JPH0613488A - Circuit and its manufacture board - Google Patents

Abstract

PURPOSE:To provide a thin type circuit board having good heat radiation characteristics and its manufacture at a low cost with respect to a circuit board and its manufacture for mounting a circuit elements containing semiconductor elements such as IC's. CONSTITUTION:A circuit board is produced by a process for forming a metal foil on the surface of a resin board 1; a process for forming a pattern of the heat radiating region of a circuit element 2 and a circuit pattern 4 by a metal foil on the metal foil; a process of irradiating laser light to the surface at the opposite side of the pattern in the radiating region of the resin board 1, of removing part of the resin board 1 of the heat radiating region, of forming a hole for housing the circuit element 2 and of exposing the metal foil in the heat radiating region; and a process for inserting the circuit element into the hole and for adhering the circuit element 2 to the exposed metal foil in the heat radiating region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board for mounting a circuit element including a semiconductor element such as an IC and a manufacturing method thereof.

[0002]

2. Description of the Related Art In general, a circuit board is formed by forming a circuit pattern made of copper foil or the like on a resin board and bonding an electric circuit element such as an IC chip, a resistance element or a capacitor element on the circuit pattern by soldering or the like. It is formed.

In recent years, small electric appliances, calculators or ICs
There is an increasing demand for miniaturization of circuit boards, particularly thin ones, as represented by cards and the like. In order to reduce the thickness of the circuit board, a method of reducing the thickness of the resin board or reducing the size of the circuit component itself is performed, but the method of mounting the circuit component on the circuit board must be improved.

At the same time, when the circuit board is downsized, the problem of heat dissipation from circuit elements, especially semiconductor elements, which generate a large amount of heat, becomes important. Therefore, a board structure having a high heat dissipation property must be considered.

FIG. 4 is a cross-sectional view of a conventional circuit board. A hole 43 is formed on one surface of the resin substrate 41 so that the semiconductor element 42 can be inserted into the middle of the substrate 41 by machining, and the semiconductor element 42 is arranged in the hole 43. Let it adhere. Then, the terminals (bonding pads) of the semiconductor element 42 and the circuit pattern 45 are wire-bonded. Since the semiconductor element 42 is inserted in the hole 43, the height of the entire circuit board becomes low.

The circuit board of FIG. 5 is a cross-sectional view of a prior art plastic pin grid array. PCB
Through hole 53 in which semiconductor element 52 is arranged on resin substrate 51
Are formed by machining.

Further, a recess 54 which is slightly wider than the through hole 53 is formed around the through hole 53 by machining, and a heat sink 55 made of a material having a high thermal conductivity is adhered to the recess 54, so that the semiconductor element 52 is attached to the heat sink 55. It is adhered with an adhesive material 56 having good thermal conductivity.

Thereafter, the terminals of the semiconductor element 52 and the circuit pattern 57 are wire-bonded to each other to form the semiconductor element 52.
A resin mold 58 is applied to cover the. Reference numeral 59 is a lead pin for connecting the circuit pattern 57 and an external circuit (not shown).

In the structure of FIG. 5, a through hole 53 is formed by machining.
This suppresses the height of the circuit board, and the heat sink 55 promotes heat dissipation from the semiconductor element 52.

[0010]

In the conventional circuit board structure shown in FIG. 4, although the height of the semiconductor element 42 can be lowered by the amount of the holes 43, the holes 43 can be machined to reduce the height. Since the holes are formed, the variation in the depth of the holes, that is, the thickness of the thin portion of the substrate increases.

Moreover, since the heat is dissipated through the resin substrate, the heat dissipation is not so good. Further, in order to maintain the mechanical strength of the board 41, the holes are machined while leaving a certain thickness of the board, and accordingly, there is a limit in thinning the circuit board.

Further, in the conventional circuit board structure of FIG. 5, the height of the semiconductor element 52 can be lowered by the amount of the holes, which is similar to the board structure of FIG. 4, but a separate heat sink 55 is used. Heat sink 55 for mounting
The height of the circuit board cannot be reduced by the thickness of the.

Further, although the heat dissipation property is improved by the heat sink 55, the number of machining processes is increased, and since the heat sink component has to be separately manufactured and adhered to the substrate 51, the manufacturing process is complicated and the cost is increased. Become. Further, since the number of bonded portions increases, it becomes difficult to secure the reliability of the bonded portion.

An object of the present invention is to provide a low-cost, thin circuit board having good heat dissipation and a method for manufacturing the same.

[0015]

A method of manufacturing a circuit board according to the present invention comprises a step of forming a metal foil on a surface of a resin substrate, a circuit pattern formed by the metal foil on the metal foil, and a heat dissipation area of a circuit element. And the step of forming a pattern, and irradiating the surface of the resin substrate on the side opposite to the pattern of the heat dissipation region with laser light to remove the resin substrate portion in the irradiation region, and a hole that can be included in the circuit element. And exposing the metal foil in the heat dissipation area, and inserting the circuit element into the hole to bond the circuit element and the exposed metal foil in the heat dissipation area.

The circuit board according to the present invention is opposite to the resin board, the circuit pattern formed by the metal foil on the surface of the resin board, the heat radiation area of the circuit element, and the surface of the resin board on which the heat radiation area is formed. A hole capable of containing the circuit element formed so that the metal foil in the heat dissipation area is exposed on the side surface, and the circuit element bonded to the surface of the metal foil exposed at the bottom of the hole. .

[0017]

The circuit board is formed by forming the heat dissipation area of the metal foil at the same time as the circuit pattern, embedding the circuit element in the hole provided in the resin substrate, and adhering the exposed metal foil at the bottom of the hole to the circuit element. In addition, heat is dissipated from the circuit element more directly through the metal foil.

[0018]

1 is a sectional view of a circuit board according to an embodiment of the present invention. A hole for arranging a semiconductor element (IC) 2, that is, a device hole 3 is formed in a resin substrate 1 formed only of a resin component such as epoxy or polyimide. The device hole 3 is formed by removing the resin of the resin substrate 1 with a laser and making a hole until the portion of the copper foil 5 is exposed.

The resin substrate generally contains a glass cloth for the purpose of making the coefficient of thermal expansion close to that of Si. However, in this embodiment, the glass cloth is not included in order to easily perform the laser processing described later. A substrate material containing only resin components is used.

A circuit pattern 4 is formed of copper foil on both sides of the resin substrate 1, and at the same time, a heat dissipation plate 5 is also formed of the same copper foil as the circuit pattern 4. Further, the semiconductor element 2 is housed in the hole 3 and is bonded to the heat dissipation plate 5 with an adhesive material or solder 6 having good thermal conductivity.

The terminals (bonding pads) of the semiconductor element 2 and the circuit pattern 4 are connected by wire bonding, and a resin mold 7 is applied so as to cover the semiconductor element 2. The circuit board of FIG. 1 is called a plastic leadless chip carrier (PLCC) which does not require lead pins like the circuit board of FIG. Of course, the present invention can be applied to a plastic pin grid array as shown in FIG.

In the circuit board of FIG. 1, since the heat sink 5 is formed of the same copper foil material in the same process as the circuit pattern 4, it is necessary to separately prepare and bond the heat sink as in the prior art of FIG. The height of the circuit board is not limited by the thickness of the heat sink and the resin board.

Therefore, the circuit board can be effectively thinned, and the heat dissipation of the semiconductor element 2 can be enhanced by the copper foil. Of course, it is not limited to the semiconductor element that needs to dissipate heat. Therefore, the resistance element that generates heat due to the flow of current and other circuit elements that generate a lot of heat and need to dissipate heat should be replaced with the semiconductor element 2 of FIG. Will have the same effect.

Next, an embodiment of a method for manufacturing the circuit board of FIG. 1 will be described in order of steps with reference to FIG. Figure 2 (A)
Then, the copper foil 14 is attached to the entire surface of the resin substrate 1. The thickness of the copper foil is about 18 μm in a normal circuit board, but in this embodiment, it is about 35 μm or more, which is thicker than that in order to maintain the mechanical strength of the heat dissipation plate.

Next, as shown in FIG. 2B, necessary etching and through hole (not shown) are performed,
The circuit pattern 4 is formed by the panel plating method. At that time, the heat dissipation plate 5 is formed simultaneously with the circuit pattern 4. Further, the circuit pattern 4 is subjected to solder resist printing and Ni and Au plating for chip component bonding and lead wire bonding, respectively. The part of the device hole 3 exposes the surface of the resin substrate 1.

Further, as shown in FIG. 2 (C), the excimer laser light is applied to the substrate portion on the opposite side of the heat dissipation plate 5, and the substrate resin material irradiated with the excimer laser light 10 is subjected to photochemical reaction for bond cleavage ( Decomposition).

Then, as shown in FIG. 2D, the substrate resin is removed until the heat dissipation plate 5 is exposed in the laser irradiation region, and the device hole 3 is formed. The formation of the device hole 3 by the excimer laser will be further described later.

Then, as shown in FIG.
Is die-bonded to the heat sink 5 with an adhesive 6 having good thermal conductivity, the aluminum pad 8 of the semiconductor element 2 and the circuit pattern 4 of the substrate are connected by an Au wire 9, and the semiconductor element 2 and the connected portion are transferred or liquid-molded. Seal with resin. Although not shown, chip components such as resistors and capacitors other than the semiconductor element 1 are also bonded to the circuit pattern 4.

It is recommended to use an excimer laser to form the device hole 3 in the above embodiment. When a high-intensity ultraviolet laser such as an excimer laser is irradiated on the surface of an organic polymer material (polymer) such as resin, a phenomenon called ablation occurs in which the irradiated portion is instantaneously decomposed and scattered.

By appropriately selecting the wavelength and intensity of the excimer laser according to the type of the substrate material, this ablation allows the device hole 3 to be accurately and sharply formed in the resin substrate, and the heat sink 5 of the copper foil to be damaged. Can be given.

Next, with reference to FIGS. 3A and 3B, an embodiment of a method of forming the device hole 3 by an excimer laser will be described below. In FIG. 3A, the excimer laser head 21 includes, for example, a KrF laser tube, and is driven by the laser driving unit 22. The excimer laser beam emitted from the excimer laser head 21 has its optical path (arrow) adjusted by the mirrors 23 and 24, and enters the max 25.

The excimer laser beam shaped by the mask 25 having the opening 38 (FIG. 3B) corresponding to the shape of the heat dissipation plate 5 is bent downward by the mirror 26, passes through the imaging lens 27, and passes through the imaging lens 27. An image is formed on the device hole formation region of the substrate 1 shown in FIG.

The positions of the mask 25 and the imaging lens 27 are adjusted by a control signal from the controller 31 so that an image is formed on the substrate at a desired magnification. The board 1 is observed from above by the imaging monitor 29, and pattern information on the board surface is converted into a signal and supplied to the controller 31. Further, the height monitor 32 monitors the height of the substrate 1 and supplies the measurement result to the controller 31 as a height signal.

The controller 31 generates a signal for controlling each control portion based on the monitor signals supplied from the image pickup monitor 29 and the height monitor 32. The controller 31 sends an alignment signal to the processing stage 35 including the X stage 33 and the Y stage 34, and positions the substrate 1 so that the excimer laser light shaped by the mask 25 is accurately applied to the device hole region. . The processing stage 35 can perform Z adjustment and θ adjustment as well as X and Y adjustment.

In the case of KrF, the excimer laser head 21 generates a laser beam of, for example, 8 mm × 25 mm with a pulse repetition rate of 200 pps, an output energy of 250 mJ, an average output of 50 W, and a pulse width of 16 ns.

The wavelength of the KrF laser is about 248 nm.
Is. When the excimer laser is ArF, the oscillation wavelength is about 193 nm, and when the excimer laser is XeCl laser,
The oscillation wavelength is about 308 nm.

Next, FIG. 3B schematically shows a method of shaping the excimer laser beam. The mask 25 is formed of a metal such as copper alloy or molybdenum, and has an opening 38 having a desired pattern.
Have. The excimer laser beam incident on the mask 25 is imaged on the substrate 1 by the imaging lens 27 using the mask 25 as a new light source.

When the distance between the mask 25 and the imaging lens 27 is a and the distance between the imaging lens 27 and the substrate 1 is b, 1 / a + 1 / b = 1 / f (f is the focus of the imaging lens 27) The relationship of (distance) is established. When changing the focal length and magnification of the optical system, the Z adjustment mechanism 36 provided in the imaging lens 27 and the drive mechanism of the mask 25 are used to adjust these positions.

In the embodiment described above, the device hole 3
An excimer laser was used to form the. The reason is as follows. Processing with other processing lasers such as a YAG laser, a CO ₂ laser, or an Ar laser is to process a material with the thermal energy of laser light, whereas with an excimer laser, as described above, excimer laser light is used. Utilizing photochemical changes in resin materials.

Therefore, the shape of the processed portion is much sharper than that of other laser processing, and a desired region can be processed accurately. Moreover, it does not damage materials other than the non-processed material such as copper foil.

However, it is possible to form the device hole by a laser other than the excimer laser as long as the processing can be controlled so as not to damage the copper foil portion serving as the heat dissipation plate. Also,
If it is possible to control the processing of the device hole, mechanical processing such as drilling can be used instead of laser processing.

It is also possible to employ a two-step processing step in which most of the device holes are machined and laser processing is performed on the resin substrate near the copper foil.

It is needless to say that the present invention is not limited to the embodiments disclosed above, and various modifications and changes can be made by those skilled in the art based on the disclosure.

[0044]

The heat dissipation area of the metal foil is formed at the same time as the circuit pattern, the circuit element is embedded in the hole provided in the resin substrate, and the exposed metal foil at the bottom of the hole is bonded to the circuit element. The circuit board can be manufactured thinly.

Moreover, since the heat is dissipated from the circuit element through the metal foil heat dissipation plate made of the same material as the circuit pattern at the same time, it is not necessary to separately prepare a heat sink and bond it to the substrate, which improves reliability. It is possible to obtain a circuit board having a high cost, a reduced thickness, and improved heat dissipation at a low cost.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a circuit board according to an exemplary embodiment of the present invention.

FIG. 2 is a diagram for explaining a manufacturing process of the circuit board of FIG.

FIG. 3 is an external view of a device hole processing apparatus using an excimer laser.

FIG. 4 is a cross-sectional view of a conventional circuit board.

FIG. 5 is a cross-sectional view of a conventional circuit board.

[Explanation of symbols]

 1 ... Resin substrate 2 ... Semiconductor element (IC) 3 ... Device hole 4 ... Circuit pattern 5 ... Heat sink 6 ... Adhesion Material 7: Sealing resin 8: Aluminum pad 9: Au wire

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H05K 3/00 N 6921-4E

Claims (5)

[Claims] 1. A step of forming a metal foil on the surface of a resin substrate; a step of forming a circuit pattern of the metal foil and a pattern of a heat dissipation area of a circuit element on the metal foil; A step of exposing the metal foil in the heat dissipation area by irradiating the surface of the heat dissipation area opposite to the pattern with laser light to remove the resin substrate part in the irradiation area and forming a hole in which the circuit element can be included. And a step of inserting the circuit element into the hole and adhering the circuit element and the exposed metal foil of the heat radiation area to each other. 2. The laser light is output light of an excimer laser, and the output light of the excimer laser is applied to a surface of the resin substrate opposite to the pattern of the heat radiation area to expose the resin substrate portion in the irradiation area. The method for manufacturing a circuit board according to claim 1, wherein the circuit board is disassembled and removed. 3. The method for manufacturing a circuit board according to claim 1, wherein the circuit element is a semiconductor element. 4. A resin substrate, a circuit pattern formed of a metal foil on the surface of the resin substrate, and a heat dissipation area of a circuit element, and the surface of the resin substrate opposite to the surface on which the heat dissipation area is formed. It is formed so that the metal foil in the heat dissipation area is exposed,
A circuit board having a hole capable of containing the circuit element and the circuit element bonded to a surface of the metal foil exposed at the bottom of the hole. 5. The circuit board according to claim 4, wherein the circuit element is a semiconductor element.