JPH10107062A - Plasma cleaning apparatus, plasma cleaning method, and circuit module manufacturing method - Google Patents

Abstract

An object of the present invention is to provide a plasma cleaning apparatus and a plasma cleaning method capable of effectively cleaning a bonding pad without Pb, Sn or the like scattered from solder adhering to the bonding pad. A chamber and a reaction gas supply unit for supplying a reaction gas containing oxygen gas into the chamber.
And an exhaust unit 23 that exhausts gas to the outside of the chamber 10, and a first unit provided in the chamber 10 and applied with a high-frequency voltage.
The electrode 15 is provided in the chamber 10 so as to be parallel to the first electrode 15 and supports the substrate 1,
It includes a second electrode 16 that is electrically grounded, and a shield 24 that surrounds the periphery of the substrate 1 supported by the second electrode 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma cleaning apparatus for cleaning an object such as a substrate of a mixed mounting type, a plasma cleaning method, and a method of manufacturing a circuit module including the object.

[0002]

2. Description of the Related Art In recent years, a board of a mixed mounting type in which a solder component and a bare chip mounted on one board by soldering are mounted has been used. In addition, circuit modules are being manufactured using this substrate.

[0003] When mounting a soldering component and a bare chip on such a substrate, if the bare chip is mounted first, it becomes troublesome to apply the solder for the soldering component. Therefore, in such a substrate, first, a soldering component is soldered to the substrate, and then the substrate is plasma-cleaned to remove dirt (mainly organic matter) on a bonding pad formed on the substrate for a bare chip. Then, a bare chip is mounted.

[0004]

A problem in performing such plasma cleaning will now be described. FIG.
FIG. 3 is an explanatory diagram of a phenomenon of a conventional plasma cleaning method. In FIG. 7, reference numeral 1 denotes a board of the mixed mounting type, 2 denotes a circuit pattern formed for the soldering component 3, and 4 denotes solder for fixing the soldering component 3 to the circuit pattern 2.

Reference numeral 5 denotes a bare chip mounting portion formed for mounting a bare chip. Around the bare chip mounting portion 5, a bonding pad 6 to which the bare chip is to be bonded by a wire is formed.

Then, plasma cleaning is performed to remove organic substances adhering to the surface of the bonding pad 6. However, when this is performed by a conventional plasma cleaning apparatus, charged particles such as Ar +, H +, and e- collide not only with the bonding pad 6 but also with the solder 4. The solder 4 is an alloy of a soft metal such as Pb or Sn, and as shown by arrows Q1 and Q2,
A phenomenon occurs in which charged particles are scattered due to collision and adhere to the bonding pad 6.

At this time, as shown by an arrow Q3, if the amount of the charged particles removing the adhered matter on the bonding pad 6 is larger than the amount of the scattered Pb and Sn adhered to the bonding pad 6, the bonding pad 6 becomes Although it becomes clean, in practice, the amount of deposits on the bonding pad 6 tends to increase over time, and the bonding pad 6 does not become clean.

Accordingly, the present invention provides a method for producing Pb scattered from solder,
An object of the present invention is to provide a plasma cleaning apparatus capable of effectively cleaning a bonding pad without Sn or the like adhering to the bonding pad.

[0009]

According to a first aspect of the present invention, there is provided a plasma cleaning apparatus comprising: a chamber; a reaction gas supply unit for supplying a reaction gas containing oxygen gas into the chamber; An exhaust unit, a first electrode provided in the chamber, and to which a high-frequency voltage is applied;
A second electrode provided in the chamber so as to face the first electrode and supporting the object to be cleaned, and electrically grounded; and protecting the object supported by the second electrode from charged particles. And a shield.

According to a second aspect of the present invention, in the plasma cleaning apparatus, a heater is provided on the first electrode.

According to a third aspect of the present invention, there is provided a plasma cleaning method, comprising: supporting an object on a grounded second electrode in a chamber; and removing the object supported on the second electrode from charged particles. Enclosing with a shield to guard, and supplying oxygen gas into the chamber, and generating oxygen radicals and charged particles by applying a high-frequency voltage to a first electrode facing the second electrode. Including.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a circuit module, comprising: soldering a soldering component to a circuit pattern for the soldering component; and grounding the substrate with a first electrode to which a high-frequency voltage is applied. Performing a plasma cleaning in a state where the substrate is surrounded by a shield having the same potential as that of the second electrode, fixing the bare chip to the substrate, and bonding the bare chip to the bonding pad. Bonding with a wire, and sealing the periphery of the bare chip with resin,
including.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the above-mentioned configuration, an object to be soldered on a board of a mixed mounting type as an object is housed in a chamber. Then, the object is supported on the second electrode, and the object is protected by the shield. Then, oxygen plasma is generated by oxygen gas. The oxygen plasma contains charged particles such as oxygen ions and electrons and electrically neutral oxygen radicals.

Then, the charged particles are accelerated by the potential difference between the first electrode and the second electrode, and collide with the shield. However, since there is no potential difference between the shield and the second electrode, the charged particles do not arrive inside the shield, that is, around the object.

Therefore, only floating oxygen radicals arrive around the object. As a result, the charged particles do not collide with the solder, so that Pb, Sn, etc. of the solder do not scatter and contaminate the bonding pad. Further, oxygen radicals collide with the bonding pad. Due to this collision, the organic matter adhering to the bonding pad is decomposed into carbon dioxide and water vapor, and the carbon dioxide and water vapor are vaporized, so that the bonding pad is cleaned.

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a plasma cleaning apparatus according to an embodiment of the present invention, and FIG. 2 and FIG.
Is a sectional view of the same, and FIG. 4 is an explanatory view of the operation. In the drawing, the same components as those in FIG. 7 showing the conventional configuration are denoted by the same reference numerals, and description thereof will be omitted.

In FIGS. 1 and 2, reference numeral 10 denotes a chamber for forming a reduced-pressure atmosphere, which is grounded. The chamber 10 has a concave portion 10a opened downward. Reference numeral 11 denotes an elevator, to which the chamber 10 is connected via a bar 12. Reference numeral 13 denotes a base plate, the upper surface of which serves as a transfer unit for guiding the transfer of the substrate 1. Reference numeral 14 denotes a transport mechanism for the substrate 1, which is driven by a driving unit (not shown) to move in the direction of arrow N, and
The substrate 1 is pitch-fed on the base plate 13 by 4a.
When the elevator 11 is driven, the chamber 10 moves up and down. FIG. 2 shows a state in which the chamber 10 is lowered and the base plate 13 is closed, and FIG. 3 shows a state in which the chamber 10 is raised and the base plate 13 is opened. As shown in FIG. 3, in a state where the chamber 10 is raised and opened, the substrate 1 is pitch-fed by the claws 14a to put the substrate 1 into and out of the chamber 10. Further, as shown in FIG. 2, the chamber 10 is lowered and closed, and plasma cleaning of the substrate 1 is performed in a state where a closed space is formed by the concave portion 10a.

In FIG. 2, reference numeral 15 denotes a first electrode which is held horizontally above the chamber 10 and to which a high-frequency voltage is applied by a high-frequency power supply 17. The chamber 10 and the first electrode 15 are insulated by an insulating material 19. 16
Is a second electrode that is below the first electrode 15 and faces in parallel with the first electrode 15 and is electrically grounded. A heater 18 is provided inside the second electrode 16 to increase the temperature of the second electrode 16 and the substrate 1 in order to promote a decomposition reaction with an organic substance and enhance a cleaning effect. Second electrode 1
6 is attached to the base plate 13 so that the upper surface thereof and the upper surface of the base plate 13 are at the same height.
The substrate 1 can be transported by the

Reference numeral 22 denotes a reaction gas supply unit for supplying a reaction gas containing oxygen gas into the chamber 10, and reference numeral 23 denotes an exhaust unit for exhausting gas from the inside of the chamber 10. 24 is the recess 10
A net-shaped shield made of a conductive material is provided substantially in the middle of step a in parallel with the first electrode 15 and the second electrode 16. This shield 24 is also grounded through the chamber 10. As will be described later, the shield 24 guards the substrate 1 so that the charged particles do not collide with the substrate 1 on the second electrode 16.

This plasma cleaning apparatus has the above-described configuration, and the operation will be described next. As shown in FIG. 2, the substrate 1 is housed in the chamber 10 and the second electrode 16
The chamber 10 is closed and the chamber 10 is closed. Next, the inside of the chamber 10 is depressurized by driving the exhaust unit 23, and the reaction gas supply unit 22 is driven to introduce a reaction gas containing oxygen gas into the chamber 10. When the pressure of the oxygen gas reaches a predetermined value, the high frequency power supply 17 is driven to apply a high frequency voltage to the first electrode 15. Then
Oxygen plasma is generated between the first electrode 15 and the second electrode 16. This oxygen plasma contains charged particles such as oxygen ions and electrons and electrically neutral oxygen radicals.

Then, as shown in FIG.
The charged particles are accelerated by the potential difference between the first electrode 16 and the second electrode 16 and reach the shield 24.
Since both are grounded and at the same potential, the charged particles are guarded by the shield 24 and do not enter the shield 24. That is, only oxygen radicals enter the inside of the shield 24.

The organic substances adhering to the bonding pad 6 are decomposed and vaporized by the oxygen radicals, and are discharged out of the chamber 10 by the exhaust unit 23, so that the bonding pad 6 is cleaned. At this time, the heater 18
Is driven to increase the temperature of the second electrode 16, that is, the substrate 1, promotes the above-described decomposition, and can perform effective cleaning in a short time.

Next, a method for manufacturing a circuit module using the above-described plasma cleaning method will be described. 5A and 5B are a flowchart of a circuit module manufacturing method according to an embodiment of the present invention, and FIG.
(A), (b), (c), (d), and (e) are process explanatory diagrams of a method for manufacturing the same circuit module.

Each step of the circuit module manufacturing method will be described with reference to FIG. 6 along with FIG. First, as shown in FIG. 6A, a solder 4 is applied on a circuit pattern 2 of a substrate 1 by a screen printing method.
The soldering component 3 is mounted on the applied solder 4 (arrow N1).

Next, the substrate 1 is put into a heating device such as a reflow device, and the solder 4 is melted and solidified.
As shown in (b), the soldering component 3 is
Solder to

Next, the substrate 1 is plasma-cleaned by the method described with reference to FIGS. This allows
Organic substances adhering to the bonding pad 6 can be removed, and Pb, Sn, etc. of the solder 4 can be removed from the bonding pad 6.
Can be prevented from adhering.

As shown in FIG. 6C, after the adhesive 26 is applied to the bare chip mounting portion 5, the bare chip 27 is mounted on the adhesive 26. Then, the substrate 1 is sent to a curing device or the like, and the adhesive 26 is cured to fix the bare chip 27 to the bare chip mounting portion 5.

Next, as shown in FIG. 6D, the bare chip 27 and the bonding pad 6 are joined by a wire 28.
By sealing the periphery of the bare chip 27 with the resin 29, a circuit module can be obtained.

Further, the manufacturing method shown in FIG.
This is a slightly modified procedure of (a). That is, FIG.
According to (b), the plasma cleaning is not performed between the step of fixing the soldered component 3 (FIG. 6B) and the step of mounting the bare chip 26 (FIG. 6C), but the step of fixing the bare chip 27. Plasma cleaning is performed immediately after the completion of (FIG. 6C), and wire bonding is performed using the newly-cleaned bonding pad 6 immediately after the cleaning. Other than that, FIG.
Is the same as

[0030]

According to the present invention, it is possible to prevent the secondary adhesion of the solder component on a mixed mounting type board or the like, and to perform effective cleaning.

[Brief description of the drawings]

FIG. 1 is a perspective view of a plasma cleaning apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view of a plasma cleaning apparatus according to an embodiment of the present invention.

FIG. 3 is a sectional view of a plasma cleaning apparatus according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating the operation of the plasma cleaning apparatus according to the embodiment of the present invention.

5A is a flowchart of a method for manufacturing a circuit module according to one embodiment of the present invention; FIG. 5B is a flowchart of a method for manufacturing a circuit module according to one embodiment of the present invention;

FIG. 6A is an explanatory view of a process of a method of manufacturing a circuit module according to an embodiment of the present invention. FIG. 6B is an explanatory view of a process of a method of manufacturing a circuit module according to an embodiment of the present invention. Process description diagram of a method of manufacturing a circuit module according to one embodiment (d) Process description diagram of a method of manufacturing a circuit module according to one embodiment of the present invention (e) Method of manufacturing a circuit module according to one embodiment of the present invention Process description diagram

FIG. 7 is an explanatory view of a phenomenon of a conventional plasma cleaning method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 10 Chamber 15 1st electrode 16 2nd electrode 18 Heater 22 Reaction gas supply part 23 Exhaust part 24 Shield

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI // H05K 3/26 H01L 21/302 B

Claims (4)

[Claims] 1. A chamber, a reaction gas supply section for supplying a reaction gas containing oxygen gas into the chamber, an exhaust section for exhausting outside the chamber, and a high frequency voltage applied in the chamber. A first electrode provided in the chamber so as to face the first electrode;
A plasma cleaning apparatus comprising: a second electrode that supports an object to be cleaned and is electrically grounded; and a shield that guards the object supported by the second electrode from charged particles. 2. The plasma cleaning apparatus according to claim 1, wherein a heater is provided on said first electrode. 3. A step of supporting an object on a second electrode grounded in a chamber, surrounding the object supported on the second electrode with a shield that guards against charged particles, and Supplying oxygen gas to the inside and applying a high-frequency voltage to a first electrode facing the second electrode to generate oxygen radicals and charged particles. 4. A method of manufacturing a circuit module using a board of a mixed mounting type having a circuit pattern for a soldering component and a bonding pad for a bare chip, wherein a soldering component is soldered to the circuit pattern. Performing plasma cleaning with the substrate positioned between the first electrode to which the high-frequency voltage is applied and the second electrode grounded, and surrounding the substrate with a shield having the same potential as the second electrode; A method for manufacturing a circuit module, comprising: a step of fixing a bare chip to a substrate; a step of bonding the bare chip and a bonding pad with a wire; and a step of sealing the periphery of the bare chip with a resin.