JPH11274355A - Plastic package with heat sink - Google Patents

Abstract

(57) [Problem] To easily damage a heat radiating plate or a plastic substrate 31, or to easily generate a crack on the surface of a Si chip 35, and it is difficult to secure the heat radiating performance of the heat radiating plate. SOLUTION: A cavity 3 for accommodating a Si chip 35.
In the plastic package 10 with a heat sink provided with the plastic substrate 31 on which the plastic substrate 1b is formed and the heat sink 13 attached to the plastic substrate 31, the Young's modulus is 15000 kg / mm ² or more and the thermal conductivity is 100 W The heat radiating plate 13 is formed by using a material that is equal to or higher than / mK.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a plastic package with a heat sink, and more particularly to a plastic package with a heat sink of a cavity-down BGA (Ball Grid Array) type.

[0002]

2. Description of the Related Art A variety of plastic packages with a cavity-down BGA type heat sink have been developed. FIG. 6 is a cross-sectional view schematically showing a conventional plastic package with a heat sink of this type. In the figure, reference numeral 31 denotes a plastic substrate. The plastic substrate 31 is formed in a substantially rectangular parallelepiped plate shape using BT (Bismaleimide Triazine) resin, polyimide resin, or the like, and a printed wiring (both not shown) formed by patterning a Cu foil is adhered to the surface 31a. Have been. The plastic substrate 31 may have a multilayer structure provided with through holes.
A plurality of pads 32a are provided at predetermined positions of the printed wiring.
Are formed, and substantially spherical solder balls 32 are attached to the respective pads 32a. On the other hand, a heat sink 33 is attached to the back surface 31c of the plastic substrate 31 via an adhesive layer 34a, and the heat sink 33 has a Young's modulus of 100.
00 to 12000 kg / mm ² , thermal conductivity 250 to 3
It is formed in a substantially rectangular parallelepiped plate shape having a thickness of t using a Cu-based metal (pure Cu, Cu-3% Fe alloy or the like) of 90 W / mK. A cavity 31b having a substantially square shape in plan view is formed at a substantially central portion of the plastic substrate 31, and a substantially square plate-like silicon (hereinafter, referred to as Si) chip 35 is provided at a predetermined position in the cavity 31b. The Si chip 35 is attached to the heat sink 33 via a layer 34b including an insulating layer and an Ag layer. The terminal 35a on the surface 35b of the Si chip and the terminal 31d of the printed wiring are connected via an Au wire 36.
B is filled with a mold resin 37 so as to cover the Si chip 35 and the Au wire 36. The plastic package 31, including the plastic substrate 31, the cavity 31b, the heat sink 33, etc., is provided with a cavity-down BGA type heat sink.

When manufacturing the plastic package 30 with a heat radiating plate configured as described above, the Cu foil adhered to the surface 31a of the plastic substrate 31 is patterned by using a photoresist technique, an etching technique or the like, and a plating technique or the like is applied. After forming the printed wiring by using this, a cavity 31b is formed at a substantially central portion of the plastic substrate 31.
Next, an adhesive layer 34a is formed on the back surface 31c of the plastic substrate 31.
Then, the solder ball 32 is attached to the printed wiring pad 32a. Next, FIG.
As shown in (a), a thermosetting Ag paste 34c is applied on an insulating layer (not shown), and a Si chip 35 is temporarily attached. Then, when a heat treatment is performed on these at a predetermined temperature T to cause a curing reaction in the insulating paste 34c, a Si chip 35 is attached on the heat sink 33 (FIG. 7).
(B)). Thereafter, the terminals 31d and 35a are connected by a wire bonding technique using an Au wire 36, and when the mold resin 37 is filled, the Si chip 35 is mounted on the plastic package 30 with a heat sink.

[0004]

In the plastic package 30 with a heat sink described above, the Si chip 35
Since the heat radiating plate 33 has a larger thermal expansion coefficient than that of the heat radiating plate 33, the heat radiating plate 33 contracts relatively significantly when cooled to room temperature after being subjected to the heat treatment, and as shown in FIG. There is a problem that a bending stress in the direction of arrow A is generated at 35b, and a crack 38 is easily generated (a crack occurrence rate is about 3 to 5%).

Although not shown, if the heat radiating plate is formed using a material having a thermal expansion coefficient substantially similar to that of the Si chip 35, it is possible to prevent cracks from being generated on the surface 35b of the Si chip. The difference between the thermal expansion coefficients of the plastic substrate 31 and the heat sink is large, and thermal stress is easily generated between them.
There is a problem that damage may be caused to the device.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and it is possible to secure the heat radiation performance of a heat radiating plate and to prevent the heat radiating plate and a plastic substrate from being damaged.
It is another object of the present invention to provide a plastic package with a heat sink that can reliably prevent cracks from being generated on the surface of a Si chip.

[0007]

FIG. 4 is a diagram showing an embodiment of the present invention.
After performing a heat treatment at a predetermined temperature T (T = 150 ° C.) on the Si chip 35 (both shown in FIG. 7) temporarily attached to the heat radiating plate via the paste 34c, the Si chip 35 is cooled to room temperature.
FIG. 10 is a curve diagram showing a result of investigation by simulation of a relationship between a bending stress applied to No. 5 and a Young's modulus of the heat sink. In the figure, the vertical axis indicates the bending stress applied to the Si chip 35, and the bending stress is relatively expressed assuming that the heat radiating plate is formed using a pure Cu material (point B) as 100%. doing. As is clear from FIG. 4, when a material having a Young's modulus of 15000 kg / mm ² or more is used, the heat radiating plate is hardly deformed, so that the bending stress applied to the Si chip 35 can be reduced to 90% or less. Become. As a result, the crack occurrence rate in the Si chip 35 can be reduced by 50% or more as compared with the conventional case.

FIG. 5 is a curve diagram showing the result of an investigation of the relationship between the thermal resistance R and the thermal conductivity λ by simulation. In FIG. 5, C shows the case where the heat sink is formed using a pure Cu material. And the thermal conductivity λ at that time is 390 W /
mK and thermal resistance R are 14.7 ° C./W. Generally, a material having a high Young's modulus has a low thermal conductivity λ, and thus has a high thermal resistance. However, as is evident from FIG. 5, a material having a thermal conductivity λ of 100 W / mK or more has a thermal resistance R of 1
6.2 ° C./W (approximately 11% higher than that of pure Cu) or less, and heat radiation performance can be secured.

The present inventors have conducted research on the relationship between the bending stress applied to the Si chip and the Young's modulus of the heat sink, the relationship between the thermal resistivity R and the thermal conductivity λ, and the like. 15000 kg / mm ² or more, thermal conductivity λ is 10
In a heat sink using a material of 0 W / mK or more, it is possible to prevent the occurrence of cracks in the Si chip while securing heat dissipation performance. Also, it is possible to prevent Cu / Ni / Cu, Cu / Fe / Cu,
The inventors have found that Cu / Mo / Cu-based, Ni / Cu / Ni-based clad materials and brazing materials have excellent properties (Young's modulus and thermal conductivity), and have completed the present invention.

That is, a plastic package with a heat sink according to the present invention is a plastic package with a heat sink provided with a plastic substrate having a cavity for accommodating a Si chip, and a heat sink attached to the plastic substrate. , Young's modulus is 15000kg /
and mm ² or more, and the thermal conductivity is characterized in that the heat radiating plate using a material is 100W / mK or more is formed (1).

According to the plastic package (1) with a heat sink, the Young's modulus is 15,000 kg / mm ^2.
The radiator plate is formed using the above materials,
Even during the cooling step after the heat treatment, the heat radiating plate is hardly deformed, so that the bending stress applied to the Si chip can be greatly reduced. As a result, it is ensured that cracks are generated on the surface of the Si chip. Can be prevented. Further, since the heat radiating plate is formed using a material having a thermal conductivity of 100 W / mK or more, the heat resistance R can be kept low, and the heat radiating performance of the heat radiating plate can be reliably ensured. Further, it is possible to form the plastic substrate using a material having substantially the same thermal expansion coefficient as the heat sink, and it is difficult for thermal stress to occur, so that damage to the heat sink and the plastic substrate can be prevented. Can be blocked.

Further, in the plastic package with a heat sink according to the present invention, in the plastic package with a heat sink (1), the heat sink is made of a Cu / Ni / Cu-based material.
u / Fe / Cu system, Cu / Mo / Cu system, or Ni /
It is characterized by comprising a clad material of a Cu / Ni-based metal plate or a brazing material (2).

According to the plastic package (2) with a heat sink described above, the heat sink is made of a Cu / Ni / Cu system.
Cu / Fe / Cu system, Cu / Mo / Cu system, or Ni
/ Cu / Ni-based metal plate clad material or brazing joining material, and has a relatively large thermal conductivity Cu-based metal plate and a relatively large Young's modulus Ni-based, Fe-based,
Alternatively, since the Mo-based metal plates are alternately laminated and joined, the Young's modulus of the heat sink is adjusted to 15,000 kg by adjusting the thickness, the number of layers, the rolling ratio, and the like of these metal plates.
/ Mm ² or more, and the thermal conductivity can be reliably set to 100 W / mK or more. Also, the heat radiating plate is Ni / C
In the case of using a u / Ni-based metal plate clad material, it is not necessary to apply Ni plating to the outer surface of the heat radiating plate, and it is possible to save time and labor for plating. In the case of a brazing material, the metal plates are bonded by brazing, and the thickness of each layer is more uniform than that of the clad material, so that bending distortion after bonding is further reduced. Can be.

In the plastic package with a heat sink according to the present invention, in the plastic package with a heat sink (2), the clad material may include a plurality of first Cu-based metal plates rolled in a longitudinal direction. Ni, Fe
Alternatively, after alternately laminating and crimping the Mo-based metal plate, slicing along the long axis direction to form a sliced body, and attaching a second Cu-based metal plate to a slice surface of the sliced body. Forming a Cu paste pack material by using
rolling the u-packed pack material in the long-axis direction along the slice plane, cutting in a direction orthogonal to the long axis to form a fixed-size pack material, and alternately orthogonally intersect the fixed-size pack material. And rolling in a predetermined direction after lamination as described above (3).

According to the plastic package with heat sink (3), the clad material is composed of a plurality of first Cu-based metal plates rolled in the longitudinal direction and a plurality of Ni, F.
e and Mo-based metal plates are alternately laminated and pressed, and then sliced along the long axis direction to form a sliced body, and a second Cu-based metal plate is attached to a slice surface of the sliced body. And forming a Cu-coated pack material by rolling the Cu-coated pack material in the long-axis direction along the slice surface, and cutting in a direction orthogonal to the long axis to form a fixed-size pack material. And a step of rolling the fixed-size pack materials alternately orthogonally and then rolling in a predetermined direction, wherein the first Cu-based metal plate is formed of the second Cu-based metal plate. Since the connection is continuously made via the metal plate, the heat generated from the Si chip can be more reliably dissipated to the outside. Further, since the first and second Cu-based metal plates are sandwiched and reinforced by the Ni, Fe or Mo-based metal plates having high Young's modulus and different rolling directions, the rigidity of the radiator plate is further increased. be able to.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a plastic package with a heat sink according to the present invention will be described below with reference to the drawings. Note that components having the same functions as those of the conventional example are denoted by the same reference numerals. FIG. 1 shows an embodiment (1).
FIG. 2 is a cross-sectional view schematically showing the plastic package with a heat sink according to the present invention, and FIG. 2 is a perspective view schematically showing a main part of the plastic package with a heat sink according to the embodiment (1). Similar to the one shown in FIG. 6, the plastic substrate 31 is formed in a substantially rectangular parallelepiped plate shape using BT resin, polyimide resin, or the like, and the surface 31a has C
A printed wiring (both not shown) formed by patterning the u foil is adhered. A plurality of pads 32a are formed at predetermined positions of the printed wiring.
A substantially spherical solder ball 32 is attached to 2a. On the other hand, the back surface 31c of the plastic substrate 31
The heat radiating plate 13 is attached via a bonding layer 34a, and the heat radiating plate 13 is formed in a substantially rectangular parallelepiped plate shape, and the length of one side is set to L. This heat sink 13 has a thickness t.
₁ of Ni-based metal plate 13a, the thickness t ₂ Cu-based metal plate 1
3b, a Ni-based metal plate 13c having a thickness of t ₃ is formed using a clad material laminated and pressed, the Young's modulus of the clad material is 15000 kg / mm ² or more, and the thermal conductivity is 100 W / mK or more. Is set to A cavity 31b having a substantially square shape in a plan view is formed at a substantially central portion of the plastic substrate 31, and a substantially square plate-shaped Si chip 35 is provided at a predetermined position in the cavity 31b. It is attached to the heat radiating plate 13 via an adhesive layer 34b formed of an insulating layer and an Ag paste layer formed on the surface of the plate 13. Si chip surface 35
b terminal 35a and the printed wiring terminal 31d are connected via a wire 36 of Au or the like.
The inside is filled with a mold resin 37 so as to cover the Si chip 35 and the wires 36. A cavity-down BGA type plastic package 10 with a heat radiating plate is configured to include the heat radiating plate 13, the plastic substrate 31, the cavity 31b, and the like.

In the case of manufacturing the plastic package 10 with a heat radiating plate configured as described above, the Cu foil adhered to the surface 31a of the plastic substrate 31 is patterned by using a photoresist technique, an etching technique or the like, and a plating technique or the like is applied. After forming the printed wiring by using this, a cavity 31b is formed at a substantially central portion of the plastic substrate 31.
Next, an adhesive layer 34a is formed on the back surface 31c of the plastic substrate 31.
Then, the solder ball 32 is attached to the pad 32a of the printed wiring. Further, as shown in FIG. 2, a thermosetting Ag paste 34c is applied to the insulating layer, and a Si chip 35 is temporarily attached. Next, these are subjected to a heat treatment at a predetermined temperature T, so that the Ag paste 3
A curing reaction is caused in 4c, and a Si chip 35 is stuck on the heat sink 13. Thereafter, the terminals 31d and 35a are connected by a wire bonding technique using a wire 36 of Au or the like, and when the mold resin 37 is filled, the Si chip 35 is mounted on the plastic package 10 with a heat sink.

As is apparent from the above description, in the plastic package 10 with a heat sink according to the embodiment (1), the heat sink 13 is formed using a material having a Young's modulus of 15000 kg / mm ² or more. Since the heat radiating plate 13 is less likely to be deformed during the cooling step after the heat treatment, the bending stress applied to the Si chip 35 can be significantly reduced. As a result, the occurrence of cracks on the surface 35b of the Si chip 35 can be reduced. It can be reliably prevented. Further, since the heat radiating plate 13 is formed using a material having a thermal conductivity of 100 W / mK or more, the heat resistance R can be suppressed low, and the heat radiating performance of the heat radiating plate can be secured. Further, the plastic substrate 31 can be formed using a material having substantially the same thermal expansion coefficient as that of the heat radiator plate 13 and is less likely to generate thermal stress.
Can be prevented from being damaged.

The heat radiating plate 13 is made of a Ni-based metal plate 13a /
Cu-based metal plate 13b made of a clad material of Cu-based metal plate 13b / Ni-based metal plate 13c and having relatively high thermal conductivity, and Ni-based metal plate 1 having relatively high Young's modulus
3a and 13c are alternately laminated and crimped.
By adjusting the thicknesses t ₁ and t _{3 of the} i-based metal plates 13a and 13c, the thickness t ₂ of the Cu-based metal plate 13c, the number of stacked layers, and the rolling ratio, the Young's modulus of the heat radiating plate 13 is reduced to 1
5000 kg / mm ² or more and thermal conductivity of 100 W /
mK or more can be reliably set. Heat sink 1
Since the outer surface of No. 3 is formed of the Ni-based metal plate 13a, the Ni plating treatment conventionally performed for anticorrosion can be omitted.

In the plastic package 10 with a heat sink according to the embodiment (1), the heat sink 13 is composed of a Ni-based metal plate 13a / Cu-based metal plate 13b / Ni-based metal plate 13a.
Although the description has been given of the case where the heat radiating plate is made of a Cu / Ni / Cu-based material,
It may be made of a clad material of a Cu / Fe / Cu-based or Cu / Mo / Cu-based metal plate, and in any case, the same effect as that shown in FIGS. 1 and 2 can be obtained. Can be.

In the plastic package 10 with a heat radiating plate according to the embodiment (1), the heat radiating plate 13 is made of a Ni-based metal plate 13a / Cu-based metal plate 13b / Ni-based metal plate 13b.
Although the description has been made of the case where the clad material is made of the clad material c, in another embodiment, the brazing is performed by joining the Ni-based metal plate 13a, the Cu-based metal plate 13b, and the Ni-based metal plate 13c using an Ag brazing material. It may be a joining material. In this case, since the thickness of each layer is uniform compared to the clad material,
The bending distortion after bonding can be further reduced.

FIG. 3 is a partial cross-sectional perspective view schematically showing a heat radiator of the plastic package with a heat radiator according to the embodiment (2).
Reference numeral 3 denotes, for example, Ni-based metal plates. Long axis D
The plurality of first Cu-based metal plates 22 and Ni-based metal plates 23 rolled in the direction are alternately laminated and pressed, and then the long axis D
The sliced body 24 is sliced along the direction to form the sliced body 24, and the second C
The u-based metal plate 25 is attached and the Cu-attached pack material 26
Are formed. Further, the Cu-attached pack material 26 is rolled in the direction of the long axis D along the slice surface 24a, and cut in a direction orthogonal to the long axis D to form a fixed-size pack material 27. The Cu-based metal plates 28 are stacked on the outermost layer and rolled in a predetermined direction. The heat radiating plate 21 includes the first and second Cu-based metal plates 22 and 25, the Ni-based metal plate 23, and the like. Other configurations are substantially the same as those shown in FIGS. 1 and 2, and therefore, detailed description of the configuration is omitted here. The plastic package with a heat radiating plate according to the embodiment (2) includes the heat radiating plate 21 and the like.

As is clear from the above description, in the plastic package with a heat sink according to the embodiment (2),
The cladding material forming the heat radiating plate 21 is composed of a plurality of first Cu-based metal plates 22 rolled in the major axis D direction and a plurality of Ni
After alternately laminating and crimping the base metal plate 23, and slicing along the major axis D direction to form a sliced body 24, and placing the second Cu-based metal plate 25 on the slice surface 24a of the sliced body 24. A step of pasting to form a Cu-pasted pack material 26, and rolling the Cu-pasted pack material 26 in the direction of the long axis D along the slice surface 24a, and cutting it in a direction perpendicular to the long axis D, And a step of rolling the predetermined-size pack materials 27 alternately orthogonally and then rolling in a predetermined direction, and the first Cu-based metal plate 22 is Since the connection is continuously made via the Cu-based metal plate 25, the heat generated from the Si chip 35 (FIG. 1) can be more reliably dissipated to the outside.
Ni-based metal plate 2 having a high Young's modulus and a different rolling direction.
Since the first and second Cu-based metal plates 22 and 25 are sandwiched and reinforced by 3, the rigidity of the radiator plate 21 can be further increased.

In the plastic package with a heat radiating plate according to the embodiment (2), the heat radiating plate 21 is composed of the first and second heat radiating plates.
Although the description has been given of the case where the first and second Cu-based metal plates are configured to include the Cu-based metal plates 22 and 25 and the Ni-based metal plate 23 in another embodiment, 2
It may be configured to include 2, 25 and an Fe-based or Mo-based metal plate.

In the plastic packages with heat sinks according to the embodiments (1) and (2), the case where the outer dimensions of the heat sinks 13 and 21 are the same as that of the plastic substrate 31 has been described. In the embodiment, it may be smaller than the plastic substrate 31.

[0026]

EXAMPLES AND COMPARATIVE EXAMPLES The results of investigations on the incidence of chip cracks and the heat dissipation performance of the plastic package with a heat sink according to the examples will be described below. As the plastic package with a heat sink according to the embodiment, the one shown in FIG. 1 is used. The thicknesses t ₁ and t ₃ of the Ni-based metal plates 13a and 13c are both about 63 μm, and the thickness of the Cu-based metal plate 13b is The one set to about 127 μm and the length L of one side to about 35 mm was used. The heat sink 13 has a Young's modulus of about 16000 kg / mm ² and a thermal conductivity of about 240
W / mK. As a comparative example, the one shown in FIG. 6 was used, and the radiator plate 33 was made of pure Cu and had a thickness t.
Was set to about 254 μm.

As a result of investigating 50 samples, chip cracks occurred in 2 out of 50 samples in the comparative example, but in the example according to the present invention, the chip cracks could be made zero and the heat radiation performance was compared. It was able to secure almost the same as the example.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing an embodiment (1) of a plastic package with a heat sink according to the present invention.

FIG. 2 is a perspective view schematically showing a main part of a plastic package with a heat sink according to Embodiment (1).

FIG. 3 is a partial cross-sectional perspective view schematically showing a heat sink of the plastic package with a heat sink according to Embodiment (2).

FIG. 4 is a graph showing a bending stress applied to a Si chip and a Young's modulus of the radiator plate when a Si chip is temporarily attached to a heat sink via an insulating paste, and is heated to a predetermined temperature T of 150 ° C. and cooled to room temperature. FIG. 4 is a curve diagram showing the result of an investigation by simulation of the relationship between the heat sink and the bending stress applied to the Si chip, where the heat sink is formed using a pure Cu material (point B) as 100%; Is displayed.

FIG. 5 is a curve diagram showing a result obtained by investigating a relationship between a thermal resistance R and a thermal conductivity λ by simulation;
Indicates a case where the heat radiating plate is formed using a pure Cu material.

FIG. 6 is a cross-sectional view schematically showing a conventional plastic package with a heat sink.

7A and 7B are cross-sectional views schematically showing a conventional process of attaching a Si chip on a heat sink, wherein FIG. 7A is a state before heat treatment is performed, and FIG. 7B is a state after heat treatment is performed. This shows a state during cooling.

[Explanation of symbols]

 Reference Signs List 10 plastic package with heat sink 13 heat sink 31 plastic substrate 31b cavity 35 Si chip

Claims (3)

[Claims] A plastic package with a heat sink provided with a plastic substrate having a cavity for accommodating a silicon chip and a heat sink attached to the plastic substrate, has a Young's modulus of 15,000 kg / m.
m is ² or more, and the heat radiating plate with plastic package thermal conductivity, wherein the heat radiating plate using a material is 100W / mK or higher is formed. 2. The heat radiation plate is made of Cu / Ni / Cu,
/ Fe / Cu system, Cu / Mo / Cu system, or Ni / C
The plastic package with a heat sink according to claim 1, wherein the plastic package is made of a clad material of a u / Ni-based metal plate or a brazing material. 3. The method according to claim 3, wherein the clad material is formed by alternately laminating and pressing a plurality of first Cu-based metal plates rolled in a longitudinal direction and a plurality of Ni, Fe or Mo-based metal plates. Forming a sliced body by slicing along the major axis direction, bonding a second Cu-based metal plate to a sliced surface of the sliced body to form a Cu-bonded pack material,
Rolling the pasted pack material in the long axis direction along the slice plane, and cutting it in a direction perpendicular to the long axis to form a fixed length pack material; 3. The plastic package with a radiator plate according to claim 2, wherein the plastic package is manufactured by including a step of rolling in a predetermined direction after laminating the plastic package.