JPH06326443A - Warpage correcting method of printed wiring board - Google Patents

Abstract

PURPOSE:To effectively correct a printed wiring board in warpage without controlling a cooling plate in temperature. CONSTITUTION:After a printed wiring board 1 is heated, cooling medium 2 is spouted against come side of the wiring board 1. Thereafter, the board 1 is pressed as it is cooled. Before a pressing process, cooling medium 2 is spouted against one side of the wiring board 1, whereby the warpage of the printed wiring board 1 can be previously relaxed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a warp correction method for a printed wiring board using a resin laminated board as a substrate.

[0002]

2. Description of the Related Art A printed wiring board is subject to various thermal histories in its working process, so that it is greatly warped. Therefore, various attempts have been made to correct the warp of the printed wiring board. For example, as shown in Japanese Patent Application Laid-Open No. 2-98442 provided by the present applicant, after heating the printed wiring board to a temperature not lower than the glass transition point of the resin of the resin laminated plate serving as the substrate, By sandwiching and pressing between the cooling plates, the printed wiring board can be rapidly cooled and pressed by the flat surface of the cooling plate to correct the warp of the printed wiring board and restore the flatness.

However, in this method, since the two cooling plates have the same temperature, both sides of the printed wiring board are cooled at the same temperature regardless of the direction of distortion of the printed wiring board, that is, the direction of warpage. In some cases, the effect of correcting warpage of the printed wiring board may not be sufficiently obtained. On the other hand, in Japanese Examined Patent Publication No. 3-2357, by changing the temperature of each of the two cooling plates, one side and the other side of the printed wiring board are cooled and pressed while being cooled. In addition, the printed wiring board can be corrected according to the direction of the warp.

[0004]

[Problems to be Solved by the Invention] However, Japanese Patent Publication No. 3-2
When changing the temperature of each of the two cooling plates as in Japanese Patent No. 357, it is necessary to quickly adjust the temperature of the cooling plates according to the direction of the warp of the printed wiring board, which does not require a large amount of temperature control of the cooling plates. Equipment was required, which was a big problem in practical use. In addition, since the printed wiring board partially has a metal foil, a warp often occurs in a part of the printed wiring board.
Even in the case of the publication No. 7, each surface of the printed wiring board is cooled at the same temperature over the entire surface where warpage is present and where warpage is not present, and some warpage remains or rather warpage is large. There was also the problem that it might become worse.

The present invention has been made in view of the above points, and it is possible to effectively correct the warp of the printed wiring board without the need to adjust the temperature of the cooling plate, and further, to partially fix the printed wiring board. It is an object of the present invention to provide a method for correcting a warp of a printed wiring board, which can also correct a warp.

[0006]

A method of correcting warpage of a printed wiring board according to the present invention comprises heating a printed wiring board 1 and then spraying a cooling medium 2 on one surface of the printed wiring board 1 and thereafter, the printed wiring board. It is characterized in that 1 is pressed while being cooled. In the present invention, the cooling medium 2 can be partially sprayed on one surface of the printed wiring board 1.

Further, in the present invention, the cooling medium 2 may be sprayed on one side of the printed wiring board 1 and the heating medium 3 may be sprayed on the other side.

[0008]

After the step of heating the printed wiring board 1, the warp of the printed wiring board 1 is caused by spraying the cooling medium 2 on one surface of the printed wiring board 1 prior to the step of pressing the printed wiring board 1 while cooling it. Therefore, the warp of the printed wiring board 1 can be corrected without the need to adjust the temperature of the cooling plate.

[0009]

EXAMPLES The present invention will be described in detail below with reference to examples. Figure 1
Shows an example of an apparatus used in the present invention.
Is a heating device formed by an infrared heater furnace, a hot-air stove, or the like.
A conveyor 5 is provided which is formed with a conveyor belt 10 passing through the heating device 4 as it emerges from b.
In the next process portion of the transport device 5, an injection device 6 formed of a pair of injection nozzles 11a and 11b facing each other in the vertical direction is provided. Further, in the next step of the injection device 6, a cooling press device 7 formed by including a pair of cooling plates 12a and 12b is arranged.

Each of the injection nozzles 11a and 11b of the injection device 6 is formed by providing a large number of nozzle holes 14 as shown in FIG. 2, and the cooling medium 2 can be ejected from the nozzle holes 14. . Injection nozzles 11a, 11
The nozzle diameter of b is preferably about 0.1 to 0.5 mm,
Spraying pressure is 0.1-8.0 kg / cm at the nozzle tip.
^{About 2} is preferable. Even if the nozzle is not circular but slit-shaped, the opening width is preferably about 0.1 to 0.5 mm. Further, the cooling medium 2 uses a fluid medium such as gas or liquid, and is not particularly limited as long as it is cooled to a temperature lower than the temperature of the heated printed wiring board 1. be able to. As the gas, nitrogen gas, carbon dioxide gas, compressed air, or the like, cold air (which may be hot air) cooled by a heat exchanger, or steam gas can be used. As the liquid, in addition to economical and easily available water, liquid chlorofluorocarbon, an alcohol-based solvent or the like so as not to contaminate the printed wiring board 1, and ethylene glycol can be used.
Since ethylene glycol has a low solidification temperature, it is particularly effective when cooled to a low temperature and sprayed. Further, a flux or the like can be used as the cooling medium 2 while also protecting the copper of the printed wiring board and the solder surface from oxidation. Further, the cooling medium 2 may be a solvent such as a small ice or a fog ice.

Cooling plates 12a, 12b of the cooling press device 7
Are arranged to face each other vertically, and the upper cooling plate 1
2a is attached to the cylinder device 13 so as to be vertically movable. Therefore, the upper cooling plate 12a is attached to the cylinder device 1
By lowering at 3, the upper and lower cooling plates 12a, 1
It is possible to press between 2b. If necessary, a heat exchanger is provided in the cooling plate 12a so that the surface temperature of the cooling plate 12 can be maintained at a predetermined temperature by the refrigerant passed through the heat exchanger.

In the present invention, the printed wiring board 1 to be warped is formed of a resin laminated board such as a paper-based phenol resin laminated board, a glass-based epoxy resin laminated board, or a glass-based polyimide resin laminated board. First, the printed wiring board 1 is placed on the conveyor belt 10 of the conveying device 5 and introduced into the heating device 4 through the entrance 4a to heat the printed wiring board 1 uniformly. The heating is performed so that the temperature of the printed wiring board 1 becomes equal to or higher than the glass transition point of the resin forming the substrate of the printed wiring board 1. For example, the substrate of the printed wiring board 1 is a glass-based epoxy resin laminated plate. In the case of heating to 120 ° C to 180 ° C,
Further, when the substrate of the printed wiring board 1 is a polyimide resin laminated board, it is necessary to heat it at a temperature of 300 ° C. or higher. The heating time by the heating device 4 is not particularly problematic, but it is necessary to set the time so that the inside of the printed wiring board 1 is uniformly heated. For example, printed wiring board 1
When the thickness is about 1.6 mm and a hot stove is used as the heating device 4, the wind speed is about 1 m / s to 3 m / s and about 1 minute to
About 5 minutes is common. When an infrared heater furnace is used as the heating device 4, about 20 seconds to 1 minute is sufficient, and when the printed wiring board 1 is sandwiched between the heating boards by using a heating board, the heating is performed for about 10 seconds to 1 minute. Minutes are enough.

After the printed wiring board 1 is heated in this way, a pair of upper and lower injection nozzles 11a of the injection device 6 are provided on the printed wiring board 1 immediately after coming out from the outlet 4b of the heating device 4.
The cooling medium 2 is sprayed from one side of 11b. Which of the ejection nozzles 11a and 11b sprays the cooling medium 2 onto the printed wiring board 1 is set according to the direction of the warp occurring in the printed wiring board 1, and the warp predicted for the printed wiring board 1 is determined. The jet nozzles 11a and 11b to be operated in advance may be set in accordance with the direction of the above, or the warp direction of the printed wiring board 1 may be detected for each printed wiring board 1 before being introduced into the heating device 4. ,
The injection nozzle 11a to be operated based on the detection result,
You may make it control 11b. This detection can be performed by measuring several to several tens of points of the printed wiring board 1 by using the warp detection sensor 13 such as a laser displacement gauge or a differential transformer displacement gauge. Based on the information on the direction of the warp detected by the injection device 6
The injection nozzles 11a and 11b for ejecting the cooling medium 2 are determined from the pair of injection nozzles 11a and 11b. For example, when the printed wiring board 1 is warped such that the upper surface is concave, the upper jet nozzle 11a is operated and the lower jet nozzle 11b is stopped to move the printed wiring board 1 as shown in FIG. Cooling medium 2 on the concave upper surface
Is what is blown. By blowing the cooling medium 2 onto the concave warped surface of the printed wiring board 1 in this manner, the concave warped surface of the printed wiring board 1 is rapidly cooled, and the surface of the printed wiring board 1 on the rapidly cooled side is not cooled. Since the other surface of the printed wiring board 1 that shrinks and is gradually cooled contracts, the warp of the printed wiring board 1 can be alleviated. Here, when liquid such as cold water is used as the cooling medium 2, it is necessary to provide a masking or a partition to prevent the cooling medium 2 from spreading to other places. The detection sensor 1
As shown in FIG. 1, 3 may be provided between the heating device 4 and the injection device 6 to detect the warp of the printed wiring board 1 immediately after being heated by the heating device 4 and coming out from the outlet 4b.

After the cooling medium 2 is sprayed on one of the concave surfaces of the printed wiring board 1 in this manner, the printed wiring board 1 is set between the cooling plates 12a and 12b of the cooling press device 7, and the cooling plate 12a. , 12b are sandwiched between the flat surfaces of the printed wiring boards 1 and 12b and pressed while being cooled. Printed wiring board 1
It is preferable that the time from heating by the heating device 4 to take out from the outlet 4b and then pressing by the cooling press device 7 is 10 seconds at the maximum and within 3 seconds as much as possible. By pressing the printed wiring board 1 while cooling it in this way, the residual stress is released by heating and the printed wiring board 1 is flattened by the pressure applied by the press while the residual stress is removed. By reducing the temperature to the following, the corrected state can be fixed, and the warp of the printed wiring board 1 can be corrected. When the temperature of the cooling plates 12a and 12b is adjusted to about 20 ° C, the printed wiring board 1 can be cooled to a temperature at which the printed wiring board 1 can be handled at 50 to 60 ° C or less by a press for about 10 seconds to 30 seconds. It can be taken out from the cooling press device 7 and sent to the next step.

When pressing the printed wiring board 1 by sandwiching the printed wiring board 1 between the cooling plates 12a and 12b of the cooling press device 7 as described above and rapidly cooling, the cooling medium 2 is sprayed on one surface of the printed wiring board 1 in advance and warped. Therefore, the warp of the printed wiring board 1 can be corrected without the need to adjust the temperatures of the cooling plates 12a and 12b.

In the above-described embodiment, the cooling medium 2 is sprayed from the spray nozzles 11a and 11b of the spray device 6 to one surface of the printed wiring board 1 over the entire surface, but the printed wiring board 1 is warped. The cooling medium 2 may be partially sprayed only on the part. FIG. 4 shows one of the embodiments in which the cooling medium 2 is partially sprayed onto the printed wiring board 1, and the injection nozzles 11a and 11b of the injection device 6 are connected to the X-axis rail 16a and the Y-axis rail 16 respectively.
It can be moved by an XY moving device 15 formed by including b. That is, the Y-axis rail 16b is movably attached along the X-axis rail 16a by driving a motor or the like, and the slider 17 is movably attached along the Y-axis rail 16b by driving a motor or the like. Each injection nozzle 11a, 11b
Is fixed. Therefore, by moving the Y-axis rail 16b along the X-axis rail 16a and moving the slider 17 along the Y-axis rail 16b, the injection nozzles 11a and 11b fixed to the slider 17 can be moved to arbitrary positions. Is something that can be done. And
The warp detection sensor 13 detects the direction and degree of warpage of the printed wiring board 1, and at the same time, the printed wiring board 1
Detect which part of the warp. In some cases, a part of the printed wiring board 1 may have a concave warp and the other part may have a convex warp. In this case, it is also detected which part is concave and which part is convex. Based on the information obtained by detecting in this manner, the control device causes the injection device 6 to
Of the pair of jet nozzles 11a and 11b, the jet nozzles 11a and 11b for jetting the cooling medium 2 are moved to positions corresponding to the warped portions of the printed wiring board 1.
Cooling medium 2 is applied to the warped portion of printed wiring board 1.
To spray. For example, as shown in FIG. 5, the cooling medium 2 is sprayed from the jet nozzles 11a and 11b to the concave warped portion of the printed wiring board 1. After partially blowing the cooling medium 2 onto the printed wiring board 1 in this manner, the cooling plates 12a and 12b of the cooling press device 7 are processed in the same manner as described above.
Press the printed wiring board 1 in between while quenching
It is to correct the warp. Since the printed wiring board 1 partially has the metal foil, a warp often occurs in a part of the printed wiring board 1, but when the entire surface of the printed wiring board 1 is cooled at the same temperature, the warpage occurs. There is a possibility that warping may occur in the non-existing portion, but the cooling medium 2 is formed only in the portion where the printed wiring board 1 is thus warped.
By spraying, the partial warp of the printed wiring board 1 can be easily corrected.

FIG. 6 shows another embodiment in which the cooling medium 2 is partially sprayed on the printed wiring board 1. In this embodiment, the spray nozzles 11a, 11a,
11b is provided with a plurality of nozzle units 18 arranged in a line, and each nozzle unit 18 is independently opened and closed by a solenoid valve or the like. Each nozzle unit 18
Are provided at intervals of 5 mm to 50 cm, and the cooling medium 2 is ejected only from the nozzle unit 18 in which the solenoid valve is open. Then, the cooling medium 2 is sprayed onto the printed wiring board 1 from the jet nozzles 11a and 11b while the printed wiring board 1 heated by the heating device 4 is being sent by a carrying device such as a carrying conveyor. At this time, the injection nozzle 11
Among the nozzle units 18 of a and 11b, control is performed so that only some of the nozzle units 18 are opened according to the warp of the printed wiring board 1, and the timing is adjusted with the feeding of the printed wiring board 1 by the transport device. Thus, the cooling medium 2 can be sprayed onto the warped portion of the printed wiring board 1. In selectively ejecting the cooling medium 2 from the nozzle unit 18, in addition to performing switching between ejection and stop of ejection using the solenoid valve as described above, the cooling medium 2 is always ejected from each nozzle unit 18. , A partition plate is provided for the cooling medium 2 at a portion which does not need to be sprayed onto the printed wiring board 1.
The direction may be changed so as not to be sprayed onto the printed wiring board 1, or a shutter may be provided at the tip of each nozzle unit 18 so as to switch between jetting and jetting stop. Further, in this way, when the cooling medium 2 is partially sprayed on the printed wiring board 1,
A hood may be used to prevent diffusion of the cooling medium 2. The hood may have any shape such as a square or a circle, but in order to achieve close contact with the printed wiring board 1, a flexible brush or a rubber plate may be provided at the tip of the hood.

In each of the above embodiments, only the cooling medium 2 is blown onto the printed wiring board 1. However, the cooling medium 2 is blown onto one side of the printed wiring board 1 and the other side of the printed wiring board 1 is blown. You may make it spray the heating medium 3 on. FIG. 7 shows an example thereof, in which the cooling medium 2 is sprayed on one concave surface of the printed wiring board 1 and the heating medium 3 is sprayed on one convex surface of the printed wiring board 1. The heating medium 3 is used by heating it to a temperature near the glass transition point of the printed wiring board 1 or higher, and prevents the temperature of the surface of the printed wiring board 1 opposite to the side on which the cooling medium 2 is sprayed from decreasing. Is what you can do.

Further, in each of the above-mentioned embodiments, the cooling plates 12a and 12b of the cooling press device 7 formed into flat plates are used. However, as shown in FIG. 8A, cold air is supplied into the hollow portion 19a. It is also possible to use cooling plates 12a and 12b formed by projecting a large number of pressing pins 20 in the hollow plate 19 and forming discharge holes 21 between the pressing pins 20. In this case, as shown in FIG. 8B, the cooling plates 12a, 12 are provided between the tips of the pressing pins 20.
The printed wiring board 1 is pressed with b and the hollow board 19
The printed wiring board 1 is cooled by the cold air discharged from the discharge holes 21.

The printed wiring board 1 may be fed horizontally in each step of heating by the heating device 4, spraying the cooling medium 2 and cooling press by the cooling press device 7, or may be fed vertically. However, either may be used. In the embodiment of FIG. 9, as the cooling medium 2 or the heating medium 3, a high-viscosity resin 22 such as silicone resin, Teflon resin, acrylic resin, epoxy resin, elastomer resin, or wax is used.
Is sprayed from the jet nozzles 11a and 11b, and the high-viscosity resin 22 is partially sprayed and adhered to the surface of the printed wiring board 1 heated by the heating device 5. The adhesion thickness of the high-viscosity resin 22 is 3 μm
It is preferably about 3 mm. The high-viscosity resin 22 is sprayed and attached to the convex warped surface of the printed wiring board 1 as shown in FIG. 9A. Next, the printed wiring board 1 to which the high-viscosity resin 22 is attached is shown in FIG. 9B. As described above, by sandwiching between the cooling plates 12a and 12b of the cooling press device 7 and pressing while cooling, the printed wiring board 1 is displaced in the direction opposite to the warp, and the warp of the printed wiring board 1 is corrected. It is a thing. Then, as shown in FIG. 9C, the printed wiring board 1 whose warpage has been corrected is taken out from the cooling press device 7, and then the high-viscosity resin 22 is peeled off from the printed wiring board 1, so that the printed wiring board 1 is subjected to the next step or the like. Can be supplied. In this way, since the warp is corrected by causing the printed wiring board 1 to warp in the opposite direction to the warp, it is possible to obtain a high effect of re-warping, and as the high-viscosity resin 22, It is preferable to use the heating medium 3 because it can prevent the temperature of the printed wiring board 1 from decreasing.

By applying this high-viscosity resin 22, as shown in FIG.
0 (a) and (b), the high-viscosity resin 22 is attached to the front and back surfaces of the printed wiring board 1 and is pressed between the cooling plates 12a and 12b as shown in FIG. The plate 1 can be shaped into any shape.

[0022]

As described above, according to the present invention, after heating the printed wiring board, the cooling medium is sprayed on one surface of the printed wiring board, and thereafter the printed wiring board is pressed while being cooled. By blowing a cooling medium onto one side of the printed wiring board prior to cold-pressing the board, it is possible to reduce the warp of the printed wiring board in advance, and it is possible to adjust the temperature of the cooling board without adjusting the temperature of the printed wiring board. The warp can be corrected.

Further, since the cooling medium is partially sprayed on one surface of the printed wiring board, when the printed wiring board is partially warped, it is possible to correct the partial warping of the printed wiring board. It can be done easily. Furthermore, since the cooling medium is sprayed onto one surface of the printed wiring board and the heating medium is sprayed onto the other surface of the printed wiring board, the heating medium can prevent the temperature of the printed wiring board from decreasing.

[Brief description of drawings]

FIG. 1 is a schematic front view of an embodiment of the present invention.

FIG. 2 is a perspective view of the above injection device.

FIG. 3 is a schematic front view showing the injection of the cooling medium of the above.

FIG. 4 is a perspective view of an injection device according to another embodiment of the present invention.

FIG. 5 is a schematic front view showing the injection of the cooling medium of the above embodiment.

FIG. 6 is a schematic plan view of still another embodiment of the present invention.

FIG. 7 is a schematic front view showing injection of a cooling medium and a heating medium according to still another embodiment of the present invention.

FIG. 8 shows still another embodiment of the present invention,
(A) is a perspective view of a cooling plate, (b) is sectional drawing which shows a cooling press.

FIG. 9 shows still another embodiment of the present invention,
(A) thru | or (d) are each a schematic front view.

FIG. 10 shows still another embodiment of the present invention, in which (a) is a perspective view and (b) and (c) are schematic front views.

[Explanation of symbols]

 1 Printed wiring board 2 Cooling medium 3 Heating medium

Claims (3)

[Claims] 1. A method for straightening a warp of a printed wiring board, which comprises heating a printed wiring board, blowing a cooling medium onto one surface of the printed wiring board, and thereafter pressing the printed wiring board while cooling the printed wiring board. 2. The method for correcting warpage of a printed wiring board according to claim 1, wherein a cooling medium is partially sprayed on one surface of the printed wiring board. 3. The method for correcting warpage of a printed wiring board according to claim 1, wherein the cooling medium is sprayed on one surface of the printed wiring board and the heating medium is sprayed on the other surface.