JP5082821B2 - Through board - Google Patents

Description

  The present invention relates to a through-hole substrate in which wirings provided on both front and back surfaces of a substrate made of prepreg are made conductive by a through-hole penetrating the substrate in the thickness direction.

  Conventionally, as this type of penetration substrate, a substrate made of a plurality of layers of prepreg formed by impregnating a glass cloth, which is a woven fabric of glass fiber, and a surface layer on which electronic components are provided by soldering on both sides of the substrate There has been proposed a printed circuit board including a wiring, an inner layer wiring provided inside the substrate, and a through hole provided through the prepreg in the stacking direction to electrically connect the surface layer wiring and the inner layer wiring (for example, a patent) Reference 1).

  When an electronic component is mounted on the outer surface of such a printed circuit board and connected by soldering, the solder connection part deteriorates due to thermal stress in the actual use environment, which is important for product reliability. It is a problem.

For example, in the above-mentioned Patent Document 1, a special cloth called a nanako weave is used to increase the driving density of the cloth. As a result, the amount of resin in the prepreg is reduced, the coefficient of thermal expansion of the substrate is reduced, and the coefficient of thermal expansion of the electronic component such as a bare chip on the substrate is made closer to improve the connection reliability.
JP-A-7-66513

  As described above, conventionally, measures have been taken for the substrate in the idea that the coefficient of thermal expansion of the substrate is matched to the electronic component mounted on the substrate, but in recent years, in the through substrate made of prepreg, Therefore, it is desired to further extend the life of the solder connection.

  Thus, the present inventors diligently studied and found experimentally that not only the thermal expansion coefficient of the substrate but also the unevenness of the glass cloth used for the substrate has an effect on the solder connection life. . In particular, when the solder joint portion is miniaturized and the joint portion has a size equal to or smaller than the uneven pitch (for example, 0.5 mm or less) of the glass cloth, the influence is remarkable.

  The present invention has been made in view of the above problems, and in a through-hole substrate in which wirings provided on both front and back surfaces of a substrate made of prepreg are made conductive by a through-hole penetrating the substrate in the thickness direction, An object of the present invention is to provide a penetrating substrate that reduces the influence of unevenness due to cloth and has excellent solder connection reliability.

In order to achieve the above object, in the invention described in claim 1, in the through-hole substrate, the surface layer portion (20) is also made of a prepreg formed by impregnating the glass cloth (11) with the resin (12). The outer surface of (20) has an unevenness smaller than the surface of the prepreg (13) constituting the substrate portion (10), and the intersection of yarns in the surface layer portion as the pitch of the unevenness and the intersection adjacent to this And an electronic component is solder-bonded to the surface of the through-hole substrate, and the size of the unevenness in the joint in the pitch direction is 0.5 mm or less .

  According to this, since the outer surface of the surface layer part (20) has smaller irregularities than the surface of the prepreg (13) constituting the substrate part (10), the influence of the irregularities caused by the glass cloth (11) is reduced, and the solder connection reliability is reduced. It can be made excellent.

  Here, as in the invention described in claim 2, the surface layer portion (20) is also made of a prepreg formed by impregnating the glass cloth (11) with the resin (12), and the prepreg constituting the surface layer portion (20). The yarn (11a) constituting the glass cloth (11) of the laminate is a laminate of laminates in cross section as compared with the yarn (11a) constituting the glass cloth (11) of the prepreg (13) constituting the substrate portion (10). It can be a flat yarn whose direction dimension is shorter than the direction perpendicular to the stacking direction.

  Further, as in the invention described in claim 3, the surface layer portion (20) is also made of a prepreg formed by impregnating the glass cloth (11) with the resin (12), and the prepreg constituting the surface layer portion (20) is formed. The distance (t1) between the outer surface and the glass cloth (11) inside the prepreg is the distance between the outer surface of the prepreg (13) constituting the substrate portion (10) and the glass cloth (11) inside the prepreg (13). It can be larger than the distance (t2).

Further, as in the invention described in claim 4 , the surface layer portion (20) is also composed of a prepreg formed by impregnating the glass cloth (11) with the resin (12), and the prepreg constituting the surface layer portion (20) is formed. The yarn constituting the glass cloth (11) can be made smaller in diameter than the yarn constituting the glass cloth (11) of the prepreg (13) constituting the substrate portion (10).

By using the surface layer portion (20) as in the second to fourth aspects, the outer surface of the surface layer portion (20) has smaller irregularities than the surface of the prepreg (13) constituting the substrate portion (10). Can be.

  In addition, the code | symbol in the bracket | parenthesis of each means described in the claim and this column is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are given the same reference numerals in the drawings in order to simplify the description.

(First embodiment)
FIG. 1 is a schematic cross-sectional view of a through substrate 100 according to the first embodiment of the present invention. The through-hole substrate 100 is roughly formed by laminating the surface layer portion 20 on both the front and back surfaces of the substrate portion 10, and the inner layer wiring 30 provided inside the laminated body and the surface layer wiring 40 provided on the surface include the laminated layer It is configured to be electrically connected by a through hole 50 penetrating in the body stacking direction.

  The substrate portion 10 is made of a prepreg 13 formed by impregnating a glass cloth 11, which is a glass fiber fabric, with a resin 12 such as an epoxy resin. The prepreg 13 can be manufactured by stacking the required number of sheets and thermosetting to produce a molded product having excellent performance. However, the prepreg 13 constituting the substrate unit 10 may be a single layer or a plurality of layers. It may be done. In the example shown in FIG. 1, the substrate unit 10 is formed by laminating two layers of prepregs 13.

  The surface layer portion 20 is a layered layer provided on the surface of the substrate portion 10 (upper surface of the substrate portion 10 in FIG. 1) and the back surface of the substrate portion 10 (lower surface of the substrate portion 10 in FIG. 1). It is. Here, the surface layer portion 20 is also configured as a prepreg formed by impregnating the glass cloth 11 with the resin 12.

  Although the inner layer wiring 30 is provided on the substrate unit 10, in this embodiment, the inner layer wiring 30 is provided on the surface of the two-layer prepreg 13 constituting the substrate unit 10. Further, the surface layer wiring 40 is provided on the outer surface of the surface layer portion 20 constituting both the front and back surfaces of the through-hole substrate 100.

  Electronic components (not shown) such as IC chips, capacitors and resistors are soldered to the surface layer wiring 40. These inner layer wiring 30 and surface layer wiring 40 form a desired wiring pattern by etching, for example, Cu foil.

  Further, the through hole 50 is provided so as to penetrate the laminated body including the substrate portion 10 and the surface layer portion 20 in the laminating direction. Thus, the through-hole 50 penetrates continuously from the front surface to the back surface of the through-hole substrate 100, thereby electrically connecting the surface layer wiring 40 and the inner layer wiring 30. The through hole 50 is formed by, for example, Cu plating.

  Such a through-hole substrate 100 is manufactured by, for example, the following general method. Cu foils to be the wirings 30 and 40 are provided on the surfaces of the prepregs 13 constituting the substrate unit 10 and the surface layer unit 20. For the inner layer wiring 30, a wiring pattern is formed by etching or the like.

  Then, the prepregs 13 are stacked, and then the Cu foil located on the outer surface of the surface layer portion 20 is patterned by etching or the like to form the surface layer wiring 40. Next, a hole constituting the through hole 50 is drilled with respect to the laminate, and the through hole 50 is formed by applying Cu plating to the hole. In this way, the through substrate 100 is completed.

  Here, FIG. 2 is a schematic plan view of the prepreg glass cloth 11 constituting the surface layer portion 20 in the through-hole substrate 100, and FIG. 3 is an outline of the yarn 11a of the prepreg glass cloth 11 constituting the surface layer portion 20. FIG. 4 is a schematic plan view of the glass cloth 11 of the prepreg 13 constituting the substrate unit 10. In FIG. 3, the cross-sectional shape of the yarn 11 a of the glass cloth 11 of the prepreg 13 constituting the substrate unit 10 is also shown by a broken line.

  Here, the yarn is a bundle of a certain number of monofilaments. As shown in FIGS. 2 and 4, the glass cloth 11 has a weave yarn 11a as a weft yarn and a yarn 11a as a warp yarn woven in a mesh shape. Is configured.

  Here, the glass cloth 11 has irregularities as shown in FIG. 1, but the irregularities are caused by the intersection of the vertical and horizontal yarns 11a. In general, as shown in FIG. 4, the pitch P of the unevenness of the glass cloth 11 corresponds to the distance between the intersecting portion of the yarn 11a and the intersecting portion adjacent to the intersecting portion. 5 mm or less.

  As shown in FIGS. 2 to 4, in this embodiment, the yarn 11 a constituting the glass cloth 11 of the prepreg constituting the surface layer portion 20 constitutes the glass cloth 11 of the prepreg 13 constituting the substrate portion 10. Compared with the yarn 11a, it is a flat yarn in which the dimension of the laminated body in the cross section is shorter than the direction perpendicular to the lamination direction.

  Specifically, as shown in FIG. 3, the yarn 11 a constituting the glass cloth 11 of the prepreg constituting the surface layer portion 20 is compared with the yarn 11 a constituting the glass cloth 11 of the prepreg 13 constituting the substrate portion 10. Thus, it is flat in the direction perpendicular to the laminating direction (that is, the plane direction of the glass cloth 11). And the glass cloth 11 of the surface layer part 20 knitted by the flat yarn 11a in this way has an unevenness suppressed smaller than the glass cloth 11 of the substrate part 10.

  For this reason, in the through-hole wiring board 100 of the present embodiment, the outer surface of the surface layer portion 20 has smaller irregularities than the surface of the prepreg 13 constituting the substrate portion 10. That is, in the conventional penetrating substrate, the unevenness of the glass cloth of the substrate portion is inherited as it is on the outer surface of the surface layer portion 20, that is, the surface layer wiring, but in this embodiment, the degree of unevenness of the surface layer wiring 40 is It is smaller than the unevenness of the glass cloth 11.

  As described above, according to the present embodiment, the outer surface of the surface layer portion 20 has smaller unevenness than the surface of the prepreg 13 constituting the substrate portion 10, so that the influence of the unevenness due to the glass cloth 11 is reduced and the surface layer wiring 40 is formed. When an electronic component is soldered, the solder connection reliability is superior to that of the prior art.

  Next, a specific effect is shown about the penetration board 100 of this embodiment, comparing with a comparative example. This comparative example corresponds to a conventional through-hole substrate made of one kind of prepreg, and specifically, the whole is constituted by a prepreg 13 made of a glass cloth 11 constituting the substrate portion 10 as shown in FIG. It is what has been.

  FIG. 5 is a diagram showing the results of actual measurement of the average thermal expansion coefficient α of the substrates for the through-hole substrate 100 of the present embodiment and the through-hole substrate of the comparative example. Here, although the thermal expansion coefficient α is a mixture of a glass component and a resin component, the through substrate is a thermal expansion coefficient of the entire substrate obtained by averaging them.

  The thermal expansion coefficient was measured by a thermal cycle test in which -30 ° C and 110 ° C were repeated for 30 minutes each. As a result, the through-hole wiring board 100 of the present embodiment had a slightly smaller thermal expansion coefficient than the comparative example, but there was no significant difference.

  FIG. 6 is a diagram showing a result of investigating a crack rate by a thermal cycle with respect to each through-hole substrate of this embodiment and the comparative example by soldering electronic components. Here, 128-pin QFN (quad-flat-non-lead-package) was used as the soldering electronic component.

  The QFN is mounted on the surface layer wiring 40 in the through-hole wiring board 100 of the present embodiment and the surface layer wiring in the through-hole wiring board of the comparative example with Pb-free solder, and the same thermal cycle test (−30 ° C.) as above. And a cycle of 30 minutes each at 110 ° C.). The crack rate is the rate at which the solder is broken, and the defective product standard is defined as when the solder connection portion is broken 100%.

  As shown in FIG. 6, in the through-hole substrate of the comparative example, the solder connection part is broken at 2000 cycles, whereas in the through-hole substrate 100 of the present embodiment, it is broken even at twice that cycle. Not reached.

  Accordingly, a two-dimensional model of the prepreg glass cloth used in each of the through-hole substrate 100 of the present embodiment and the through-hole substrate of the comparative example is modeled, and how the distortion generated depending on the position of the glass cloth changes is simulated. And confirmed. The result is shown in FIG.

  As a simulation model, a QFN terminal 200 is connected to a surface wiring 40 on a prepreg 13 via a solder 300 as shown in FIG. In this case, the end portion of the solder connection portion is a strain concentration portion that is a portion where the strain is concentrated. And the equivalent plastic strain amplitude as a distortion | strain was calculated | required about the case where this strain concentration part is located on the convex of the glass cloth 11 of the prepreg 13, and the case where it is located on the concave of the glass cloth 11. FIG.

  From the results shown in FIG. 7, it was found that the distortion generated at the position of the glass cloth is greatly different in the through-hole substrate of the comparative example as compared with the present embodiment. In particular, in the comparative example, it was shown that the distortion on the convexity of the glass cloth is large, and the solder connection portion is likely to be broken at a portion where the distortion is large.

  As an actual product, even when the solder connection portion is 100% broken even at one location, it becomes defective. Therefore, the through-hole substrate 100 of the present embodiment, which generally has a lower strain, has a portion where the strain becomes larger. It is more advantageous for extending the life of the solder connection than the conventional penetration substrate.

  As described above, as a result of the study of the through substrate made of the prepreg by the present inventor, the unevenness of the glass cloth in the prepreg affects the case where the electronic component is solder-connected to the surface wiring located on the substrate surface. A problem that did not exist was found, and this embodiment has been made as a countermeasure for this problem.

  In particular, when the solder joint portion is miniaturized and becomes a size equal to or smaller than the pitch P of the above-described unevenness of the glass cloth, for example, a size equal to or smaller than 0.5 mm, the influence becomes remarkable. In this embodiment, the problem is solved by reducing the unevenness of the glass cloth 11 in the surface layer portion 20 of the through-hole substrate 100.

(Second Embodiment)
FIG. 8 is a schematic cross-sectional view of the through-hole wiring board 101 according to the second embodiment of the present invention. The through-hole substrate 101 of the present embodiment is obtained by modifying the structure of the surface layer portion 20 in the through-hole substrate 100 shown in the first embodiment. Hereinafter, the difference from the first embodiment will be mainly described.

  In the first embodiment, by using the yarn 11 a that is flatter than the substrate portion 10 in the surface layer portion 20, the outer surface of the surface layer portion 20 is less uneven than the surface of the prepreg 13 that constitutes the substrate portion 10. .

  On the other hand, in the present embodiment, the surface layer portion 20 is made of a prepreg formed by impregnating the glass cloth 11 with the resin 12, and here, the outer surface of the prepreg constituting the surface layer portion 20 and the glass inside the prepreg. The distance t <b> 1 with the cloth 11 is larger than the distance t <b> 2 between the outer surface of the prepreg 13 constituting the substrate unit 10 and the glass cloth 11 inside the prepreg 13.

  In addition, these distances t1 and t2 are distances between the convex portion of the glass cloth 11 and the outer surface, ie, the convex portion of the glass cloth 11. The prepreg yarn as the surface layer portion 20 may be a yarn having the same shape as the substrate portion 10 as long as the relationship between the distances t1 and t2 described above is satisfied, or may be a flat yarn as described above. May be. For example, the surface layer portion 20 of the present embodiment is easily formed if the amount of the resin 12 is increased as compared with the prepreg 13 of the substrate portion 10.

  In the present embodiment, the relationship between the distances t1 and t2 is used to increase the thickness of the resin 12 that seals the glass cloth 11 in the surface layer portion 20 and reduce the unevenness of the glass cloth 11 that appears on the outer surface. ing. Accordingly, also in the present embodiment, the outer surface of the surface layer portion 20 has an unevenness smaller than the surface of the prepreg 13 constituting the substrate portion 10, and the influence of the unevenness due to the glass cloth 11 is reduced, so that the surface wiring 40 When electronic parts are soldered to each other, the solder connection reliability is superior to that of the prior art.

(Third embodiment)
FIG. 9 is a schematic cross-sectional view of the through-hole wiring board 102 according to the third embodiment of the present invention. The through-hole substrate 102 of the present embodiment is also a modification of the configuration of the surface layer portion 20 in the through-hole substrate 100 shown in the first embodiment. Hereinafter, the difference from the first embodiment will be mainly described.

  In the said 1st Embodiment, although the surface layer part 20 consisted of the prepreg formed by impregnating the resin 12 in the glass cloth 11 like the board | substrate part 10, the surface layer part 20 of this embodiment is a glass cloth. It is a resin layer made of polyimide 14 without containing. This resin layer is like a base of a general flexible printed circuit board.

  In the present embodiment, since the surface layer portion 20 is configured as a resin layer made of polyimide 14 and does not include glass cloth, the outer surface of the surface layer portion 20 is more uneven than the surface of the prepreg 13 constituting the substrate portion 10. It is supposed to be small.

  Also according to the present embodiment, the influence of unevenness due to the glass cloth 11 is reduced, and when an electronic component is solder-connected to the surface layer wiring 40, the solder connection reliability is superior to that of the related art. Further, since the surface layer portion 20 is made of polyimide having excellent heat resistance, the heat resistance of the surface of the through substrate 102 is also improved.

(Fourth embodiment)
FIG. 10 is a schematic cross-sectional view of the through-hole wiring board 103 according to the fourth embodiment of the present invention. The through-hole wiring board 103 of the present embodiment is also a modification of the structure of the surface layer portion 20 in the through-hole wiring board 100 shown in the first embodiment, and the difference from the first embodiment will be mainly described.

  Also in this embodiment, the surface layer portion 20 is made of a prepreg obtained by impregnating the glass cloth 11 with the resin 12. However, here, the yarn constituting the glass cloth 11 of the prepreg constituting the surface layer portion 20 includes the substrate portion 10 as the yarn. Compared with the yarn which comprises the glass cloth 11 of the prepreg 13 to comprise, a diameter dimension is small. Specifically, both the surface layer portion 20 and the yarn of the substrate portion 10 have the same cross section, for example, a circular shape, and the surface layer portion 20 has a smaller diameter.

  In the present embodiment, the outer surface of the surface layer portion 20 is configured to have smaller irregularities than the surface of the prepreg 13 constituting the substrate portion 10 by configuring the surface layer portion 20 with yarn having a small diameter. Also according to the present embodiment, the influence of unevenness due to the glass cloth 11 is reduced, and when an electronic component is solder-connected to the surface layer wiring 40, the solder connection reliability is superior to that of the related art.

(Other embodiments)
In each of the above-described embodiments, one surface layer 20 is provided on each of the front and back surfaces of the substrate unit 10, but not only one layer but two or more layers are stacked on each surface. Also good. Moreover, the board | substrate part 10 may be comprised not only with what was comprised by the prepreg 13 of multiple layers but by the prepreg of 1 layer.

It is a schematic sectional drawing of the penetration substrate concerning a 1st embodiment of the present invention. It is a schematic plan view of the glass cloth of the prepreg which comprises the surface layer part in the penetration board | substrate shown by FIG. It is a schematic sectional drawing of the yarn of the glass cloth shown by FIG. It is a schematic plan view of the glass cloth of the prepreg which comprises the board | substrate part in the penetration board | substrate shown by FIG. It is a figure which shows the measurement result of the average thermal expansion coefficient of a board | substrate about the penetration board of 1st Embodiment, and the penetration board of a comparative example. It is a figure which shows the result of having investigated the crack rate by a thermal cycle, connecting an electronic component with solder about each penetration board of this embodiment and a comparative example. It is a figure which shows the result of having calculated | required the distortion generate | occur | produced by the position of a glass cloth by simulation. It is a schematic sectional drawing of the penetration substrate concerning a 2nd embodiment of the present invention. It is a schematic sectional drawing of the penetration substrate concerning a 3rd embodiment of the present invention. It is a schematic sectional drawing of the penetration substrate concerning a 4th embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Substrate part 11 Glass cloth 11a Yarn 12 Resin 13 Prepreg 20 Surface layer part 30 Inner layer wiring 40 Surface layer wiring 50 Through hole t1 Distance between the outer surface of the prepreg constituting the surface layer part and the glass cloth inside thereof t2 The prepreg constituting the substrate part Distance between outer surface and glass cloth inside

Claims (4)

Substrate portion made of prepreg (13) of one layer or multiple layers formed by impregnating the resin (12) to the gas Rasukurosu (11) and (10),
A layered surface layer part (20) provided on both front and back surfaces of the substrate part (10);
A surface wiring (40) provided on the outer surface of the surface layer portion (20), to which an electronic component is solder-connected,
An inner layer wiring (30) provided in the substrate part (10);
A through-hole (50) provided to penetrate in the stacking direction of the laminate composed of the substrate portion (10) and the surface layer portion (20) and electrically connecting the surface layer wiring (40) and the inner layer wiring (30). )
The surface layer part (20) is also made of a prepreg formed by impregnating a glass cloth (11) with a resin (12),
The outer surface of the surface layer portion (20) has an unevenness smaller than the surface of the prepreg (13) constituting the substrate portion (10), and the intersection of yarns in the surface layer portion as a pitch of the unevenness the distance between the intersection adjacent thereto Ri der less 0.5 mm,
Electronic components on the surface of the through substrate is soldered, through the substrate size in the pitch direction of the irregularities in the joint, characterized in der Rukoto below 0.5 mm. The yarn (11a) constituting the glass cloth (11) of the prepreg constituting the surface layer portion (20) constitutes the glass cloth (11) of the prepreg (13) constituting the substrate portion (10). 2. The penetration according to claim 1, wherein, compared with the yarn (11 a) to be cut, the cross-sectional dimension is a flat yarn whose dimension in the stacking direction of the stacked body is shorter than the direction perpendicular to the stacking direction. substrate. The distance between the inside of the glass cloth of the outer surface and the prepreg of the prepregs that constitute the surface layer portion (20) (11) (t1) is an outer surface of the prepreg (13) constituting the substrate portion (10) The through-hole wiring board according to claim 1, wherein the through-hole wiring board is larger than a distance (t2) from the glass cloth (11) inside the prepreg (13). The yarn constituting the glass cloth (11) of the prepreg constituting the surface layer portion (20) is the yarn constituting the glass cloth (11) of the prepreg (13) constituting the substrate portion (10). The through-hole substrate according to claim 1, wherein the through-hole substrate has a smaller diameter dimension.

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