JP2005302864A - High frequency package mounted board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high frequency package mounted board which decreases various electric influences caused by a metal plate connected to a thin film substrate and also improves a transmission characteristic. <P>SOLUTION: A substrate for a high frequency package is a thin film substrate and the metal plate is provided on the lower face of the thin film substrate for preventing the warp of the thin film substrate and facilitating mounting. The metal plate is connected to the ground of the thin film substrate and also connected to the ground of the substrate for mounting the thin film substrate. A solder resist is used for connection between the metal plate and the thin film substrate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a mounted substrate of an IC package excellent in high frequency transmission.

  Conventionally, a metal plate to be attached to a thin film substrate for a high frequency package has been provided in order to prevent the substrate from warping and facilitate mounting, and has been attached to the upper surface of the thin film substrate in a shape where the IC chip is mounted. . Since it is a thin film substrate, the line in the thin film substrate and the metal plate arranged on the upper surface of the thin film substrate are electrically coupled to each other as the frequency becomes higher. This coupling causes distortion in the high frequency pulse transmitted through the thin film substrate. In addition to high-frequency pulse distortion, electromagnetic radiation from the metal plate also occurs due to electrical coupling.

  In addition, a high-frequency pulse transmitted without distortion in the thin film substrate also causes a very large distortion at the connection portion where the thin film substrate is mounted on a different substrate because the transmission form is lost. Thus, various electrical influences appear in the transmission characteristics depending on the metal plate connected to the thin film substrate.

The known literature is shown below.
JP 2003-152124 A

  The present invention provides a high-frequency package mounted substrate that reduces various electrical effects due to the metal plate connected to the thin film substrate and further improves the transmission characteristics.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and the invention according to claim 1 is a metal plate for facilitating mounting by preventing the warp of the thin film substrate and the substrate for the high frequency package being a thin film substrate. Is provided on the lower surface of the thin film substrate, and the metal plate is connected to the ground of the thin film substrate, and is further connected to the ground of the substrate on which the thin film substrate is mounted. .

  Here, by connecting the metal plate and the mounting substrate to the ground, an external signal such as noise is cut off in the signal portion around the metal plate, and various electrical influences can be reduced and transmission characteristics can be improved.

  The invention according to claim 2 of the present invention is the substrate mounted with the high-frequency package according to claim 1, wherein a solder resist is used for connection between the metal plate and the thin film substrate.

  Here, by connecting with a solder resist having a low relative dielectric constant and low dielectric loss, it is possible to achieve better radio frequency transmission. A known resin such as an epoxy resin can be used as the solder resist.

  According to a third aspect of the present invention, there is provided the high frequency package mounted substrate according to the first or second aspect, wherein the signal connection portion and the metal plate are characteristic impedance matched.

  Here, the characteristic impedance matching between the signal connection portion and the metal plate ensures reliable transmission characteristics and enables transmission of a signal with less reflection.

  As described above, according to the present invention, by connecting the metal plates to the GND, it is possible to give a favorable effect on the transmission characteristics to the metal plates that adversely affect the transmission characteristics.

  FIG. 1 is an explanatory view showing a cross-section of an embodiment of a substrate mounted with a high-frequency package according to the present invention. A metal plate 3 in which signal pins connected to the mounting substrate 5 are hollowed out is provided on one surface (lower surface) of the thin film substrate 2, and the IC chip 1 is connected to the other surface by a half ball. . The IC chip 1 and the signal pin are connected through a line in the thin film substrate 2. The thin film substrate 2 is connected to the mounting substrate 5 with a signal line, a power source, and GND by a half ball.

  2 is an enlarged view of signal pins, and FIG. 3 is an enlarged view of ground pins. Here, the connection with solder balls is taken as an example, but other connection methods such as pins are also possible. In the present invention, the metal plate 3 is attached to the lower surface of the thin substrate with the adhesive 6. The adhesive 6 serves as a solder resist. The metal plate 3 has a hole only in the connecting portion for mounting the substrate 5 and the substrate (thin film substrate).

  As shown in FIG. 2, the signal pin and the metal plate 3 are separated by a certain distance. This is because the characteristic impedance at the connection portion is matched with the characteristic impedance of the line. For example, if the characteristic impedance is adjusted to 50 [Ω], in the case of a solder ball as shown in FIG. 2, if the diameter is 0.5 [mm], and the air between the ball and the metal plate is air, the ball and the metal plate The distance is 0.325 [mm]. If a material of ε = 4.2 is filled between the ball and the metal plate, the distance is 1.13 [mm]. In FIG. 3, the ground pins are arranged so as to be connected to the metal plate.

  An example of the manufacturing method of the high frequency package mounted substrate of the present application is shown below.

  First, a pad is patterned on the surface opposite to the chip mounting surface on a BGA substrate.

  Next, a solder resist is applied thereon, and patterning is performed to remove the solder resist at the pin connection portion on the pad.

  Next, a chip is mounted and a BGA substrate is created.

  Next, a metal plate having holes in portions corresponding to the positions of the signal pins and the GND pins is prepared. In order to prevent the signal pin from coming into contact with the metal plate and short-circuiting, it is preferable to provide a thin film insulator in advance on the side surface of the hole formed in the metal plate at the location of the signal pin.

  Next, a metal plate is affixed on the surface of the patterned BGA substrate so that the center positions of the pads and holes coincide.

  Next, put the ball into the hole.

  Next, pads are formed on the surface of the PCB substrate to be mounted on the BGA substrate by patterning portions corresponding to the pins.

  Next, a solder resist is applied to the surface of the PCB substrate, and patterning is performed to remove the solder resist at the pin connection portion on the pad.

  Next, the PCB substrate is affixed to the BGA substrate containing the previous balls so that the pads are connected to the balls.

  When the metal plate is bonded to the thin film substrate, the GND pin of the thin film substrate and the metal substrate are connected. In addition, the gap between the signal pin of the thin film substrate and the metal substrate is set to have a characteristic impedance of 50 [Ω]. Here, the pad diameter was 0.6 [mm], the bump diameter was 0.5 [mm], and the gap was 0.325 [mm]. Thereafter, a thin film substrate is mounted. The result of measuring the electrical characteristics at this time is shown in FIG. The structure of the arrangement of the general metal plates compared is, as in the example of the present invention, the pad diameter: 0.6 [mm], the bump diameter: 0.5 [mm], and the distance between the ball and the metal plate is 0. 325 [mm]. FIG. 4 shows S11 in S-Parameter notation. S11 represents a reflection coefficient. The smaller the value, the smaller the percentage of reflection. It can be seen that the band of the reflection coefficient is wider in the arrangement of the present invention than in the arrangement of the general metal plate. From this, it can be said that the present invention can obtain good characteristics in the high frequency region.

It is explanatory drawing which showed the Example of the high frequency package mounting board | substrate of this invention in the cross section. It is explanatory drawing which expanded and showed the signal pin of the Example of the high frequency package mounting board | substrate of this invention in the cross section. It is explanatory drawing which expanded and showed the ground pin of the Example of the high frequency package mounting board | substrate of this invention in the cross section. It is a characteristic view of the Example of the high frequency package mounting board | substrate of this invention.

Explanation of symbols

1: IC chip 2: Thin film substrate 3: Metal plate 4: Mounting portion 5: Mounting substrate 6: Adhesive

Claims (3)

  The substrate for the high-frequency package is a thin film substrate, and a metal plate is provided on the lower surface of the thin film substrate to prevent warpage of the thin film substrate, and the metal plate is connected to the ground of the thin film substrate. A high-frequency packaged board that is also connected to the ground of the board on which the board is mounted.   The high frequency package mounted substrate according to claim 1, wherein a solder resist is used for connection between the metal plate and the thin film substrate.   The high frequency package mounted substrate according to claim 1 or 2, wherein the signal connection portion and the metal plate are characteristic impedance matched.

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