of the semiconductor element 3 via, for example, the conductor bumps 15, whereby the semiconductor element 3 is electrically connected to the wiring conductor of the wiring board 4.

The wiring board 2 with lead pins and the electronic component 1 with lead pins according to the present invention are characterized in that, in the above-mentioned configuration, a C-plane or an R-plane is provided at least on the peripheral edge 5c on the top side of the head 5a of the lead pin 5. Is what you do.
In the lead pin 5 according to the present invention, for example, as shown in FIGS. 1 and 5, an R surface is also provided on a peripheral edge 5d of the head portion 5a of the head portion 5a on the shaft portion 5b side, and a peripheral edge 5c on the top side from the R surface. A nail head side surface having a continuous curved surface is formed over the R surface provided in the head, or a C surface is provided only on the top peripheral edge 5c of the head 5a as shown in FIG. 2, or as shown in FIG. As shown in FIG.
A C-plane may be provided on both the edge 5d and the peripheral edge 5d on the side of the shaft 5b.
As shown in FIG. 5, various forms can be adopted, such as providing an R surface only on the peripheral edge 5c on the top of the head 5a. Further, although not shown, the C-plane and the R
Surface, or an edge 5c on the shaft 5b side having an R surface, or an edge 5d on the shaft portion 5b side having a C surface, or an edge 5c from the edge 5d on the shaft portion 5b side to the head edge 5c. Various combinations may be used, such as those in which the C-plane or the R-plane changes continuously.

In particular, from the viewpoint that the stress applied to the brazing material 14 is effectively dispersed from the moment generated by the oblique pulling, and the joining strength equivalent to the vertical pull is easily obtained with respect to the oblique pulling, FIG. As shown in FIG. 5, it is desirable to provide an R surface on the periphery 5c on the top of the head 5a and also provide an R surface on the periphery 5d on the shaft portion 5b side.

The lead pin 5 used in the present invention as described above
As the C surface provided on the peripheral edge 5c on the top of the head 5a,
From the viewpoint of securing a bonding area between the brazing material 14 and the head 5a in order to obtain a sufficient bonding strength, the stress applied to the bonding material is effectively dispersed from the moment generated by the oblique pulling so that the vertical From the viewpoint that the same joining strength as that of pulling can be easily obtained, the thickness of the head 5a should be within 2/3 of the thickness of the head 5a from the top of the head 5a, and the angle of the shaft 5b should be 50 to 80 °. It is desirable to have.

The size of the plane C is 2/2 of the thickness of the head 5a.
If it exceeds 3, the thin portion of the head 5a increases, so that the head 5a cannot be pulled against the lead pin 5.
The lead pin 5 itself may be broken, and it tends to be difficult to obtain the bonding strength inherent to the lead pin 5. The size of the C-plane is preferably at least 1/4 of the thickness of the head 5a from the viewpoint of the stable workability of the dimensions and the shape of the C-plane.

Further, the angle of the C plane is set with respect to the shaft 5b.
When the angle is less than 50 °, the angle formed by the top surface of the head 5a and the C-plane rises, so that the above-described effect of dispersing the stress tends to decrease. If the angle exceeds 80 °, the bonding area between the brazing material 14 and the head material 5a becomes small, so that it may be broken at the interface between the head material 5a and the brazing material 14 due to tension, and the lead pin 5 originally has It tends to be difficult to obtain the desired bonding strength.

On the other hand, it is desirable that the R-plane has a radius of curvature of 25 to 150% of the thickness of the head 5a from the same point as described above. Further, considering that the bubbles contained in the brazing material 14 are effectively discharged at the time of joining the lead pins 5, it is more preferable that the head 5a has a radius of curvature of 100 to 130% of the thickness of the head 5a. It is.

The radius of curvature of the R surface is 25 times the thickness of the head 5a.
%, The effect of the above-mentioned stress dispersion tends to decrease because the corner of the peripheral edge 5c on the top of the head 5a rises. On the other hand, when the thickness exceeds 150% of the thickness of the head 5a, Since the bonding area between the brazing material 14 and the head 5a is reduced, the brazing material 14 may be broken at the interface between the head 5a and the brazing material 14 due to tension, and the bonding strength inherent to the lead pin 5 tends to be hardly obtained. There is.

Further, an R-shaped surface having a radius of curvature of 100 to 130% of the thickness of the head 5a is provided on the peripheral edge 5c on the top side of the head 5a of the lead pin 5, and the shaft 5 of the head 5a is provided.
It is most desirable to provide an R surface having a radius of curvature of 25 to 35% of the thickness of the head 5a also on the peripheral edge 5d on the b side. As described above, in addition to the above-described operation and effect due to the R surface of the peripheral edge 5c on the top side, by providing the R surface also on the peripheral edge 5d on the shaft portion 5b side, the flow of the brazing material 14 at the time of joining the lead pin 5 is made smooth. It is easy to form a good fillet shape of the brazing material 14, and it is easy to reduce the variation in joining.
Stabilization of the bonding strength by pressing the outer peripheral side surface of the lead pin 5 can be expected, and the lead pins 5 having extremely good bonding strength can be brazed.

At this time, the peripheral edge 5 of the head 5a on the shaft 5b side
If the radius of curvature of the R surface provided in d is less than 25% of the thickness of the head 5a, the effective flow of the brazing material 14 tends to be insufficiently effective, while the thickness of the head 5a is 35%. %, The brazing material 14 excessively covers the entire head 5a, so that more brazing material is used to form a good fillet shape.
14 tends to be needed.

The present invention is further characterized in that the Young's modulus of the shaft 5b of the lead pin 5 is 30 to 80 GPa, and the moment applied to the lead pin 5 is specified by specifying the Young's modulus of the shaft 5b in this range. The fulcrum shifts from the joint of the lead pin 5 with the brazing material 14 toward the shaft portion 5b, and the moment itself acting on the brazing material 14 can be reduced. Effectively reduces the stress applied to the shaft 5b
This can be dispersed on the side, and the same joining strength can be obtained in oblique pulling as in vertical pulling.

If the Young's modulus of the shaft portion 5b is smaller than 30 GPa, the shaft portion 5b tends to be easily stretched when the lead pin 5 is pulled, so that the shaft portion 5b cannot be practically used. On the other hand, if it exceeds 80 GPa, the effect of reducing the moment applied to the brazing material 14 tends to be lost because the shaft portion 5b becomes rigid.

In particular, when the wiring board 2 with lead pins and the electronic component 1 with lead pins are repeatedly inserted into and removed from the socket of the external electric circuit board, good electrical contact between the lead pins 5 and the socket terminals is maintained. 5b
Is more preferably 50 to 80 GPa.
This is because when the Young's modulus of the shaft portion 5b is smaller than 50 GPa,
This is because the shaft portion 5b is somewhat soft, and when repeatedly inserted into and removed from the socket, the contacts on the shaft portion 5b side may gradually become concave, making it difficult to maintain good electrical contacts.

As described above, according to the wiring board 2 with lead pins and the electronic component 1 with lead pins of the present invention, the lead pins 5 can be inserted into and removed from the socket of the external electric circuit board, and the oblique pulling force of 15 to 35 ° can be reduced. When it is applied to the lead pin 5, the concentration of stress at the joint with the brazing material 14 due to the moment caused by the oblique external force applied to the shaft 5b of the lead pin 5 is greatly reduced, Since the amount of the brazing material 14 at the top peripheral edge 5c of the head 5a is increased, the stress applied to the brazing material 14 can be effectively dispersed.

In the wiring board with lead pins 2 and the electronic component with lead pins 1 of the present invention, the dimensions of each part of the lead pins 5 can be arbitrarily selected as those used for the PGA type, but the diameter of the shaft 5b is not limited. 0.2
It is preferably 0.7 mm to 0.7 mm, and most preferably 0.35 to 0.55 mm in consideration of the bending strength of the shaft portion 5b. When the diameter of the shaft portion 5b of the lead pin 5 is less than 0.2 mm, the shaft portion 5b is easily bent when inserted into the socket, and thus tends to be unusable. On the other hand, when the diameter exceeds 0.7 mm, Since the bending strength of the shaft portion 5b is large and rigid, the moment applied to the pin joint portion when a lateral external force is applied to the shaft portion 5b increases, and the joint portion tends to be easily broken.

When the head 5a has a nail head shape, the diameter is the diameter of the land 12 of the wiring board 4, in this example, the land 12 formed on the surface of the solder resist layer 13.
It is preferably 50% or more and 90% or less of the opening diameter of the opening for exposing the opening. If the diameter of the head 5 a is less than 50% of the diameter of the land 12, the lead pin 5 is inclined and joined when joining the lead pin 5 to the land 12 of the wiring board 4. In addition, there is a tendency that the stress distribution to the joints due to the moment caused by the oblique pulling is not effective and sufficient joint strength cannot be obtained. On the other hand, the diameter of the head 5a is
If the diameter is larger than 90% of the diameter, the head 5a may protrude from the land 12 and be joined, and the joining strength of the lead pin 5 tends to decrease due to the decrease in the joining area.

Further, regarding the thickness of the head 5a,
It is preferably 10% or more and 100% or less of the diameter of b. If the thickness of the head portion 5a is less than 10% of the diameter of the shaft portion 5b, the strength between the head portion 5a and the shaft portion 5b will be small, and the joining strength of the lead pin 5 will tend to be small. On the other hand, when the diameter exceeds 100% of the diameter of the shaft 5b, a large amount of the brazing material 14 to be joined to the head 5a is required, and it is difficult to control the joining at the time of joining. May spread and cause poor insertion into the socket,
Alternatively, there is a risk that the lands 12 may be bridged and short-circuited. In particular, from the viewpoint of stable workability of the size and shape of the head 5a, it is more preferable that the thickness of the head 5a is not less than 20% and not more than 60% of the diameter of the shaft portion 5b.

In the case where the wiring board 4 of the present invention is made of, for example, an organic material, both surfaces of a core base material 6 made of a glass-epoxy composite material having through-hole conductors 8 are made of an organic resin material. The insulating layer 7 and the wiring conductor layers 9 having a predetermined pattern made of copper or the like are alternately laminated, and the wiring conductor layers 9 formed between different layers are connected to each other via via conductors formed inside the insulation layer 7. They are connected via 10 through conductors. The semiconductor element 3 is mounted and mounted on the upper surface of the wiring board 4, and the electrodes of the semiconductor element 3 are electrically connected to pads 11 formed on the surface of the wiring board 4 via flip-chip connecting conductor bumps 15. It has been installed.

The wiring substrate 4 according to the present invention is not limited to the above-mentioned organic materials, but may be formed by firing copper powder on an insulating substrate using an insulating layer made of a glass ceramic material containing silica or the like as a main component. It may be formed with a wiring conductor made of a sintered body or the like. An insulating substrate using an insulating layer made of a material such as alumina ceramics, silicon nitride ceramics, or aluminum nitride ceramics is formed of a high melting point metal such as tungsten or molybdenum. Even when wiring conductors are formed, heat-curable metal powders such as copper and silver are applied to an insulating substrate using an insulating layer made of a composite material in which various ceramic powders are bonded with a thermosetting resin such as epoxy resin. A wiring conductor formed by bonding with a resin may be formed. Further, instead of the organic resin material containing an inorganic filler, a material obtained by impregnating an organic resin material into glass fiber, woven fabric, or the like can be used as the insulating layer 7.

When the insulating layer 7 of the wiring board 4 is made of an organic resin material, a thermosetting resin such as epoxy or polystyrene / polyphenylene ether can be applied as a main component, and it is made of silica or alumina. A material containing an appropriate amount of an inorganic filler can also be used. However, if the glass transition temperature of the organic resin material is lower than about 150 ° C., the insulating layer 7 will be
The glass transition temperature of the organic resin material is desirably about 150 ° C. or higher because there is a possibility that the glass transition temperature may be affected by heat treatment at the time of bonding with the organic resin material.

The wiring conductor layer 9 according to the present invention is formed on the insulating layer 7 mainly by plating or etching in the wiring substrate 4 made of an organic material. 7 is electrically connected to the inside of the through-hole formed by a via-hole conductor 5 made of copper or the like formed by plating or etching.

On the other hand, the outermost layer of the wiring board 4 is formed of a solder resist layer 13 containing an organic resin material having a photosensitive group as a main component. Land 12 to be a terminal and pad 11 for flip chip connection to be a terminal for IC connection
Are opened by photolithography or the like.

The brazing material 14 contains, for example, tin (Sn) and / or lead (Pb) as main components and antimony (S
b) or bismuth (Bi) / indium (In) / copper (C
u), silver (Ag), gold (Au), or other suitable metal is preferably used as a solder. In view of the heat resistance of the insulating layer 7 mainly composed of an organic resin material, the melting point of the brazing material 14 Preferably, the temperature does not exceed the glass transition temperature of the insulating layer + about 100 ° C. If the above tin-lead solder has a melting point of about 270 ° C. or less, it can be used for the above thermosetting resin which is an organic resin material having a glass transition temperature lower than about 150 ° C. Things. The melting point in this case indicates the liquidus temperature in the case of alloy solder.

Further, the yield stress of the brazing material 14
In order to secure a sufficient yield stress and to obtain sufficient pin bonding strength while avoiding breakage from the inside of the brazing material 14, the pressure is preferably 5 MPa or more.

On the other hand, from the viewpoint that the amount of elastic displacement of the brazing material 14 is sufficient, stress can be effectively alleviated, and high joining reliability of the lead pin 5 is obtained, the Young's modulus of the brazing material 14 is 100 GPa or less. Desirably.

The brazing material 14 contains 75 to 85% by weight of lead, 5 to 15% by weight of tin, and 5 to 10% by weight of antimony as a main component and has a melting point of about 270 ° C. or less. And, the yield stress is about 40 MPa or more, the Young's modulus is about 50 GPa or less lead-tin-based solder is suitable, but considering the recent lead-free movement taking into account the adverse effect of lead on the human body,
This solder contains 90 to 95% by weight of tin and 5 to 10% by weight of antimony as main components, has a melting point of about 260 ° C. or less, a yield stress of about 20 MPa or more, and a Young's modulus of about 80 GP.
The tin-antimony solder having a value of a or less is most suitable as the brazing material 14 in the present invention.

Regarding the material of the lead pin 5, the land 12
In view of the pin joint strength in consideration of the difference in thermal expansion between the lead pin 5 and the lead pin 5, it is preferable to use a material having a thermal expansion coefficient substantially equal to that of the conductor material forming the land 12, even if the land 12 is made of copper. If the coefficient of thermal expansion is about 1-20 ppm /
C. is preferred. Examples of such a material include an Fe-Ni-Co alloy and an Fe-Ni alloy.

However, these Fe—Ni—Co alloys and F
The Young's modulus of a lead pin manufactured using an e-Ni alloy is generally as high as 100 to 130 GPa, which deviates from the range of 30 to 80 GPa which is the range of the Young's modulus of the shaft portion 5b of the lead pin 5 in the present invention as described above. Therefore, it is inappropriate to use it as it is. Therefore, for the lead pins 5 made of these materials, it is possible to promote the recrystallization of the alloy material by performing a heat treatment at a temperature of 700 to 1100 ° C. for a predetermined time to control the Young's modulus to a desired range. Required.

The surfaces of the lands 12 and the lead pins 5 have a plating film containing nickel (Ni) as a main component and gold (A).
u) as a main component, it is desirable that the gold plating film be formed on the land 12 and the lead pin 5.
Since the surface oxidation can be effectively prevented, it is possible to obtain a highly reliable electrical connection even when joined by the brazing material 14. Further, by forming a nickel plating film under the gold plating film, the land 12
Alternatively, the adhesion between the lead pin 5 and the gold plating film is improved, and the deterioration in strength due to the peeling of the gold plating film is effectively prevented.

[0063]

Next, the bonding reliability of the lead pins in the wiring board with lead pins of the present invention was evaluated as follows.

<Example 1> First, an epoxy resin containing an appropriate amount of silica filler as an insulating layer was used as an insulating layer. The conductor constituting the land had a diameter of 1.6 mm, and the opening diameter of the solder resist layer corresponding to the land was 1.6 mm. A PGA type wiring board provided with a land pattern of 1.4 mm was used as a test board, an alloy solder of 95% by weight of tin / 5% by weight of antimony was used as a brazing material, and lead pins were shown in FIGS. 1 and 5. The diameter of the shaft part is 0.45 mm, the length of the shaft part is 3 mm, and the nail head diameter of the head is 0.9 mm.
A disk with a nail head thickness of 0.2 mm, an R surface with a radius of 0.06 mm at the corner of the periphery of the head on the shaft side, and an R surface with a radius of 0.23 mm at the corner of the periphery on the top of the head. This lead pin is joined to a land of a test board using a 95% by weight tin / 5% by weight antimony alloy solder, using a copper alloy having a nail head in a shape of
An evaluation sample according to the present invention was obtained.

As a comparative example, a lead pin having the same dimensions as a conventional nail head having a disk-shaped conventional nail head with a sharp corner at the top of the head was used. A joint using solder was produced, and a sample for evaluation was obtained in the same manner.

Using each evaluation sample thus obtained,
The following evaluation items were measured.

First, the bonding strength of the lead pin was fixed to the stage of the tensile tester at an angle of 20 ° and 30 ° by inclining the sample for evaluation, and after chucking the lead pin to the pulling jig, 15 mm / min. The total load at the time of breaking was measured by pulling at a speed of, and the evaluation was made based on the result of measuring 30 pins for each sample.

As a result, in the evaluation sample of the comparative example, the bonding strength per pin was as low as 4.7 to 27.4 N when the inclination was 20 °, and 3.9 to 21.6 N when the inclination was 30 °. In the destruction mode, more than 70% was destruction in solder.

On the other hand, the sample for evaluation according to the present invention was extremely large in the range of 44.1 to 68.6 N in the case of the inclination of 20 ° and in the range of 43.1 to 58.8 N in the case of the inclination of 30 °. All were broken at the interface between the land conductor and the insulating layer, and had sufficient strength for practical use even in oblique pulling.

Further, when a pseudo silicon chip imitating an actual semiconductor element was mounted on the evaluation sample according to the present invention and the warpage was evaluated, no warpage was generated even in a thermal load state assuming actual use. No mounting reliability problems were found.

<Example 2> An alloy solder containing 82% by weight of lead, 10% by weight of tin, and 8% by weight of antimony was used as a brazing material for the same test substrate as in Example 1, and the lead pins were replaced with those shown in FIGS. The diameter of the shaft part is 0.45 mm, similar to the shape shown in Fig. 5.
・ The length of the shaft part is 3 mm, and the nail head diameter of the head is 0.9 mm or 1.1 mm. ・ The nail head thickness is 0.2 mm.
In addition, a radius of 0.06 mm is set at the corner of the periphery of the head on the side of the shaft, and a radius is set at the corner of the periphery of the top of the head.
Using a Fe-Ni-Co alloy having a disk-shaped nail head provided with each 0.23 mm R-plane, this lead pin is attached to the land of the test substrate by 82% by weight of lead / 10% by weight of tin / 8% by weight of antimony. Weight percent alloy solder,
An evaluation sample according to the present invention was obtained.

Here, the lead pins were subjected to a heat treatment at about 790 ° C. to adjust the Young's modulus of the shaft to 60 to 70 GPa, and the joining of the lead pins was carried out by reflow joining having a temperature profile of 270 ° C. peak.

As a comparative example, the same alloy was attached to the land of the same test board using the same size lead pins having a conventional disk-shaped nail head having a rounded corner at the top of the head. A joint was similarly formed using solder, and a sample for evaluation was obtained in the same manner.

Using each evaluation sample thus obtained,
Tensile tests at a 20 ° inclination and a 30 ° inclination were performed in the same manner as in Example 1, and evaluation was made based on the results of measuring 30 pins for each sample. Table 1 shows the results.

[0075]

[Table 1]

From the results shown in Table 1, in the evaluation samples of Comparative Examples (Sample Nos. 6 and 7), sufficient bonding strength could not be obtained even when the nail head diameter and the solder weight were changed. The evaluation samples (sample numbers 1 to 5) according to the present invention have practically sufficient strength irrespective of the nail head diameter and the solder weight. In particular, the nail head diameter is 1.1 mm and the solder weight is 0.80 mg / In the case of pin, the joint strength per pin is 20 °
47.7 to 61.9N in the range of 52.3 to 73.6N at 30 ° inclination
And an extremely large strength could be obtained.

In the above embodiments, a wiring board using an insulating substrate made of an insulating layer made of an insulating material containing an organic resin has been described in detail. However, an inorganic material glass such as silica fired at a low temperature is used as the insulating layer. Similar evaluations were performed with a material using a ceramic material as an insulating material, or with a material using a ceramic material such as alumina ceramics as an insulating material. Was.

[0078]

According to the wiring board with lead pins and the electronic component with lead pins of the present invention, the lead pins whose heads are brazed to the lands of the wiring board are provided with a C-plane or an R-plane on the periphery of the top of the head. Since it is provided and the Young's modulus of the shaft is 30 to 80 GPa, the 15 to 35 mm diagonal tensile stress applied to the brazing material at the joint by the shaft of the lead pin is effectively dispersed. In addition to obtaining the same bonding strength as vertical pulling even when the lead pin is pulled in an oblique direction, the brazing material does not spread and spread on the shaft of the lead pin. Even if used, good bonding strength can be obtained.

As a result, according to the present invention, a high-density low-resistance wiring is possible in the case of an organic material-based wiring board.
It has low dielectric constant, excellent electrical characteristics at high frequencies, and low cost, while making use of its excellent characteristics. While taking advantage of the characteristics such as excellent electrical characteristics against high frequency and easy multilayering, and even taking advantage of the original high reliability even in the case of wiring boards made of ceramic material fired at high temperature, all of them are pulled obliquely with respect to the lead pins. Lead pins can be brazed with extremely high bonding strength and bonding reliability even under load, and the density of wiring conductors formed in the wiring board can be increased, and the demand for multi-pins can be sufficiently satisfied. The present invention can provide a wiring board with lead pins and an electronic component with lead pins using the same.

Further, a resin board or the like for fixing lead pins is not required, and the layer structure of the wiring board can be reduced by using any of an organic material and a glass ceramic material having difficulty in heat resistance as a main component of the insulating layer. Since the front and back surfaces can be symmetrical, the wiring board does not warp even when a thermal load is applied, and as a result, to provide a wiring board with lead pins and an electronic component with lead pins with high mounting reliability. Can be.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of an embodiment of a wiring board with lead pins and an electronic component with lead pins of the present invention.

FIG. 2 is a side view showing an example of the shape of the head of a lead pin used in a wiring board with lead pins and an electronic component with lead pins of the present invention.

FIG. 3 is a side view showing another example of the shape of the head of a lead pin used in a wiring board with lead pins and an electronic component with lead pins of the present invention.

FIG. 4 is a side view showing another example of the shape of the head of a lead pin used in a wiring board with lead pins and an electronic component with lead pins of the present invention.

FIG. 5 is a side view showing another example of the shape of the head of the lead pin used in the wiring board with the lead pin and the electronic component with the lead pin of the present invention.

FIG. 6 is a cross-sectional view showing an example of a conventional wiring board with lead pins and an electronic component with lead pins.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Electronic component with a lead pin 2 ... Wiring board with a lead pin 3 ... Semiconductor element 4 ... Wiring board 5 ... Lead pin 5a ... Head 5b ... Shaft 5c ... Top Side edge 7 ・ ・ ・ Insulating layer 9 ・ ・ ・ Wiring conductor layer (Wiring conductor) 10 ・ ・ ・ Via conductor (Wiring conductor) 12 ・ ・ ・ Land 14 ・ ・ ・ Brazing material

Claims (5)

[Claims] An insulating substrate, a surface of the insulating substrate and / or
Or a plurality of wiring conductors formed therein, a land formed on the lower surface of the insulating substrate, electrically connected to the wiring conductor, and a lead pin whose head is brazed to the land. A wiring board with lead pins, wherein the semiconductor element is mounted on the upper surface of the insulating substrate and is electrically connected to the wiring conductor, wherein the lead pins are provided on the periphery of the top of the head at a C-plane or an R-plane. And a Young's modulus of the shaft portion is 30 to 80 GPa. 2. The C-plane has a size within 2/3 of the thickness of the head and 50 to 80 with respect to the direction of the shaft.
2. An angle of about 1.degree.
The wiring board with lead pins described. 3. The R-plane has a thickness of 25 to 1 of the thickness of the head.
2. The wiring board with lead pins according to claim 1, wherein the wiring board has a radius of curvature of 50%. 4. An R-shaped surface having a radius of curvature of 100 to 130% of the thickness of the head is provided on the periphery of the top of the head, and the thickness of the head is provided on the periphery of the head on the shaft side. 25
2. The wiring board with lead pins according to claim 1, further comprising an R surface having a radius of curvature of about 35%. 5. A wiring board with lead pins according to claim 1, wherein a semiconductor element is mounted on an upper surface of said insulating substrate and said electrodes and said wiring conductor are electrically connected. Electronic components.