JPH0897316A - Plastic package for integrated circuit - Google Patents

Abstract

PURPOSE: To apply a package for an integrated circuit operating at ultra-high frequencies or microwave frequencies, by providing a die, attaching pad surrounded by a main body and waveguides on the same plane for guiding the propagating signals. CONSTITUTION: A die-attaching pad 201 for attaching an integrated circuit is surrounded by the main body of plastic material. Furthermore, a plurality of wave guides on the same plane extending outwards from the die-attaching pad 201 are provided through the plastic material. The waveguide consists of a lead 202 on the first same plate, a lead 204 on the second same plane and a lead 206 on a third same plane extending outward froms the die-attaching pad 201. In this case, the first lead 202 is the credit lead, and the second and third leads 204 and 206 are the grounding leads. The wave guide on each same plane is electrically connected to the integrated circuit chip. Thus, the package can be applied on the integrated circuit operating at the ultra-high frequencies and the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is generally directed to integrated circuit packages, and more particularly to low cost standardized plastic packages suitable for integrated circuits operating at very high or microwave frequencies. It is intended for.

[0002]

2. Description of the Related Art Conventionally, low cost is very important for the successful introduction of a new communication technology product into the mass consuming electronic equipment market. Cellular horns, electronic paper, satellite receivers, wireless networks for portable computers, etc. can all benefit from integrated circuits operating at very high or microwave frequencies. Reducing the component packaging cost for such integrated circuits is an important factor in reducing the overall cost of these new products to consumers.

Standardization of integrated circuit packages provides not only cost advantages, but also other advantages in electronics manufacturing. For example, standardized integrated circuit packages are easily handled by automatic feed and placement equipment used in the manufacture of printed circuit board assemblies. Further, in the standardized integrated circuit package, the uniformity of the standardized package is used to efficiently attach the integrated circuit to the standardized package. In addition, standardized plastic packages such as the plastic quad flat package (PQFP) are available at a relatively low cost due to their high volume, ease of manufacture and low material cost. For example, 1-2 in US currency per package
At a cost of $ 68, the 68-pin plastic quad flat package is currently one of the lowest cost packages of all 68-pin integrated circuit packages.

[0004]

Despite these cost and manufacturing advantages, standardized packaging still has drawbacks. Currently available integrated circuits mounted in standardized plastic packages suffer significant performance degradation when operating at very high or microwave frequencies. As discussed in this document, the poor frequency performance of these packages has many causes.

One of the reasons for poor frequency performance is that such standardized plastic packages have uneven lead
Since a frame is used, a discontinuity may occur with respect to a signal having a very high frequency or a microwave frequency propagating in the frame. In general, a discontinuity is a break in a continuous state in a medium or material in which reflection of wave energy can occur. The greater the discontinuity, the greater the reflection. Theoretically, leadframe discontinuities cause reflections that significantly degrade the performance of standardized plastic packages when the integrated circuits to which they are installed operate at very high or microwave frequencies. Become.

Referring to FIG. 12, a typical prior art 68
68 non-uniform leads used for pin PQFP
A top view of the frame 100 is shown. In theory,
The non-uniform lead frame 100 increases unwanted reflections of very high frequency or microwave frequency signals propagating along the conductive leads, which significantly increases the frequency performance of the prior art 68-pin PQFP. It means that it will deteriorate. As shown in FIG. 12, each component conductive lead of the lead frame includes an abrupt discontinuity along the respective longitudinal dimension of each component conductive lead. For example, FIG.
As shown in FIG. 2, the lead frame 100 includes a first component conductive lead 105 adjacent a die attach pad 106 for attaching an integrated circuit. In particular, the first conducting lead 105 has abruptly changing features 107, 109, resulting in a discontinuity that partially reflects the first signal propagating along the lead.

Another problem arises if the source impedance and load impedance mismatches are not compensated for. For example, if the load impedance ZL of an integrated circuit mounted in a prior art package is significantly different from the source impedance Zs of the source material coupled to the first conductive lead 105 at an external point of the package, the source impedance. If the mismatch between the load impedance and the load impedance is not compensated, it will be reflected at an external point of the package according to the reflection coefficient r obtained by the following equation.

[0008]

[Equation 1]

Where ω is the frequency of the first signal, Zo is the characteristic impedance associated with the first conducting lead, and Vo is the phase of the signal propagating along the first conducting lead. It's speed.

Another standardized plastic package
One drawback is insufficient heat dissipation for many integrated circuits operating at very high frequencies or microwave frequencies. For example, a typical 48-pin PQFP consumes less than 1 watt of heat dissipation in stagnant air at room temperature.
For many integrated circuits operating at very high or microwave frequencies, it is desirable to dissipate the integrated circuit package's heat above 2 watts. Obviously, in general, integrated circuits operating at very high frequencies generally generate more heat than integrated circuits operating at low frequencies. Therefore, enhanced heat dissipation is particularly desirable for integrated circuits operating at very high or microwave frequencies.

Known solutions to dissipate the increased heat of a PQFP are conventional heat slugs or sinks that are coupled to the package. Such an approach adds undesirable size, weight, and cost to the package.
Even using these schemes, PQFPs typically dissipate only about 2 watts into stagnant air at room temperature.

Another known approach to increasing the heat dissipation of a PQFP involves providing a die attach pad for attaching an integrated circuit, which has four corner regions. The scheme further includes four wide tie bars each thermally coupled to each of the four corner areas of the die attach pad. An example of such a plan is the 7th
"The design and charact" by Tom Moore presented at the IEEE SEMI-THERM Symposium (1991).
erization of a high thermal efficiency leadframe w
It is an integral heat spreader ”. This paper provides useful background information and is included here for reference.

According to such a plan, the heat dissipation of the PQFP is strengthened to some extent, but further improvement is required. Since the tie bars are only coupled to the corner areas of the die attach pad, the heat leaving the die attach pad through the tie bars is a “bottle” in the corner area.
Limited by There is a need for an improved plastic package that overcomes these heat flow limitations, but at the same time does not add the size, weight, and cost of conventional heat slugs or sinks.
Further, as mentioned above, it is necessary to enhance frequency performance.

[0014]

The present invention provides a low cost standardized plastic package suitable for integrated circuits operating at very high or microwave frequencies. Because the adaptive plastic package of the present invention has a standardized form factor, the adaptive plastic package is easy to handle by the automated feed and placement equipment used in the manufacture of printed circuit board assemblies.
Such standardization also enables efficient mounting of integrated circuits in standardized packages. In addition, standardized plastic packages such as the plastic quad flat package (PQFP) are easy to manufacture and the materials are low cost, so the adaptive plastic package of the present invention provides relatively low cost and frequency Performance can be improved.

In summary, generally speaking, the novel plastic package according to the present invention includes a body of plastic material having an outer periphery. A die attach pad for attaching the integrated circuit is surrounded by a body of plastic material. The present invention further includes
Included are a plurality of coplanar waveguides disposed adjacent the die attach pad and extending outwardly from the die attach pad through the plastic material. Each coplanar waveguide is electrically coupled to the integrated circuit chip to conduct signals between the integrated circuit and points adjacent the outer circumference of the plastic body. The coplanar waveguide has controlled impedance to enhance frequency performance.

Generally, integrated circuits operating at high frequencies are
It produces more heat than integrated circuits operating at low frequencies. Thus, the preferred embodiment of the present invention enhances heat dissipation while avoiding the added size, weight and cost inherent in conventional heat slugs or sinks. Each coplanar waveguide has its own ground lead that is thermally coupled to the die attach pad so that some of the heat the die attach pad receives from the integrated circuit is It is preferably adapted to be removed from the integrated circuit via the ground lead of the.

The present invention further provides a novel packaging method for integrated circuits. The method includes providing a coplanar waveguide having a die attach pad and leads extending outwardly from the die attach pad for conducting signals propagating along the waveguide. The method further includes coplanar waveguide lead thickness based on the intrinsic impedance of the plastic material such that the impedance is controlled as the signal propagates along the waveguide. Includes selecting dimensions for width, width, and spacing. Additional steps include
Includes attaching an integrated circuit to a die attach pad, electrically connecting a coplanar waveguide with the integrated circuit, molding a plastic material around the integrated circuit, and curing the plastic material .

Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrates the principles of the invention.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The plastic package of the present invention is compatible with integrated circuits operating at very high frequencies or microwave frequencies and has relatively low cost and enhanced frequency performance. The adaptive plastic package of the present invention includes a die attach pad for attaching an integrated circuit and an electrical connection to the integrated circuit that is located adjacent to the die attach pad and extends outwardly to the waveguide. A plurality of waveguides are included for conducting desired ultra high frequency or microwave frequency electromagnetic signals that propagate along. The coplanar waveguide preferably includes a substantially uniform lead frame structure 200, as shown in the plan view of FIG. That is, in FIG.
1 and a preferred embodiment of an outwardly extending coplanar waveguide positioned adjacent to the die attach pad.

For example, as shown in FIG. 1, the coplanar waveguide includes a first coplanar waveguide having a longitudinal dimension extending outwardly from the die attach pad 201. There is. In the preferred embodiment, the first coplanar waveguide is coupled to the first coplanar lead 20.
2 and further comprises a second coplanar lead 204 and a third coplanar lead 206 extending outward from the die attach pad 201. As shown, the first coplanar lead 202 is a signal lead, and is the second and third coplanar lead 20.
Reference numerals 4 and 206 are ground leads.

Briefly, in the preferred embodiment, there is a structural overlap between coplanar waveguides located adjacent to each other. For example, a structural overlap between a first coplanar waveguide and a second coplanar waveguide located adjacent to the first coplanar waveguide. Exists. That is, the first coplanar waveguide second
The coplanar leads 204 are also part of a second coplanar waveguide. The second coplanar waveguide further comprises another signal lead 208 and yet another ground lead 210.

Ground leads 204, 206, 210
Are thermally coupled to the die attach pad 201, so that some of the heat that the die attach pad 201 receives from the integrated circuit is conducted through the ground leads 204, 206, 210 and removed from the integrated circuit. Be done. For example, in the preferred embodiment, the ground leads 204, 2 described above.
06 and 210 are members of the first group of ground leads. As shown, the first group of ground leads are integrated with the first edge of the die attach pad 201 to remove heat from the integrated circuit.

The die attach pad 201 is provided with a perimeter including a plurality of corner regions and a plurality of edge regions extending therebetween. In the preferred embodiment of FIG. 1, die attach pad 201 has four corner regions and four edge regions extending between the corner regions. Thus, in the preferred embodiment, the second group of ground leads is integrated with the second edge region of the die attach pad 201 and the third group of ground leads is the third group of die attach pads 201. Integrated with the edge region of the die and the fourth group of ground leads are integrated with the fourth edge region of the die attach pad 201.

The substantially uniform lead frame structure 200 provides a controlled electrical impedance. In contrast to the non-uniform lead frame 100 common in the prior art, which was previously described in connection with FIG. 12 described in the prior art, the present invention shown in FIG. , There are no sharp discontinuities due to unwanted reflections that are increased by very high frequency or microwave frequency signals propagating along the conductive leads. Like above-mentioned,
Such sharp discontinuities are undesirable because they significantly degrade frequency performance.

FIG. 2 is a cutaway isometric view of the adaptive plastic package of the present invention. Adaptive plastic packages include a body of plastic material such as a compatible epoxy compound. In the preferred embodiment, the body has a perimeter that corresponds to a standardized form factor, such as in a plastic quad flat package (PQFP). The body is cut away in FIG. 2 so that a substantially uniform lead frame structure is visible. The lead frame is made of copper alloy or other compatible conductive material. As shown in FIG. 2, a plurality of coplanar waveguides are located adjacent the die attach pad and extend outwardly through the plastic material.

FIG. 2 shows an integrated circuit mounted in the package 300 of the present invention. That is, the integrated circuit is attached to the die attach pad and electrically grounded to the die attach pad. As mentioned above, in the preferred embodiment, the coplanar ground leads 204, 206, 210 are integrated with the die attach pad. As shown in FIG. 2, wire bonds provide an electrical connection between coplanar signal leads 202, 208 and matching contacts on the surface of the integrated circuit.

FIG. 3 is a detailed cross-sectional view of the adaptive package of the present invention showing a first coplanar waveguide. As mentioned above, in the preferred embodiment, the first coplanar waveguide has a first coplanar lead 202, which is the signal lead of the first coplanar waveguide, and A first coplanar waveguide ground lead, a second coplanar lead 204 and a third coplanar lead 20.
It consists of 6. The first lead 202 has a thickness of T
And the width is W. Further, the first coplanar lead 202 is arranged adjacent to the second lead 204 with a distance S from the second lead 204. Similarly, in the preferred embodiment, the first coplanar lead 202 is spaced adjacent the third lead 206 by a distance S from the third lead 206.
As will be described in more detail below, the thickness T and width W of the first lead 202 and the spacing distance S from the second lead 204.
Are all selected based on the intrinsic impedance of the plastic material to control the impedance along the longitudinal dimension of the first coplanar waveguide. The height of the plastic body of the package is H
And is selected to match the desired form factor of the adaptive package.

FIG. 4 is a detailed view showing a cross-sectional view of an electromagnetic signal at a very high frequency or a microwave frequency propagating along the longitudinal dimension of the first coplanar waveguide. Of course, electric field lines and magnetic field lines are not visible. However, for purposes of illustration, electric field lines 402 are shown in solid lines in FIG. 4 as a typical example. Similarly, in FIG. 4, the magnetic field lines 404 are shown by a dash line as a typical example. Furthermore, to clearly show the electric and magnetic field lines,
In FIG. 4, the plastic material is shown without the cross hatching.

As mentioned above, the intrinsic impedance of the plastic material of the package is a factor in controlling the impedance of the coplanar waveguide of the adaptive plastic package according to the present invention. In general, the intrinsic impedance of a plastic material is almost determined by the dielectric constant Er of the plastic material. As shown in the cross-sectional view of FIG. 3, in the preferred embodiment, the lead frame extends through a body of epoxy compound having a dielectric constant Er of about 4.6. In contrast to plastic materials, air has a dielectric constant of 1. To show how the intrinsic impedance of the plastic material affects the impedance of the coplanar waveguide of the adaptive plastic package, the discussion below will refer to the coplanar conductor of the plastic package shown in FIG. Compare the impedance of the waveguide with the impedance of the coplanar waveguide surrounded by air shown in FIG. 1 with only the lead frame. Further, the discussion below provides examples of teachings that demonstrate how to modify the lead thickness, the lead width, and the lead-to-lead spacing to control the impedance of the coplanar waveguide.

In general, the impedance of coplanar waveguides in adaptive plastic packages is estimated using the method of moments for very high frequency or microwave frequency signals. For example, Figures 5-9 each show the impedance of each coplanar waveguide for signals propagating along various coplanar waveguide embodiments with different physical dimensions. It is the graph which estimated the curve. A useful basic theory, Hoff, published by Artech House, incorporated by reference.
"Handbook of Microwave Integrated Cir by man et al.
cuits ". As an alternative to the method of moments, more sophisticated analytical methods can be used to estimate impedance and obtain useful results. As shown in FIGS. 5-9, the impedance curve associates impedance values for coplanar waveguides with various values for the spacing distance S described above.

For each of the graphs of FIGS. 5 to 9, the impedance curve of each waveguide is 2 based on the dielectric constant Er.
It is divided into two respective families. Therefore, FIG.
For each chart in FIG. 9, directly based on the dielectric constant Er = 4.6 of the plastic material of the package of FIG.
Indirectly, the respective first family of waveguide impedance curves based on the intrinsic impedance of the plastic material of the package of FIG. 3 is shown. For illustrative comparison, each of the charts of FIGS. 5-9 is further based on the dielectric constant Er = 1 of the air around the lead frame shown in FIG. 1, indirectly based on the intrinsic impedance of the air, respectively. The waveguide impedance curves that make up the second family of are shown. Further, it should be understood that the dielectric constant Er of the plastic material of the package is 4.
An alternative embodiment waveguide impedance curve that is greater than 6 or less than 4.6 is that it can be interpolated from the first and second family of curves.

All illustrated curves in the graph shown in FIG. 5 assume a coplanar lead thickness T of about 1 mil. As mentioned above, the waveguide impedance curves forming the first family of FIG. 5 are based on the dielectric constant Er = 4.6 of the plastic material of the package. The waveguide impedance curve forming the first family shown in FIG.
One member is included, each member corresponding to a respective selected width dimension W of the first coplanar leads. That is, the first member corresponds to a width of 4 mils, the second member corresponds to a width of 8 mils, the third member corresponds to a width of 16 mils, and the fourth member corresponds to It corresponds to a width of 32 mils. For example, if it is desired that the coplanar waveguide of the adaptive plastic package have a controlled impedance of about 50 ohms, then in one of the embodiments, according to FIG. On the same plane, the lead thickness T is 1 mil and the lead width W is 4
Mil, distance from second coplanar lead about 1
That's 0.1 mil. For example comparison, FIG. 5 further shows the impedance curve of a second family of waveguides based on the dielectric constant Er = 1 of the air surrounding only the lead frame shown in FIG. 4 of the waveguide impedance curve forming the second family shown in FIG.
Lead width dimensions of 4, 8, 16 and
And 32 mils.

In contrast to FIG. 5, all curves in the graph shown in FIG. 6 assume a lead thickness T of about 2 mils. As mentioned above, the first family of waveguide impedance curves in FIG. 6 is based on the dielectric constant Er = 4.6 of the plastic material of the package. The first family of waveguide impedance curves shown in FIG. 6 includes four members, each member corresponding to a respective selected width dimension W of the first coplanar leads. are doing. Each of the four members of the first family of waveguide impedance curves shown in FIG.
Supports lead width dimensions of 4, 8, 16 and 32 mils. For example, if the coplanar waveguide of the adaptive plastic package is desired to have a controlled impedance of about 50 ohms, then according to FIG.
In another embodiment of the present invention, the first coplanar lead has a lead thickness T of 2 mils and a lead width W of 8 mils.
The spacing distance from the second coplanar lead will be about 7.8 mils. For example comparison, FIG. 6 further shows a second family of waveguide impedance curves based on the dielectric constant Er = 1 of the air surrounding only the lead frame shown in FIG. The four members of the second family of waveguide impedance curves shown in FIG. 6 correspond to lead width dimensions of 4, 8, 16 and 32 mils, respectively.

In contrast to FIGS. 5 and 6, all curves in the graph shown in FIG. 7 assume a lead thickness T of about 4 mils. As mentioned above, the first family of waveguide impedance curves in FIG. 7 is based on the dielectric constant Er = 4.6 of the plastic material of the package. The first family of waveguide impedance curves shown in FIG. 7 includes four members, each member corresponding to a respective selected width dimension W of the first coplanar leads. are doing. The four members of the first family of waveguide impedance curves shown in FIG. 7 correspond to lead width dimensions of 4, 8, 16 and 32 mils, respectively. For example, if the coplanar waveguide of the adaptive plastic package is desired to have a controlled impedance of about 50 ohms, then according to FIG. 7, yet another embodiment of the present invention. In the first
The lead thickness T of the lead on the same plane is 4 mils, the lead width W is 16 mils, and the distance from the lead on the second same plane is about 7.8 mils. For example comparison,
FIG. 7 further shows a second family of waveguide impedance curves based on the dielectric constant Er = 1 of the air surrounding only the lead frame shown in FIG. The four members of the second family of waveguide impedance curves shown in FIG. 7 have lead width dimensions of 4, 8, respectively.
Corresponds to 16 and 32 mils.

In contrast to FIGS. 5, 6 and 7, all curves in the graph shown in FIG. 8 assume a lead thickness T of about 8 mils. As described above, the waveguide impedance curve forming the first family in FIG. 8 has the dielectric constant Er = 4.
Based on 6. The first family of waveguide impedance curves shown in FIG. 8 includes four members, each member corresponding to a respective selected width dimension W of the first coplanar leads. are doing. The four members of the first family of waveguide impedance curves shown in FIG. 8 correspond to lead width dimensions of 4, 8, 16 and 32 mils, respectively. For example, adaptive plastic
If it is desired that the coplanar waveguide of the package has a controlled impedance of about 50 ohms, then in accordance with FIG. 8, in yet another embodiment of the present invention, the first The lead thickness T of the leads on the same plane is 8
This means that the mil, the lead width W is 8 mils, and the distance from the second coplanar lead is about 13 mils. For illustrative comparison, FIG. 8 further shows a second family of waveguide impedance curves based on the dielectric constant Er = 1 of the air surrounding only the lead frame shown in FIG. The four members of the second family of waveguide impedance curves shown in FIG. 8 correspond to lead width dimensions of 4, 8, 16 and 32 mils, respectively.

In the case of all the curves in the graph shown in FIG. 9, the impedance assumes that each lead width W is approximately equal to the respective spacing distance S at each point of the curve. The first family of waveguide impedance curves in FIG. 9 is based on the dielectric constant Er = 4.6 of the plastic material of the package. The first family of waveguide impedance curves shown in FIG. 9 includes four members, each member having a first respective coplanar lead thickness selected T. It corresponds. That is, the first member corresponds to a thickness of 4 mils, the second member corresponds to a thickness of 8 mils, the third member corresponds to a thickness width of 16 mils, and the fourth member Members correspond to a thickness of 32 mils. For example, if it is desired that the coplanar waveguide of the adaptive plastic package has a controlled impedance of about 50 ohms, then according to FIG. 1 coplanar lead has a lead thickness T of 2 mils, a lead width W of about 7.9 mils, a second
Will be approximately 7.9 mils from the coplanar leads. For example comparison, FIG.
A second family of waveguide impedance curves based on the dielectric constant Er = 1 of the air surrounding only the lead frame shown in FIG. 1 is shown. The four members of the second family of waveguide impedance curves shown in FIG. 9 correspond to lead thickness dimensions of 1, 2, 4 and 8 mils, respectively.

In the case of the adaptive plastic package of the present invention, the impedance of the coplanar waveguide is controlled so that the impedance of the integrated circuit mounted in the package and the impedance of the package outside the package are electrically connected to the leads of the package. It is desirable to have an impedance match with the impedance of the device coupled to. For example, as shown in the partial cutaway isometric view in FIG. 10, in the preferred embodiment, by controlling the impedance of the coplanar waveguide, the impedance of the integrated circuit mounted in the adaptive package 300, and An impedance match is made with the impedance of the electronic assembly 1002 outside the package. That is, if the package is externally coupled to an electronic assembly that has an impedance of 50 ohms, and if the impedance of the integrated circuit mounted in the plastic package is 50 ohms, the coplanar waveguide The impedance is controlled to provide a 50 ohm impedance that matches the impedance of the integrated circuit mounted in the package and the impedance of the assembly.

As another example, assuming that the longitudinal dimension of the coplanar waveguide is chosen to be approximately an integral multiple of a quarter wavelength of the signal, the coplanar waveguide may be coplanar. The impedance of the waveguide is controlled so as to be approximately equal to the square root of the product of the impedance of the integrated circuit and the impedance of the external device, so that the desired impedance matching is achieved. That is, if the package is externally coupled to an electronic assembly that has an impedance of 5 ohms, and if the impedance of the integrated circuit mounted in the plastic package is 500 ohms, the impedance of the coplanar waveguide. Is controlled to obtain an impedance of 50 ohms, again allowing the impedance of the integrated circuit mounted in the package and the impedance of the assembly. Alternatively, assuming that the longitudinal dimension of the coplanar waveguide is not approximately an integer multiple of the quarter wavelength of the signal, a suitable calculation technique can be used to achieve the desired impedance match. The required control impedance value is calculated.

Structurally, the first lead of the coplanar waveguide is located adjacent the first end for electrical coupling to the integrated circuit and the outer circumference of the plastic body of the package. A second end for electrically coupling to the device. For example, as shown in FIG. 10, the first ends of the leads are electrically coupled to the integrated circuit by wire bonds. The other end of the lead
In contact with the conductive traces of the electronic assembly, which assembly is further electrically coupled to another electronic device 1004 external to the package. The width and thickness of the first lead and the distance from the second lead are all selected to provide an impedance match between the impedance of the integrated circuit mounted in the package and the impedance of the device. . It should be understood that the adaptive package and the external device can be coupled by utilizing strip lines or microstrip transmission lines instead of the conductive traces shown in FIG. Package 30
When 0 is attached and electrically coupled to the electronic assembly, transparent silicon with a dielectric constant Er of about 3.5 at the location where the leads protrude from the plastic body of the package.
It may be desirable to apply a compatible conformal compound, such as a gel compound, around the lead. This application of the conformal compound enhances the frequency performance of the electronic assembly used in connection with the adaptive plastic package of the present invention.

The width and thickness of the first lead, and the distance from the second lead, keep the characteristic impedance along the longitudinal dimension of the first coplanar waveguide constant, thereby As the signal propagates along the longitudinal dimension of the first coplanar waveguide, it is desirable to significantly reduce signal reflection. Therefore, it is desirable to perform the above-mentioned impedance matching and at the same time keep the impedance substantially constant. However, in an alternative embodiment, the width and thickness of the first lead and the distance from the second lead are determined by the first coplanar plane along the longitudinal dimension of the waveguide on the first coplanar plane. The impedance of the upper waveguide is chosen to be a gradual change. Since the impedance changes gradually, the reflection of signals propagating along the waveguide is also greatly reduced. Desirably, the impedance of the waveguide is gradually changed by tapering the physical dimensions of the leads in increments of one quarter wavelength of the longitudinal dimension of the waveguide.
It should be understood that various tapers such as linear tapers, exponential tapers and hyperbolic tapers can be utilized with beneficial results. A valid basic theory of tapered line and quarter-wave impedance transformers is the second edition of "Lines, Waves, and Antennas" by Brown et al., Published by Ronald press (1973).
(Year), page 99, sections 4-6, incorporated herein by reference.

FIG. 11 is a flow chart showing the novel plastic packaging method according to the present invention. As shown in block 1102 of FIG. 11, a die attach pad with leads and a coplanar waveguide are provided. The pads and coplanar waveguides are preferably arranged like the lead frame described above and shown in FIG. According to block 1104 of FIG. 11, the respective dimensions of the lead thickness T, the width W and the spacing S are based on the intrinsic impedance of the plastic material, as described in detail earlier in this document. Is selected to control. An integrated circuit is attached to the die attach pad, as shown in block 1106. According to block 1108, wire bonds are utilized to electrically interconnect the coplanar waveguides with the integrated circuit, as previously described. The lead frame of the present invention is, for example, a plastic quad flat package, PQFP.
, In a conforming mold corresponding to the standardized form factor. According to block 1110, a plastic resin such as an epoxy compound resin is injection molded to form a plastic mold around the integrated circuit mounted on the lead frame. Block 11
According to 12, when the plastic is hardened, the resin is hardened to form the plastic main body as shown in FIG. After sufficient time for curing, the adaptive plastic package of the present invention is removed from the mold.

The packaging method and plastic package according to the present invention are suitable for integrated circuits operating at very high frequencies or microwave frequencies, and have relatively low cost and improved frequency performance. Although the present invention has been described in detail based on some preferred embodiments, many modifications and changes can be made by those skilled in the art.
Accordingly, the appended claims are intended to cover all such modifications and changes as fall within the true spirit and scope of this invention.

As described above, according to the present invention, a low-cost plastic package having enhanced electrical and thermal performance, which is used at an ultrahigh frequency or a microwave frequency, can be realized by the following configuration and method. .

(1). A body of plastic material having a perimeter, a die attach pad surrounded by the plastic body for attaching an integrated circuit, and an electrical connection with the integrated circuit disposed adjacent to the die attach pad and extending outwardly from the plastic material. To enable dynamic binding,
A plastic for integrated circuits consisting of coplanar waveguide means for guiding signals propagating along the waveguide
It is a package.

(2). The package according to (1) above, wherein the waveguide on the same plane is a means for guiding an ultrahigh frequency wave signal propagating along the waveguide.

(3). The coplanar waveguide means is the package according to (2) above, which exhibits a substantially constant characteristic impedance when an ultrahigh frequency signal propagates along the waveguide.

(4). The coplanar waveguide is the package according to (1) above, which is a means for guiding a microwave frequency signal propagating along the waveguide.

(5). The package according to (4) above wherein the coplanar waveguide means exhibits a substantially constant characteristic impedance as the microwave frequency signal propagates along the waveguide.

(6). The package according to (1) above, wherein the waveguide means on the same plane includes a substantially uniform lead frame structure.

(7). A coplanar waveguide means has a first end for electrically coupling to an integrated circuit and another end for electrically coupling to a device adjacent the outer periphery of the plastic body. And the characteristic impedance of the coplanar waveguide means is selected such that an approximate impedance match is achieved between the impedance of the integrated circuit and the impedance of the device. .

(8). A plastic material having an inherent impedance and a first coplanar waveguide having longitudinal dimensions extending outwardly from the die attach pad to the coplanar waveguide means. And a first coplanar waveguide comprising first and second coplanar leads extending outwardly from the die attach pad through the plastic material of the body. And a first lead having a thickness and a width and located a distance from the second lead and adjacent to the second lead; Thickness and width and distance from the second lead are all based on the intrinsic impedance of the plastic material to control the impedance along the longitudinal dimension of the first coplanar waveguide. Has been selected on A package according to (1).

(9). The width and thickness of the first lead and the distance from the second lead are selected to keep the characteristic impedance of the first coplanar waveguide substantially constant, so that the signal is The package according to (8) above, in which the reflection of signals when propagating along the longitudinal dimension of a waveguide on the same plane is significantly reduced.

(10). The first lead has a first end for electrical connection to the integrated circuit and another end for electrical connection to a device adjacent the outer periphery of the plastic body; The width and thickness of one lead and the distance from the second lead are all selected to provide an impedance match between the impedance of the integrated circuit mounted in the package and the impedance of the device. It is a package.

(11). The width and thickness of the first lead and the distance from the second lead gradually increase the impedance of the first coplanar waveguide along the longitudinal dimension of the first coplanar waveguide. The package according to (8) above, in which the reflection of signals is significantly reduced because the package is selected to be changed to.

(12). The waveguide includes a plurality of coplanar leads that electrically conduct, and at least one of the coplanar leads is a ground lead thermally coupled to the die attach pad. Therefore, a part of the heat received by the die attachment pad from the integrated circuit is conducted through the ground lead and removed from the integrated circuit.

(13). Since the waveguide includes a plurality of coplanar conductive leads and at least one of the coplanar leads is a ground lead integrated with the die attach pad, Some of the heat that the die attach pad receives from the integrated circuit
The package according to (1) above, which is conducted through the leads and removed from the integrated circuit.

(14). A die attach for mounting an integrated circuit having a body of plastic material with a perimeter, a perimeter having a plurality of corner regions and a plurality of edge regions extending therebetween and surrounded by the body of the plastic material. At least one pad and a plurality of groups of ground leads located adjacent to the die attach pad and extending outwardly from the die attach pad through a plastic material to enable a ground connection to the integrated circuit; Since one ground lead group is thermally coupled to one of the edge regions of the die attach pad, some of the heat the die attach pad receives from the integrated circuit will cause at least one ground lead group to Plastic package for integrated circuits that conducts through and is removed from the integrated circuit That.

(15). The package according to (14) above, wherein each ground lead group is thermally coupled to each of the edge areas of the die attach pad.

(16). The package of (14) above, wherein the at least one of the ground lead groups is integrated with the one of the edge regions of the die attach pad.

(17). Providing a die attach pad and a coplanar waveguide that extends outward from the die attach pad and guides the signal to propagate along the waveguide, and the impedance as the signal propagates along the waveguide. Controlling the thickness, width and spacing of coplanar waveguide leads based on the intrinsic impedance of the plastic material and mounting the integrated circuit on the die attach pad so that And a step of electrically connecting the integrated circuit to the waveguide on the same plane, a step of forming a plastic material around the integrated circuit, and a step of curing the plastic material. It is the Lang method.

[0061]

With the above-described structure, the plastic package for an integrated circuit according to the present invention has the mounting pad for mounting the integrated circuit on the body of the plastic material having the outer periphery by the body of the plastic material. A plurality of coplanar waveguides that are enclosed and that are located adjacent to the die attach pad, extend through the plastic material, and extend outwardly from the die attach pad, thereby providing each coplanar surface. The upper waveguide can be electrically coupled to the integrated circuit chip to conduct signals between the integrated circuit and points adjacent to the outer perimeter of the plastic body, which is low cost and coplanar. This has an extremely excellent effect that the frequency performance of the waveguide can be improved.

[Brief description of drawings]

FIG. 1 illustrates a preferred embodiment of the lead frame of the present invention.

FIG. 2 is a cutaway perspective view of a preferred embodiment of an adaptive plastic package of the present invention using a coplanar waveguide.

FIG. 3 is a cross-sectional view of a first of the coplanar waveguides of the plastic package shown in FIG.

FIG. 4 is a cross-sectional view of an electromagnetic signal propagating along the longitudinal dimension of a first coplanar waveguide.

FIG. 5 is a graph showing estimated impedance curves for various examples of coplanar waveguides used in the plastic package of the present invention.

FIG. 6 is a graph showing estimated impedance curves for various examples of coplanar waveguides used in the plastic package of the present invention.

FIG. 7 is a graph showing estimated impedance curves for various examples of coplanar waveguides used in the plastic package of the present invention.

FIG. 8 is a graph showing estimated impedance curves for various examples of coplanar waveguides used in the plastic package of the present invention.

FIG. 9 is a graph showing estimated impedance curves for various examples of coplanar waveguides used in the plastic package of the present invention.

FIG. 10 is a perspective view showing a main part of an electronic assembly used in connection with a preferred embodiment of the plastic package of the present invention.

FIG. 11 is a flowchart showing a preferred embodiment of the packaging method according to the present invention.

FIG. 12 is a plan view of a typical prior art plastic quad flat package (PQFP) lead frame.

[Explanation of symbols]

 200 lead frame structure 201 die attach pad 202, 208 signal lead 204, 206, 210 ground lead 300 package 402 electric field line 404 magnetic field line 1002 electronic assembly 1004 electronic device

Claims (1)

[Claims] 1. A body formed of a plastic material having an outer periphery, a die attach pad surrounded by the body for attaching an integrated circuit, and a body attached to the die attach pad, the die attach pad being disposed adjacent to the die attach pad. Extends outward and enables electrical coupling with integrated circuits,
A coplanar waveguide means for guiding a signal propagating along the waveguide.