JP2006093571A - Wiring board with lead pin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that lead pin connection through brazing materials to a wiring board constituted of glass ceramics with low thermal expansion coefficients enlarges the thermal expansion coefficient difference of glass ceramics and brazing materials to make the glass ceramics yield to a breaking stress when an external force is added to the lead pin in an oblique direction, with the tendency of such a breakdown as crack to occur. <P>SOLUTION: An insulating substrate 5 constituted of glass ceramics whose thermal expansion coefficients in 40 to 400°C are ranging from 2.3×10<SP>-6</SP>/°C to 4.5×10<SP>-6</SP>/°C is formed with a wiring conductor 6, and a head part 1a of a lead pin 1 is connected through a connection pad constituted of Ag-Cu alloy grazing materials containing at least one type of Ti, Zr, and Hf to the wiring conductor 6 of the insulating substrate 5 so that a wiring board 3 with a lead pin can be configured. The outline dimension of the connection pad is made larger than the outline dimension of the head part 1a, and a distance between the outer peripheral end of the connection pad and the side face of the head part 1a is set so as to be not less than 0.125 mm across the overall periphery. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a so-called pin grid array (PGA) in which lead pins for input / output terminals are erected, which are used for a semiconductor element housing package, a circuit board, an electronic circuit module, etc. for housing semiconductor elements. The present invention relates to a wiring board with lead pins.

  Conventionally, a semiconductor element housing package for housing a semiconductor element such as a semiconductor integrated circuit element such as an IC or LSI, a circuit board or an electronic circuit module constituting a high-frequency circuit or a power circuit, etc. are made of ceramics. A wiring board having a wiring conductor on at least one of the surface and the inside of an insulating base is used. In general, the wiring board is used to airtightly accommodate a semiconductor element in a terminal member such as a lead pin or a ball terminal, a heat radiating plate, a heat radiating member such as a heat radiating fin, or a container including a wiring board and a lid. In addition, a metal member such as a seal member such as a seal ring for attaching a metal lid is joined to a wiring conductor made of a metallized layer on the surface of the wiring board via a brazing material.

  In the above wiring board, in order to transmit a high-frequency signal at a high speed, the resistance of the conductor forming the wiring conductor is required to be low, and the insulating base is also required to have a lower dielectric constant.

  For example, a wiring board in which glass ceramics having a low dielectric constant and suitable as an insulating base for high frequency is used for the insulating base and a metallized layer of a low resistance metal such as Cu, Ag, Au or the like is formed as a wiring conductor is widely used.

  However, in such a high-frequency wiring board, glass ceramics with a low dielectric constant contain a large amount of glass components. Therefore, their ceramic strength is lower than that of conventional alumina ceramics, etc. Since the melting point is low, it is necessary to fire at a low temperature, so that the bonding strength of the wiring conductor made of the metallized layer to the glass ceramic is also low.

  Therefore, when lead pins are joined to the metallized pads of such a wiring board via a brazing material to form a wiring board with a pin grid array type lead pin, the lead pins are connected to the external electric circuit in order to attach the wiring board to the external electric circuit. If an external force is applied to the lead pin in the vertical or oblique direction when it is pulled out due to failure or replacement, etc., and maintenance is required after mounting the wiring board on the external electrical circuit, the insulation base will Destruction stress occurs at the interface between a certain glass ceramic and metallized pad, causing the metallized pad to peel off, or the glass ceramic itself to bend and break due to the destructive stress, resulting in reduced joint reliability. was there.

  Therefore, as a technique for avoiding breakage at the interface between the insulating base such as glass ceramics having weak porcelain strength and the metallized pad, an Ag—Cu alloy brazing material containing at least one of Ti, Zr and Hf as an active metal is used. Without forming a metallized pad for lead pin bonding on the wiring board, the lead pin is formed in a region including a portion where a through conductor (via conductor) as a wiring conductor led out from the inside of the wiring board is exposed on the surface of the insulating substrate. There has been proposed a method of directly joining the two.

  In this method, the portion exposed to the surface of the insulating base of the through conductor, which is a part of the wiring conductor of the wiring board, and the lead pin without using the metallized pad, and Ag containing at least one of Ti, Zr, and Hf Electrical connection can be made by direct connection via a connection pad made of a Cu alloy brazing material (hereinafter referred to as a brazing material pad). In addition, since the exposed portion of the through conductor is usually as small as about 100 μm or less in diameter, the lead pin is substantially bonded via the insulating base and the brazing material pad, so that the bonding strength between the metallized pad and the insulating base is increased. Lead pins can be joined without depending on each other, and destruction at the interface between the insulating base and the metallized pad can be avoided.

  On the other hand, in the semiconductor element mounted on the above-described high-frequency wiring board, in order to reduce the wiring capacity of the semiconductor element and increase the signal transmission speed with the recent further higher integration and higher speed, It has been studied to lower the dielectric constant of the insulating film used for the above.

For example, the relative dielectric constant required for an insulating film of a semiconductor element that transmits a high-frequency signal of about 10 GHz and has a fine design wiring (MPU gate length) of the semiconductor element of about 130 nm is 2.5 or less. In order to achieve this, an insulating film formed by thermal polymerization of silsesquioxane-based inorganic oligomer (low molecular weight polymer) or polyaromatic ether-based organic oligomer is formed by spin coating. A porous insulating film containing air was developed.
JP-A-8-162563 JP-A-8-298381 JP-A-9-18144

  However, since the strength of the porous insulating film formed in such a semiconductor element decreases as the porosity increases, a thermal load is applied when the semiconductor element is mounted on the above-described wiring board or when the semiconductor element is operated. At this time, the problem that the porous insulating film itself is destroyed due to the thermal stress generated due to the difference in the thermal expansion coefficient between the semiconductor element and the wiring board is significantly generated compared to a general insulating film. There was a point.

Therefore, in order to reduce the thermal stress generated, the thermal expansion coefficient at 40 to 400 ° C. by using a 2.3 × ^{10 -6} /℃~4.5×10 ^-6 / ℃ glass ceramics insulating substrate The thermal expansion coefficient of the wiring board is as close as possible to 2 × 10 ⁻⁶ / ° C. to 4 × 10 ⁻⁶ / ° C., which is the thermal expansion coefficient at 40 to 400 ° C. of a semiconductor element made of Si (silicon) or the like. A method can be considered.

However, if the thermal expansion coefficient at 40 to 400 ° C. was used 2.3 × ^{10 -6} /℃~4.5×10 ^-6 / ℃ and glass ceramics with low thermal expansion as the insulating substrate, the wiring board wiring conductor In the method of directly connecting the portion exposed to the surface of the insulating base of the through conductor, which is a part of the lead wire, and the lead pin through the Ag—Cu alloy brazing material pad containing at least one of Ti, Zr and Hf, low heat The difference in thermal expansion coefficient between the expanded glass ceramic and the brazing material pad is large, and the thermal stress resulting from this difference in thermal expansion coefficient is inherent in the interface between the brazing material pad and the insulating substrate as a large residual stress after brazing.

  As a result, when stress exceeding the ceramic strength of ceramics acts as an external force on the lead pins in a concentrated manner at the outer peripheral edge of the joint surface between the ceramic insulating base and the brazing material, this stress and residual stress are in phase. As a result, there was a problem that a large breaking stress was generated, and cracks and the like progressed inside the insulating base from this point, leading to a decrease in bonding reliability and lead pins being detached from the wiring board. .

  The present invention has been completed in order to solve the above-mentioned problems, and its purpose is to mount a semiconductor element on which a porous insulating film is formed and attach it to a wiring board made of low-thermal-expansion glass ceramics. An object of the present invention is to provide a highly reliable wiring board with lead pins that can secure a bonding strength between a lead pin and an insulating base made of glass ceramics that can withstand practical use even when an external force is generated on the lead pin in an oblique direction.

Wiring substrate with lead pins of the present invention, at least on the surface of the insulating substrate made of glass ceramics is a thermal expansion coefficient at 40 to 400 ° C. is 2.3 × ^{10 -6} /℃~4.5×10 ^-6 / ℃ A wiring conductor is formed, and the head portion of the lead pin is connected to the wiring conductor on the surface of the insulating base via a connection pad made of an Ag—Cu alloy brazing material containing at least one of Ti, Zr, and Hf. In the wiring board with lead pins thus formed, the external dimensions of the connection pad are larger than the external dimensions of the head portion, and the distance between the outer peripheral edge of the connection pad and the side surface of the head portion is 0 over the entire circumference. It is characterized by being 125 mm or more.

  The wiring board with lead pins of the present invention preferably has a thickness of a reaction layer formed between the insulating base and the connection pad and containing the glass ceramic component and at least one of Ti, Zr and Hf. It is 0.2 μm to 1 μm.

  In the wiring board with lead pins of the present invention, preferably, the diameter of the head portion of the lead pin is 0.4 mm or more and the thickness is 0.05 mm to 0.2 mm.

According to the wiring board with lead pins of the present invention, the connection pad has an outer dimension larger than the outer dimension of the head part, and the distance between the outer peripheral end of the connection pad and the side surface of the head part is 0.125 mm over the entire circumference. since at least the insulating substrate thermal expansion coefficient at 40 to 400 ° C. is made of glass ceramics is ^{2.3 × 10 -6 /℃~4.5×10 -6 / ℃} , the lead pins Ti, Zr A sufficient meniscus can be formed on the connection pad formed on the nail head of the lead pin even if the connection is made via the connection pad made of an Ag—Cu alloy brazing material containing at least one of Hf and Hf. As a result, the initial residual stress generated at the joint between the insulating base and the lead pin when the lead pin is joined can be suppressed to a small level, and an external force is applied to the lead pin in an oblique direction to cause the stress to Even when acting on the outer peripheral edge of the joint surface, the total stress (the sum of the initial residual stress and the stress due to the external force) does not exceed the ceramic strength of the insulating base. Therefore, the occurrence of breakage such as cracks in the insulating substrate can be greatly suppressed, and the lead pins can be prevented from being detached from the wiring board, and higher bonding strength can be obtained.

  In the present invention, preferably, the thickness of the reaction layer formed between the insulating substrate and the connection pad and containing the glass ceramic component and at least one of Ti, Zr and Hf is 0.2 μm to 1 μm. Thus, a reaction layer containing at least one of the components of glass ceramics and Ti, Zr, and Hf that are active metal components can be formed evenly. Therefore, it is possible to prevent the occurrence of poor connection due to insufficient formation of the reaction layer between the glass ceramic and the active metal. In addition, although the reaction layer of glass ceramics and active metal is fragile, by setting the thickness to 1 μm or less, the reaction layer is destroyed by the initial residual stress due to the difference in thermal expansion between the glass ceramics and the brazing material. It can be firmly joined without any problems.

  Preferably, in the present invention, since the diameter of the head portion of the lead pin is 0.4 mm or more, the bonding area between the lead pin and the connection pad is sufficiently secured and the bonding strength is increased. Even if it adds, it can suppress that peeling arises in the interface of a lead pin and a brazing material. Preferably, since the thickness of the head portion of the lead pin is 0.05 mm to 0.2 mm, even if an external force in an oblique direction is applied to the lead pin, the connection pad is a starting point for breaking the glass ceramic and the connection pad. The concentration of stress on the outer peripheral edge of the joint surface with the insulating substrate can be reduced.

  The wiring board with lead pins of the present invention will be described in detail below. FIG. 1 is a cross-sectional view showing an example of an embodiment in which the wiring board with lead pins of the present invention is applied to a semiconductor element housing package for housing semiconductor elements. In FIG. 1, 1 is a lead pin, 2 is an Ag—Cu alloy brazing material (hereinafter also referred to as a brazing material) as a connection pad containing at least one of Ti, Zr and Hf as an active metal, and 3 is a wiring with a lead pin A substrate (hereinafter also referred to as a wiring substrate) and 4 are semiconductor elements. The insulating base 5 made of glass ceramics of the wiring board 3 has a mounting portion 7 for mounting the semiconductor element 4 at the center of the upper surface.

  The insulating base 5 is, for example, a rectangular plate-shaped body made of a glass ceramic sintered body, and has a wiring conductor 6 on the surface and at least the surface of the inside. Such a wiring board 3 is manufactured as follows, for example.

  First, a slurry is obtained by adding a solvent (organic solvent, water, etc.) to a ceramic powder, a resin binder, and a molten component, and a predetermined amount of a plasticizer and a dispersant for adjusting the hardness and strength as necessary, to obtain a slurry. A glass ceramic green sheet (hereinafter also referred to as a green sheet) is produced on a support such as a film or paper by a sheet molding method such as a doctor blade method, a lip coater method, or a die coater method.

As the ceramic powder for thermal expansion coefficient at 40 to 400 ° C. to obtain an insulating substrate 5 made of glass ceramic is ^{2.3 × 10 -6 /℃~4.5×10 -6 / ℃} , for example SiO _{2 -Al 2 O 3 -MgO-ZnO-} B 2 O 3, SiO 2 -B 2 O 3 -Al 2 O 3 -NaO 2, SiO 2 -B 2 O 3 -K 2 O-Al 2 O 3 -NaO etc. It is sufficient to use a mixture of low thermal expansion coefficient glass powder such as borosilicate glass and filler powder such as alumina, cordierite, quartz glass, and mullite. The content is appropriately selected.

More to be specific, _SiO 2 of 30 to 55 wt%, 15 to 40 wt% of _Al 2 _O 3, 3 to 25 wt% of MgO, 2 to 15 wt% of ZnO, 2 to 15 wt% _{B 2} O ₃ glass powder 64.5 to 98.5 mass% containing, and 0.5 to 20 wt% cordierite powder, mullite, anorthite, Surausonaito, celsian, at least one selected from the group consisting of quartz glass Containing 1 to 35 mass% of filler powder. By subjecting this glass powder to a heat treatment at 1050 ° C. or lower, at least cordierite is precipitated as a crystalline phase, and at least one selected from the group of garnite, spinel and mullite is precipitated as a crystalline phase together with cordierite. As a result, it is possible to achieve low thermal expansion, low dielectric constant, and low Young's modulus of the insulating substrate 5. Lowering the thermal expansion and lowering the Young's modulus achieves an improvement in the reliability of primary mounting and secondary mounting, which is more preferable.

  Next, on this ceramic green sheet, a conductor paste obtained by pasting a powder of a conductor material is printed by a screen printing method or a gravure printing method, or a method such as transferring a metal foil having a predetermined pattern shape, A wiring conductor 6 is formed. As the conductive material of the conductive paste, Cu, Ag, Ag—Pt, Ag—Pd, Au, or the like is suitably used for the glass ceramic sintered body.

  The wiring conductor 6 also includes through conductor portions such as via conductors and through-hole conductors for connecting the conductor patterns respectively disposed on the upper surface and the lower surface of the insulating substrate 5 inside the insulating substrate 5. It is. This through conductor is formed by, for example, filling a through hole formed in the ceramic green sheet by punching or the like with a conductor paste.

  Next, a plurality of ceramic green sheets on which the wiring conductors 6 are formed are stacked and fired at a predetermined temperature (about 900 ° C. in the case of glass ceramics), whereby the wiring substrate 3 is manufactured.

  Then, an Ag-Cu containing at least one of Ti, Zr and Hf as an active metal in a region including a portion where the through conductor as the wiring conductor 6 is exposed on the surface of the insulating base 5 on the lower surface of the wiring substrate 3. A paste of the alloy brazing material 2 is printed by a screen printing method, a gravure printing method, or the like, and the nail head type lead pin 1, the wiring conductor 6 and the insulating base 5 of the wiring substrate 3 are replaced with an Ag-Cu alloy brazing material. Braze through 2

  This Ag—Cu alloy brazing material 2 is composed of a brazing material such as BAg-8 (JIS Z-3261: 72 mass% Ag-28 mass% Cu), Ag is 60 to 80 mass%, and Cu is 20 to 40 mass%. A material obtained by adding 2 to 10% by mass of at least one of Ti, Zr, and Hf, which are active metals, in the state of metal or hydride is used in the Ag—Cu alloy brazing material 2 having the composition: .

  In order to join the lead pin 1 to the insulating base 5 through the brazing material 2, for example, the powder of the brazing material 2 is combined with an organic solvent, a resin binder, and a solvent (organic solvent, water, etc.) to 5 to 15 mass%. Corresponding to the part where the lead pin 1 is erected on the surface of the insulating base 5 including the exposed end surface of the through conductor, for example, the surface of the insulating base 5 including the exposed end surface of the through conductor, by mixing the brazing paste obtained by external addition The head portion 1a of the lead pin 1 is placed on the predetermined pattern, and the head portion 1a is placed on the predetermined pattern. The head portion 1a is placed in a vacuum, in a neutral atmosphere, or in a reducing atmosphere to a predetermined temperature (for example, about 800). The brazing material 2 is melted, and the wiring conductor 6 and the insulating base 5 are joined to the lead pin 1 by brazing.

  At this time, considering the melting point of the brazing material 2 and the appearance of the joint after brazing, the thickness of the reaction layer and the alloy layer, the content of active metal in the brazing material 2, volume (volume), maximum brazing temperature It is necessary to determine a holding time at a temperature equal to or higher than the melting point of the brazing material 2.

As an example, after brazing the surface of the insulating substrate 5 using a brazing material 2 in which 3 mass% of TiH ₂ is added as an active metal to a so-called BAg-8 brazing material of 72 mass% Ag-28 mass% Cu. When a connection pad having a diameter of 0.90 mm is formed, a lead pin 1 having a pin diameter of 0.20 mm, a head portion 1a thickness of 0.15 mm, and a head portion 1a diameter of 0.45 mm is applied to a predetermined portion of the insulating substrate 5. In the state of contact, if a maximum temperature of 795 ° C. to 850 ° C. is maintained for 5 minutes to 1 hour in a vacuum furnace, a good bonded state having high strength can be obtained.

Here, when the insulating substrate 5 is glass ceramics is a thermal expansion coefficient at 40 to 400 ° C. is ^{2.3 × 10 -6 /℃~4.5×10 -6 / ℃} , and the side of the head portion 1a It is necessary that the distance from the outer peripheral edge of the connection pad is 0.125 mm or more over the entire circumference.

When the distance between the outer peripheral edge of the connection pad and the side surface of the head portion 1a is less than 0.125 mm, the thermal expansion coefficient at 40 to 400 ° C. is 2.3 × 10 ⁻⁶ / ° C. to 4.5 × 10. When the lead pin 1 is connected to the insulating base 5 made of glass ceramics at ⁻⁶ / ° C. via a connection pad of an Ag—Cu alloy brazing material containing at least one of Ti, Zr and Hf, the head of the lead pin 1 A sufficient meniscus cannot be formed on the connection pad formed in the portion 1a. As a result, when the lead pin 1 is joined, the initial residual stress generated in the joint portion between the insulating base 5 and the lead pin 1 is increased, and an external force is applied to the lead pin 1 in an oblique direction so that the stress is applied to the insulating base 5 and the connection pad. When concentrated on the outer peripheral edge of the joint surface, the total stress (the sum of the initial residual stress and the stress due to the external force) exceeds the ceramic strength of the insulating base 5, and the insulating base 5 is broken such as cracks. May occur and the lead pin 1 may be detached from the wiring board 3 in some cases.

  Further, the thickness of the reaction layer formed between the insulating substrate 5 and the connection pad and containing the glass ceramic component and at least one of Ti, Zr and Hf is 0.2 μm to 1 μm. If the thickness of the reaction layer containing glass ceramics and at least one of Ti, Zr and Hf which are active metal components is less than 0.2 μm, it is difficult to form the reaction layer uniformly on the insulating substrate 5. is there. As a result, the reaction layer is formed in a mottled pattern, and the bonding strength is weakened. On the other hand, when the thickness of the reaction layer exceeds 1 μm, the fragile reaction layer is likely to be broken by the initial residual stress due to the difference in thermal expansion between the glass ceramic and the connection pad.

  The thickness of the reaction layer is changed by adjusting the content of Ti, Zr and Hf, which are active metal components in the Ag—Cu alloy brazing material containing at least one of Ti, Zr and Hf. it can. The thickness of the reaction layer can be measured by observing the cross section with a wavelength dispersive X-ray microanalyzer (EPMA) or a scanning electron microscope (SEM).

  The lead pin 1 has a head portion 1a with a diameter of 0.4 mm or more and a thickness of 0.05 mm to 0.2 mm. If the diameter of the head portion 1a is less than 0.4 mm, the absolute bonding area between the brazing material 2 and the lead pin 1 is insufficient. As a result, when an external force in an oblique direction is applied to the lead pin 1, peeling or cracking is likely to occur at the interface between the lead pin 1 and the connection pad. The upper limit of the diameter of the head portion 1a can be set according to the outer dimensions of the insulating base 5, the installation interval of the lead pins 1, the arrangement method of the lead pins 1, and the like. For example, when the wiring board 3 of the present invention is applied to a semiconductor element storage package for mounting the semiconductor element 4, the head portion 1a preferably has a diameter of about 0.4 to 1 mm, and the side surface of the head portion 1a and the brazing material It is easy to secure a distance between the outer peripheral ends of 2 and 0.125 mm or more over the entire circumference.

  Further, when the thickness of the head portion 1a is less than 0.05 mm, the brazing material 2 tends to creep up to the upper portion of the head portion 1a, that is, near the root of the lead pin 1. As a result, the meniscus shape of the connection pad becomes unstable, an external force is applied to the lead pin 1 in an oblique direction, and when the stress concentrates on the outer peripheral edge of the joint surface between the connection pad and the insulating base 5, the insulation is generated. Breaking such as cracks is likely to occur in the substrate 5. If the thickness of the head portion 1a exceeds 0.2 mm, the angle of the meniscus tends to increase when the brazing material 2 crawls up by the thickness of the head portion 1a. As a result, when the lead pin 1 is joined, the initial residual stress generated at the joint portion between the insulating base 5 and the lead pin 1 is increased, and an external force is applied to the lead pin 1 in an oblique direction, so that the stress becomes the insulating base 5. When concentrated on the outer peripheral edge of the joint surface with the material 2, the total stress (the sum of the initial residual stress and the stress due to external force) exceeds the ceramic strength of the insulating base 5, and the insulating base 5 is cracked. In some cases, breakage occurs and the lead pins 1 are detached from the wiring board 3.

  The material of the lead pin 1 used in the wiring board 3 of the present invention, the length of the pin portion, the thickness of the head portion 1a, and the like can be selected according to the shape of the socket of the external electric circuit, the connection method, and the like. For example, in the case of a lead pin 1 applied to a package for housing a semiconductor element, one made of an Fe-Ni-Co alloy or Cu alloy is used, and a pin having a length of about 1 to 6 mm is used. The

  By joining the lead pin 1 and the insulating base 5 as described above, even if an external force is applied to the lead pin 1 from an oblique direction, a high joint is obtained at the joint portion between the insulating base 5 and the lead pin 1 via the brazing material 2. Strength can be ensured, and it is possible to obtain the wiring substrate 3 to which the lead pins 1 are bonded in a good brazed state.

  In the wiring board 3 of the present invention, the surface of the portion of the wiring conductor 6 formed on the surface of the insulating base 5 where the lead pin 1 is not joined and the portion where the lead pin 1 on the exposed surface of the through conductor is not joined are Before or after joining the insulating substrate 5 and the lead pin 1, a metal layer of Ni, Au or the like having excellent corrosion resistance and good wettability with the Ag—Cu alloy brazing material 2 is plated with a thickness of 1 to 20 μm. It may be applied by, for example.

  The Ni plating layer is composed of, for example, an electroless Ni—P plating layer containing about 4 to 12% by mass of P. In such a Ni plating layer, first, the insulating base 5 on which the wiring conductor 6 is formed is immersed in an acidic cleaning solution having a temperature of 25 to 50 ° C. composed of a surfactant and an aqueous hydrochloric acid solution for 1 to 5 minutes. After the exposed surface of the conductor 6 is cleaned and then washed with pure water, it is 1 to 5 in a palladium active solution having a temperature of 25 to 40 ° C. composed of palladium chloride, potassium hydroxide and ethylenediaminetetraacetic acid. Immerse for about a minute to deposit a palladium catalyst on the surface of the wiring conductor 6 and then wash it with pure water, followed by a temperature comprising nickel sulfate, sodium citrate, sodium acetate, sodium hypophosphite, ammonium chloride. Is deposited on the exposed surface of the wiring conductor 6 by dipping in an electroless Ni plating solution at 50 to 90 ° C. for 2 to 60 minutes.

  When the Ni plating layer has a thickness of less than 1 μm, the surface of the wiring conductor 6 formed on the surface of the insulating substrate 5, in the example shown in FIG. 2, the portion that becomes the electrode pad 8 to which the electrode of the semiconductor element 4 is connected. However, the exposed surface of the wiring conductor 6 tends to be oxidized or discolored. On the other hand, when the thickness exceeds 20 μm, cracks and peeling are likely to occur in the Ni plating layer due to internal stress of the Ni plating layer. Therefore, the thickness of the Ni plating layer is preferably in the range of 1 to 20 μm.

  Further, when the Ni plating layer is formed by electroless Ni-P plating as described above, the Ni plating layer is formed on the exposed surface of the wiring conductor 6 when the content of P in the Ni plating layer is less than 4% by mass. The deposition rate of Ni plating becomes slow when depositing, and it takes a long time to obtain a Ni plating layer with a predetermined thickness, so the productivity becomes extremely poor. On the other hand, if it exceeds 12% by mass, the reactivity with the Au plating layer deposited on the Ni plating layer becomes poor, and it tends to be difficult to satisfactorily coat the Ni plating layer with the Au plating layer. Therefore, the content of P in the Ni plating layer is preferably in the range of 4 to 12% by mass.

  In particular, when Ni-P plating is performed by electroless plating after joining the insulating base 5 and the lead pin 1, Ni plating is deposited on the insulating base 5 around the brazing material 2 and the adjacent wiring conductors 6 are short-circuited. There is a case. In order to prevent this, the amount of the resin binder in the brazing filler metal 2 paste is reduced, the carbon residue on the surface of the insulating base 5 is reduced, and the factor that the Ni plating layer is deposited on the surface of the insulating base 5 is reduced. By etching the surface of the insulating base 5 in the pretreatment stage of plating, the brazing filler metal components such as Ag and Cu attached to the surface of the insulating base 5 around the connection pads are removed by melting and vaporizing at the time of brazing. Such measures should be taken.

  Here, the amount of the resin binder in the paste of the brazing material 2 is preferably externally added at a rate of 8 to 12% by mass from the above reasons and from the viewpoint of printability. Furthermore, in order to improve the decrease in heat resistance and discoloration of the plating layer due to electroless plating, it is effective to densify the plating layer by heat treatment at 400 ° C. or higher after plating.

  In the wiring board 3 of the present invention, the semiconductor element 4 is mounted on the mounting portion 7 using epoxy resin, Ag epoxy resin, or the like, and the electrode on the semiconductor element 4 and the mounting portion 7 of the insulating base 5 are in the vicinity. The electrode pad 8 formed as a part of the wiring conductor 6 is electrically connected with a fine metal wire (bonding wire) such as Au, Cu, Al, etc. A ceramic lid body 9 such as a bonded body is attached and sealed by adhesion or welding with a resin such as an epoxy resin, a brazing material such as an Au—Sn alloy or an Au—Ge alloy, or the like, thereby obtaining a semiconductor device. .

  Examples of the wiring board with lead pins of the present invention will be described below.

First, _SiO 2 of 44 wt%, 28 wt% of _Al 2 _O 3, 11 wt% of MgO, 5 wt% of ZnO, 5 wt% of _B 2 _O 3, 6% by weight of CaO, 1 wt% of BaO A glass powder containing 85% by weight, 5% by weight of cordierite powder as filler powder, and 10% by weight of mullite powder are mixed, and a resin binder, an organic solvent, a plasticizer, and a dispersant are added to the slurry. This was obtained, and a ceramic green sheet was produced by a doctor blade method on a PET film support.

  Next, a through-hole was formed in this ceramic green sheet by punching, and a via conductor was formed by filling a conductor paste.

  Next, a conductor paste obtained by pasting Cu powder was printed by a screen printing method to form a wiring conductor (a conductive paste layer serving as a wiring conductor).

Next, a plurality of ceramic green sheets on which these via conductors and wiring conductors are formed are stacked and fired at a temperature of 950 ° C. so that the thermal expansion coefficient at 40 to 400 ° C. is 3.2 × 10 ⁻⁶ / ° C. An insulating substrate made of glass ceramics was manufactured.

An insulating base made of glass ceramics having a thermal expansion coefficient of 4.5 × 10 ⁻⁶ / ° C. at 40 to 400 ° C. was produced using anorthite powder instead of the mullite powder of the filler powder.

Similarly, 72.5 wt glass powder containing 44 wt% of _SiO 2, 29 wt% of _Al 2 _O 3, 11 wt% of MgO, 7% by weight of ZnO, 9 wt% of _B 2 _{O 3} %, Using a mixture of cordierite powder as filler powder at 2.5 mass% and quartz glass powder at 25 mass%, and firing at a temperature of 950 ° C., the coefficient of thermal expansion at 40 to 400 ° C. An insulating substrate made of glass ceramics having a temperature of 2.3 × 10 ⁻⁶ / ° C. was produced.

Next, a ratio of 3% by mass of TiH ₂ as an active metal and 10% by mass of a resin binder on an Ag—Cu alloy brazing material (BAg-8) composed of 72% by mass of Ag and 28% by mass of Cu on the surfaces of these insulating substrates. The active metal brazing material paste externally added in (1) was screen-printed as a connection pad for joining the lead pin and the insulating substrate to form a connection pad having a diameter of 0.90 mm after brazing.

  Next, through this connection pad, a lead pin made of Fe—Ni—Co alloy having a pin portion diameter of 0.20 mm, a head portion thickness of 0.15 mm, and a head portion diameter of 0.45 mm is evacuated. Bonding was performed by maintaining the maximum temperature of 800 ° C. for 15 minutes in a furnace.

  Thereafter, the minimum distance over the entire circumference between the side surface of the head portion and the outer peripheral edge of the connection pad was measured using a three-dimensional measuring machine.

  Thereafter, the bonding strength (45 ° tensile strength) of this lead pin was evaluated by a tensile test in which the lead pin was pulled upward at 45 ° at a speed of 10 mm / min.

Note that the lead pin can withstand bending if the 45 ° tensile strength (breaking strength) is 15 N or more for the lead pin, but if the 45 ° tensile strength is less than 15 N, the lead pin is not bent when an external force is applied to the lead pin. In addition, since the insulating base made of glass ceramics is destroyed, there is a problem that the lead pin can be removed when the socket is inserted. As a result, as a criterion for determining the bonding strength, if the 45 ° tensile strength is 15 N or more, there is no practical problem. The results are shown in Table 1.

From Table 1, a 40 to thermal expansion coefficient of 2.3 × ^{10 -6} /℃~4.5×10 ^-6 / ℃ at 400 ° C. of glass ceramic forming the insulating substrate, the connection pads and the side surface of the head portion The wiring board with lead pins of the present invention (sample Nos. 4, 5, 9, 10, 14, and 15) of the present invention in which the distance between the outer peripheral ends of the lead pins is 0.125 mm or more over the entire circumference is 45 ° tensile strength of the lead pins. The minimum value was 15 N or more, which was a sufficient bonding strength. Moreover, the state of destruction was not the outer peripheral edge of the joint surface between the connection pad and the insulating base, which is the starting point of the destruction of the glass ceramics, but was cut at the pin portion.

  On the other hand, Sample No. whose distance from the side surface of the head portion to the outer peripheral edge of the brazing pad is less than 0.125 mm over the entire circumference. 1, 2, 3, 6, 7, 8, 11, 12, 13 have an average value of 45 ° tensile strength of the lead pins of less than 15 N, and all start from the outer peripheral edge of the joint surface between the connection pad and the glass ceramic. As a result, the destruction of porcelain occurred.

In the same manner as in Example 1, using different ceramic green sheet compositions, 40 to the thermal expansion coefficient at 400 ° C. is 2.3 × ^{10 -6} /℃,3.2×10 ^-6 /℃,4.5 An insulating substrate made of glass ceramics of × 10 ⁻⁶ / ° C. was manufactured.

Next, TiH ₂ as an active metal is added in an amount of 1% by mass, 1.5% by mass, 3% by mass to Ag—Cu alloy brazing material (BAg-8) comprising 72% by mass of Ag and 28% by mass of Cu on the surfaces of these insulating substrates. An active metal brazing paste with externally added 10% by mass and a binder of 10% by mass is screen-printed as a connection pad for joining the lead pin and the insulating substrate, and the diameter after brazing becomes 0.90 mm Formed.

  Next, through this brazing material, a lead pin made of Fe-Ni-Co alloy having a pin portion diameter of 0.20 mm, a head portion thickness of 0.20 mm, and a head portion diameter of 0.45 mm, Bonding was performed by maintaining the maximum temperature of 800 ° C. for 15 minutes in a vacuum furnace.

  Next, the minimum distance over the entire circumference between the side surface of the head part and the outer peripheral edge of the connection pad is measured using a coordinate measuring machine, and the distance between the side surface of the head part and the outer peripheral edge of the connection pad is It was confirmed that it was 0.125 mm or more over the circumference.

  Thereafter, the sample of the produced wiring board with lead pins was divided into two groups, and one group was used as a sample for observing the thickness of the reaction layer, and the thickness of the reaction layer was measured by examining the Ti element with EPMA. . In the other group, the lead pin joint strength (45 ° tensile strength) was measured by conducting a pull test on the lead pin 50 pins at a rate of 10 mm / min 45 ° upward to determine the breaking strength and the breaking mode. Was evaluated.

  Note that the lead pin can withstand bending if the 45 ° tensile strength (breaking strength) is 15 N or more for the lead pin, but if the 45 ° tensile strength is less than 15 N, before the lead pin bends when an external force is applied to the lead pin. Since the insulating substrate may be destroyed, a problem that the lead pin can be removed when the socket is inserted is likely to occur. If it is less than 10N, the insulating substrate is completely destroyed.

  Accordingly, as a criterion for determining the bonding strength, the 45 ° tensile strength is 15 N or more, and the failure mode is not the outer peripheral end portion of the bonding surface between the connection pad and the insulating substrate, which is the starting point of the breakdown of the insulating substrate, but the pin portion. It was determined that there was no problem if the fracture rate (pin breakage rate) was 100% (indicated by a circle in Table 2).

  Further, if the tensile strength is 10 N to 15 N and the pin breakage rate in the fracture mode is 50% or more, there is no practical problem (indicated by Δ in Table 1).

Further, if the tensile strength is less than 15 N and the pin breakage rate in the fracture mode is less than 50%, it cannot be actually used (indicated by x in Table 2). The results are shown in Table 2. In addition, the tensile strength in Table 2 shows the minimum strength.

From Table 2, the thermal expansion coefficient at 40 to 400 ° C. of glass ceramic forming the insulating substrate is the ^{2.3 × 10 -6 /℃~4.5×10 -6 / ℃} , the connection pads and the insulating substrate The wiring board with lead pins of the present invention in which the thickness of the reaction layer containing glass ceramic component and Ti formed between them is 0.2 μm to 1 μm, the 45 ° tensile strength of the lead pins is 15 N or more even at the minimum value, The failure mode also had a pin breakage rate of 100% and was in a sufficiently joined state (indicated by a circle in Table 2).

  On the other hand, a sample in which the thickness of the reaction layer containing glass ceramic component and Ti formed between the insulating substrate and the connection pad is less than 0.1 μm or more than 1 μm has an average value of 45 ° tensile strength of the lead pin. The failure mode was a pin breakage rate of 50% or more (indicated by Δ in the table).

In the same manner as in Example 1, using different ceramic green sheet compositions, 40 to the thermal expansion coefficient at 400 ° C. is 2.3 × ^{10 -6} /℃,3.2×10 ^-6 /℃,4.5 An insulating substrate made of glass ceramics of × 10 ⁻⁶ / ° C. was manufactured.

Next, an active metal brazing material in which TiH ₂ as an active metal is externally added at a ratio of 3% by mass to an Ag—Cu alloy brazing material (BAg-8) composed of 72% by mass of Ag and 28% by mass of Cu is formed on the surfaces of these insulating substrates. The material paste was screen-printed as a connection pad for joining the lead pin and the insulating substrate to form a connection pad having a diameter of 0.90 mm after brazing.

  Next, through this brazing material, the diameter of the pin part is 0.20 mm, the diameter of the head part is 0.3 mm, 0.4 mm, and 0.5 mm, and the thickness of the head part is 0.05 mm and 0.1 mm. , 0.15 mm, 0.20 mm, and 0.25 mm lead pins made of an Fe—Ni—Co alloy were joined by holding at a maximum temperature of 800 ° C. for 15 minutes in a vacuum furnace.

  Next, the minimum distance over the entire circumference between the side surface of the head part and the outer peripheral edge of the connection pad is measured using a coordinate measuring machine, and the distance between the side surface of the head part and the outer peripheral edge of the connection pad is It was confirmed that it was 0.125 mm or more over the circumference.

  Thereafter, the lead pin 50 pin was pulled by a tensile test in which the lead pin was bonded at a rate of 10 mm / min (45 ° tensile strength), and the breaking strength and the breaking mode were evaluated.

  Note that the lead pin can withstand bending if the 45 ° tensile strength (breaking strength) is 15 N or more with respect to the lead pin, but if the 45 ° tensile strength is less than 15 N, before the lead pin bends when an external force is applied to the lead pin. Since the insulating substrate may be destroyed, a problem that the lead pin can be removed when the socket is inserted is likely to occur. If it is less than 10N, the insulating substrate is completely destroyed.

  Accordingly, as a criterion for determining the bonding strength, the 45 ° tensile strength is 15 N or more, and the failure mode is not the outer peripheral end portion of the bonding surface between the connection pad and the insulating substrate, which is the starting point of the breakdown of the insulating substrate, but the pin portion. It was determined that there was no problem if the fracture rate (pin breakage rate) was 100% (indicated by a circle in Table 3).

  Further, if the tensile strength is 10 N to 15 N and the pin breakage rate in the fracture mode is 50% or more, there is no practical problem (indicated by Δ in Table 3).

Further, if the tensile strength is less than 15 N and the pin breakage rate in the fracture mode is less than 50%, it cannot be actually used (indicated by x in Table 3). The results are shown in Table 3. In addition, the tensile strength in Table 3 shows the minimum strength.

From Table 3, the thermal expansion coefficient at 40 to 400 ° C. of glass ceramic forming the insulating substrate is the ^{2.3 × 10 -6 /℃~4.5×10 -6 / ℃} , the diameter of the head portion of the lead pin The lead pin-equipped wiring board of the present invention having a thickness of 0.4 mm or more and a thickness of 0.05 mm to 0.2 mm has a 45 ° tensile strength of the lead pin of 15 N or more even at the minimum value, and the break mode is 100%. Yes, it was in a sufficiently joined state (indicated by a circle in Table 3).

  On the other hand, samples with a lead pin head portion diameter of less than 0.4 mm or a thickness of more than 0.2 mm have an average 45 ° tensile strength of the lead pin of less than 15 N, and the break mode has a pin breakage of 50% or more. (Indicated by Δ in Table 3).

  As described above, by using the wiring board with lead pins of the configuration of the present invention, it is possible to obtain a bonding strength having no practical problem, and a wiring board having high bonding reliability even when an external force is applied to the lead pins in an oblique direction. I was able to get it.

  In addition, this invention is not limited to the example of the above embodiment, A various change may be performed in the range which does not deviate from the summary of this invention. For example, in the example of the above-described embodiment, an example in which the wiring board of the present invention is applied to a package for housing a semiconductor element has been shown.

It is sectional drawing which shows the example of embodiment of the wiring board with a lead pin of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Lead pin 1a ... Head part 2 ... Brazing material 3 ... Wiring board 4 with a lead pin ... Semiconductor element 5 ... Insulation base 6 ... Wiring conductor 7 ... Mounting part 8 ... Electrode pads

Claims (3)

With at least the surface on the wiring conductor of the insulating substrate made of glass ceramics is formed having a coefficient of thermal expansion 2.3 × ^{10 -6} /℃~4.5×10 ^-6 / ℃ at 40 to 400 ° C., the In the wiring board with lead pins, wherein the head portion of the lead pin is connected to the wiring conductor on the surface of the insulating base via a connection pad made of an Ag-Cu alloy brazing material containing at least one of Ti, Zr and Hf. The connection pad has an outer dimension larger than an outer dimension of the head portion, and a distance between an outer peripheral end of the connection pad and a side surface of the head portion is 0.125 mm or more over the entire circumference. Wiring board with lead pins. The thickness of the reaction layer formed between the insulating base and the connection pad and containing the glass ceramic component and at least one of Ti, Zr and Hf is 0.2 μm to 1 μm. The wiring board with lead pins according to claim 1. 3. The wiring board with lead pins according to claim 1, wherein the head portion of the lead pins has a diameter of 0.4 mm or more and a thickness of 0.05 mm to 0.2 mm.

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