JP4364033B2 - Wiring board with lead pins - Google Patents

Description

  The present invention relates to a so-called pin grid array (PGA) type lead pin 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 and the like for housing a semiconductor element. The present invention relates to an attached wiring board.

  Conventionally, a package for housing a semiconductor element for housing a semiconductor element such as a semiconductor integrated circuit element, a circuit board or an electronic circuit module constituting a high-frequency circuit, a power circuit, and the like have a surface of an insulating base made of ceramics and A wiring board having a wiring conductor in at least one of the inside is used. The wiring board has a metal lid for hermetically accommodating the semiconductor element in a terminal member such as a lead pin and a ball terminal, a heat radiating member such as a heat radiating plate and a heat radiating fin, or a container composed of the wiring board and the lid. A metal member such as a seal member such as a seal ring for attaching the body is joined to the metallized wiring conductor or metallized layer on the surface of the wiring board or directly to the insulating base of the wiring board via a brazing material.

  For example, in the case of a package for housing a semiconductor element, it is generally made of an electrically insulating material such as alumina ceramics, a recess for accommodating a semiconductor element at a substantially central portion of the upper surface thereof, and W led out from the periphery of the recess to the outer periphery. , A wiring board made of an insulating base having a plurality of metallized wiring conductors made of refractory metal powder such as Mo, and metallized wiring formed on the lower surface of the wiring board to electrically connect the semiconductor element to the external electric circuit board It has a configuration (so-called pin grid array type) having a conductive electrode pad and lead pins as external terminals joined via a brazing material such as Ag brazing, and a metal heat dissipating member or the like can be attached if necessary. It is worn.

  Then, the semiconductor element is bonded and fixed to the bottom surface of the concave portion of the wiring board via an adhesive made of glass, resin, etc., and each electrode of the semiconductor element and the metallized wiring conductor are electrically connected via a bonding wire or the like. A semiconductor device is configured by bonding a lid to the upper surface of the wiring board via a sealing material such as glass or resin and hermetically sealing the semiconductor element inside a container composed of the wiring board and the lid. The

  In general, a lead pin as a terminal member of such a semiconductor device is formed by externally processing one end of the lead pin by plastic working in order to increase the bonding area with the brazing material and increase the bonding strength with the electrode pad. It is a so-called nail head type having a pin portion inserted into a socket of an electric circuit board and a head portion having a disk shape or the like joined to an electrode pad of a wiring board.

  On the other hand, with the recent advanced information age, the frequency band used for high frequency signals of communication equipment is increasingly shifting to the high frequency band. In such a high-frequency wiring board that transmits a high-frequency signal, the resistance of the conductor forming the wiring conductor is required to be low in order to transmit the high-frequency signal at high speed, and the insulating substrate also has a lower dielectric constant. Is required.

  Therefore, as a high-frequency insulating substrate having a low dielectric constant, a wiring substrate in which a metallized wiring conductor made of a low-resistance metal such as Cu, Ag, Au or the like is used 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 metallized wiring conductor to the glass ceramic is also low.

  In particular, an electrode pad made of a metallized layer on the surface of a wiring board among metallized wiring conductors has a structure in which only one main surface thereof is bonded to glass ceramics, and the metallized wiring conductor inside the wiring board is made of glass ceramics. Compared to the firm structure embedded so as to be surrounded, the bonding strength of the electrode pad made of this metallized layer to the glass ceramic is low.

  Furthermore, the lead pad is connected to the electrode pad made of the metallized layer via a brazing material, and when an external force is applied to the lead pin from a vertical direction or an oblique direction, the external force is composed of the brazing material and the metallized layer through the lead pin. Acting on the electrode pad, especially when an external force is applied to the lead pin from an oblique direction, a moment of force is applied with the rotational movement of the head portion of the lead pin, so the outer periphery of the electrode pad consisting of the metallized layer and the glass ceramic interface There is a problem in that a large stress is generated in the portion, and an interface failure starting from the outer peripheral portion of the bonding interface between the electrode pad made of the metallized layer and the glass ceramics occurs.

  Therefore, the same composition is formed on the outer periphery of the electrode pad made of the metallized layer and the glass ceramic so that a region for forming the brazing material for joining the lead pin of the electrode pad made of the metallized layer is opened on the surface of the wiring board. After the glass ceramic paste is printed, it is fired and a glass ceramic coating layer is formed on the upper part of the outer periphery of the electrode pad made of the metallized layer to hold down the electrode pad made of the metallized layer. A method has been used in which the outer peripheral portion of the interface of glass ceramics is reinforced to prevent interface breakdown.

On the other hand, as means for avoiding breakage at the interface between the insulating substrate made of glass ceramics and the electrode pad made of metallized layer, a brazing material made of an Ag—Cu alloy containing at least one of Ti, Zr or Hf as an active metal ( (Hereinafter also referred to as an active metal brazing material), without forming electrode pads for joining lead pins on the wiring board, the through conductor (via conductor) as a wiring conductor led out from the inside of the wiring board is insulated. A method of directly joining a lead pin to a portion exposed on the surface of the substrate is also conceivable. In this method, the electrical connection is established by directly connecting the exposed portion of the through conductor (via conductor) to the surface of the insulating base and the lead pin via the active metal brazing material without using the electrode pad made of the metallized layer. 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 joined to an insulating base made of glass ceramics through an active metal brazing material, and thus consists of a metallized layer. The lead pin can be bonded without depending on the bonding strength between the electrode pad and the glass ceramic, and the breakage at the interface between the electrode pad and the glass ceramic can be avoided.
JP-A-8-162563 JP-A-8-298381 JP-A-9-18144

  However, as in the prior art described above, the glass ceramic layer is formed on the outer periphery of the electrode pad made of the metallized layer and the electrode pad made of the metallized layer is pressed down to reinforce the outer periphery of the electrode pad made of the metallized layer. In this method, the diameter of the electrode pad made of the metallized layer is reduced and the area of contact with the glass ceramic is reduced, and the external force applied to the lead pin from an oblique direction is metallized. There is a problem in that interface breakage occurs starting from the outer peripheral portion because it is concentrated on the outer peripheral portion of the interface between the electrode pad made of layers and the glass ceramic.

  On the other hand, in the method of directly joining the lead pin to the glass ceramic using the active metal brazing material, since the brazing temperature is as high as about 800 ° C., the difference in thermal expansion coefficient between the active metal brazing material and the glass ceramic becomes large. In the cooling process during melting and solidification of the active metal brazing material, if the thermal stress exceeds the strength of the glass ceramics, the active metal brazing material and the glass ceramics can be used without applying external force to the lead pins. There is also a problem that cracks are generated in the insulating base starting from the end of the joint surface of the lead and the joint reliability of the lead pin is lowered.

  The present invention has been completed in order to solve the above-described problems. The object of the present invention is, for example, when the strength of glass ceramics or the like is low as an insulating base, and when an external force in an oblique direction is applied to a lead pin. Of the interface between the active metal brazing material and the insulating substrate due to the difference in thermal expansion coefficient between the active metal brazing material and the insulating substrate. An object of the present invention is to provide a highly reliable wiring board with lead pins capable of solving the problem of cracks occurring inside an insulating substrate starting from an end and ensuring a bonding strength between a lead pin and an insulating substrate that can be practically endured. .

In the wiring board with lead pins of the present invention, a wiring conductor is formed on at least one of the surface of the insulating base and the inside thereof, and an electrode pad made of a metallized layer formed on the surface of the insulating base is formed in a disk shape at one end. A lead pin-attached wiring board in which the head part of a lead pin having a head part is attached via a low melting point brazing material, wherein the outer peripheral part of the electrode pad and the surface of the insulating substrate around it are made of Ti as an active metal. , Zr or Hf, which is covered with an active metal brazing material having a melting point higher than that of the low melting point brazing material, which is made of an Ag-Cu alloy containing at least one of Zr and Hf.

According to the wiring board with lead pins of the present invention, the outer peripheral portion of the electrode pad made of the metallized layer and the surface of the surrounding insulating substrate are made of an Ag—Cu alloy containing at least one of Ti, Zr or Hf as an active metal. Since the entire circumference is covered with an active metal brazing material having a melting point higher than that of the low melting point brazing material , when an external force is applied to the lead pin in an oblique direction, the outer peripheral portion of the joint surface between the electrode pad and the insulating base is formed. Even if the stress is concentrated, the active metal brazing material forms a reaction layer with the insulating substrate, so that the brittle glass component does not go through, so the outer peripheral portion of the bonding portion between the electrode pad and the insulating substrate is reduced. It is possible to prevent the occurrence of interface breakage or the like as a starting point.

  In addition, since the active metal brazing material is used only on the outer peripheral portion of the electrode pad made of the metallized layer, the amount of the active metal brazing material can be reduced as compared with the method of forming the electrode pad only with the active metal brazing material. In addition, due to the difference in thermal expansion coefficient between the active metal brazing material and the insulating base, it is possible to reduce the thermal stress generated in the cooling process when the active metal brazing material is melted and solidified. Furthermore, as a bonding material for bonding the electrode pad and the lead pin, a low melting point solder such as solder having a melting point lower than that of the active metal brazing material formed on the outer periphery of the electrode pad made of the metallized layer is used. It becomes possible to lower the brazing temperature when brazing to the electrode pad, and the thermal stress generated in the cooling process at the time of melting and solidifying the low melting point brazing material becomes small enough to withstand the ceramic strength of the insulating substrate. Therefore, it is possible to prevent cracks from occurring inside the insulating substrate.

The wiring board with lead pins of the present invention will be described in detail below. FIG. 1 is a cross-sectional view of an electrode pad of the present invention, and FIG. 2 is a cross-sectional view showing an example of an embodiment in which the electrode pad of the present invention is applied to a package for housing a semiconductor element that houses a semiconductor element. . In these drawings, 1 is a lead pin, 2 is an electrode pad with an active metal brazing material with an active metal brazing material 2b attached to the outer periphery, 2a is an electrode pad made of a metallized layer, 2b is Ti, Zr or an active metal as an active metal An active metal brazing material made of an Ag-Cu alloy containing at least one Hf, 3 is a low melting point brazing material having a lower melting point than the active metal brazing material 2b , and 4 is a wiring board with lead pins (hereinafter also referred to as a wiring board). Reference numeral 5 denotes a semiconductor element. The insulating base 6 made of glass ceramics that forms the wiring substrate 4 has a semiconductor element mounting portion 8 for mounting the semiconductor element 5 at the center of the upper surface.

  The insulating base 6 is, for example, a rectangular plate-like body made of a glass ceramic sintered body, and has a wiring conductor 7 on at least one of its surface and inside. Such a wiring board 4 is manufactured as follows, for example.

Insulating substrate 6 made of glass ceramics, for example, _SiO 2 _-B 2 _{0 3} system as a glass _{component, SiO 2 -B 2 O 3 -Al} 2 O 3 _{based, SiO 2 -B 2 O 3 -Al} 2 O 3 - MO system (where M represents Ca, Sr, Mg, Ba or Zn), SiO ₂ —Al ₂ O ₃ —M ¹ O—M ² O system (where M ¹ and M ² are the same or different) , Ca, Sr, Mg, Ba or Zn), SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —M ¹ O—M ² O system (where M ¹ and M ² are the same as above) , SiO ₂ —B ₂ O ₃ —M ³ ₂ O system (where M ³ represents Li, Na or K), SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —M ³ ₂ O system (provided that M ³ is the same as above), and is made of PB glass, Bi glass, or the like. Glass powder, for example, composite oxide of Al ₂ O ₃ , SiO ₂ , ZrO ₂ and alkaline earth metal oxide, composite oxide of TiO ₂ and alkaline earth metal oxide, Al ₂ O ₃ and SiO _{2 And} a filler powder such as a composite oxide containing at least one selected from ₂ (for example, spinel, mullite, cordierite) in a mass ratio of 40:60 to 99: 1, and further a suitable organic solvent , A solvent is added and mixed to form a mud, which is formed into a sheet by a doctor blade method or a calender roll method to obtain a ceramic green sheet (ceramic green sheet).

  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, An electrode pad 2a made of a metallized layer and a wiring conductor 7 are formed.

  As the conductive material of the conductive paste, Cu, Ag, Ag—Pt, Ag—Pd, Au, or the like is used for the glass ceramic sintered body.

  The wiring conductor 7 also includes through conductor portions such as via conductors and through-hole conductors for connecting the conductor patterns respectively disposed on the upper and lower surfaces of the insulating base 6 inside the insulating base 6. 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. Further, in FIG. 2, the through conductors are illustrated with emphasis over the actual scale for the sake of explanation.

  Next, a plurality of ceramic green sheets on which the wiring conductors 7 are formed are stacked and fired at a predetermined temperature, for example, about 900 ° C. in the case of glass ceramics, whereby the wiring substrate 4 is manufactured.

  Then, an active metal brazing material is formed on the outer peripheral portion of the electrode pad 2a made of a metallized layer in which the through conductor as the wiring conductor 7 is exposed on the surface of the insulating base 6 on the lower surface of the wiring board 4 and on the surface of the surrounding insulating base 6 The pasted 2b is printed by a screen printing method, a gravure printing method, or the like.

  This active metal brazing material 2b 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 brazing filler is used in which at least one of Ti, Zr and Hf, which are active metals, is added in the form of metal or hydride in an external addition in an amount of 2 to 10% by mass. A paste prepared by adding an organic solvent, a resin binder, and a solvent to metal powder and mixing 5 to 15% by mass with external addition is used.

  This is heat-treated at a predetermined temperature (for example, about 800 ° C.) in accordance with the melting temperature of the active metal brazing material 2b in a vacuum or in a neutral atmosphere or a reducing atmosphere, and the active metal brazing material 2b is melted to form a metallized layer. The electrode pad 2a is formed on the outer periphery of the electrode pad 2a.

  Next, a paste obtained by pasting a low melting point solder material 3 such as solder on the electrode pad 2 with the brazing material is printed by a screen printing method or a gravure printing method, and the head portion 1a of the lead pin 1 is brought into contact therewith. Then, this is heat-treated at a predetermined temperature (for example, about 200 ° C.) in accordance with the melting temperature of the low melting point brazing material 3 in an air atmosphere or a nitrogen atmosphere, and the low melting point brazing material 3 is melted. The insulating base 6 and the lead pin 1 are joined.

Specifically, for example, a brazing material (BAg-8 made of 72 mass% Ag-28 mass% Cu) is formed on the outer peripheral portion of the electrode pad 2a made of a metallized layer having a diameter of 0.6 mm and on the surface of the insulating base 6 around it. ), Using an active metal brazing material 2b to which 3% by mass of TiH ₂ is added as an active metal, a ring-shaped pattern having an inner diameter of 0.5 mm and an outer diameter of 0.8 mm is concentrically formed on the outer periphery of the electrode pad 2a made of a metallized layer. And is held in a vacuum furnace at a maximum temperature of 795 to 850 ° C. for 5 minutes to 1 hour, and an active metal brazing material 2b is applied to the outer peripheral portion of the electrode pad 2a made of a metallized layer and the surface of the surrounding insulating base 6 Form.

  Next, a paste obtained by pasting a low melting point brazing material 3 made of, for example, 63 mass% Sn-37 mass% Pb (so-called eutectic solder) on the electrode pad 2 with the brazing material is used for screen printing, gravure printing, etc. The head portion 1a of the lead pin 1 having a pin diameter of 0.2 mm, a head portion 1a diameter of 0.5 mm, and a head portion 1a thickness of 0.15 mm is brought into contact therewith. Then, this is heated and melted at a predetermined temperature (for example, about 200 ° C.) in accordance with the melting temperature of the low melting point brazing material 3 in an air atmosphere or a nitrogen atmosphere, and the lead pin 1 is soldered on the electrode pad 2 with the brazing material. If attached, a bonded state having high strength and high reliability can be obtained.

  That is, since the outer peripheral portion of the electrode pad 2a made of the metallized layer where the external force on the lead pin 1 is most concentrated and the surface of the surrounding insulating base 6 are coated with the active metal brazing material 2b, the active metal brazing material Since these reaction layers are formed and firmly bonded to the interface between 2b and the insulating substrate 6, the interfacial strength between the electrode pad 2a made of a metallized layer via a brittle glass component and the insulating substrate 6 is reinforced, A better bonding state can be created. For this reason, it is possible to prevent the occurrence of interface breakdown or the like starting from the outer peripheral portion of the joint portion between the electrode pad 2 a made of the metallized layer and the insulating base 6.

  In addition, since the active metal brazing material 2b is formed on the outer peripheral portion of the electrode pad 2a made of the metallized layer, the amount of the active metal brazing material 2b is smaller than that in the case where the electrode pad 2 with the brazing material is formed only by the active metal brazing material 2b. Since it can be reduced, the thermal stress generated in the cooling process when the active metal brazing material 2b is melted and solidified due to the difference in thermal expansion coefficient between the active metal brazing material 2b and the insulating base 6 can be reduced. When the strength of the insulating base 6 is exceeded, it is possible to prevent a phenomenon that a crack is generated in the outer peripheral portion of the joint portion between the insulating base 6 and the active metal brazing material 2b.

  Further, since the low melting point brazing material 3 is used as a bonding material for bonding the lead pin 1 onto the brazing material electrode pad 2, the brazing temperature when the lead pin 1 is brazed to the brazing material electrode pad 2 is used. Since the thermal stress generated during the cooling process when the low melting point brazing filler metal 3 is melted and solidified becomes small enough to withstand the ceramic strength of the insulating base 6, there are cracks in the insulating base 6. Can be prevented.

  As described above, by these actions, an external force is applied to the lead pin 1 in an oblique direction, or the active metal brazing material 2b or the low melting point brazing material 3 and the insulating base when the lead pin 1 is joined to the electrode pad 2a made of a metallized layer. Even when a thermal stress is generated due to a difference in thermal expansion coefficient with respect to 6, the lead pin 1 and the insulating base 6 can be firmly joined, and the wiring substrate 4 with lead pins having high mechanical reliability can be obtained. it can.

  On the other hand, on the electrode pad 2a made of a metallized layer having an opening diameter of 0.6 mm, in which the outer peripheral portion of the metallized pattern having a diameter of 0.8 mm and the surrounding insulating base 6 are coated with the same insulating base 6 component, Ni plating, Au In the case where the lead pin 1 is soldered after plating, when an external force in the oblique direction is applied to the lead pin 1, breakage is likely to occur at the interface between the electrode pad 2 a made of a metallized layer and the insulating substrate 6. . The cause is that when an external force (indicated by an arrow in FIG. 1) is applied to the lead pin 1 from an oblique direction, the head portion 1a of the lead pin 1 rotates (indicated by a curved arrow in FIG. 1), and consists of a metallized layer. A moment of force acts on the outer peripheral portion of the joint between the electrode pad 2a and the insulating base 6. At this time, stress exceeding the interface strength between the electrode pad 2a made of the metalized layer and the insulating base 6 is generated. That is, interface breakage starting from the outer peripheral portion of the bonding interface between the electrode pad 2a and the insulating base 6 is formed.

  On the other hand, when a brazing material pad having a diameter of 0.8 mm is formed from the active metal brazing material 2 b and the lead pin 1 is joined to the brazing material pad and the insulating base 6, the difference in thermal expansion coefficient between the active metal brazing material 2 b and the insulating base 6. As a result, the thermal stress generated in the cooling process at the time of melting and solidifying the active metal brazing material 2b exceeds the strength of the insulating base 6, so that an external force is applied to the outer peripheral portion of the joint surface between the insulating base 6 and the active metal brazing material 2b. Without adding, a crack occurs in the insulating substrate 6, which is a fatal problem in the reliability of joining the lead pins 1.

  In addition, the material of the lead pin 1 used for the wiring board 4 with a lead pin of this invention, and the dimension of each part can be selected according to the shape of the socket of an external electric circuit board, a connection method, etc. 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

  Further, in the wiring board 4 of the present invention, the surface of the part where the lead pin 1 of the wiring conductor 7 formed on the surface of the insulating base 6 is not joined, and the part where the lead pin 1 on the surface where the through conductor is exposed are not joined, Before or after joining the insulating substrate 6 and the lead pin 1, a metal layer of Ni, Au or the like having excellent corrosion resistance and good wettability with the active metal brazing material 2b made of Ag-Cu alloy or the like is 1 to 20 μm. It may be deposited by a plating method or the like with a thickness of.

  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 substrate 6 on which the wiring conductor 7 is formed is immersed in an acidic cleaning solution having a temperature of 25 to 50 ° C. composed of a surfactant and a hydrochloric acid aqueous solution for 1 to 5 minutes. The exposed surface of the conductor 7 is cleaned and then washed with pure water, and then 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 attach a palladium catalyst to the surface of the wiring conductor 7, 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 7 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 7 formed on the surface of the insulating substrate 6, in the example shown in FIG. 2, the portion that becomes the bonding pad 9 to which the electrode of the semiconductor element 5 is connected. Therefore, the exposed surface of the wiring conductor 7 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 7 when the P content in the Ni plating layer is less than 4 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 6 and the lead pin 1, Ni plating is deposited on the insulating base 6 around the active metal brazing material 2b, and adjacent wiring conductors 7 are connected to each other. May short circuit. In order to prevent this, is it possible to reduce the amount of resin binder in the active metal brazing paste and reduce the carbon residue on the surface of the insulating base 6 to reduce the cause of Ni plating deposition on the surface of the insulating base 6? Alternatively, a brazing material such as Ag or Cu adhered to the surface of the insulating base 6 around the active metal brazing material 2b by being melted and vaporized at the time of brazing by etching the surface of the insulating base 6 in the pretreatment stage of plating. What is necessary is just to take measures, such as removing a component.

  Here, the amount of the resin binder in the paste of the active metal brazing material 2b 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 4 with lead pins of the present invention, the semiconductor element 5 is mounted on the mounting portion 8 using an epoxy resin, Ag epoxy resin, or the like, and the electrodes on the semiconductor element 5 and the mounting portion 8 of the insulating base 6 are provided. A bonding pad 9 formed as a part of the wiring conductor 7 in the vicinity is electrically connected with a fine metal wire (bonding wire) such as Au, Cu, or Al, and then made of metal or aluminum oxide made of Cu, Al, or the like. By attaching and sealing the ceramic lid 10 such as a sintered material by bonding with a resin such as an epoxy resin, a brazing material such as an Au-Sn alloy or an Au-Ge alloy, or by welding, a semiconductor device is obtained. It becomes.

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

First, Au-Cu composed of 72% by mass of Ag and 28% by mass of Cu is formed on the outer peripheral portion of the electrode pad composed of a 0.6 mm diameter metallized layer formed on the surface of an insulating substrate made of glass ceramics and the surface of the surrounding insulating substrate. Using an active metal brazing paste in which 3% by mass of TiH ₂ as an active metal and 10% by mass of a resin binder are added to an alloy (BAg-8), an inner diameter of 0.5 mm and an outer diameter of 0.8 mm A ring-shaped pattern was screen printed concentrically on the electrode pad. The insulating substrate was held in a vacuum furnace at a maximum temperature of 800 ° C. for 15 minutes to form a brazed electrode pad having a fired active metal braze pattern.

  Next, a solder paste obtained by pasting 63% by mass of Sn-37% by mass Pb on the electrode pad with the brazing material is screen-printed, and the pin diameter is 0.2 mm and the head part diameter is 0 on the solder paste layer. Solder the lead pin by contacting the head part of the lead pin made of Fe-Ni-Co alloy with a thickness of .5 mm and a head part of 0.15 mm and holding the maximum temperature of about 200 ° C for 1 minute in a nitrogen atmosphere. did.

  Thereafter, the bonding strength (45 ° tensile strength) of this lead pin was evaluated by a tensile test in which the lead pin was pulled at a rate of 10 mm / min 45 ° upward with respect to the axial direction of the pin portion.

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. In addition, since the insulating base made of glass ceramic is destroyed, a problem arises in 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, in Example 1 in which the lead pin was soldered on the electrode pad with the brazing material according to the present invention, the 45 ° tensile strength of the lead pin was 15 N or more even at the minimum value, and the bonding strength was sufficient. Moreover, the state of destruction was not the outer peripheral portion of the joint surface between the active metal brazing material and the insulating base, which is the starting point of the destruction of the glass ceramics, but was broken at the pin portion.

  On the other hand, an electrode pad having an opening diameter of 0.6 mm is formed by coating the outer periphery of an electrode pad made of a metallized layer having a circular pattern with a diameter of 0.8 mm and the surrounding insulating substrate with a glass ceramic layer having the same component as the insulating substrate. In Comparative Example 1 in which the lead pin was soldered after the Ni plating layer and the Au plating layer were deposited on the exposed upper surface of the lead pin, the maximum 45 ° tensile strength of the lead pin was less than 15N, Interfacial fracture occurred starting from the outer periphery of the joint surface.

  Further, in Comparative Example 2 in which an electrode pad having a diameter of 0.8 mm is formed only from the active metal brazing material and the lead pin is joined to the insulating substrate through this electrode pad, the average value of the 45 ° tensile strength of the lead pin is 15N. In some samples, cracks occurred in the outer peripheral portion of the bonding surface between the insulating substrate and the electrode pad without applying external force after bonding, and the cracks progressed inside the insulating substrate.

  From the above, since the outer peripheral portion of the electrode pad where the external force in the oblique direction to the lead pin is most concentrated and the surface of the surrounding insulating base is covered all over by the active metal brazing material, brittle glass is formed. Compared with the interfacial strength between the electrode pad made of metallized layer and the insulating substrate, the active metal brazing material and the insulating substrate are directly bonded, so the bonding strength is high and stable against the external force in the oblique direction to the lead pin. It was found that a junction structure having

  Further, since the active metal brazing material is used only for the outer peripheral portion of the electrode pad made of the metallized layer, the amount of the active metal brazing material can be reduced as compared with the case where the electrode pad is formed only by the active metal brazing material. . Furthermore, it is possible to select a brazing material such as solder having a melting point lower than that of the active metal brazing material as a joining material for joining the lead pin to the electrode pad made of the metallized layer. The thermal stress generated in the process can be reduced, and when the thermal stress exceeds the strength of the insulating base, the occurrence of a crack in the outer periphery of the joint between the insulating base and the active metal brazing material is prevented. Therefore, it was possible to provide a wiring board with lead pins having high bonding reliability.

  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 embodiment, the example in which the wiring board with lead pins of the present invention is applied to a package for housing a semiconductor element is shown, but it may be applied to other uses such as a hybrid integrated circuit board.

It is a principal part expanded sectional view which shows the lead pin junction part in the wiring board with a lead pin of this invention. It is sectional drawing which shows the example which applied the wiring board with a lead pin of this invention to the package for semiconductor element accommodation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Lead pin 1a ... Head part 2 ... Electrode pad 2a with brazing material ... Electrode pad 2b ... Active metal brazing material 3 ... Low melting point brazing material 4 ... Wiring board with lead pin DESCRIPTION OF SYMBOLS 5 ... Semiconductor element 6 ... Insulation base | substrate 7 ... Wiring conductor 8 ... Mounting part 9 ... Bonding pad 10 ... Cover

Claims (1)

The head portion of the lead pin having a wiring conductor formed on at least one of the surface and the inside of the insulating substrate and having a disk-shaped head portion at one end on an electrode pad formed of a metallized layer formed on the surface of the insulating substrate. Is a wiring board with lead pins attached through a low melting point brazing material, wherein the outer peripheral portion of the electrode pad and the surface of the surrounding insulating substrate are made of at least one of Ti, Zr or Hf as an active metal. A wiring board with lead pins, which is covered with an active metal brazing material made of an Ag-Cu alloy and having a melting point higher than that of the low melting point brazing material .

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