JPH0783083B2 - Ceramic board having metal pins and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a metal having high strength and excellent heat resistance suitable for connecting pins used as signal input / output terminals to wiring boards such as ceramic boards or printed boards. The present invention relates to a ceramic board having pins and a method for manufacturing the same.

[Conventional technology]

Conventionally, a pin used as a signal input / output terminal is joined to a wiring board such as a ceramic board or a printed board with a brazing material. In this case, Japanese Patent Laid-Open Nos. 59-26985 and 59-35075 are already known in which the pin-bonding surface of the ceramic substrate is metallized in advance and silver brazing is performed on the pins of the thin metal wires. However, in these methods, since the joining temperature is as high as about 800 ° C., there is a problem that a large thermal stress is generated between the ceramics having different thermal expansion coefficients and the metal, and the non-ductile ceramics are destroyed. As a method of preventing thermal stress destruction of such ceramics, for example, Al
_In the case of oxide-based ceramics such as ₂ O ₃ or the like, there is a method of joining with a metal via an intermediate material having a coefficient of thermal expansion approximately in between. This intermediate material has a coefficient of thermal expansion of 5-8 × 10 ^-6 / ° C.
Ni-Fe alloys are used.

However, even when the above intermediate material is used, its coefficient of thermal expansion is relatively small in the temperature range from room temperature to about 400 ° C.
Since it rapidly increases above 00 ° C, brazing filler metal JISBAg8 (Ag
In the case of brazing with -28% Cu), the generation of thermal stress in the joining process was unavoidable, and it was difficult to completely prevent the thermal stress destruction of the ceramics. Further, residual stress remains in the ceramics even if thermal stress fracture does not occur during the joining process, which causes the ceramics to break during use. On the other hand, in the case of non-oxide type ceramics such as SiC, Si ₃ N ₄ and sialon, the coefficient of thermal expansion is 4 × 10 ⁻⁶ / ° C or less, which is smaller than that of oxide type such as Al ₂ O ₃ , so both Even in the case of joining, it becomes impossible to prevent thermal stress fracture with the intermediate material in the previous term. Also, since many pins are joined at the same time and at a high temperature of 800 ° C, the thin metal pin is annealed, the hardness is reduced, and the joint strength of the pin is not high. There was a defect that the joint part was damaged.

As a joining method for preventing these problems and drawbacks, there is a method of using a solder material that can be joined at a lower temperature than silver solder. However, when a solder material or the like is used for joining at a low temperature, not only the strength of the joining portion is lowered but also the heat resistance is deteriorated, which limits the use range.

[Problems to be solved by the invention]

An object of the present invention is to provide a ceramic substrate having a metal pin that eliminates the above-mentioned drawbacks, does not reduce the bonding strength, has a small annealing effect on the metal pin, has a small warpage of the substrate, and has excellent heat resistance, and a method for manufacturing the same. is there.

[Means for solving problems]

The above-mentioned object is a ceramic substrate in which ceramics, a metal coating film coated on the ceramics, and metal pins standing on the metal coating are joined, and the metal pin and the metal coating are the components of the surface of the metal pin. This can be achieved by directly joining by an alloy layer composed of the components of the metal coating and the components of the brazing filler metal having a melting point of 400 ° C or lower and having a remelting temperature of 600 ° C or higher.

The above-mentioned object is a method for manufacturing a ceramic substrate having a metal pin in which a metal pin is erected in the axial direction on a metal film formed on the ceramic substrate and joined, in which a brazing material having a melting point of 400 ° C. or less is attached to the metal film. Then, the attached brazing filler metal and the lower end of the metal pin standing in the axial direction are brought into contact with each other, and the metal pin is heated by energization to melt the brazing filler metal, thereby melting the components of the metal pin surface and the metal coating and the brazing filler metal. By forming an alloy layer consisting of the components and having a remelting temperature of 600 ℃ or higher, press the metal pin in the axial direction of the metal pin to eliminate the brazing material, and directly bond the metal coating and the metal pin by the alloy layer. To be achieved.

[Action]

A brazing material is attached to the metal film to form an alloy layer with the brazing material, and a brazing material is also attached to the metal pins to form an alloy layer with the brazing material, and each of the gold alloys is heated and pressed to melt. The brazing filler metal with a low point is discharged and joined.

The joining is performed at a lower temperature than the conventional melting temperature of the brazing material, while an alloy layer having a remelting point higher than the melting point of the brazing material remains on the joining surface between the metal pin and the metal coating.

〔Example〕

 Examples of the present invention will be described below.

A feature of the present invention is that a brazing material having a low melting point is used, and when a brazing material having a low melting point is required, selecting a turf crystal component or a component in the vicinity thereof is a commonly used method. As a preferable brazing material for forming an alloy layer between the joining materials at 400 ° C. or lower, the combinations shown in Table 1 can be considered.

Next, a method for joining pins to the ceramic substrate will be described.

First Embodiment FIG. 1a is an external view of a portion where a thin metal wire pin is joined to a multilayer Al ₂ O ₃ ceramic substrate by the joining method of the present invention, and a sectional view before the main joining by brazing to one side in advance. FIG. 1c is a cross-sectional view showing the main joining. That is, a metal pin 3 having a fine metal wire of 0.7φ is joined to the metallized pad 2 of the 50 mm square multilayer ceramic substrate 1. More specifically, the metallized pad 2 of the ceramic substrate 1 is metallized by firing tungsten 4, and Ni plating 5 is applied thereon. Then, soldering 6 is applied in advance to these metallized surfaces so that the joining of the present invention becomes easier. This method is excellent in workability.
This is accomplished by immersing the metallized ceramic substrate 1 in a molten solder bath. By this soldering, the alloy layer 7 is formed at the interface between the Ni plating 5 and the solder. The solder used was Sn50-Pb50, and soldering was 25
Since it took several seconds at 0 ° C., the thickness of the Ni—Sn composite metal was formed to several μm, and the surface of the alloy layer 7 was covered with unreacted solder of 20 μm. Next, the metal pin 3 is placed and the main joining is started. Heating is performed using resistance welding electrode 8 at 350-450 ° C
Heat in the range. At this stage, the applied pressure is not intentionally applied, but the applied current is used to heat the alloy layer 9 on the pin side as shown in FIG. 1c. Regarding the heating method, it is conceivable to heat the ceramic substrate 1 and the entire metal pin in addition to the local heating of the metal pin 3 by the electrode 8. When the alloy layer 7 is formed on the metal pin 3 side by 0.5 μm, pressure is applied by the electrode 8 next. The applied pressure was ² to 5 kgf / mm ² . Through this joining process, the alloy layers 9 formed on both joining materials come close to each other and are joined. The thickness of the alloy layer formed here was 2 to 5 μm. This alloy layer 9 has a higher melting point than the liquid phase point of the brazing material because it is a phase that has reacted with the bonding material base material and Sn of the solder component. That is, unreacted Sn-Pb having a low melting point is not found in the alloy layer. On the other hand, the unreacted solder component that melts at the brazing temperature is 2 to 5 kgf / m
The brazing filler metal 10 is discharged to the outside of the joint surface by the pressing force of m ² . Then, depending on the amount, remove the discharged solder. The removal is performed by a vacuum suction method or a blowing method while the solder is melting. Further, if the wax to be adhered in advance is extremely thin as 5 μm or less, it can be used as it is as a product.

Second Embodiment FIG. 2a shows the assembled state before joining, and FIG. 2b shows the assembled state. Al ₂ O here for brazing to work
₃ Au plating 11 on top of Ni plating 5 on one substrate and Fe on one side
-Au plating 12 is applied on the Ni alloy pin. The brazing filler metal is the Au-6Si foil 13 listed in Table 1. Next, the main joining of the present invention is started. If the main joining is performed under substantially the same conditions as in the process of the first embodiment, an alloy layer is formed at the joining interface between both base materials, and the alloy layers 14 are joined. Unreacted by this method
The Au-Si component is discharged as a brazing filler metal 15 out of the joint surface. Then, the discharged brazing material is removed, and the method is as described above.

Third Embodiment The multilayer ceramic substrate is the same as that of the first embodiment, and Kovar is used as the mating pin material, and Au plating is similarly applied thereto. The Au-20Sn foil is used as the brazing material, and the main joining is completed through the same joining process as in the second embodiment. Unreacted Au at that time
-Sn component is also discharged.

Fourth Embodiment Application of the present invention will be described by taking a semiconductor PGA (Pinging Array) as an example. Figure 3 shows the cross-sectional structure of the PGA package. PGA is the heat sink 4 of SiC such that the multilayer wiring Al ₂ O ₃ ceramic substrate 1 and the Si chip 30 is metal pin 3 for signal input and output on the back side are connected a number in a lattice form as shown in the figure is the tower
0 is joined and further sealed by a sealing material 50 such as Kovar. FIG. 4 shows an enlarged view of part A of the PGA connected by the method of the present invention. That is, the metal pin 3 of Kovar is bonded to the metallized pad 2 of the multilayer Al ₂ O ₃ substrate 1. For details, see the metallized pad 2 on the ceramic substrate 1.
Is metallized by firing tungsten 4, Ni plating 5 is formed on it, and Au plating 11 is formed on it. On the other hand, Au plating 12 is also applied to the surface of Kovar's metal pin 3, and Sn50-Pb50 solder is used for both of these (preliminarily soldering is performed at 250 ° C. for 10 seconds) by means of a current pressure and pressure device. It was heated to 450 ° C. or lower and a pressure of 4 kgf / mm ² was applied at the same time. By this operation, the alloy layer 14 having a thickness of 3 μm was bonded. That is, Sn in the first Sn50-Pb50 solder reacts with Au in the plating to form an Au-Sn alloy layer. And unreacted Sn and Pb are discharged out of the joint surface as the brazing filler metal 15 by pressurization at the time of melting, and the Au-Sn component layer which is higher than the heating temperature at the time of joining remains as an alloy layer joint. Become. As a result, the Au plating is eroded by the reaction between Au and Sn, and the thickness of the plating becomes thin.

First Comparative Example The same metallized Al ₂ O ₃ substrate and fine metal wire pins as in the first example were brazed in a furnace at 810 ° C. using a Ag—Cu 28 high temperature silver brazing foil. Since this is a general brazing method, no pressure is applied.

Second Comparative Example The same metallized Al ₂ O ₃ substrate and thin metal wire pins as in the first example were sandwiched between Sn50-Pb50 low temperature brazing foils and brazed in a furnace at 250 ° C. using a flux. Since this is also a general brazing method, no pressure is applied.

A characteristic test was performed on the joints joined by the methods of the above-described three examples and two comparative examples. FIG. 5 shows the tensile test results.
Three test pieces were produced under each condition, and they are expressed by breaking load. In the embodiment of the present invention, there is no great difference between the three cases,
It showed stable high strength in the range of 5-6 kg. On the other hand, in the comparative example, the Sn50-
The joint strength is higher than that of joints joined with low temperature brazing of Pb50.
However, compared with the present invention, the joint of silver solder is also slightly weak.
It is considered that the cause of this is that extremely small micro-cracks were observed at the interface between the ceramic and the metallization, and that they were slightly weakened. Since the micro-cracks are heated to a high temperature of 800 ° C, thermal stress may have occurred at the joint.

It has been clarified that the bonding method of the present invention can provide high and stable bonding strength. In order to clarify the cause, a cross section of the joint joined by the method of the present invention was analyzed by EPMA (electron probe microanalyzer). As a result, Fe-Ni-Sn composite metal was formed to 3 μm in the first embodiment. The main component of brazing material, Pb, was not detected. In the second embodiment
Au-Si is the main, and Fe and Ni are slightly recognized, and its thickness is 4μ.
It was m. In the third example, Au-Sn was the main component, and Fe, Ni and Co were slightly observed, and the thickness was 5 μm. That is, these alloy layers are extremely thin as compared with the conventional brazing method, and since they are layers that have reacted with the joining base metal, their melting points are also high, and accordingly, it is considered that the heat resistance and tensile strength of the joining portion are further improved. . FIG. 6 shows a measurement of the warp of the Al ₂ O ₃ ceramic substrate surface of 50 mm square. According to this result, the value of the warp of the first comparative example brazed with the high temperature silver brazing material is the largest, and is as large as 20 μm. The Sn-Pb solder of the second comparative example had a small brazing temperature and thus had a small warpage, and showed a value of 5 μm. On the other hand, the warpage of the substrate surface in Examples 1 to 3 of the present invention is stable at a small value, and the value is 5 μm or less. The slightly lower value than Sn-Pb is considered to be due to the fact that the heating of the substrate was small because the bonding method of the present invention uses a resistance heating and pressurizing device.

In addition to the above embodiments, the method of the present invention can be applied to a combination of phosphor bronze pins or a metallized mullite substrate. Similarly, brazing filler metals other than those listed in Table 1 can be joined at a relatively low temperature and improve the joint strength.
The method of the present invention can be applied to other brazing filler metals, such as Au-Ge, which have a relatively low melting point. The method of the present invention can be accomplished by using a laser, a light beam or the like as a heat source in addition to the electric heating and pressurizing device and separately disposing a pressurizing device.

〔effect〕

According to the manufacturing method of the present invention, since the metal coating on the ceramic substrate and the metal pin can be bonded at a low temperature, destruction and deformation due to thermal stress at the time of manufacturing the ceramic substrate, damage during use due to residual stress, and metal pin Prevents deformation during use caused by hardness reduction due to the annealing effect, and since an alloy layer is formed on the bonding surface between the ceramic substrate and the metal pin, the bonding strength is higher than in the conventional manufacturing method and the ceramic substrate has a highly reliable metal pin. There is an effect that can be provided.

[Brief description of drawings]

FIG. 1a is an external view showing an embodiment of the present invention, FIG. 1b is a cross-sectional view of a metallized ceramic substrate that is pre-soldered to face the other metal pin and is placed in a resistance heating / pressurizing device. Fig. 1c is a cross-sectional view immediately after resistance heating and pressurizing and joining, and Fig. 2a is Au plating on the metallized ceramic substrate and metal pins, sandwiching low melting point brazing filler metal, and resistance heating and pressing. Fig. 2b is a sectional view immediately after joining by resistance heating and pressurization, Fig. 3 is a sectional view of the structure of the pin grid array package, and Fig. 4 is a pin of the pin grid array. FIG. 6 is a sectional view immediately after joining the metallized ceramics, FIG. 5 is a diagram showing tensile test results of joints joined by the method of the present invention and the conventional method, and FIG.
The figure is a diagram in which the warpage of the ceramic substrate surface after the bonding by the method of the present invention and the conventional method is measured. 1 ... Ceramic substrate, 2 ... Metal film, 3 ... Metal pin, 6 ... Brazing material, 8 ... Electrode, 9 ... Alloy layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Asahiko Shida 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Hitachi, Ltd. (56) References JP-A-60-83356 (JP, A) JP-A-62 -63454 (JP, A) JP-A-63-104460 (JP, A)

Claims (4)

[Claims] 1. A ceramic substrate in which ceramics, a metal coating film coated on the ceramics, and a metal pin standing on the metal coating are joined, wherein the metal pin and the metal coating are formed on the surface of the metal pin. A ceramic substrate having metal pins, characterized in that it is directly bonded by an alloy layer having a remelting temperature of 600 ° C. or higher, which is composed of a component, the metal coating component, and a brazing filler metal component having a melting point of 400 ° C. or lower. 2. The brazing material is any one of tin, an alloy containing tin and lead, at least one of gold, silicon and zinc, an alloy containing gold and silicon, and an alloy containing bismuth, lead, silver and zinc. A ceramic substrate having metal pins according to claim 1, characterized in that 3. The ceramic substrate having metal pins according to claim 1, wherein the alloy layer has a thickness of 0.5 to 5 μm. 4. A method for manufacturing a ceramic substrate having a metal pin formed on a ceramic substrate, the metal pin being erected in the axial direction of the metal pin so as to be joined thereto, wherein a brazing material having a melting point of 400.degree. After adhering, the adhering brazing filler metal and the lower end of the metal pin standing upright in the axial direction are brought into contact with each other, and the metal pin is energized and heated to melt the brazing filler metal and the components of the metal pin surface and An alloy layer having a remelting temperature of 600 ° C. or higher formed of the components of the metal coating and the brazing filler metal is formed, and the brazing filler metal is removed by pressing the metal pin in the axial direction of the metal pin, A method for manufacturing a ceramic substrate having a metal pin, wherein the coating film and the metal pin are directly bonded by the alloy layer.