JPH10135363A - Manufacturing method of ceramic lid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the generation rate of a solder ball, by adjusting the viscosity of a conductor paste to form an underlying metal layer in such a manner that a ceramic plate board is less exposed to an outer circumferential edge of an exposed surface. SOLUTION: On a ceramic plate board 11, underlying metal layers 12a, 12b and 12c having solder wettability are formed on a sealing surface 15 of an outer circumferential portion 14, an outer circumferential sidewall surface 16, and an outer circumferential edge portion of an exposed surface 17. A solder paste 19 is formed on portions including the underlying layers 12a, 12b and 12c. By setting the viscosity of the conductor paste to an appropriate value, the wettability to the ceramic surface 11 is improved, and the underlying metal layer 12c is formed in such a manner that the covering ratio of the underlying metal layer 12c formed on the exposed surface 17 with respect to the ceramic surface 11 is not less than 80%. Thus, generation of a solder ball may be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a ceramic lid, and more particularly, to a method for manufacturing a ceramic lid used for sealing a ceramic package.

[0002]

2. Description of the Related Art A semiconductor element such as an integrated circuit which constitutes a semiconductor device is usually accommodated in a cavity provided in a package base, and the cavity is hermetically sealed with a lid, so that it is put to practical use. . Since ceramics such as alumina are excellent in heat resistance, durability, reliability, and the like, they are suitable as materials for the package base and the lid, and ceramic IC packages made of alumina or the like are currently in active use.

When the cavity of a ceramic package base (hereinafter, also referred to as a package base) is sealed with a ceramic lid (hereinafter, also referred to as a lid), low-cost sealing at a low temperature as a sealing material is possible. Solder is often used. However, since it is difficult to directly join the ceramics by the solder, a base metal layer is usually formed on the package base and the sealing portion of the lid,
The package base and the lid are joined via the base metal layer and the solder layer.

The structure of a conventional ceramic package (semiconductor device) on which a semiconductor element is mounted and a method of manufacturing the semiconductor device will be described in detail. In the following, a portion of the semiconductor device other than a wiring portion such as a semiconductor element and a wire is referred to as a package.

FIG. 5A is a bottom view schematically showing a lid constituting a ceramic package, FIG. 5B is a cross-sectional view taken along line II of the lid shown in FIG.
FIG. 2 is a cross-sectional view schematically showing a semiconductor device using the lid.

As shown in FIGS. 5A and 5B, the lid 20 includes a ceramic substrate 11, a base metal layer 22 formed on a sealing surface 15 of an outer peripheral portion 14 and an outer peripheral side wall surface 16, and
And a solder layer 23 covering the base metal layer 22. The outer peripheral portion 14 of the surface 17 on which the solder layer 23 is not formed (hereinafter also referred to as an exposed surface) 17
A cutout (edge relief) 18 is formed to reduce the thickness of the base metal layer 4 and reduce the width of the base metal layer 22 formed on the outer peripheral side wall surface 16. Base metal layer 22
Is made of an Ag—Pd alloy or the like, and the solder layer 23 has, for example, Pb as a main component, and Bi, Sn, In, A
g and the like.

On the other hand, as shown in FIG. 5C, a cavity 32 is formed at the center of a package base 31 in a semiconductor device using the lid 20 having the above-described structure, and the lid 20 is formed around the cavity 32. A base metal layer 33 used for sealing is formed, and external connection pins 34 for connecting to a motherboard (not shown) are fixed around the base metal layer 33. A pad portion 35 is formed in a step portion in the cavity portion 32, and a semiconductor device 37 is fixed to a semiconductor device mounting portion 36 on the bottom surface.
7 and a cavity portion 3 (not shown)
2 is connected to the pad portion 35 formed by wire bonding using a wire 38. The solder layer 23 is interposed between the base metal layer 33 formed on the package base 31 and the base metal layer 22 formed on the lid 20.
By this, the package base 31 and the lid 20 are joined,
The semiconductor element 37 is sealed.

Next, a method of sealing the cavity 32 will be described. First, the solder layer 23 of the lid 20 is attached to the semiconductor element 37.
Is mounted on the base metal layer 33 formed on the upper surface of the package base 31 and the lid 20 is temporarily fixed on the package base 31 by a fixing jig. Next, the package base 31 to which the lid 20 is temporarily fixed is carried into the heating furnace, the solder layer 23 is melted to join the lid 20 and the package base 31, and then the cavity 20 is sealed by cooling. To end.

The semiconductor device sealed by the above method is
Although it is mounted on electronic components, it may be placed in an environment where the temperature difference is severe depending on the use. In this case, the ceramic substrate 21 forming the lid 20 and the solder layer 23
Since the thermal expansion coefficient is different from that of the (base metal layer 22), the ceramic package is used, and a thermal stress acts between the two due to a change in temperature of the electronic component.
Is subjected to tensile stress. However, as shown in FIGS. 5A and 5B, conventionally, the base metal layer 22 for forming the solder layer 23 includes the sealing surface 15 of the outer peripheral portion 14 of the lid 20 and the outer peripheral side wall surface 16. Therefore, the base metal layer 22 may be peeled off from the ceramic substrate 21 due to long-term use, resulting in a problem that the reliability of the semiconductor device is impaired.

[0010]

Therefore, the present inventors previously formed a base metal layer also on the outer peripheral edge of a surface (hereinafter also referred to as an exposed surface) of the ceramic substrate facing the sealing surface. Suggests the lid.

FIG. 6 shows an outer peripheral sealing surface of a ceramic substrate;
FIG. 5 is a partially enlarged cross-sectional view schematically showing a lid in which a base metal layer is formed on an outer peripheral side wall surface and an outer peripheral edge of an exposed surface, and a solder layer is formed on a portion including a surface of the base metal layer.

In the lid 40, the base metal layer 42c is also formed on the outer peripheral edge of the exposed surface 17 of the ceramic substrate 11, so that the base metal layer 42c is caught and the ceramic of the base metal layer 42 is formed. Since the adhesive strength to the substrate 11 is increased, it is possible to prevent peeling of the base metal layer 42, which is likely to occur after long-term use. The following method is used to form the base metal layer 42.

FIG. 7 is a perspective view schematically showing a metallizing apparatus for forming the base metal layer 42 on the outer peripheral side wall 16 of the lid 40 and the outer peripheral edge of the exposed surface 17.

The metallizing apparatus 50 includes a metallizing paste plate 51, a lid holding unit 52, and a rotary drive unit 53. The lid holding section 52 has a suction plate 54.
Hold. The lid holding section 52 is attached to an elevating rod 57 provided at the tip of a multi-axis machine 56 constituting the rotary movement driving section 53. Therefore, the suction plate 5 is attached to the plate body 58 to which the paste for forming the base metal layer is applied.
Applying a metallizing paste to the outer peripheral side wall surface 16 of the lid 40 by pressing the outer peripheral side wall surface 16 of the lid 40 held by 4 and rotating the lid 40 by driving the multi-axis machine 56. Can be.
In order to apply the metallizing paste to the outer peripheral edge of the exposed surface 17, the amount of the metallizing paste applied to the plate body 58 may be increased, and the thickness of the metallizing paste may be made larger than usual.

The formation of the metallizing paste layer on the sealing surface 15 of the outer peripheral portion 14 can be performed by a normal printing method such as screen printing. The application of the solder paste can be performed in the same manner.

FIG. 8A is a partially enlarged cross-sectional view schematically showing the vicinity of the solder paste layer when the solder paste layer is formed on the portion including the base metal layer of the lid by the above method. () Is a partially enlarged cross-sectional view schematically showing the vicinity of the solder layer after the solder paste layer has been reflowed.

As shown in FIG. 8A, when a solder paste is printed on the portion including the surface of the base metal layer 42 to form a solder paste layer 44 and then reflowed, as shown in FIG. There is a problem that solder fine particles (hereinafter, referred to as solder balls) 45 are easily formed in the exposed surface 17 near the base metal layer 42c. When the generated solder ball 45 falls in a later process and adheres to the external connection pin 34, the pad portion 35, the wire 38 (FIG. 5), or the like, a short circuit or the like occurs.
Since there is a possibility of causing a failure of the electronic device, it is necessary to prevent the generation of the solder balls 45.

[0018]

The present inventors have conducted various studies on the cause of the occurrence of the solder balls 45. As a result, the printing method has been used to apply the base metal to the outer peripheral side wall surface 16 and the exposed surface 17 of the lid 40. When the layers 42b and 42c are formed, the plate body 58 coated with the base metal layer forming paste is pressed against the outer peripheral side wall surface 16 so that the dense base metal layer 42b is uniformly formed on the entire outer peripheral side wall surface 16. However, since the plate body 58 cannot be pressed against the exposed surface 17, it was found that the base metal layer forming paste was not applied densely. Therefore, the exposed surface 1
In the region where the base metal layer 42c is formed, the coating ratio of the base metal layer 42c is low, the ceramic surface is exposed at a considerable ratio, and when the solder paste layer 44 is reflowed, the solder is hardly wetted on the ceramic surface, so that it is repelled. , Solder ball 4
5 causes the occurrence. Therefore, based on the above considerations, further investigations are made to reduce the number of solder balls 45 generated, and the base metal layer 42c is adjusted so that the ceramic surface is not exposed as much as possible to the outer peripheral portion of the exposed surface 17 by adjusting the viscosity of the conductive paste. It has been found that the formation rate of the solder balls 45 is reduced by the formation of, and the present invention has been completed.

Further, when the solder paste layer 44 is formed on the outer peripheral side wall surface 16 and the exposed surface 17 of the lid 40 by the above-described method, if the solder paste layer 44 is formed substantially inside the end of the base metal layer 42c. In addition, it has been found that the contact area between the solder paste and the hardly wettable ceramic surface increases, so that the probability of occurrence of the solder balls 45 increases. Therefore, further investigation is performed based on the above consideration, and the exposed surface 17 is examined.
It has been found that the rate of occurrence of solder balls 45 is reduced by minimizing the amount of solder paste applied to the outer peripheral edge of the present invention, thereby completing the present invention.

That is, the method (1) for manufacturing a ceramic lid according to the present invention comprises the steps of:
When forming an underlying metal layer having solder wettability on the outer peripheral side wall surface and the outer peripheral edge of the surface (exposed surface) facing the sealing surface,
The method further includes a base metal layer forming step of setting a coverage ratio of the base metal layer in the base metal layer formation region on the exposed surface to 80% or more.

According to the method (1) for manufacturing the ceramic lid, the base metal layer is formed on the outer peripheral edge of the exposed surface so that the exposure ratio of the ceramic surface having poor wettability with the solder paste is reduced. Therefore, when the solder paste is reflowed, the rate at which the solder is repelled by the ceramic surface is small, and the probability of occurrence of solder balls can be reduced.

The method (2) for manufacturing a ceramic lid according to the present invention comprises the method (1) for manufacturing a ceramic lid described above.
, The width of the exposed surface is 10 to 110 μm
And a step of forming a base metal layer.

According to the method (2) for manufacturing the ceramic lid, since the base metal layer having an appropriate width is formed on the outer peripheral edge of the exposed surface, the solder is applied to the base metal layer during reflow of the solder paste. It becomes easy to get wet, and the probability of occurrence of solder balls can be reduced.

The method (3) for manufacturing a ceramic lid according to the present invention comprises the method (1) for manufacturing a ceramic lid described above.
Or (2) includes a base metal layer forming step of applying a conductive paste by using a conductive paste having a viscosity of 1000 to 1700 cP and pressing a flat plate having the conductive paste adhered to the outer peripheral side wall surface of the ceramic substrate. It is characterized by:

According to the method (3) for producing a ceramic lid, by using a conductive paste having an appropriate viscosity, the wettability of the conductive paste on the ceramic surface is improved, and the conductive paste adheres to the outer peripheral side wall surface. The base metal layer can be formed so that the covering ratio is 80% or more when the flat plate is pressed against the outer peripheral edge of the exposed surface, and the rate at which the solder is repelled by the ceramic surface during reflow of the solder paste is determined. It is possible to reduce the probability of occurrence of solder balls by reducing the number.

In the method (4) for manufacturing a ceramic lid according to the present invention, a base metal layer having solder wettability is formed on an outer peripheral portion of an outer peripheral sealing surface, an outer peripheral side wall surface, and an exposed surface of a ceramic substrate. A base metal layer forming step, and applying a solder paste to a region within 20 μm from the end of the base metal layer formed on the surface of the base metal layer formed in the step of forming the base metal layer and the outer peripheral edge of the exposed surface. It is characterized by including a solder paste layer forming step of applying.

According to the method (4) for manufacturing the ceramic lid, the solder paste layer is formed so that the contact area with the ceramic surface having poor wettability with the solder paste is not increased. The ceramic surface makes it difficult to be repelled, and the probability of occurrence of solder balls can be reduced.

The method (5) for manufacturing a ceramic lid according to the present invention comprises the method (1) for manufacturing a ceramic lid described above.
(3) and a solder paste layer forming step described in the method (4) for manufacturing a ceramic lid.

According to the method (5) for manufacturing a ceramic lid, the base metal layer is formed so that the exposure ratio of the ceramic surface having poor wettability with the solder paste is reduced, and the base metal layer is not formed. Since the solder paste layer is formed so that the contact area with the bare ceramic surface does not become large, the solder is less likely to be repelled by the ceramic surface at the time of reflow of the solder paste, thereby reducing the probability of generating solder balls more effectively. be able to.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a method for manufacturing a ceramic lid according to the present invention will be described with reference to the drawings. FIG. 1 is a partially enlarged cross-sectional view schematically showing the vicinity of a solder paste layer when a solder paste layer is formed by a method for manufacturing a ceramic lid according to an embodiment.

The material for forming the ceramic substrate 11 constituting the lid is not particularly limited, but specific examples thereof include alumina, aluminum nitride, and mullite, among which alumina is preferred.

The ceramic substrate 11 made of the above-mentioned material is provided on the sealing metal surface 15 of the outer peripheral portion 14, the outer peripheral side wall surface 16, and the outer peripheral edge portion of the exposed surface 17 with the solder wettable base metal layer 12.
a, 12b, and 12c are formed, and the solder paste layer 1 is formed on a portion including the base metal layers 12a, 12b, and 12c.
9 are formed. The width d of the portion of the solder paste layer 19 formed on the exposed surface 17 further inside than the end of the base metal layer 12c is referred to as an overhang width.

Base metal layer 12c formed on exposed surface 17
In the formation region, the base metal layer 12c is formed such that the coverage ratio of the base metal layer 12c is 80% or more. This base metal layer 12c is formed as shown in FIG.
Is formed by applying a conductive paste using the metallizing apparatus 50 shown in FIG. 1 and then baking it. By setting the viscosity of the conductive paste to an appropriate value, the wettability to the ceramic surface is improved, The base metal layer 12c is formed so that the coating ratio of the layer 12c to the ceramic surface is 80% or more. In this case, as a conductive metal in the conductive paste, an Ag-
By including about 78% of a Pt alloy (Ag content: about 77 wt%) and setting the viscosity of the conductive paste to be in the range of 1000 to 1700 cP, the coverage ratio of the base metal layer 12c after firing is set to the above range. can do. As the resin and the solvent in the conductor paste, the same ones as those in the related art are used, but the viscosity is adjusted by further adding, for example, terpineol as a solvent to the conductor paste. If the viscosity of the conductive paste is less than 1000 cP, the base metal layer 12 c becomes porous after the solvent evaporation during baking because of a large amount of solvent, and if the viscosity exceeds 1700 cP, the conductive paste does not easily adhere to the ceramic surface and does not adhere. Part increases. By using a conductor paste having a viscosity in the above range, a dense base metal layer 12c can be formed on the outer peripheral portion 14 of the exposed surface 17. In order to increase the covering ratio of the base metal layer 12c to the ceramic surface, it is more preferable that the viscosity of the conductive paste be in the range of 1200 to 1400 cP. The underlying metal layer 12a of the sealing surface 15 is formed by a method similar to the conventional method.

The width D of the base metal layer 12c formed on the exposed surface 17 is adjusted by the number of times of applying the conductive paste to the plate body 58 (FIG. 7) using a squeegee (the thickness of the applied film). The width D is preferably in the range of 10 to 110 μm. When the width of the base metal layer 12c is less than 10 μm, when a package is manufactured using the lid manufactured by the above method, the base metal layer 12c is easily peeled off due to a large change in temperature. If the width D exceeds 110 μm, the thickness of the underlying metal layer 12b on the outer peripheral side wall surface 16 increases, and solder wetting failure occurs.

Next, a method for forming a solder paste layer will be described. The solder paste layer 19 is formed on the portion including the surface of the base metal layer 12, and the number of solder balls generated per reflow (pieces / per lid) is as described above. It can be reduced by increasing the coating ratio of 12c to the ceramic surface. Further, the overhang width d of the solder paste layer 19 can be further reduced by reducing it. Therefore, it is preferable to suppress the overhang width d to 20 μm or less. Solder paste layer 1
When the overhang width of No. 9 exceeds 20 μm, the amount of solder paste having poor wettability with the surface becomes too large,
Solder balls are easily generated.

The formation of the solder paste layer is similarly performed using a metallizing apparatus, and the overhang width d is adjusted by the number of times of application (thickness of the applied film) when applying the solder paste to the plate body 58 using a squeegee. I do.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for manufacturing a ceramic lid according to the present invention will be described below. In the following examples, the covering ratio of the underlying metal layer 12c on the exposed surface 17 was observed while changing the viscosity of the conductive paste, and the number of generated solder balls was examined. At the same time, the solder paste layer 19
Was also changed, and the number of generated solder balls was similarly examined. The conditions are described below.

<Conditions for Implementation> (1) Dimensions and the like of ceramic substrate 11 Material: Alumina Side dimensions: about 54 mm × about 34 mm Thickness: 1.0 mm, height of outer peripheral side wall surface 16: 0.66 m
m The dimensions of the cutout 18 (FIG. 1) (W ₁ : 0.25 mm,
(W ₂ : 41 mm) (2) Formation of base metal layer 12 Forming method Ag-Pt alloy paste Ag-Pt alloy (Ag: about 77 wt%, Pt: 0.5 to
1.0 wt%) Coating method: Use metallizing apparatus 50 (FIG. 7) Plate main body: 200 M Firing conditions Temperature: 900 ° C. Atmosphere: Air atmosphere Dimensions of base metal layer 12 c Width D of base metal layer 12 c: about 100 μm base metal layer Thickness of 12c: about 20 μm (3) Formation of solder paste layer 19 Forming method Composition of solder paste Flux: 10 wt%, solder alloy: 90 wt% Composition of solder alloy Sn: 4.1 wt%, Ag: 1.0 wt%, In: 1.
1 wt%, Bi: 8.2 wt%, Pb: remainder Coating method: Use metallizing device 50 (FIG. 7) Plate body: 80M Overhang width d: Adjusted by the number of times solder paste is applied to plate body 58 by squeegee Reflow Conditions Temperature: 300 ° C. Atmosphere: Nitrogen atmosphere with less than 100 ppm of oxygen <Results and Evaluation> (1) Relationship among Viscosity of Conductor Paste, Coverage in Base Metal Layer 12c, and Number of Solder Balls FIG. It is a graph which showed the relationship between the viscosity of a Pt alloy paste, and the covering ratio of the base metal layer 12c in the base metal layer 12c formation area, and the number of samples is 15.

FIG. 3 shows the viscosity of the Ag—Pt alloy paste and the average number of solder balls generated (pieces / per lid).
6 is a graph showing the relationship between the number of samples and the number of samples.

The overhang width at this time was 60 μm.

As is clear from the graph shown in FIG.
By changing the viscosity of the Ag-Pt alloy paste, the base metal layer 12 in the formation region of the base metal layer 12c is formed.
The covering ratio (area ratio) of c can be changed.
Further, as is clear from the graph shown in FIG.
The number of solder balls generated can be controlled by changing the viscosity of the Pt alloy paste.

From the above results, by controlling the viscosity of the Ag-Pt alloy paste, it is possible to control the coverage ratio (area ratio) of the base metal layer 12c in the formation region of the base metal layer 12c, and to generate solder balls. Obviously, the number can be controlled. By setting the viscosity of the Ag-Pt alloy paste in the range of 1000 to 1700 cP, the covering ratio of the base metal layer 12c can be made 80% or more, and about 140 pieces were conventionally generated at maximum per one lid. The number of generated solder balls was greatly reduced to a maximum of about 40 per lid.

(2) Relationship between Viscosity of Conductor Paste, Overhang Width d, and Number of Solder Balls Generated FIG. 4 shows the relationship between the overhang width d when the viscosity of the Ag—Pt alloy paste is taken as a parameter. 6 is a graph showing a relationship with the number of generated solder balls.

As is clear from the graph shown in FIG.
The number of solder balls generated can be reduced by reducing the overhang width d. In particular, when the viscosity of the conductive paste is 1300 cP and the covering ratio of the base metal layer 12 c is 80% or more, the number of generated solder balls is Was set to 0, and generation of solder balls was completely prevented.

A package was manufactured using a lid in which the number of generated solder balls became 0, and the airtightness was evaluated and the peeling of the solder layer was evaluated by a heat cycle test. Was.

[Brief description of the drawings]

FIG. 1 is a partially enlarged cross-sectional view schematically showing the vicinity of a solder paste layer when a solder paste layer is formed on a portion including a base metal layer of the lid in a method for manufacturing a ceramic lid according to an embodiment of the present invention. FIG.

FIG. 2 is a graph showing the relationship between the viscosity of an Ag—Pt alloy paste and the coverage of a base metal layer in a base metal layer formation region in an example.

FIG. 3 is a graph showing the relationship between the viscosity of an Ag—Pt alloy paste and the average number of solder balls generated in Examples.

FIG. 4 is a graph showing the relationship between the overhang width and the number of generated solder balls in the example.

5A is a bottom view schematically showing a lid constituting a ceramic package, FIG. 5B is a cross-sectional view taken along line II in FIG. 5A, and FIG. FIG. 4 is a cross-sectional view schematically showing the obtained semiconductor device.

FIG. 6 shows an outer peripheral sealing surface, an outer peripheral side wall surface,
FIG. 3 is a partially enlarged cross-sectional view schematically showing a lid in which a base metal layer is formed on an outer peripheral edge of an exposed surface, and a solder layer is formed on a portion including the surface of the base metal layer.

FIG. 7 is a perspective view schematically showing a metallizing device.

FIG. 8A is a partially enlarged cross-sectional view schematically showing the vicinity of a solder paste layer when a solder paste layer is formed on a portion including a base metal layer of a lid by a conventional method;
(B) is a partial enlarged sectional view schematically showing the vicinity of the solder layer after the solder paste has been reflowed.

[Explanation of symbols]

 Reference Signs List 11 ceramic substrate 12 (12a, 12b, 12c) base metal layer 14 outer peripheral portion 15 sealing surface 16 outer peripheral side wall surface 17 exposed surface 19 solder paste layer

Claims (5)

[Claims] When a base metal layer having solder wettability is formed on an outer peripheral portion sealing surface, an outer peripheral side wall surface, and an outer peripheral portion of a surface opposite to the sealing surface of a ceramic substrate, the sealing surface is formed on the sealing surface. A method for manufacturing a ceramic lid, comprising a base metal layer forming step of setting a coverage ratio of a base metal layer in a base metal layer formation region on an opposing surface to 80% or more. 2. The ceramic according to claim 1, further comprising a base metal layer forming step of forming a base metal layer having a width of 10 to 110 μm on an outer peripheral edge of a surface facing the sealing surface. Lid manufacturing method. 3. A base metal layer forming step of using a conductive paste having a viscosity of 1000 to 1700 cP and applying a conductive paste by pressing a flat plate having the conductive paste adhered to an outer peripheral side wall surface of a ceramic substrate. The method for producing a ceramic lid according to claim 1 or 2, wherein: 4. A base metal layer forming step of forming a solder wettable base metal layer on an outer peripheral portion sealing surface, an outer peripheral side wall surface, and an outer peripheral portion of a surface facing the sealing surface of the ceramic substrate.
And applying a solder paste to a region within 20 μm from an end of the base metal layer formed on the surface of the base metal layer formed in the base metal layer forming step and an outer peripheral edge of a surface facing the sealing surface. A method for manufacturing a ceramic lid, comprising a step of forming a solder paste layer. 5. A method for manufacturing a ceramic lid, comprising: a base metal layer forming step according to any one of claims 1 to 3; and a solder paste layer forming step according to claim 4. .