Source: http://www.google.com/patents/US7061080?dq=ascentive
Timestamp: 2015-01-29 05:11:28
Document Index: 287869040

Matched Legal Cases: ['art 240', 'art 240', 'art 240', 'art 340', 'art 340', 'art 340', 'art 340']

Patent US7061080 - Power module package having improved heat dissipating capability - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA power module package is provided. The power module package includes a power circuit element, a control circuit element, a lead frame, a heat sink, and an epoxy molding compound (EMC). The control circuit element is connected to the power circuit and controls chips in the power circuit. The lead frame...http://www.google.com/patents/US7061080?utm_source=gb-gplus-sharePatent US7061080 - Power module package having improved heat dissipating capabilityAdvanced Patent SearchPublication numberUS7061080 B2Publication typeGrantApplication numberUS 10/167,067Publication dateJun 13, 2006Filing dateJun 10, 2002Priority dateJun 11, 2001Fee statusPaidAlso published asUS7208819, US20030011054, US20050056918Publication number10167067, 167067, US 7061080 B2, US 7061080B2, US-B2-7061080, US7061080 B2, US7061080B2InventorsGi-young Jeun, Sung-Min Park, Joo-Sang Lee, Sung-won Lim, O-seob Jeon, Byoung-ok Lee, Young-Gil Kim, Gwi-gyeon YangOriginal AssigneeFairchild Korea Semiconductor Ltd.Export CitationBiBTeX, EndNote, RefManPatent Citations (17), Referenced by (52), Classifications (27), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetPower module package having improved heat dissipating capabilityUS 7061080 B2Abstract A power module package is provided. The power module package includes a power circuit element, a control circuit element, a lead frame, a heat sink, and an epoxy molding compound (EMC). The control circuit element is connected to the power circuit and controls chips in the power circuit. The lead frame has external connecting means formed at the edges thereof, and a down set part, namely, formed between the external connecting means. The lead frame has a first surface to which the power circuit and the control circuit are attached, and a second surface used as a heat dissipating path, in particular, the power circuit is attached to the down set part. The heat sink which is closely attached to the down set part of the second surface of the lead frame by an adhesive. The EMC surrounds the power circuit, the control circuit, the lead frame and the heat sink, and exposes the external connecting means of the lead frame and a side of the heat sink.
3. The power module package as claimed in claim 2, wherein the aluminum wire has the diameter of 250�500 μm.
7. The power module package as claimed in claim 5, wherein the high temperature tape has a thickness of 10�20 μm.
11. The power module package as claimed in claim 10, where the thickness of the high thermal liquid epoxy is 3�7 μm.
14. The power module package as claimed in claim 12, wherein the heat sink made of plastic or ceramic has a thickness of 1�3 mm.
FIG. 1 is a sectional view of a conventional power module package, which is disclosed in U.S. Pat. No. 5,703,399, published on May 15, 1996, titled �Semiconductor Power Module�.
SUMMARY OF THE INVENTION To solve the above problems, it is an object of the present invention to provide a power module package which more effectively dissipates heat generated in a power circuit chip and is simpler and cheaper to manufacture.
It is preferable that the power circuit includes power circuit chips and an aluminum wire for connecting the power circuit chips to the lead frame, and the aluminum wire has the diameter of 250�500 μm.
It is also preferable that the adhesive for attaching the lead frame to the heat sink is a high temperature tape, and the high temperature tape is formed of a material selected from the group consisting of alumina (Al2O3), aluminum nitride (AIN), silicon oxide (SiO2), and beryllium oxide (BeO), and the high temperature tape has a thickness of 10�20 μm. The high temperature tape can comprise particles including such thermally conductive materials embedded in a medium such as a polymer medium.
It is also preferable that the adhesive for attaching the lead frame to the heat sink is high thermal liquid epoxy, and the thickness of the high thermal liquid epoxy is 3�7 μm.
It is also preferable that the heat sink is made of plastic or ceramic, and the heat sink made of plastic or ceramic is formed of a material selected from the group consisting of alumina (Al2O3), aluminum nitride (AIN), silicon oxide (SiO2), and beryllium oxide (BeO), and the heat sink made of plastic or ceramic has a thickness of 1�3 mm.
FIG. 2 is a sectional view of a power module package according to an embodiment of the present invention. Referring to FIG. 2, the power module package 200 includes a lead frame 210, a power circuit element 220, a control circuit element 230, a heat sink 250, and an epoxy molding compound (EMC) 270. The power circuit element 220 includes a power circuit chip 221 and an aluminum wire 222. The aluminum wire 222 has a diameter of about 250�500 μm such that the aluminum wire 222 can withstand a high current rating. The control circuit element 230 includes a control circuit chip 231 and a gold wire 232. The aluminum wire 222 and the gold wire 232 connect the power circuit chip 221 to the control circuit chip 231.
The heat sink 250 has a thickness of about 1�3 mm and can be manufactured by using a material selected from the group consisting of alumina (Al2O3), aluminum nitride (AIN), silicon oxide (SiO2), and beryllium oxide (BeO). For example, a heat sink 250 made of ceramic can be manufactured by adding a material from the group consisting of alumina (Al2O3), aluminum nitride (AIN), silicon oxide (SiO2), and beryllium oxide (BeO) to a filling material including ceramic. Also, a heat sink 250 made of plastic can be manufactured by adding a material from the group consisting of alumina (Al2O3), aluminum nitride (AIN), silicon oxide (SiO2), and beryllium oxide (BeO) to a filling material including plastic. Meanwhile, if solder is used instead of the high temperature tape, metal is formed on a side of the heat sink 250 to be attached to the lead frame 210. Similarly, the high temperature tape 260 can be manufactured by using a material from the group consisting of alumina (Al2O3), aluminum nitride (AIN), silicon oxide (SiO2), and beryllium oxide (BeO) and has a thickness of about 10�20 μm such that the lead frame 210 and the heat sink 250 are completely attached to each other.
Referring to FIGS. 2, 5 and 6, first, the lead frame 210 having the down set part 240 formed in the middle thereof is prepared. The power circuit chip 221 and the control circuit chip 231 are attached to the first surface 211 of the lead frame 210 by performing a die attach process. The power circuit chip 221 is attached to part of the down set part 240 of the lead frame 210. Next, a wire bonding process is performed, thereby properly connecting the power circuit chip 221 to the control circuit chip 231. The gold wire 232 is used as a wire for the control circuit chip chip 231, and the aluminum wire 222 is used as a wire for the power circuit chip 221. Preferably, the aluminum wire 222 has a diameter of about 250�500 μm such that the aluminum wire 222 can withstand a high current rating. Bonding methods such as a wedge bonding method and a ball bonding method, are used in performing the wire bonding process. In order to perform the wire bonding process smoothly, it is preferable that the aluminum wire 232 is first bonded and then the gold wire 222 is bonded.
Next, the heat sink 250 is fixed in a groove 524 which is formed on a heat sink block 522 of the bottom mold die (520 of FIG. 5). The heat sink 250 has a thickness of about 1�3 mm and can be manufactured by using a material selected from the group consisting of alumina (Al2O3), aluminum nitride (AIN), silicon oxide (SiO2), and beryllium oxide (BeO). For example, the heat sink made of ceramic can be manufactured by adding a material from the group consisting of alumina (Al2O3), aluminum nitride (AIN), silicon oxide (SiO2), and beryllium oxide (BeO) to a filling material including ceramic. Also, the heat sink 250 made of plastic can be manufactured by adding a material from the group consisting of alumina (Al2O3), aluminum nitride (AIN), silicon oxide (SiO2), and beryllium oxide (BeO) to a filling material including plastic.
Next, after the wire bonding process, the lead frame 210 is placed in a molding apparatus. Here, the heat sink 250 has already been fixed in the groove 524 of the bottom mold die 520. Subsequently, the high temperature tape 260 is melted such that the heat sink 250 is completely attached to the second surface 212 of the down set part 240 of the lead frame 210. Here, the temperature and pressure for melting the high temperature tape 260 are about 160�220� C. and about 30 kg/cm2, respectively. The high temperature tape 260 can be manufactured by using a material selected from the group consisting of alumina (Al2O3), aluminum nitride (AIN), silicon oxide (SiO2), and beryllium oxide (BeO) and has a thickness of about 10�20 μm.
Next, a top mold die 510 is lowered, and the EMC 270 is flowed into an EMC apparatus through a gate 530. The EMC 270 is changed into a liquid by heat and pressure. Thus, the EMC 270 flows in a direction indicated by the arrows and fills the inside of a mold 500 uniformly. A transfer molding equipment including a plurality of gates and runners is used as the molding equipment, and preferably, the temperature for a sealing process is about 160�170� C.
FIG. 3 is a sectional view of a power module package according to another embodiment of the present invention. Referring to FIG. 3, the power module package 300 includes a lead frame 310, a power device 320, a control device 330, a heat sink 350, and an epoxy molding compound (EMC) 370. The power device 320 includes a power circuit chip 321 and an aluminum wire 322. The control device includes a control circuit chip 330 and a gold wire (not shown). The lead frame 310 has a thickness of about 0.5�1.0 mm and includes a down set part 340 that is formed in the middle of the lead frame 310. The power device 320 and the control device 330 are attached to one surface of the lead frame 310. In particular, the power device 320, which generates a large amount of heat, is attached to the down set part 340 of the lead frame 310.
The heat sink 350 is attached to the opposite surface of the down set part 340 of the lead frame 310 using high thermal liquid epoxy 360, and a side of the heat sink 350 is completely exposed to the outside of the power module package 300. The high thermal liquid epoxy 360 can be made by adding a filling material including a material from the group consisting of alumina (Al2O3), aluminum nitride (AIN), silicon oxide (SiO2), and beryllium oxide (BeO) to epoxy. The thickness of the high thermal liquid epoxy 360 is about 3�7 μm and represents thermal resistance less than about 1.5� C./W, and thus has improved thermal conductivity in comparison with a conventional power module package in which epoxy molding compounds are used.
FIGS. 7A through 7D are sectional views illustrating the method for manufacturing the power module package according to another embodiment of the present invention. First, referring to FIG. 7A, the lead frame 310 having a thickness of about 0.5�1.0 mm is prepared. The power circuit chip 321 and the control circuit chip 330 are attached to the surface of the lead frame 310 by performing a die attach process. The power circuit chip 321 is attached to part of the down set part 340 of the lead frame 310. The die attach process may be performed using solder or silver (Ag) epoxy as an adhesive. In a case where the die attach process is performed using solder as an adhesive, the temperature and pressure for the die attach process is about 350�380� C. and about 3�5 kg/cm2, respectively, and the die attach process is performed in a hydrogen atmosphere. In a case where the die attach process is performed using Ag epoxy as an adhesive, the die attach process is performed at the room temperature and pressure under about 1�2 kg/cm2.
Next, referring to FIG. 7B, the high thermal liquid epoxy 360 is attached to the upper surface of the heat sink 350 made of ceramic having a thickness of about 1�3 mm. The high thermal liquid epoxy 360 can be made by adding a filling material including a material from the group consisting of alumina (Al2O3), aluminum nitride (AIN), silicon oxide (SiO2), and beryllium oxide (BeO) to epoxy.
Next, referring to FIG. 7C, the heat sink 350 made of ceramic is attached to the lead frame 310 onto which the power circuit chip 321 is attached, using the high thermal liquid epoxy 360 as an adhesive. The attach process is performed at a temperature of about 150�180 � C. and pressure under about 0.5�1.0 kg/cm2 for about 3�5 minutes.
In order to manufacture the power module package 400, first, the lead frame 410 is attached to the DBC substrate 450. The attach process may be performed using an adhesive such as solder or thermal tape, or by welding using a laser or spot, or by thermal compression using silver (Ag) or Ag/Sn plating. Next, the power circuit chip 421 and the control circuit chip 430 are attached to the lead frame 410. The die attach process may be performed using solder and Ag epoxy. The solder is used to attach the power circuit chip 421 to the lead frame 410, and in this case, the die attach process is performed at a temperature of about 330�360� C. The Ag epoxy is used to attach the control circuit chip 430 to the lead frame 410, and in this case, the die attach process is performed at the room temperature. Next, the power circuit chip 421 and the control circuit chip 430 are electrically connected to the lead frame 410 by performing a wire bonding process. An aluminum wire is used as a wire for the power circuit chip 421, and a gold wire is used as a wire for the control circuit chip 430. Next, an encapsulation process is performed using the EMC 470, and then, general trim and forming processes are performed.
First, since the heat sink is directly attached to the back side of the down set part of the lead frame by using the high temperature tape, heat which is generated during operation of the power module package can be effectively dissipated, thereby increasing the reliability of the power module package. As an example, when the structure and material of the heat sink of the power module package are changed like those in the prevention invention, RΘjc, as the thermal resistance of the conventional power module package was measured to be 0.19� C./Watt. On the other hand, RΘjc of the power module package according to the present invention was measured to be 0.15� C./Watt, and as a result, the heat dissipating capability is improved by 20�30%. For reference, RΘjc is an index representing a difference in temperature from the PN junction of the power circuit chip 121 to a case, as a mold line. Similarly, RΘjc, was measured to be 0.15� C./Watt even in a case where the high thermal liquid epoxy instead of the high temperature tape is used.
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