JP4360625B2 - Electronic component storage package - Google Patents

Description

  The present invention relates to an electronic component storage package having lead terminals for storing elements and electronic components mainly composed of semiconductor elements such as CCD and C-MOS.

  In recent years, dealing with global environmental issues has become an indispensable issue, and reducing or eliminating the use of lead in electronic components is an essential issue as a measure to reduce the use of environmentally hazardous substances. It has become.

  Conventionally, as a package for storing electronic components, a lead terminal is sandwiched between a substrate for mounting electronic components and a frame body, and these are joined via a low melting point glass mainly composed of lead oxide for storing electronic components The package was mainly used. However, recently, in order to abolish the use of lead, which is an environmentally hazardous substance, an electronic component storage package having a structure in which a low melting point glass is replaced with a thermosetting resin is being studied.

  FIG. 2 shows a lead-free electronic component storage package (hereinafter also referred to as a package) using this thermosetting resin. In FIG. 2, 11 is a frame made of ceramics, 12 is a thermosetting resin, 13 is a substrate for mounting electronic components made of ceramics, 14 is an electronic element, and 15 is a lead terminal.

  This package uses a thermosetting resin 12 in a portion where a conventional low-melting-point glass has been used, and is manufactured by the following method. A paste-like thermosetting resin 12 is applied in advance to a portion to be bonded to the frame 11 on the upper surface of the substrate 13 by a method such as a screen printing method or a dispensing method, and after placing the lead terminals 15 on the upper surface, the oven is used. The thermosetting resin 12 is temporarily cured by heating, and the lead terminals 15 are temporarily fixed to the substrate 13. Next, the thermosetting resin 12 is applied to the upper surface of the lead terminal 15 by a method such as a screen printing method or a dispensing method, and after placing the frame body 11 on the upper surface, the lead terminal 15 is attached to the substrate 13 and the frame body 11 The thermosetting resin 12 is completely cured by passing it through a tunnel-type atmosphere furnace or oven while sandwiched in between, and the substrate 13, the frame 11 and the lead terminal 15 are firmly joined to produce a package. .

The lead terminal 15 has an electrolytic nickel plating layer as a lower layer on the surface and an electrolytic gold plating layer as an upper layer in advance. As the electrolytic nickel plating layer, conventionally, matte plating to which no brightener is added is used. In the case of bright plating, generally, a high-molecular organic substance or sulfur is used as a brightening agent for the nickel plating layer, and the organic crystal or sulfur inhibits the grain growth of the nickel plating layer, thereby depositing the nickel crystal grains to be deposited. Can be made fine and dense, and a glossy plating layer can be obtained. However, at the same time, a trace amount of organic matter and sulfur may be co-deposited in the plating layer, and this impurity becomes a factor that degrades the reliability of bonding by wire bonding connecting to the lead terminal. On the other hand, in the matte plating without adding a brightener, these impurities are not co-deposited, and a plated layer with high reliability of bonding by wire bonding can be obtained.
JP-A-9-45804 Japanese Patent Laid-Open No. 2-54249

  However, in matte electroless nickel plating, there is nothing that hinders the growth of crystal grains in the nickel plating layer under plating conditions of the same current density, so the nickel crystal grains become larger and rougher than the bright electrolysis nickel plating layer, Since the crystal grains of the gold plating layer deposited on the upper surface of the crystal grains become interlockingly rough, the low molecular components of the thermosetting resin are dispersed in the grain boundaries in the process of thermosetting after applying the thermosetting resin. There is a problem in that it may flow irregularly (bleed) due to a capillary phenomenon or the like to reach the region for wire bonding of the lead terminal and wire bonding may not be possible.

  Therefore, the present invention has been completed in view of the above-mentioned conventional problems, and the object thereof is high reliability because the thermosetting resin does not flow (bleed) in the region for wire bonding of the lead terminal. A lead-free electronic component storage package capable of wire bonding is provided.

An electronic component storage package according to the present invention includes a substrate made of ceramics on which a mounting portion on which an electronic component is mounted at the center of the upper surface, and a plurality of lead terminals attached to the outer peripheral portion of the upper surface of the substrate. And an electronic component storage package comprising: a frame body made of ceramic bonded with a thermosetting resin over the entire periphery of the outer peripheral portion of the upper surface of the substrate across the plurality of lead terminals. In this case, a nickel plating layer and a gold plating layer are sequentially formed on the surface, and light in the entire wavelength region of visible light has an incident angle of 60 ° on the glass surface having a refractive index of 1.567 on the surface of the gold plating layer. A glossiness of 0.8 or more and 1.3 or less is defined as a glossiness of 1 when the reflectivity reflected by the glass surface is 10% when incident .

According to the electronic component storage package of the present invention, the crystal grain of the gold plating layer is made fine and dense, and the incident angle of 60 ° of light in the entire wavelength region of visible light on the surface of the glass surface having a refractive index of 1.567. If the reflectance reflected on the glass surface is 10%, the glossiness defined as glossiness 1 is 0.8 or more and 1.3 or less, so that the crystal grain size of the gold plating layer is small. It becomes dense and the thermosetting resin does not flow (bleed) along the grain boundary of the gold plating crystal grains to the area for wire bonding of the lead terminal and does not hinder the bonding by wire bonding. impurities eutectoid even without, since it does not cause degradation of the bonding junction may be a joining by reliable wire bonding. That is, it is possible to provide a highly reliable electronic component storage package that can stably operate the stored electronic component over a long period of time.

  Hereinafter, an electronic component storage package according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a view showing an example of an embodiment of an electronic component storage package according to the present invention, in which (a) is a plan view of the package, (b) is a cross-sectional view taken along line AA ′ of (a), (c) is sectional drawing in the BB 'line of (a).

  The electronic component storage package of the present invention can be used for electronic components such as semiconductor devices such as CCD (Charge Coupled Device) and C-MOS (Complementary Metal Oxide Semiconductor) sensors, light emitting diodes, and light receiving diodes, and piezoelectric devices. However, a case where it is adopted as an image sensor such as a CCD or C-MOS as a specific electronic component will be described as a representative example.

  The electronic component storage package of the present invention is made of a ceramic such as a square plate having a mounting portion on which an electronic component 4 as an image pickup element made of a semiconductor element such as CCD or C-MOS is mounted at the center of the upper surface. A substrate 3, a lead terminal 5 made of metal attached to a pair of opposing sides of the outer peripheral portion of the upper surface of the substrate 3, and the entire outer periphery of the upper surface of the substrate 3 across the lead terminal 5 And a frame 1 made of ceramics joined by a thermosetting resin 2.

In FIG. 1, the lead terminal 5 has a nickel plating layer on the lower layer and a gold plating layer on the upper layer. The surface of the gold plating layer has all the wavelengths of visible light on the glass surface with a refractive index of 1.567. When the area light is incident at an incident angle of 60 °, the surface of the gold plating layer has a glossiness of 0.8 or more, defined as a glossiness of 1 when the reflectance reflected by the glass surface is 10%. As a result, the low molecular component of the thermosetting resin 2 is a region for wire bonding of the lead terminal 5 along the grain boundary of the gold plating layer (lead inside the frame 1). The terminal 5 does not flow (bleed), and the plating layer does not co-deposit impurities that cause bonding strength deterioration due to wire bonding. High wa Can ya bonding to provide an electronic component storing package possible.

The glossiness is defined in accordance with the JIS standard ( JIS Z 8741). When light in the entire wavelength region of visible light is incident at an incident angle of 60 ° on a glass surface having a refractive index of 1.567, A case where the reflected reflectance is 10 % is defined as a glossiness of 1, and can be measured with a glossmeter capable of measuring the glossiness using this principle index. A high glossiness value means that light is difficult to diffusely reflect, that is, the surface particles are dense and smooth. Generally, in the case of the glossiness of the plating, it is 1.2 or higher glossiness gloss plating, gloss of less than 1.2 more than 0.8 semigloss plating, glossiness is 0.8 or less called matte plating. The control of the gloss nickel plating is possible by adjusting the amount and components of the gloss agent added.

Further, as a result of various tests in making the present invention, it was found that there was a good relationship between the bleed of the thermosetting resin 2 and the glossiness of the surface of the gold plating layer, and the glass surface having a refractive index of 1.567. Glossiness defined as Glossiness 1 (hereinafter simply referred to as Glossiness) when the reflectance of light reflected by the glass surface is 10% when light in the entire wavelength region of visible light is incident at an incident angle of 60 ° that.) it is Heading that bleed when 0.8 or more is favorably suppressed. Moreover, when the state of the gold plating surface at this time was observed with an electron microscope of 1000 times, when the glossiness was less than 0.8, the surface of the gold plating layer had coarse crystal grains with a grain size of about 1 to 5 μm. Although unevenness is observed, glossiness in the case of 0.8 or more, a dense and smooth, the crystal grains of uneven that can recognize the absence is confirmed.

  The frame 1 and the substrate 3 are insulators, and are made of ceramics such as an aluminum oxide sintered body (alumina ceramics), a mullite sintered body, a steatite sintered body, an aluminum nitride sintered body, and the like, for example, oxidized In the case of an aluminum-based sintered body, an appropriate organic binder, solvent, plasticizer, and dispersant are added to and mixed with raw material powders such as aluminum oxide, silicon oxide, magnesium oxide, and calcium oxide to make a mud. Is granulated using a well-known spray-drying method, and the granules are press-molded with a press mold having a predetermined shape and then fired at a high temperature of about 1500 ° C.

  The thermosetting resin 2 is a thermosetting epoxy resin, for example, a main agent made of bisphenol A type liquid epoxy resin, bisphenol F type liquid epoxy resin, phenol novolac type liquid resin, etc., and a filler made of spherical silicon oxide or the like. Then, a hardener mainly composed of acid anhydride such as tetrahydromethylphthalic anhydride and the like and carbon powder as a coloring agent are added and mixed and kneaded using a centrifugal stirrer to obtain a paste. Next, the paste-like thermosetting resin 2 is applied to a necessary portion of the substrate 3 or the like by a screen printing method, a dispensing method, or the like, and then cured by heating at 150 ° C. for about 90 minutes.

  Other examples of the thermosetting resin 2 include bisphenol A type epoxy resins, bisphenol A modified epoxy resins, bisphenol F type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, special novolac type epoxy resins, and phenols. Derivative epoxy resin, epoxy resin such as bisphenol skeleton type epoxy resin, etc. with addition of curing agent such as imidazole, amine, phosphorus, hydrazine, imidazole adduct, amine adduct, cationic polymerization, dicyandiamide, etc. Can be used.

  The lead terminal 5 is made of a metal such as iron (Fe) -nickel (Ni) -cobalt (Co) alloy, 42 alloy (Fe58-Ni42 alloy), copper (Cu), or copper alloy. The lead terminal 5 is a lead terminal having a frame on the outer peripheral portion and extending inward from the inner periphery of the frame by punching a plate material made of one of these metals using a conventionally known stamping mold. After forming the lead frame of the shape in which 5 is developed, the developed lead terminal 5 is bent into a desired L shape by bending using a bending die, and then the surface thereof is nickel-plated. A layer and a gold plating layer are deposited.

  Then, after placing the lead frame on which the lead terminals 5 are formed on the substrate 3 to which the paste-like thermosetting resin 2 is applied, the lead frame is applied to the substrate 3 by heating in an oven or the like to be temporarily cured. Temporarily fix. Thereafter, a paste-like thermosetting resin 2 is further applied thereon by a method such as a screen printing method or a dispensing method, and the frame 1 is placed on the thermosetting resin 2 to form a lead frame. The formed lead terminal 5 is sandwiched, and the assembled thermoset resin 2 is completely cured by passing it through a tunnel-type atmosphere furnace or oven in an assembled state. Thereby, the board | substrate 3, the frame 1, and the lead terminal 5 are joined firmly and integrally via the thermosetting resin 2, and a package is completed.

  After being punched and bent, the lead terminal 5 is further provided with a nickel plating layer having a thickness of about 2 to 15 μm as a lower layer and a gold plating layer having a thickness of 0.03 to 0.3 μm as an upper layer on the surface of the lead terminal 5. To be attached. By depositing these plating layers, it becomes easy to electrically connect the electronic component 4 as the imaging device and the lead terminal 5 by a bonding wire (not shown) made of a gold wire or an aluminum wire, It becomes easy to solder-bond the portion of the lead terminal 5 extending to the outside of the package and the wiring conductor (not shown) of the external electronic circuit board.

  If the thickness of the nickel plating layer is less than 2 μm, the solder joint strength with the wiring conductor of the external electronic circuit board tends to be deteriorated, and if it exceeds 15 μm, the bondability of the joint by wire bonding tends to be deteriorated.

  Also, if the thickness of the gold plating layer is less than 0.03μm, the bonding strength of the joint due to wire bonding tends to deteriorate, and if it exceeds 0.3μm, the cause of deterioration of the solder bonding strength with the wiring conductor of the external electronic circuit board It is easy to become.

  The lower nickel plating layer is preferably subjected to semi-gloss plating. In semi-bright plating, it is possible to add an organic polymer that does not easily co-deposit into the plating layer or a brightener based on sulfur in the nickel plating solution, so the crystals of the nickel plating layer deposited by electrolytic plating Grain growth can be suppressed, and the crystal grains of the nickel plating layer become fine and dense. Examples of organic polymer brighteners that are difficult to eutect in the plating layer include benzene, naphthalene sulphonic acid, and sulfonated acrylic aldehydes. Brighteners that are difficult to eutect sulfur include saccharin, Examples thereof include metal salts such as cadmium.

The glossiness of the nickel plating layer depends mainly on the brightener composition and plating current density conditions, and these conditions are determined by a combination of conditions such that the glossiness of the gold plating layer surface is 0.8 or more and 1.3 or less. A nickel plating layer and a gold plating layer are sequentially formed. Specifically, for example, Ebara Yuji is used for an electrolytic nickel plating solution composed of H ₂ SO ₄ (265 g / L (liter)), NiCl ₂ (57.5 g / L), and H ₂ BO ₄ (42.5 g / L). Using a plating solution with nickel brightener carrier leveler ( 1 mL / L), NL-DL (4 mg / L) manufactured by Wright Co., Ltd., and # 82 (2 mg / L) manufactured by Sugawara Eugelite Co., Ltd. as a wetting agent , by a current density 4.67A / dm ² subjected to nickel electroplating, semi-gloss nickel plating layer is formed gloss nickel plating layer is 1.0 to 0.9. Furthermore, by forming a gold plating layer having a thickness of 0.03 to 0.3 μm on the nickel plating layer by electrolytic plating or the like, the glossiness of the surface of the gold plating layer can be made 0.8 to 1.3.

  Furthermore, it is preferable not to apply a surfactant to the surface of the gold plating layer. By applying the surfactant, the adhesion between the gold plating and the thermosetting resin deteriorates, and the bonding reliability tends to deteriorate.

  In other words, by applying a gold plating layer on a nickel plating layer, the crystal grain of the gold plating layer becomes dense following the fineness and fineness of the crystal grain of the nickel plating layer, so that the surface becomes smooth and thermosetting. It is possible to prevent the low molecular components of the thermosetting resin 2 from flowing (bleeding) along the grain boundaries of the crystal grains of the gold plating layer in the process of curing the resin 2.

Adjust the amount and content of brightener added to the nickel plating solution, when the glossiness of the surface of the on applied to the gold-plated layer to less than 0.8, the crystal grain size of the gold plating layer is rough, It is considered that the thermosetting resin 2 flows irregularly along the grain boundaries of the crystal grains of the gold plating layer, and the region for wire bonding of the lead terminal 5 is covered with the thermosetting resin 2, which is favorable. Wire bonding may not be possible. In addition, when the gloss level of the gold plating layer deposited on the surface of the gold plating layer is adjusted to be higher than 1.3 by adjusting the amount and content of the brightener added to the nickel plating solution, that is, the gloss level of the gold plating layer exceeds 1.3. to so can not select a eutectoid difficult brightener organic polymer and sulfur for use in semi-gloss plating, as a result, the added organic as brighteners in the electroless nickel plating solution polymer component and sulfur simultaneously codeposited with the deposition of the nickel plating layer cause adhesion failure between the nickel plating layer and a gold plating layer, causing strength degradation of the bonding by wire bonding. Therefore, it is important that the surface gloss of the gold plating layer is 0.8 or more and 1.3 or less.

Examples of the package of the present invention are described below.
The substrate 3 and the frame body 1 made of an aluminum oxide sintered body are mixed with an organic binder, a solvent, a plasticizer, a dispersant and mixed with raw material powders of aluminum oxide, silicon oxide, magnesium oxide, and calcium oxide to produce a slurry. The slurry was granulated using a spray drying method, and the granule was press-molded with a press mold having a predetermined shape and then fired at about 1500 ° C. The substrate 3 has a rectangular parallelepiped shape of 56 mm in length, 9.65 mm in width, and 1.02 mm in thickness, and the frame 1 has an outer dimension of 57 mm in length, 9.65 mm in width, and 0.9 mm in thickness. In (a), the width of the horizontal frame portion is 2.75 mm, and a pair of adjacent short side frame portions (vertical frame portion in FIG. 1A) has a width of 2.68 mm. It was a thing of.

  The lead frame having the lead terminals 5 was processed by using a continuous mold that was punched out of a 42 alloy thin plate having a thickness of 0.25 mm with a conventionally known stamping mold and then bent into an L shape with a bending mold. By forming a nickel plating layer having a thickness of 2 to 3 μm on the lower layer by electroplating on the surface of the lead terminal 5 formed on this lead frame, the glossiness of this nickel plating layer is changed by changing the addition amount of the brightener, etc. Each of the 40 packages was prepared by changing the glossiness of the surface of the gold plating layer having a thickness of 0.07 to 0.09 μm applied to the upper layer of the nickel plating layer in steps of 0.1 from 0.6 to 1.4.

  The resin paste used as the thermosetting resin 2 is composed of bisphenol A type liquid epoxy resin 3.3% by mass, bisphenol F type liquid epoxy resin 5.9% by mass and phenol novolac type liquid resin 9.9% by mass in the form of spherical silicon oxide. Using a centrifugal stirrer, 72.1% by mass of a filler composed of 77.9% by mass, 7.9% by mass of a curing agent mainly composed of tetrahydromethylphthalic anhydride, 0.5% by mass of an imidazole-based curing agent, and 0.4% by mass of carbon powder as a colorant It was prepared by mixing and kneading.

  This resin paste was printed and applied to the entire outer periphery of the substrate 3 with a thickness of 0.03 mm using a screen printing method, with a long side of 2.25 mm wide from the outer periphery to the inside and a short side of 4.03 mm wide from the outer periphery to the inside. Later, after the lead frame of the lead terminal 5 was placed at a predetermined position, it was temporarily cured in an oven at 150 ° C. for 10 minutes. Thereafter, φ (diameter) 1.4 mm along the outer peripheral portion of the substrate 3 so that the resin paste overlaps the previously temporarily cured resin paste from the upper portion of the lead terminal 5 placed on the upper portion of the substrate 3 using a dispenser method. It apply | coated to the ring from the nozzle of this, and it mounted on the resin paste which apply | coated the frame 1 after that.

  Thereafter, the substrate 3, the lead terminals 5, and the frame body 1 assembled through the thermosetting resin 2 are heated in an oven at 150 ° C. for 90 minutes to completely complete the thermosetting resin 2. It was cured and joined together, and the following evaluations were performed on the obtained package samples.

  First, a sample of the obtained package was observed using a 500 × electron microscope, whether or not the thermosetting resin 2 flowed (bleeded) on the surface of the gold plating layer of the lead terminal 5, and the substrate 3 and the frame body. It was confirmed that the space between the first and second layers was completely filled with the thermosetting resin 2.

  In addition, an aluminum wire having a diameter of 30 μm is placed by ultrasonic bonding between the arbitrary adjacent lead terminals 5 of the package produced in this manner at a position 0.5 mm from the end of the lead terminal 5 on the image sensor mounting surface side. A total of 80 bonding wires, 4 locations x 20 packages, are connected, and 10 of these packages are connected to MIL STD 883E METHOOD2011.5 2-point bond for all 40 bonding wires after connection. A state in which the wire breaks or peels off when the center of the wire loop is hooked and supported by an arbitrary saddle-shaped wire according to the tensile test method and pulled up vertically to the straight line connecting the joints Was observed with a stereomicroscope.

  The remaining 10 packages are left in an oven at an ambient temperature of 150 ° C. for 1.5 hours, and then the same tensile test is performed on 40 bonding wires in the same manner as the above 10 samples, and then bonding wires are bonded. The presence or absence of peeling of the plating on the part was observed.

Table 1 shows the rate of occurrence of the flow (bleed) of the thermosetting resin 2 and the strength of the bonding joint in each case where the glossiness of the surface of the gold plating layer was changed.

As shown in Table 1, as a result of observation using an electron microscope, the sample with a gold plating layer surface glossiness of 0.8 or more gels during the curing of the thermosetting resin 2 and the viscosity decreases. Thus , it was confirmed that the gap between the substrate 3 and the frame 1 was completely filled with the thermosetting resin 2 without flowing (bleeding) the surface of the gold plating layer of the lead terminal 5. Then, this sample, the curing of the thermosetting resin 2 is completed, the substrate 3 and the frame 1 could be confirmed to have been joined and fixed without any gaps.

In the bonding wire tensile test, it was found that if the glossiness of the gold plating layer surface was 1.4 or more, peeling was observed at the bonding joint, resulting in deterioration of the strength of the bonding joint. Moreover , when the peeling part was analyzed by Auger analysis , sulfur and carbon were confirmed and it was confirmed that the component of a brightener co-deposited.

Incidentally, it is more than 1.3 gloss of the surface of the gold plating layer, all is only breaking of the aluminum wire, it was confirmed not occurrence of peeling of the bonding joint.

Also, the glossiness of the surface of the gold plating layer is 0.7 or less, since the thermosetting resin 2 is present in a region for wire bonding could not wire bonding.

From the above results, when the surface of the gold plating layer, a refractive index of light of the entire wavelength range of visible light is incident at an incident angle of 60 ° in the glass surface is 1.567, the reflectivity is reflected by the glass surface When the glossiness is 0.8 or more and 1.3 or less, where the glossiness is defined as 1 glossiness of 10%, the flow of the thermosetting resin 2 that reaches the region for wire bonding along the grain boundary of the crystal grain of the gold plating layer It has been found that it is possible to form a package having excellent bonding joint strength without any (bleed) and no deterioration of the bonding joint strength due to the eutectoid of the brightener component.

  The present invention is not limited to the above-described embodiments and examples, and various modifications may be made without departing from the scope of the present invention. For example, the lead terminals 5 may be attached to the entire periphery of the outer peripheral portion of the upper surface of the substrate, or may be attached to only one arbitrary side. Moreover, although the base | substrate 1 took the square plate shape as an example, polygonal shape, a disk shape, etc. may be sufficient.

An example of embodiment of the electronic component storage package of this invention is shown, (a) is a top view of an electronic component storage package, (b) is sectional drawing in the AA 'line of (a), (c) FIG. 4 is a cross-sectional view taken along line BB ′ in FIG. The example of the conventional electronic component storage package is shown, (a) is a top view of an electronic component storage package, (b) is sectional drawing in the AA 'line of (a), (c) is (a). It is sectional drawing in a BB 'line.

Explanation of symbols

1: Frame 2: Thermosetting resin 3: Substrate 4: Electronic component 5: Lead terminal

Claims (1)

A substrate made of ceramics on which a mounting portion on which an electronic component is mounted is formed at the center of the upper surface, a plurality of lead terminals attached to the outer peripheral portion of the upper surface of the substrate, and the plurality of lead terminals sandwiched therebetween An electronic component storage package comprising a frame made of ceramic bonded with a thermosetting resin over the entire circumference of the outer peripheral portion of the upper surface of the substrate, wherein the lead terminal has a nickel plating layer and a gold plating on the surface When the light in the entire wavelength region of visible light is incident at an incident angle of 60 ° on the glass surface having a refractive index of 1.567 on the surface of the gold plating layer, the layer is formed on the surface of the gold plating layer. A package for storing electronic parts, characterized in that the glossiness is 0.8 or more and 1.3 or less, where the glossiness is defined as 1 when the reflected reflectance is 10% .

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