JPH0823189A - Electronic part mounting film, soldering material feeding method and electronic part mounting method - Google Patents

Abstract

PURPOSE:To prevent the occurrence of defective soldering after a reflow process by controlling the cross-sectional dimensions of each of the openings, formed in a desired pattern in an insulating and heat-resistant film, so that the length of the upper side will be smaller than that of the lower side. CONSTITUTION:Electronic parts 28, 38 are soldered to a circuit board 4 by heating the entire circuit board 4 to melt cream solder using heat sources; the part 38 with a small pitch is subjected to heating with an electronic part mounting film 10 stuck thereto. Though cream solder 6 was continuously injected above the openings 32 in the electronic part mounting film 10 in the preceding process, the film remains insulating and heat-resistant. The cross-sectional dimensions of each of the openings are so controlled that the length of its upper side < that of its lower side. The film 10 has been placed between adjacent electrodes. Thus the cream solder slumps due to heating during the reflow process, and solder flows down the slope in the cross sections in the film during the subsequent melting cycle. Therefore, solder is divided opening by opening, which prevents the occurrence of defective soldering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component mounting film used for supplying a bonding material such as cream solder to a land on a circuit board, a method for supplying a bonding material to a circuit board using the film, and a land. The present invention relates to an electronic component mounting method for joining electrodes of an electronic component with a joining material.

[0002]

2. Description of the Related Art Conventionally, in the manufacture of electronic circuit boards, the step of mounting electronic parts such as QFP parts and chip parts on the circuit board by soldering is performed by a cream solder printing step, an electronic part mounting step, and a reflow step. Has been done. This will be described with reference to the drawings.

FIG. 8 shows a conventional cream solder printing process, 1 is a metal mask having a desired pattern opening 2 formed therein, 3 is a printing squeegee which moves linearly on the mask 1 along the printing direction, 4 Is a circuit board, and 5 is a land for printing the cream solder 6. In this step, first, the mask 1 is positioned and superposed on the circuit board 4, and the squeegee 3 is linearly moved along the printing direction in a state where the squeegee 3 is in contact with the mask 1 with an appropriate printing pressure, and the cream solder 6 is applied to the mask 1. After filling the opening 2 of the circuit board 4 as shown in FIG.
Is separated from the mask 1 to print and apply the cream solder 6 in a desired pattern on the circuit board 4 through the mask 1.

Next, in the electronic component mounting step, as shown in FIG. 9, the electronic component 8 is sucked and positioned by the electronic component mounting nozzle 7, and then mounted on the circuit board 4. At this time, the electrode 9 of the electronic component 8 is placed on the cream solder 6 printed on the land 5 in the previous step, and the adhesive force of the cream solder 6 holds the electronic component 8 and sends it to the next step.

In the final reflow step, as shown in FIG. 10, the cream solder 6 printed in the previous step is melted by heating with a heat source such as hot air or an infrared heater, and the electronic component 8 is soldered onto the circuit board 4. It is to join.

[0006]

However, the above-mentioned mounting method has a problem that the quality of the solder joint of the circuit board deteriorates due to the occurrence of the following defect factors in each step. In recent years, a method of mounting a QFP component, in which the pitch of the leads (showing electrodes of the QFP component etc.) has been narrowed, will be described as an example. First, in the cream solder printing step, as shown in FIG. At the time of releasing the plate after the cream solder 6 is filled in the opening 2 of the mask 1 by 3, all the cream solder 6 filled in the opening 2 is not printed or applied on the circuit board 4 and is applied to the opening 2. Since the residual solder particles 6a adhere to the plate, defective printing may occur due to a decrease in print amount, variation, and the like, resulting in defective solder joining such as unjoined solder after the reflow process. Further, since the solder particles also wrap around to the back surface of the mask 1 and the residual solder particles 6b are attached, printing defects such as print bleeding and bridges occur when continuous printing is performed, and solder joint defects such as short circuits occur after the reflow process. .

Further, in the next electronic component mounting step, when the electronic component 8 is mounted on the circuit board 4, the electronic component 8 is pushed into the cream solder 6 by the electronic component mounting nozzle 7 and mounted, so that the process is shown in FIG. The shape of the cream solder 6 thus printed is deformed and spreads in the width direction of the land. At this time, as described above, if the printing defect such as the print bleeding or the bridge or the printing amount is excessive, the solder joint defect such as the short circuit after the reflow process easily occurs.

In the final reflow process, as shown in FIG. 10, the substrate is heated by a heat source such as hot air or an infrared heater. Therefore, the flux in the cream solder 6 is softened by the heat and flows out between the lands 5, and then the cream solder 6 is added. The shape of is broken and so-called cream solder dripping occurs. Therefore, as shown in FIG. 10B, a solder joint defect such as a short circuit or a solder unjoint after the reflow process is likely to occur.

As described above, in the conventional mounting method, it is difficult to maintain the solder joint quality of the circuit board due to the occurrence of a solder joint defect such as a short circuit or a non-solder joint. Also,
With the miniaturization and high density of electronic circuit boards, the lead pitch has become narrower and smaller, such as QFP parts with a lead pitch of 0.5 mm and chip parts with a size of 1.0 x 0.5 mm. QFP parts have appeared.
Lead pitch 0.5mm QFP parts and 1.0 x 0.5m
For small parts such as m-chip parts, the cream solder printing method using a metal mask of uniform thickness (usually around 0.15 mm) is used as a method of supplying cream solder onto the circuit board. The printed thickness is constant for all electronic components, and the thickness is also determined by the thickness of the mask, and the printed amount (solder amount) is controlled by the size of the opening. However, the lead pitch is 0.3 mm
Since the amount of solder required for QFP parts is much smaller than that of conventional parts, there is a limit to reducing the size of the mask opening (the mask plate making limit is mask thickness: opening size = 1: 1). On the contrary, if the thickness is decreased, the amount of solder of the conventional component is decreased, and the solder joint strength after mounting is weakened, resulting in deterioration of joint reliability. In this way, the difference in the required amount of solder between conventional components and narrow-pitch components increases due to the narrower pitch of the leads of electronic components, and the cream solder printing method using a metal mask of uniform thickness provides both conventional and narrow-pitch components. On the other hand, it was not possible to supply an appropriate amount of cream solder. Therefore, the mask 1 as shown in FIG.
It was also possible to use a half-processed mask in which the mask thickness of the narrow-pitch component part was thinned by partially changing the thickness of the mask, but as in the case of the conventional metal mask of uniform thickness, there are variations in the printing amount and printing bleeding, Printing defects such as bridges occurred, and solder joint defects such as short circuits and solder non-joints occurred after the reflow process.

The present invention solves the above problems and prevents the occurrence of a solder joint failure such as a short circuit or a solder non-joint after the reflow step, improves the solder joint quality of the circuit board, and individually. Control the amount of solder arbitrarily,
An electronic component mounting film and a bonding material capable of easily supplying an appropriate amount of cream solder to both conventional components and narrow-pitch components and mounting the conventional components and the narrow-pitch components on the circuit board in a mixed manner. It is an object of the present invention to provide a supply method and an electronic component mounting method.

[0011]

In order to solve the above-mentioned problems, the present invention has an insulating property and heat resistance, and the dimension of the cross section of the opening of the film in which the opening of the desired pattern is formed is the upper surface. The present invention is characterized in that a mounting film having a part size A <a bottom part size B is provided.

Further, the invention is characterized in that after a film having openings of a desired pattern is mounted at a desired position on a circuit board, an arbitrary amount of bonding material is supplied onto the openings of the film. Is. Further, using a film having a desired pattern opening formed, the step of mounting the film at a desired position on the circuit board, the step of supplying an arbitrary amount of bonding material on the opening of the film, The method is characterized by including a step of mounting the electronic component by aligning the opening and the electrode, and a step of joining the land and the electrode by heating or the like.

Further, a step of printing a bonding material on the lands for the conventional parts of the circuit board, and a bonding material is supplied to the lands for the ridge pitch using a film in which openings having a desired pattern are formed. The method is characterized by including a step, a step of mounting each component on a land for a conventional component and a ridge pitch component, and a step of joining the land and the electrode by heating or the like.

[0014]

By the above means, the electronic component mounting film in which the openings of the desired pattern are formed has insulation and heat resistance, and the cross-sectional dimension is the upper surface dimension A <the lower surface dimension B.
When the bonding material is continuously supplied to the opening of the film or the bonding material is connected between the adjacent electrodes due to the deformation of the bonding material when the electronic parts are mounted, the film is placed between the adjacent electrodes. However, the sagging of the bonding material due to heating during reflow and the subsequent melting of the bonding material causes the bonding material to separate for each opening due to the inclination of the cross-section of the film. The joining quality can be improved. Also, after mounting the electronic component mounting film having a desired pattern opening formed at a desired position on the circuit board, by supplying an arbitrary amount of bonding material onto the opening of the film, the conventional printing It is possible to easily supply the bonding material without printing defects such as printing defect, bleeding, and printing defects such as bridges. Further, since the supply amount of the bonding material can be individually controlled and supplied only to a necessary portion, a proper amount of the bonding material is supplied to each of the conventional component and the narrow pitch component, resulting in solder bonding failure. The conventional components and the narrow pitch components can be mixedly mounted on the circuit board without being mounted.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The same components as those shown in FIGS. 8, 9, and 10 showing the conventional mounting method are designated by the same reference numerals, and the description thereof will be omitted. FIG. 1 is a schematic view showing a film for mounting an electronic component in which an opening having a desired pattern is formed in this embodiment, and FIG. 2 is an enlarged sectional view of the opening in FIG. The shape and size of the electronic component mounting film are arbitrarily selected according to the shape and size of the electronic component to be mounted. FIG. 1 shows an example of the shape and size.

First, the electronic component mounting film 10 is formed into a desired pattern by etching or laser processing so that the dimension of the cross section of the film having insulation and heat resistance such as polyimide is the upper surface dimension A <the lower surface dimension B. The opening 32 is formed. The thickness of the film 10 is arbitrarily selected depending on the amount of bonding material supplied, the lead size of electronic components, the pitch, and the like.

In addition to the film shown in FIG. 1, the electronic part mounting film 10 may be formed by removing the area of the main body of the electronic part as shown in FIG. This is because when the electronic component is placed on a flat surface and the gap between the flat surface and the electronic component main body portion (usually called the standoff height in the QFP portion) is small, the film and the electronic component main body contact each other during mounting. This is because the electronic component is in a floating state, and a bonding failure such as floating of the lead is likely to occur. This is to prevent this.

Although etching and laser processing have been shown as means for forming the opening 32, a method such as punching or molding with a die may be used. Next, a cream solder supply method according to an embodiment of the bonding material supply method will be described. FIG. 4 is a schematic view showing the cream solder supply method in this embodiment. First, as shown in FIG. 4A, the electronic component mounting film 10 is adsorbed by the electronic component mounting film mounting nozzle 11 and positioned at a desired position on the circuit board, and then mounted on the circuit board 4. After that, as shown in FIG.
Cream solder 6 is discharged onto 2 to supply an arbitrary amount of material. The supply amount of the cream solder 6 can be arbitrarily controlled by changing the amount discharged from the cream solder discharge nozzle 12.

Incidentally, when the electronic component mounting film 10 is mounted on the circuit board 4, an adhesive is applied to the circuit substrate 4, or an adhesive is applied to the lower surface of the electronic component mounting film 10. The electronic component mounting film 10 is attached to the circuit board
It may be fixed on the top. Further, although the cream solder 6 is continuously discharged and supplied onto the opening 32 in the present embodiment, it may be discharged and supplied individually to the opening 32.

Next, a mounting method of a mixed mounting of a narrow pitch component and a conventional component using cream solder according to an embodiment of an electronic component mounting method will be described. 4 and 5 to 7 are schematic diagrams showing the steps of the electronic component mounting method according to this embodiment.
In the cream solder supply step, first, cream solder is supplied to the conventional part 28. As shown in FIG. 5 (A), a cream solder printing method is applied to the land 25 for the conventional component 28, the circuit board 4 is positioned and superposed on the mask 21, and the squeegee 3 is appropriately printed on the mask 21. After the cream solder 6 is linearly moved along the printing direction while being in contact with the pressure to fill the opening 2 of the mask 21 with the cream solder 6, as shown in FIG.
As shown in (B), the circuit board 4 is separated from the mask 21 to print the cream solder 6 on the circuit board 4 through the mask 21. Mask 21 used at this time
No opening is provided for the narrow pitch component 38, and cream solder is supplied only to the land 25 for the conventional component 28.

Next, cream solder is supplied to the narrow pitch component 38 portion. As shown in FIG. 4A, after the electronic component mounting film 10 is sucked and positioned by the electronic component mounting film mounting nozzle 11, it is mounted on the circuit board 4. After that, as shown in FIG. 4B, the cream solder 6 is put on the opening 32 from the cream solder discharge nozzle 12.
To discharge the cream solder to the land 35 for the narrow pitch component 38. The supply amount of the cream solder 6 can be arbitrarily controlled by changing the amount discharged from the cream solder discharge nozzle 12.

As described above, an appropriate amount of cream solder 6 is supplied to each of the conventional component 28 and the narrow pitch component 38. Next, in the electronic component mounting step, as shown in FIG.
After 38 is sucked and positioned, it is mounted on the circuit board 4. At this time, the electrodes 29, 39 of the electronic components 28, 38 are placed on the cream solder 6 supplied to the lands 25, 35 in the previous step, and the adhesive force of the cream solder 6 holds the electronic components 28, 38. .

Finally, in the reflow process, as shown in FIG. 7A, in the narrow pitch component 38, the circuit board 4 as a whole is heated by a heat source such as hot air or an infrared heater with the electronic component mounting film 10 attached. Is heated to melt the cream solder supplied in the previous step, and the electronic components 28 and 38 are solder-bonded onto the circuit board 4. At this time, even when the cream solder 6 is continuously discharged and supplied onto the opening 32 of the electronic component mounting film 10 in the previous step, it has insulation and heat resistance, and the dimension in cross section is the dimension of the upper surface portion A <lower surface. Since the electronic component mounting film 10 having the part size B is disposed between the adjacent electrodes, the solder flows along the inclination of the film cross section during sagging of the cream solder 6 due to heating during reflow and subsequent melting. Since the solder is separated in each opening, the electrode 39 and the land 35 can be solder-bonded without causing a solder-bonding failure such as a short circuit as shown in FIG. 7B. When the dimension of the cross section of the electronic component mounting film 10 is the upper surface dimension A ≧ the lower surface dimension B, the flat portion of the film upper surface becomes large and the inclination of the film cross section is reversed, so that a short circuit occurs during reflow. It is necessary that the dimension of the cross section of the electronic component mounting film 10 is such that the upper surface portion dimension A <the lower surface portion dimension B because soldering defects such as the above are likely to occur.

In this embodiment, the entire circuit board 4 is heated for reflow, but each electronic component may be individually reflowed by a laser or the like. In the present invention, the dimension in the cross section of the electronic component mounting film may be set as the upper surface portion dimension A <the lower surface portion dimension B, but the upper surface portion dimension A should be made extremely smaller than the lower surface portion dimension B, that is, for example, in the cross section. By making the shape closer to a triangle, the flat portion of the upper surface becomes extremely small, so that the separating action of the joining material at the time of reflow is increased, and the occurrence of a joining defect such as a short circuit can be further prevented.

[0025]

As described above, according to the present invention, the dimension in the cross section of the opening of the film having the insulating property and the heat resistance and having the opening of the desired pattern is the upper surface dimension A.
<Being the bottom surface dimension B prevents the occurrence of solder joint failure such as short circuit due to separation of the joint material due to heating during reflow and subsequent separation of the joint material at the time of melting. There is an effect that the bonding quality of the substrates can be improved. Also, after mounting the film with the desired pattern opening at the desired position on the circuit board,
By supplying an arbitrary amount of the bonding material on the opening of the film, it is possible to easily supply the bonding material. Furthermore, since the bonding material can be individually supplied to the conventional component and the ridge pitch component and the supply amount thereof can be controlled, an appropriate amount of the bonding material can be supplied to each of the conventional component and the narrow pitch component. There is an effect that the narrow pitch components can be mixedly mounted on the circuit board.

[Brief description of drawings]

FIG. 1 is a schematic view showing a film for mounting an electronic component of an example of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a film for mounting electronic components of an example of the present invention.

FIG. 3 is a schematic view showing another embodiment of the electronic component mounting film of the present invention.

FIG. 4 is a schematic view showing a cream solder supplying step according to an embodiment of the present invention. (A) shows the mounting process of the electronic component mounting film, and (B) shows the cream solder supply process.

FIG. 5 is a schematic view showing a step of supplying cream solder to a land for a conventional component according to an embodiment of the present invention. (A) shows the step of supplying cream solder to the land, and (B) shows the step of separating the circuit board from the mask.

FIG. 6 is a schematic view showing an electronic component mounting step of the embodiment of the present invention.

FIG. 7 is a schematic view showing a reflow process of an example of the present invention. (A) shows a heating step, and (B) shows a solder joint state between the electrode and the land after reflow.

FIG. 8 is a schematic view showing a cream solder printing process of a conventional example. (A) shows a cream solder printing process, and (B) shows a state in which the circuit board is separated from the mask.

FIG. 9 is a schematic diagram showing a conventional electronic component mounting process.

FIG. 10 is a schematic view showing a reflow process of a conventional example.
(A) shows a heating step, and (B) shows a solder joint state between the electrode and the land after reflow.

[Explanation of symbols]

 1, 21 Mask 2, 32 Opening 3 Squeegee 4 Circuit board 5, 25, 35 Land 6 Cream solder 6a, 6b Residual solder 7 Electronic component mounting nozzle 8 Electronic component 9, 29, 39 Electrode 10 Electronic component mounting film 11 Film mounting nozzle for electronic component mounting 12 Cream solder discharge nozzle 28 Conventional component 38 Narrow pitch component

Claims (4)

[Claims] 1. An electronic component having insulating properties and heat resistance, wherein a dimension of a cross section of an opening of a film in which an opening having a desired pattern is formed is an upper surface dimension A <a lower surface dimension B. Mounting film. 2. A bonding method, comprising: mounting a film having openings having a desired pattern on a circuit board at a desired position, and then supplying an arbitrary amount of bonding material onto the openings of the film. Material supply method. 3. When mounting an electronic component in which a land of a circuit board and an electrode of the electronic component are bonded with a bonding material such as solder, a film having an opening of a desired pattern is used, and the film is placed on the circuit board. Mounting at a desired position, supplying an arbitrary amount of bonding material on the opening of the film, aligning the opening of the film with an electrode to mount an electronic component, heating, etc. A method of mounting an electronic component, the method including a step of joining a substrate and an electrode. 4. A land for a conventional component of a circuit board,
Printing the bonding material, supplying the bonding material to the lands for the ridge pitch using the film with the opening of the desired pattern, and mounting each component to the land for the conventional parts and the ridge pitch parts. 4. The electronic component mounting method according to claim 3, further comprising the step of joining and the step of joining the land and the electrode by heating or the like.