JPH07336027A - Printed board, manufacture thereof and mounting method for surface mounting component - Google Patents

Abstract

PURPOSE:To improve the reliability of mounting a surface mounting component. CONSTITUTION:A printed board has a printed board body 1, and a conductive pad 2 formed at a predetermined position on the body 1, and comprises a resin paste layer 8 made of rosin resin, thickening agent, activator and solvent and provided on the pad 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit board used for mounting surface mount components, a method for manufacturing the same, and a method for mounting surface mount components.

In recent years, the pitch of leads of surface mount components has been narrowed to 0.3 to 0.5 mm as the density is increased, and the leads are soldered to conductive pads (footprints) on a printed circuit board. It is becoming important to ensure the reliability of the.

[0003]

2. Description of the Related Art A conventional printed circuit board 40 is shown in FIG.
As shown in (A), each conductive pad 2 is formed on the printed circuit board body 1, and the solder coat layer 3 is formed by preliminarily covering the conductive pad 2 with a pre-flux layer and a solder layer. It has the structure

An IC for such a printed circuit board 40
The component 5 was mounted as follows.

First, as shown in FIGS. 10A and 10B, a solder paste layer 4 is formed on the pre-flux layer and the solder coat layer 3 above each conductive pad 2.

Next, as shown in FIG. 1C, the IC component 5, which is a surface-mounted component, is mounted by adhering its leads 6 to the respective conductive pads 2 and bonded, and reflow soldering is performed. . As a result, the IC component 5 is mounted on the surface of the printed board by soldering the leads 6 to the conductive pads 2 with the solder 7.

The layer 4 of solder paste described above is shown in FIG.
As shown in (A), the solder paste mask 10 is positioned and placed on the printed circuit board body 1, and the squeegee 11
Is moved in the direction of arrow A to fill the solder paste 12 into the holes 13 of the solder paste mask 10.

Thereafter, as shown in FIG. 1B, the solder paste mask 10 is peeled off, so that the solder paste mask 10 is relatively removed from the holes 13 and the pre-flux layer and the solder coat layer 3 above each conductive pad 2. A layer 4 of solder paste is formed on top.

[0009]

The leads 6 of the IC component 5 are to be solved.
When the pitch P of the conductive pads 2 is narrowed to 0.3 to 0.5 mm, the pitch of the conductive pads 2 is correspondingly narrowed, and the width W1 of the conductive pads 2 is reduced to 0.15 to 0.20 mm. The width W2 of the hole 13 is 0.10 to 0.1
It becomes as small as 5 mm, and the hole 1 of the solder paste mask 10 becomes smaller.
The volume (size) V1 surrounded by 3 becomes smaller.

When the size V1 (volume surrounded by the inner peripheral surface) of the hole 13 of the solder paste mask 10 becomes small, the hole 1
The adhesive force of the solder paste 12 with respect to 3 increases.

Therefore, the difference between the adhesive force of the solder paste 12 to the preflux layer and the solder coat layer 3 and the adhesive force of the solder paste 12 to the holes 13 becomes small.

As a result, when the solder paste mask 10 is peeled off, only a small amount of the solder paste 12 is removed from the holes 13 and a large amount of the solder paste 12 remains in the holes 13, as shown by reference numeral 18 in FIG. A small amount of the solder paste layer 4 is formed on the flux 2 above the conductive pad 2.

As a result, finally, as shown by reference numeral 19 in FIG. 10 (D), some of the leads 6b are defectively soldered to the conductive pads 2. That is, it was not possible to solder with an appropriate amount of solder. As a result, the reliability of the mounting becomes low.

More specifically, as shown in Comparative Example 1 of FIG.
The filling rate was 40 to 60%.

With respect to this filling rate, the volume surrounded by the holes 13 of the solder paste mask is set to V1, and the volume V2 of the solder paste layer 4 which has come out from the holes 13 and adhered onto the pre-flux layer and the solder coat layer 3 is V2. Is divided by the above volume V1.

The minimum filling factor required for proper mounting of surface mount components is 60%. 40-60 above
The value of% is not good because it does not exceed the minimum value of this filling factor.

In the worst case, when the solder paste mask 10 is peeled off, the solder paste 12 does not escape from the hole 13 but remains in the hole 13, and as shown by reference numeral 14 in FIG. Flux 2 above the pad 2
The solder paste layer 4 is not formed on the upper surface.

As a result, finally, as shown by reference numeral 15 in FIG. 10 (D), some of the leads 6a are not soldered to the conductive pads 2, resulting in poor soldering, resulting in mounting reliability. There is no nature.

It is an object of the present invention to provide a printed circuit board, a method of manufacturing the same, and a method of mounting surface mount components, which are intended to improve the reliability of mounting the surface mount components.

[0020]

According to a first aspect of the present invention, there is provided a printed circuit board including a printed circuit board main body and a conductive pad formed at a predetermined position on the printed circuit board main body. A resin paste layer composed of a rosin-based resin, a thickener, an activator, and a solvent is provided.

According to a second aspect of the present invention, there is provided a conductive pad forming step of forming a conductive pad at a predetermined position on a printed circuit board body, and a resin paste comprising a rosin resin, a thickener, an activator and a solvent. A method of manufacturing a printed circuit board, comprising a step of forming a layer of a resin paste for forming a layer on the conductive pad.

According to a third aspect of the present invention, there is provided a conductive pad forming step of forming a conductive pad at a predetermined position on the printed circuit board body, and the position is determined so that the hole of the resin paste mask is located on the conductive pad. A resin paste mask positioning step, and a resin paste composed of a rosin resin, a thickener, an activator, and a solvent is printed on the conductive pad through the holes of the resin paste mask to form a resin paste layer. A method of manufacturing a printed circuit board, comprising: a resin paste printing step to be formed.

According to a fourth aspect of the present invention, a rosin-based material is formed on the conductive pads which are formed at positions corresponding to all the leads of the surface mount component to be mounted on the printed circuit board body. A resin paste layer forming step of forming a resin paste layer consisting of a resin, a thickener, an activator, and a solvent, and a solder paste on each resin paste layer formed by the resin paste layer forming step. Solder mask mask positioning step of determining the position so that each hole of the mask for soldering is positioned, and the solder paste is printed on the layer of each resin paste through each hole of the mask for solder paste, respectively. A solder paste printing step for forming each layer, a surface mounting component mounting step for bonding the surface mounting component body and mounting it on a printed circuit board body, A method of mounting a surface mount component, comprising a step of melting a layer of the paste and soldering the leads to the corresponding conductive pads on the printed circuit board body. .

[0024]

In the printed circuit board according to the first aspect of the present invention, a layer of resin paste including a rosin resin, a thickener, an activator, and a solvent is provided on the conductive pad.
Acts to increase the viscosity (viscosity) of the resin paste,
It acts so as not to adversely affect the melting of the solder paste.

Since the method of manufacturing a printed circuit board according to the second aspect of the invention includes a conductive pad forming step and a resin paste layer forming step, the conductive pad is formed on the printed circuit board body. It acts to form a layer of resin paste on this conductive pad.

Further, in the resin paste mask positioning step and the resin paste printing step of the printed circuit board manufacturing method according to the third aspect of the present invention, the resin paste is printed on the conductive pads through the holes of the positioned resin paste mask. Therefore, the resin paste is not printed on the printed circuit board body except the conductive pads.

Further, in the resin paste layer forming step of the surface mounting component mounting method according to the fourth aspect of the present invention, all the solder pastes are apt to adhere to the respective resin paste layers through the holes of the solder paste mask. To work.

The solder paste mask positioning step and the solder paste printing step act so that the amount of the solder paste printed on each resin paste layer escapes from the solder paste hole in an appropriate amount.

The surface mounting component mounting process and the soldering process are
It works so that all the leads are soldered to each electrode pad with an appropriate amount of solder.

[0030]

1 is a perspective view showing a structure of a printed circuit board 30 according to an embodiment of the present invention, FIG. 1 (A) is a perspective view thereof, and FIG. 1 (B) is a conductive pad and a resin paste. 2 is an enlarged view of the layer of FIG. 2, and FIG. 2 is a cross-sectional view of the printed circuit board 30 taken along the line II-II in FIG. 1.

The printed circuit board 30 includes a printed circuit board body 1, a conductive pad 2 made of copper, and a layer 8 of resin paste formed on the conductive pad 2.

The conductive pad 2 is a surface mount component QFP (Quad) that is to be mounted on the printed circuit board body 1 at a predetermined position, that is, as indicated by a two-dot chain line X in the figure. Flat Package) type IC parts 5
Are formed at positions corresponding to all the leads 6.

Although not shown in the figure, the number of leads 6 of the IC component 5 is about 100, and the pitch P thereof is 0.3 mm.
Is.

The number of conductive pads 2 is about 100 corresponding to the number of leads 6, the pitch P thereof is 0.3 mm, and the width W1 thereof is 0.15 mm.

The components of the resin paste are a rosin resin, a thickener, an activator, and a solvent. Specific components and composition ratios will be described later (see FIG. 7).

This resin paste layer 8 increases the adhesive force of the solder paste to the resin paste layer 8 when the solder paste is printed on the resin paste layer 8, and the solder paste to the resin paste layer 8 is The viscosity is increased so as to increase the difference between the adhesive force and the adhesive force of the solder paste with respect to the holes of the metal or silk solder paste mask.

The rosin-based resin is a liquid that is highly resistant to metal oxidation, has high fluidity at high temperatures, and has high wettability, and has heat resistance and moisture resistance.

The thickener increases the viscosity of the resin paste layer 8, maintains the shape of the resin paste layer 8, prevents bleeding, and prevents discoloration of the surface of the conductor pad 2, such as hardened castor oil. Is suitable. The activator removes oxides of the conductive pad 2, prevents oxidation of the conductive pad 2, and improves solderability, and organic acids containing COOH, amine bromide, amine hydrochloride, etc. are suitable.

As the solvent, glycol ethers having a high boiling point are suitable.

Next, a method of manufacturing the printed circuit board 30 will be described with reference to FIGS.

First, the conductive pad forming step 100 of FIG. 3 is performed. In this step, as shown in FIG. 4A, the pitch P is 0.3 mm and the width W is at a predetermined position of the printed circuit board body 1.
1 forms a conductive pad 2 of 0.15 mm.

Next, a resin paste mask positioning step 200, which is a step of forming a resin paste layer, is performed. In this step, as shown in FIG. 4B, the resin paste mask 20 is positioned on the printed circuit board body 1 and placed so that the holes 23 are positioned on the conductive pads 2.

The resin paste mask 20 in this case is
It is made of metal or silk, and the width W3 of the hole 23 is 0.15 m.
m, and the thickness H1 is 0.03 mm.

Next, a resin paste printing step 300, which is a step of forming a resin paste layer, is performed. In this process,
The squeegee 21 is moved in the direction of arrow A to fill the resin paste 22 into the holes 23 of the resin paste mask 20.

The resin paste 22 in this case is composed of a rosin resin, a thickener, an activator, and a solvent, and has an adhesive force of the resin paste 22 to the conductive pad 2 and an adhesive force of the resin paste 22 to the hole 23. The difference is large.

Thereafter, as shown in FIG. 7C, the resin paste mask 20 is peeled off from the conductive pad 2, whereby the resin paste 22 relatively comes out from the hole 23. After that, when a drying process is performed, an appropriate amount of the resin paste layer 8 is formed on each conductive pad 2, and the printed circuit board 30 of FIGS. 1 and 2 is completed.

A humidification test (50 ° C., 90% RH, 100 hours) is performed on the printed circuit board 30.

After this test, no oxidation of the conductive pad 2 due to deterioration of the resin paste layer 8 was observed, and no decrease in adhesiveness with the solder paste 12 was observed.

Next, a mounting method for mounting the IC component 5 will be described with reference to FIGS.

First, the solder paste mask positioning step 400 of FIG. 3 is performed. In this step, as shown in FIG. 5A, the solder paste mask 10 is positioned on the printed circuit board body 1, and the holes 1 are formed on the resin paste layer 8.
Place so that 3 is located.

The solder paste mask 10 in this case is
It is made of metal or silk, and the width W2 of the hole 13 is 0.10 m.
m, and the thickness H2 is 0.15 mm.

Next, a solder paste printing step 500 is performed. In this step, the squeegee 11 is moved in the direction of the arrow A to move the solder paste 12 into the solder paste mask 10
Are filled in the respective holes 13.

In this case, the solder paste 12 is a resin paste composed of a rosin resin, a thickener, an activator, and a solvent mixed with solder powder balls.

After that, as shown in FIG. 3B, the solder paste mask 10 is peeled from the resin paste layer 8, so that the solder paste 12 relatively comes out from the hole 13.

After that, when a drying process is performed, an appropriate amount of solder paste layer 4 is formed on each resin paste layer 8.

Next, an IC component mounting process 600, which is a surface mounting component mounting process, is performed. In this step, as shown in FIG. 6, the IC component 5 is positioned above the predetermined position of the completed printed circuit board 30 while being conveyed, and the lower surface of the package body 5a is the IC component of the printed circuit board body 1. It is mounted by adhering to an adhesive (not shown) applied at the mounting position.

As a result, as shown in FIG. 5C, the IC component 5 is formed on each solder paste layer 4 on each resin paste layer 8 on each corresponding conductive pad 2 on the printed circuit board body 1. The tip side portion of each lead 6 is brought into contact with or brought close to.

In this state, infrared rays are radiated to cure the adhesive applied to the IC component mounting planned position of the printed circuit board body 1 to fix the IC component 5 to the printed circuit board body 1.

Then, a soldering process 700 is performed. In this step, as shown in FIG. 3D, the solder paste layer 4 is melted, and the leads 6 of the IC component 5 are soldered to the conductive pads 2 and the solder 7.

Specifically, hot air is blown to each lead 6,
Alternatively, infrared rays or the like is applied to each lead 6 to melt the solder paste layer 4 and the resin paste layer 8. As a result, all the leads 6 are connected to the conductive pads 2 by the solder 7.
Then, the IC component 5 is mounted on the printed circuit board body 1 with certainty. The printed circuit board 30 that has been subjected to the humidification test maintains good reflow solderability.

Therefore, since the layer 8 of the resin paste including the rosin resin, the thickener, the activator, and the solvent is provided on the conductive pad 2, the viscosity of the layer 8 of the resin paste is increased. You can

Therefore, when the solder paste 12 is printed on the resin paste layer 8, the adhesive force of the solder paste 12 to the resin paste layer 8 can be increased.

As a result, the difference between the adhesive force of the solder paste 12 with respect to the resin paste layer 8 and the adhesive force of the solder paste 12 with respect to the holes of the solder paste mask can be increased, and the solder paste 12 becomes the solder paste. It is possible to make the resin paste layer 8 easily adhere to the holes 13 of the mask 10 for use.

Therefore, the solder paste 12 easily comes out of the holes 13 of the solder paste mask 10. An appropriate amount of solder paste 12 is printed on all the resin paste layers 8 to form an appropriate amount of solder paste layer 4.

When the layer 4 of the solder paste is melted,
The lead 6 can be reliably soldered to the electrode pad 2 with an appropriate amount of solder 7. As a result, the reliability of mounting the IC component 5 on the printed circuit board 30 is improved.

Further, the resin paste layer 8 prevents oxidation of the conductor pad 2 even when a humidification test is performed, prevents the adhesiveness with the solder paste 12 from being lowered, and maintains good solderability. That is, it does not adversely affect the melting of the solder paste 12.

Further, the resin paste 22 is transferred to the conductive pad 2 through the hole 23 of the positioned resin paste mask 20.
Since it is printed on top, the resin paste 22 is not printed on the printed circuit board body 1 except the conductive pads 2.

Therefore, the step of removing the unnecessary resin paste layer 8 is unnecessary.

Next, the result of using the resin paste having the components shown in FIG. 7 as an example of the resin paste 12 will be described with reference to FIG.

The resin paste of Example 1 in FIG. 7 contains 60% of polymerized rosin, 4% of hydrogenated castor oil thickener and 0.03% of dimethylamine hydrochloride activator in the resin paste of Example 1. And the balance is a solvent of glycol ethers.

In the case of this Example 1, the thickness O.D. 03 mm
The resin paste 22 of Example 1 of FIG. 7 is printed on the electrode pad 2 having a width W1 of 0.10 mm by using the silk-made resin paste mask 20 of, and dried at 150 ° C. for 5 minutes. A layer 8 of resin paste is formed on the electrode pad 2.

On the layer 8 of the resin paste, a solder paste 12 in which a solder powder ball is mixed in a resin paste composed of a rosin-based resin, a thickener, an activator, and a solvent, has a thickness O.V.
Printing is performed using the 15 mm silk solder paste mask 10 to form the solder paste layer 4 on the resin paste layer 8.

The volume of this layer 4 of solder paste was calculated. For this calculation, a filling rate was calculated using a non-contact shape measuring device (manufactured by SVS) based on the principle of the light cutting method. As shown in FIG. 8, the filling rate was 80% or more.

This filling rate is determined by the solder paste mask 10
The volume surrounded by the holes 13 is defined as V1, and the volume V2 of the solder paste layer 4 attached on the resin paste layer 8 is divided by the volume V1.

Since the value of 80% exceeds the filling rate of 60% required to properly mount the surface mount component,
It is a good result.

Similarly, in the resin paste of Example 2 shown in FIG. 7, the weight% of the components was such that polymerized rosin was 60%, hydrogenated castor oil thickener was 4%, and adipic acid activator was 0.5%. % And the balance is a solvent of glycol ethers. In the case of this Example 2, the filling rate was 80% or more.

In the resin paste of Example 3 shown in FIG. 7, 60% by weight of the components were polymerized rosin, 4% of hydrogenated castor oil thickener, and 0.03% of dimethylamine hydrochloride activator.
%, The adipic acid activator is 0.5%, and the balance is a solvent of glycol ethers. In the case of this Example 3, the filling rate was 80% or more.

A humidification test (50 ° C., 90% RH, 100 hours) was performed on the printed board 30 on which the resin paste 22 of Examples 1 to 3 was printed to form the resin paste layer 8.

Even after this test, no oxidation of the conductive pad 2 due to the deterioration of the resin paste layer 8 was observed, no decrease in the adhesiveness with the solder paste 12 was observed, and good reflow solderability was maintained. Was confirmed.

FIG. 9 is a vertical sectional view of a printed circuit board 31 according to another embodiment of the present invention.

The printed board 31 includes a printed board body 1, a conductive pad 2 made of copper, and a resin paste layer 9 formed on the conductive pad 2 and the entire surface of the printed board body 1. .

The resin paste layer 9 is used as a solvent.
Which has a lower boiling point than the solvent of layer 8 of the resin paste of one embodiment,
Alcohol with good dryness is suitable. For example, IPA
(Isopropyl alcohol) is good.

The printed circuit board 31 of the other embodiment requires a post-treatment to remove the resin paste layer 9 formed on the entire surface of the printed circuit board body 1 other than the conductive pads 2, but the solder paste 12 is used. Can be formed on the resin paste 9 above all the conductive pads 2 in an appropriate amount.

[0084]

As described above, according to the invention of claim 1, since the resin paste layer composed of the rosin resin, the thickener, the activator and the solvent is provided, the resin paste The viscosity of the layer can be increased.

Therefore, when the solder paste is printed on the resin paste layer, the adhesive force of the solder paste to the resin paste layer can be increased.

As a result, the difference between the adhesive force of the solder paste with respect to the resin paste layer and the adhesive force of the solder paste with respect to the holes of the solder paste mask can be increased, and the solder paste can be removed from the holes of the solder paste mask. It can be more easily adhered to the resin paste layer.

Therefore, the amount of the solder paste that escapes from the holes for the solder paste onto the resin paste layer can be made appropriate, and the leads of the surface mount component can be soldered to the electrode pads with an appropriate amount of solder. it can.

Since the resin paste layer does not adversely affect the melting of the solder paste, good solderability can be maintained.

According to the second aspect of the invention, since the structure includes the conductive pad forming step and the resin paste layer forming step, the conductive pad is formed on the printed circuit board body, and the conductive pad is formed on the conductive pad. A layer of resin paste can be formed.

According to the third aspect of the present invention, the resin paste is printed on the conductive pads through the holes of the positioned resin paste mask. Therefore, the resin paste is printed on the printed circuit board body excluding the conductive pads. Try not to. Therefore, the step of removing the unnecessary resin paste layer can be omitted.

Further, according to the invention of claim 4, all the solder paste is made to easily adhere to the resin paste layer through the holes of the solder paste mask, and the solder paste printed on each resin paste is soldered. It is possible to make the amount of the paste coming out of the paste hole appropriate and solder all the leads to each electrode pad with an appropriate amount of solder.

That is, all the leads of the surface mount component can be reliably soldered to the corresponding conductive pads without fail, and all the leads can be soldered with an appropriate amount of solder.

As a result, the surface mount component can be mounted with high reliability, and it is particularly effective when applied to the mounting of the surface mount component having leads with a narrow pitch.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a printed circuit board according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the printed circuit board taken along the line II-II in FIG.

FIG. 3 is a process diagram showing a method for manufacturing the printed circuit board and a method for mounting surface mount components shown in FIG.

FIG. 4 is a diagram for explaining a conductive pad forming process to a resin paste printing process of FIG.

FIG. 5 is a diagram for explaining a solder paste mask positioning step to a soldering step of FIG. 3;

FIG. 6 is a diagram for explaining the IC component mounting process of FIG. 3;

FIG. 7 is a diagram showing components of a resin paste.

FIG. 8 is a diagram showing a result of screen printing.

FIG. 9 is a vertical sectional view showing a configuration of a printed circuit board according to another embodiment of the present invention.

FIG. 10 is a diagram showing a conventional mounting method of surface mount components.

[Explanation of symbols]

1 Printed Circuit Board Body 2 Conductive Pad 4 Solder Paste Layer 5 IC Component 6 Lead 8 Resin Paste Layer 9 Resin Paste Layer 10 Solder Paste Mask 11 Squeegee 12 Solder Paste 13 Hole 20 Resin Paste Mask 21 Squeegee 22 Resin Paste 23 Hole 30 Printed circuit board 31 Printed circuit board 100 Conductive pad forming step 200 Resin paste mask positioning step (resin paste layer forming step) 300 Resin paste printing step (resin paste layer forming step) 400 Solder paste mask positioning step 500 Solder paste Printing process 600 IC component mounting process 700 Soldering process

Claims (4)

[Claims] 1. A printed circuit board comprising a printed circuit board body (1) and a conductive pad (2) formed at a predetermined position on the printed circuit board body (1), wherein the conductive pad (2) is provided. A printed circuit board, wherein a resin paste layer (8, 9) comprising a rosin-based resin, a thickener, an activator, and a solvent is provided on the printed circuit board. 2. A conductive pad forming step (1) for forming a conductive pad (2) at a predetermined position on a printed circuit board body (1).
00), a resin paste layer (8, 9) consisting of a rosin-based resin, a thickener, an activator, and a solvent, is formed on the conductive pad (2) to form a resin paste layer (200, 30).
0) and a configuration including: 3. A conductive pad forming step (1) for forming a conductive pad (2) at a predetermined position on a printed circuit board body (1).
00) and the resin paste mask (2) on the conductive pad (2).
0) the resin paste mask positioning step (200) for determining the position so that the hole (23) is located, and the resin paste (22) made of a rosin resin, a thickener, an activator, and a solvent. Paste mask (2
0) a resin paste printing step (300) of forming a resin paste layer (8) by printing on the conductive pad (2) through the hole (23). Printed circuit board manufacturing method. 4. The conductive material is formed at a position corresponding to all the leads (6) of the surface mount component (5) to be mounted on the printed circuit board body (1), and has the same number as the number of the leads (6). A resin paste layer forming step (200, 30) for forming a resin paste layer (8, 9) made of a rosin-based resin, a thickener, an activator, and a solvent on the pad (2).
0) and the holes (13) of the solder paste mask (10) are located on the resin paste layers (8, 9) formed by the resin paste layer forming step (200, 300). Solder paste mask positioning process (4)
00) and the solder paste (12) is printed on the respective resin paste layers (8, 9) through the respective holes (13) of the solder paste mask (10) to form the solder paste layer (4). Solder paste printing step (50)
0) and the surface mount component main body (1) are adhered and mounted on the printed circuit board main body (1).
And a soldering step (70) of melting the solder paste layer (4) and soldering the leads (6) to the corresponding conductive pads (2) on the printed circuit board body (1).
0) and a configuration including: