JP3174764B2 - Manufacturing method of printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a printed wiring board, and more particularly to a technique for simultaneously manufacturing a plurality of printed wiring boards using a multi-piece board.

[0002]

2. Description of the Related Art Conventionally, as a method of manufacturing a printed wiring board, a wiring pattern or the like is formed on the surface of a substrate, and finally, an insulating surface resist (or a permanent resist or a solder resist) is formed on the surface of the substrate. After removing unnecessary portions of the resist such as electrode portions, the surface resist is cured.

[0003] The surface resist is formed of a photo-setting or thermosetting resin or the like, but may shrink during the curing, causing the substrate to warp. In order to prevent or correct this, conventionally, Japanese Patent Application Laid-Open No. 6-2835
No. 76, a method in which a flexible substrate is cured in a state of being wound in a coil shape with a solder resist coating surface outside, a plastic layer on a metal foil as disclosed in JP-B-62-13066. After curing,
Japanese Patent Laid-Open No. 55-534
As disclosed in Japanese Patent Publication No. 84-84, there is disclosed a method in which both ends of a warped printed board are held and heating is performed while applying an external force in a direction opposite to the warpage.

[0004] By the way, in recent years, there has been a demand for miniaturization of various parts and a demand for portability of various devices, etc., so that miniaturization and thinning of printed wiring boards have been required. For this reason, a large number of small printed boards, such as a few cm square, are also being manufactured. In the case of such a small printed board, a large number of wiring portions are formed in a relatively large large-sized board, and completed. There is an increasing number of manufacturing methods that use multi-cavity substrates in which individual wiring portions are later separated by cutting or the like.

[0005]

However, since a device incorporating a small-sized printed wiring board manufactured by using a multi-piece substrate as described above is also often downsized, the printed wiring board is often used. There is also a very strict requirement for the flatness of the film. However, conventionally, in the case of a multi-cavity board, the correction of the warp is performed for each individual printed wiring board, which takes a lot of trouble, and since each printed wiring board is small, the effect of correcting the warp is also reduced. There was a problem that it was difficult to obtain.

Accordingly, as disclosed in Japanese Patent Application Laid-Open No. 57-20492, after the individual printed wiring boards are pressed out of the multi-piece board, they are fitted into the multi-piece board again by pushback, and in this state, the individual printed circuit boards are printed. A method has been proposed in which a multi-piece substrate other than a wiring board is subjected to a press starring to flatten the entire multi-piece board. However, this method has a problem that the effect of improving the warpage is small and is not always sufficient for the current required level.

In addition, when heat treatment is performed after warpage occurs as described above, a separate step is required, and a long heat treatment is required to obtain a sufficient effect. There is a problem that the manufacturing cost is increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method of manufacturing a printed wiring board using a multi-piece board in which the warpage of each printed wiring board is reduced as compared with the conventional method. It is an object of the present invention to provide a method which can be carried out easily.

[0009]

Means taken by the present invention to solve the above-mentioned problem is to form a plurality of wiring portions along a plate surface of a substrate and then to separate the wiring portions from each other. In a method for manufacturing a printed wiring board to be formed,
After the wiring portion is formed on the substrate, an uncured or semi-cured surface protection layer is formed on the surface of the wiring portion, and then a plate having a larger coverage area of the surface protection layer on the wiring portion is formed. The surface protection layer is cured while the substrate is kept curved in a predetermined direction so that the surface becomes convex.

[0010] The plate surface having the larger surface area of the surface protective layer has a large shrinkage force when the surface protective layer is cured, and a concave warp is generated. According to various experiments performed by the present inventors,
In the method of manufacturing a printed wiring board using a multi-piece board, the amount of warpage of each wiring portion after being separated by performing a hardening treatment of the surface protection layer in a state where the multi-piece board is entirely curved. It has been found that it can be reduced. For this reason, the final warpage of the printed wiring board is reduced by performing the curing treatment of the surface protection layer in a state where the surface of the multi-piece substrate having the larger coverage area of the surface protection layer is convexly curved. Therefore, it is not necessary to perform a warp correction process for each printed wiring board, and it is possible to efficiently manufacture a printed wiring board with less warpage without adding a separate process. Will be possible.

In the first aspect of the present invention, it is preferable that the substrate is curved by keeping a distance between both ends of the substrate narrow. By narrowing the gap between both ends of the multi-piece board, the multi-piece board can be bent with good reproducibility by adjusting the gap between both ends, and without applying excessive stress to the multi-piece board. , Can be uniformly curved.

3. A method according to claim 2, further comprising the step of: providing a pair of holding frames capable of holding both ends of the substrate, adjusting and fixing the mutual interval between the holding frames, and setting the mutual interval to both ends of the substrate. It is preferable that the surface protection layer is hardened in a state where both ends of the substrate are engaged with the holding frame. The degree of curvature of the substrate can be precisely adjusted by the distance between the pair of holding frames.

[0013] In any one of the first to third aspects, it is preferable that a bending direction of the substrate is set to a longitudinal direction of the substrate. By bending the longitudinal direction of the substrate, the degree of curvature of the substrate can be easily set more precisely, and the burden on the substrate due to the bending can be reduced. Warpage can also be reduced.

It is preferable that a pair of holding pieces for engaging and holding both ends of the substrate are formed at a predetermined interval in the holding frame. It is preferable that the predetermined interval is set so as not to apply a deformation stress to both ends of the curved substrate. Further, it is preferable that the holding frame is configured to be adjustable in position with respect to a supporting portion such as a frame.

[0015]

Next, an embodiment of a method for manufacturing a printed wiring board according to the present invention will be described in detail. FIG.
1 shows a multi-piece board 10 used when manufacturing the printed wiring board of the present embodiment. Multi-cavity board 1
A plurality of wiring portions 20 are formed on the surface of the
In 0, desired wiring patterns, conductive pads, and the like are formed. The pattern structures in the plurality of wiring portions 20 may be the same as each other, or may be different from each other.

The manufacturing steps common to the prior art in this embodiment are roughly as follows. First, the pattern structure of the plurality of wiring portions 20 arranged on the plate surface of the multi-piece substrate 10 is completed. Next, a thermosetting liquid solder resist is applied to the entire surface of the multi-piece substrate 10 by printing or spin coating on the upper surface and / or lower surface thereof, and in order to obtain a certain hardness of the surface if necessary. To perform a temporary curing treatment (for example, a heating treatment at 80 ° C. for about 25 minutes),
The surface resist layer is brought into a semi-cured state. Thereafter, a dry laminate film having a photo-curing type resist layer is laminated, and unnecessary portions of the surface resist layer are exposed by respective steps of exposure and development, and removed by a solvent or the like. In addition,
Instead of the step of patterning the surface resist layer, a solder resist can be selectively applied to the upper surface and / or lower surface of the multi-piece substrate 10 from the beginning by a screen printing method or the like.

Here, a typical plane pattern of the surface resist layer in the wiring section 20 in the present embodiment will be described. FIGS. 4A and 4B show plane patterns of the surface resist layers 21 and 22 on the upper surface 20a and the lower surface 20b of the wiring section 20 of the present embodiment, and FIG. It shows a cross section. Upper surface 2
In 0a, only a small area is covered with the surface resist layer 21, but the surface resist layer 22 is formed entirely on the lower surface 20b. For this reason,
When the surface resist layers 21 and 22 are cured as they are, the shrinkage force at the time of curing of the solder resist causes the shrinkage force of FIG.
As shown in the figure, the individual wiring portions 20 extend along the bowl shape on the side of the lower surface 20b. In this example, the upper surface 20a of the wiring portion 20
Although the surface resist layers 21 and 22 are formed on both the lower surface 20b and the lower surface 20b, the surface resist layer may be formed only on one of them.

In this embodiment, in order to prevent the warpage, the multi-piece substrate 10 is mounted on a jig 30 shown in FIG. The jig 30 includes a frame 31 and a frame 3
1, a holding frame 32 that can be attached and fixed at an appropriate position in the longitudinal direction from the front left side to the rear right side in the drawing,
33 are provided. The holding frames 32 and 33 may be configured to engage with an engaging groove or an engaging rib (not shown) provided on the frame 31 or may be guided along the frame 31 so as to be movable along a predetermined distance. A fastening means for fixing to the frame 31 at the position may be provided. Plural sets of a pair of vertically extending holding pieces 32a, 33a are fixed to the holding frames 32, 33 in the width direction, and a large number of one pieces are provided between the pair of holding pieces 32a, 33a. Both ends of the substrate 10 are engaged. The holding pieces 32a and 33a are provided with a predetermined mutual interval to support the end of one multi-piece substrate 10 from both front and back sides. In this case, when the end face of the multi-piece substrate 10 is supported on one of the bases of the pair of holding pieces, the plate face of the multi-piece board 10 does not contact the other end, and the multi-piece board 10 Without impairing the curved state of
Alternatively, it is preferable that the interval is set so that no stress is applied to the multi-piece substrate and the substrate is not damaged.

By making the distance between the holding frames 32 and 33 in the jig 30 slightly smaller than, for example, the width of the multi-piece board 10 in the longitudinal direction, the multi-piece board 10 is curved in the longitudinal direction as shown in the figure. It is kept in the state. At this time, in the case of the multi-piece substrate 10 provided with the wiring portion 20 shown in FIGS. 4 and 5, the multi-piece substrate 1 on which the lower surface 20b having a large coverage area of the surface resist layer 22 is formed.
The surface of 0 is curved so as to be convex. When only one of the upper surface and the lower surface is coated with the surface resist layer, the one surface is curved so as to be convex.

The degree of curvature is determined by the difference in the material and dimensions of the multi-cavity substrate and the wiring portion, the difference in the area covered by the surface resist layer,
Since there are various optimum values depending on the thickness of the surface resist layer and the like, the values are appropriately set while observing the results. In the case of the present embodiment, for example, the thickness is 0.44 mm, and the plane dimension is 340 mm.
A board with a large number of × 255 mm glass epoxy substrates
No. 0, and a number of 24.74 mm square wiring portions were arranged on the plate surface. Then, in the jig 30, the length 34
The distance between both ends of the multi-piece substrate 10 of 0 mm is 330 m
m, the holding frames 32 and 33 were fixed. In other words, the multi-piece substrate 10 is engaged with the holding pieces 32a, 33a, thereby forming the board in the longitudinal direction, that is, 340 mm.
Is maintained such that the distance between both ends of the side is shortened by about 10 mm.

In this way, the multi-piece substrate 10 is set in the jig 30 and introduced into the heating furnace, for example, 150
C. for about 60 minutes to form a surface resist layer 2
Dry and cure 1,22. Thereafter, the multi-piece substrate 10 is taken out of the furnace while being set on the jig 30, and cooled at room temperature. Finally, the multi-piece substrate 10 sufficiently cooled to a temperature close to room temperature is taken out of the jig 30.

From the multi-piece substrate 10 processed as described above, the individual wiring portions 20 are punched by pressing or the like, or cut by a laser beam or the like to separate the individual printed wiring boards. As shown in FIG. 3, the printed wiring board manufactured as described above has a total of five surfaces including a highest part (circled in the figure) and four corners (x in the figure) when arranged on a flat surface. Measure the height and calculate the maximum amount of warpage (height difference) of the printed wiring board individually from these relationships,
(Maximum warpage / length of one side of printed wiring board) x 100
The warpage rate (%) was obtained by the following. Table 1 shows the results of totalizing and averaging the values for each of the multi-piece substrates. The other conditions are exactly the same as those of the above-described embodiment, but the results obtained by performing the above-described curing processing without using the jig 30 are shown as comparative examples.

[0023]

[Table 1] Overall warpage rate (%) of printed wiring board Substrate A Maximum value of warpage rate Minimum value of warpage rate Average value of warpage rate Embodiment 0.438 0.158 0.309 Comparative Example 0.690 0.440 0.560 Substrate B Maximum value of warpage ratio Minimum value of warpage ratio Average value of warpage ratio Embodiment 0.359 0.128 0.243 Comparative Example 0.572 0.369 0.477 Substrate C Maximum value of warpage ratio Warpage Minimum value of rate Average value of warpage rate Embodiment 0.451 0.175 0.271 Comparative example 0.645 0.372 0.498 Maximum value of overall warpage rate Minimum value of warpage rate Average value of warpage rate Embodiment 0 .451 0.128 0.274 Comparative Example 0.690 0.369 0.512

As described above, in any of the substrates,
In the present embodiment, the amount of warpage is significantly reduced as compared with the comparative example, and an improvement in the warpage of 45 to 50% is seen. Also,
An overall average of 46.47% was obtained. As a result, the defect rate has been reduced to 1 to 2%, whereas the defect rate of 30 to 50% depending on the amount of warpage has conventionally been exhibited.

Next, ten pieces are randomly extracted from each of the above printed wiring boards for each of the multi-piece boards, and as shown in FIGS.
And the amount of warpage between the direction X and the direction Y on the plate surface orthogonal to the direction X were separately calculated and tabulated in the same manner as described above. Table 2 shows the results.
(X direction) and Table 3 (Y direction).

[0026]

Table 2 Amount of warpage of printed wiring board in X direction (mm) Substrate A Maximum value of warpage Minimum value of warpage Average value of warpage Embodiment 0.0777 0.0490 0.0693 Comparative Example 0.1255 0 .1032 0.1096 Substrate B Maximum amount of warpage Minimum value of amount of warping Average value of amount of warping Embodiment 0.0728 0.0356 0.0507 Comparative Example 0.1109 0.0794 0.0956 Substrate C Maximum amount of warpage Value Minimum value of the amount of warpage Average value of the amount of warpage Embodiment 0.0676 0.0380 0.0523 Comparative Example 0.1109 0.0721 0.0949

[0027]

Table 3 Amount of warpage of printed wiring board in Y direction (mm) Substrate A Maximum value of warpage Minimum value of warpage Average value of warpage Embodiment 0.0897 0.0565 0.0794 Comparative Example 0.1170 0 .1011 0.1091 Substrate B Maximum value of the amount of warpage Minimum value of the amount of warpage Average value of the amount of warpage 0.0881 0.0314 0.0591 Comparative Example 0.1056 0.0853 0.0927 Value Minimum value of the amount of warpage Average value of the amount of warpage Embodiment 0.0882 0.0430 0.0650 Comparative Example 0.1113 0.0793 0.0937

From the data described in Tables 2 and 3 above,
The amount of warpage in the X direction with respect to the comparative example in the embodiment is 43
%, And the amount of warpage in the Y direction was improved by 31%.
Therefore, according to the present embodiment, the multi-piece substrate 10
It has been found that not only the warp in the bending direction but also the warp in the direction perpendicular thereto can be reduced.

In the present embodiment, since the surface resist layer is cured while being bent in the longitudinal direction of the multi-piece substrate, the adjustment of the degree of curvature and reproducibility can be easily obtained, and the number of substrates can be easily obtained. This has the effect of reducing the load on the individual substrate and also reducing the warpage in a direction different from the bending direction.

In the above embodiment, a material mainly composed of a thermosetting resin is used as the surface resist layer. However, if there is no problem in other processes or products, a photocurable resin or a thermoplastic resin is used. The present invention is similarly effective, since a shrinkage phenomenon during curing or drying occurs even in a surface resist layer made of these materials.

[0031]

As described above, according to the present invention, the hardening treatment of the surface protective layer is performed in a state where the surface of the multi-piece substrate having the larger coverage area of the surface protective layer is curved in a convex shape. As a result, the final amount of warpage of the printed wiring board can be reduced, so that it is not necessary to perform the warp correction processing for each individual printed wiring board, so that an additional process can be efficiently performed. Thus, it is possible to manufacture a printed wiring board with less warpage.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing the structure of a jig 30 used in a printed wiring board manufacturing method according to an embodiment of the present invention.

FIG. 2 is a plan view of the multi-piece substrate of the embodiment.

FIG. 3 is an explanatory diagram showing a method for measuring the amount of warpage of the printed wiring board manufactured according to the embodiment.

FIG. 4 is a plan view (a) and a bottom view (b) showing a surface state of the printed wiring board manufactured according to the same embodiment.

FIGS. 5A and 5B are cross-sectional views showing a cross-sectional structure of a printed wiring board manufactured according to the same embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Multi-piece board 20 Wiring part (printed wiring board) 21, 22 Surface resist layer 30 Jig 31 Frame 32, 33 Holding frame 32a, 33a Holding piece

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H05K 3/00 H05K 3/28

Claims (2)

(57) [Claims] 1. A rectangle based on glass epoxy resin
The longitudinal direction X of the substrate on the plate surface of the
After forming a plurality of wiring portions vertically and horizontally along the intersecting direction Y , in a method of manufacturing a printed wiring board formed by separating each wiring portion from each other, after forming the wiring portion on the substrate, After forming an uncured or semi-cured surface protection layer on the surface of the wiring portion, the substrate is formed such that the surface of the surface protection layer on the wiring portion having a larger coverage area becomes convex. Keep the distance between both ends of the
A method of manufacturing the printed wiring board , wherein the surface protection layer is cured while the substrate is curved along the longitudinal direction X. 2. The method according to claim 1, wherein both ends of the substrate are
A pair of holding frames that can be held are provided, and a mutual interval between the holding frames is set.
Adjustable and fixable so that said mutual spacing is
Adjust smaller than the distance between both ends of the substrate,
In the state where both ends of the substrate are engaged,
A method for producing a printed wiring board, comprising curing .