JP2008159859A - Printed board and manufacturing method of printed board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a printed board to which BGAs are mounted at the same positions on both surfaces, to reduce distortion generated when heating or cooling the printed board to which the BGAs are mounted on both surfaces. <P>SOLUTION: The printed board is provided with a laminate substrate 10, a first BGA 11 mounted to the front surface of the laminate substrate 10, and a second BGA 12 mounted to the back surface of the laminate substrate 10. The mounting position of the first BGA 11 and the mounting position of the second BGA 12 are turned to positions plane-symmetrical to the laminate substrate 10. The laminate substrate 10 has a core material layer 13 at the center, and prepreg layers 14 and 15 are formed symmetrically on both surfaces. The prepreg layers 14 and 15 have depletion parts 18 and 19 at positions overlapped with the mounting position of the first BGA 11 and the mounting position of the second BGA 12. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a printed board and a method for manufacturing the printed board.

  In response to rapid technological advances in the information and communication field, semiconductor devices are strongly required to be small and light and to be low in cost. High integration and high density of semiconductor devices and their mounting substrates are essential. A BGA (Ball Grid Array) is a semiconductor device having contacts in which small ball electrodes (also called bumps) made of solder are arranged in a grid. The BGA can use the entire back surface of the IC package for connection with the substrate, so that the number of contacts with the substrate can be greatly increased. However, when the substrate on which the BGA is mounted is heated or cooled, distortion occurs due to the difference in coefficient of thermal expansion between the BGA and the substrate. This distortion may cause the solder ball of the connection part to peel off. Up to now, BGA mounting at the same position on the front and back sides may cause distortion due to the difference in thermal expansion coefficient between the BGA and the substrate, which may cause the solder pole of the connection part to peel off. There was a problem. For this reason, conventionally, as shown in FIG. 1, the BGA is not mounted at the same position on the front and back sides. In FIG. 1, a first BGA 101 having solder balls 103 is mounted on the front surface of a printed board 100, and a second BGA 102 is mounted on the back surface. The mounting position of the first BGA 101 and the mounting position of the second BGA 102 are arranged at different positions.

  As publicly known documents related to a printed circuit board on which BGA is mounted, Japanese Patent Application Laid-Open No. 2001-217514 (see Patent Document 1), Japanese Patent Application Laid-Open No. 2002-185094 (see Patent Document 2), Japanese Patent Application Laid-Open Publication No. 2004-146656 ( JP-A-2006-196874 (see Patent Document 4) and JP-A-11-298147 (see Patent Document 5) are known. The invention of the multilayer wiring board described in Patent Document 1 has a multilayer insulating layer mainly composed of a resin material. Also, a conductor pattern is provided between the surface and the insulating layer. In addition, the surface is a mounting surface on which the surface mounting component is soldered. Further, resin materials having different characteristics are employed between the insulating layer located on the mounting surface side and the insulating layer located on the opposite side.

  The invention of the BGA package mounting substrate described in Patent Document 2 includes a printed wiring board and a BGA package mounted on the printed wiring board via solder balls. In the printed wiring board, a low linear expansion coefficient material layer having a smaller linear expansion coefficient than that of the base material was disposed between three or more stacked base materials. In Patent Document 2, a buffer layer is inserted between a core material (glass epoxy substrate) and an insulating layer.

  In the invention of the multilayer wiring board described in Patent Document 3, a multilayer insulating layer having a conductor pattern between layers is provided. Moreover, the surface mounting component is equipped with the mounting part by which the surface is soldered. Further, a notch recess in which a part of the insulating layer is notched is provided at a position corresponding to the mounting portion on the side opposite to the mounting portion. Patent Document 3 aims at single-sided mounting of BGA.

  The invention of the semiconductor device described in Patent Document 4 includes a printed wiring board. The peripheral type first semiconductor package includes a first ball electrode group arranged in a peripheral first array region, and a first auxiliary ball electrode group partially provided in a region inside the first array region. And is disposed on the first surface of the printed wiring board. A peripheral-type second semiconductor package includes a second ball electrode group arranged in a peripheral second array region, and a second auxiliary ball electrode group partially provided in a region inside the second array region. And is disposed on the second surface of the printed wiring board. Furthermore, a ball electrode located at at least one corner of the first ball electrode group is disposed at a position facing the second auxiliary ball electrode group with the printed wiring board interposed therebetween. In addition, the ball electrode located at at least one corner of the second ball electrode group is disposed at a position facing the first auxiliary ball electrode group with the printed wiring board interposed therebetween. In Patent Document 4, although the BGA is mounted on both sides, the connection reliability is improved by not mounting the BGA at the same position.

  In the invention of the multilayer printed wiring board described in Patent Document 5, the inner layer material is formed by filling a through hole of a compressible porous substrate made of an aromatic polyamide impregnated with a thermosetting resin with a conductive paste. A conductive pattern is formed of metal foil bonded to both sides. The interstitial via hole has an insulating resin layer formed on both surfaces of the inner layer material, and a conductive pattern for the outer layer formed on the outer surface of the insulating resin layer in a non-through hole formed in the insulating resin layer by laser processing. And the conductive pattern of the inner layer material are connected. Patent document 5 aims at making a multilayer substrate without a through hole.

JP 2001-217514 A JP 2002-185094 A JP 2004-146656 A JP 2006-196874 A Japanese Patent Laid-Open No. 11-298147

  The subject of this invention is making the printed circuit board which mounted BGA in the same position of the both surfaces. Another object of the present invention is to reduce distortion generated when a printed board having BGAs mounted on both sides is heated or cooled. Moreover, the other subject of this invention is forming a through hole in the printed circuit board which mounted BGA on both surfaces.

  [Means for Solving the Problems] will be described below using the numbers and symbols used in [Best Mode for Carrying Out the Invention]. These numbers and symbols are added in parentheses in order to clarify the correspondence between the description of [Claims] and [Best Mode for Carrying Out the Invention]. However, these numbers and symbols should not be used for the interpretation of the technical scope of the invention described in [Claims].

  In the printed board according to the present invention, the multilayer substrate (10, 25, 30, 45) and the first BGA (11, 31) mounted on the front surface of the multilayer substrate (10, 25, 30, 45) And a second BGA (12, 32) mounted on the back surface of the multilayer substrate (10, 25, 30, 45). The mounting position of the first BGA (11, 31) and the mounting position of the second BGA (12, 32) are plane-symmetric with respect to the multilayer substrate (10, 25, 30, 45). The position becomes. In the printed board according to the present invention, the multilayer substrate (10, 25, 30, 45) has a core material layer (13, 33) in the center, and symmetrically on both sides of the prepreg layer (14, 15, 34, 35).

  In the printed board according to the present invention, each of the prepreg layers (14, 15) has a depletion portion at a position overlapping the mounting position of the first BGA (11) and the mounting position of the second BGA (12). (18, 19). In the printed board according to the present invention, the depletion portions (18, 19) are filled with a resin (21, 22) having an elastic modulus lower than that of the prepreg layers (14, 15).

  In the printed board according to the present invention, the multilayer substrate (30, 45) may be one of the mounting position of the first BGA (31) and the mounting position of the second BGA (32). A plurality of through holes (50, 51) are provided. Each of the prepreg layers (34, 35) has a mounting position of the first BGA (31) and the second second except for an area portion through which the one or more through holes (50, 51) pass. A depletion portion (38, 39) is provided at a position overlapping the mounting position of the BGA (32). In the printed board according to the present invention, the depletion portions (38, 39) are filled with a resin (43, 44) having an elastic modulus lower than that of the prepreg layer (34, 35).

  Moreover, in the method for producing a printed board according to the present invention, in the step of making a hole, a hole is made in the prepreg film. In the first laminating step, prepreg films having holes are laminated on both surfaces of the core material layer. In the forming step, a prepreg piece is formed in a region portion through which one or a plurality of through holes penetrates in the hole formed in the prepreg film. In the second laminating step, another insulating layer is further laminated on both surfaces of the prepreg layer composed of the prepreg film and the prepreg piece. The step of penetrating penetrates one or a plurality of through holes. In the double-sided mounting step, the BGA is double-sided mounted so as to overlap the hole formed in the prepreg film. Further, in the method for producing a printed board according to the present invention, the prepreg film is formed except for a region portion where the prepreg piece is formed between the step of forming the prepreg piece and the step of laminating the other insulating layer. A step of filling the hole formed in the resin with a resin having an elastic modulus lower than that of the prepreg film.

  According to the present invention, it is possible to make a printed board on which BGA is mounted at the same position on both sides. Moreover, the distortion which arises when the printed board which mounted BGA on both surfaces is heated or cooled can be decreased. Moreover, a through hole can be formed in the printed board which mounted BGA on both surfaces.

  In the future, as the integration and density of the BGA mounting substrate further increases, it is desirable that the BGA can be mounted at the same position on both sides. When BGA is mounted on a printed board, it is very convenient if it can be mounted not only on one side of the printed board but also on both sides. However, when a substrate on which the BGA is mounted at the same position on the front and back sides is heated or cooled, distortion occurs due to the difference in thermal expansion coefficient between the BGA and the substrate. This distortion causes the solder ball of the connection portion to peel off. In this embodiment, when the BGA is mounted on the printed board at the same position on the front and back, the connection reliability between the BGA and the mounting board is improved by sandwiching a depletion layer or a flexible resin layer between the mountings. .

  2 and 3 show a first embodiment according to the present invention. FIG. 2 is a plan view of the printed board, and FIG. 3 is an explanatory side sectional view of the printed board with exaggerated thickness and the like. As shown in FIG. 2, the BGA 11 on the surface is mounted at a substantially central position of the laminated substrate 10. Further, as shown in FIG. 3, the BGA 12 on the back surface is mounted at the same mounting position as the mounting position of the BGA 11 on the front surface. In FIG. 3, the laminated substrate 10 includes a core material layer 13 in the center, and the prepreg layers 14 and 15 and the insulating layers 16 and 17 are laminated so as to be vertically symmetrical about the core material layer 13. It consists of The laminated substrate 10 and the BGAs 11 and 12 are connected by solder balls 20. As shown in FIG. 3, depletion portions 18 and 19 are provided in the prepreg layers 14 and 15 sandwiching the core material layer 13, respectively. The depletion portions 18 and 19 are provided at the same positions as the mounting positions of the BGAs 11 and 12. That is, the prepreg layers 14 and 15 are provided with depletion portions having the same size as the area occupied by the BGA 11 on the surface shown in FIG. The depletion portions 18 and 19 effectively absorb the stress caused by the difference in thermal expansion between the BGAs 11 and 12 and the laminated substrate 10. That is, the strain applied to the solder balls 20 of the BGAs 11 and 12 can be absorbed, and the connection reliability between the BGAs 11 and 12 and the laminated substrate 10 is improved.

  FIG. 4 is an explanatory view of a side cross section showing a modification of FIG. In FIG. 3, the prepreg layers 14 and 15 are provided with depletion portions 18 and 19. However, in FIG. 4, the depletion portions are filled with a flexible resin and deformed as resin portions 21 and 22. Yes. This resin has a softer property than prepreg and uses a resin having high adhesiveness. The elastic modulus is characterized by being smaller than the elastic modulus of the prepreg. Such a resin effectively absorbs stress caused by the difference in thermal expansion between the BGAs 11 and 12 and the laminated substrate 25. That is, the strain applied to the solder balls 20 of the BGAs 11 and 12 can be absorbed, and the connection reliability between the BGAs 11 and 12 and the multilayer substrate 25 is improved.

  5 and 6 show a second embodiment according to the present invention. FIG. 5 is a plan view of the printed board, and FIG. 6 is an explanatory side sectional view of the printed board with exaggerated thickness and the like. As shown in FIG. 5, the BGA 31 on the surface is mounted at a substantially central position of the laminated substrate 30. In addition, through holes 50 and 51 are formed below the BGA 31 as indicated by dotted lines. As apparent from FIG. 6, the BGA 32 on the back surface is mounted at the same mounting position as the mounting position of the BGA 31 on the front surface. In FIG. 6, the laminated substrate 30 includes a core material layer 33 at the center, and the prepreg layers 34 and 35 and the insulating layers 36 and 37 are laminated so as to be vertically symmetrical about the core material layer 33. It consists of The laminated substrate 30 and the BGAs 31 and 32 are connected by solder balls 40. As shown in FIG. 6, prepreg layers 34 and 35 sandwiching the core material layer 33 are provided with depletion portions 38 and 39, respectively. The depletion portions 38 and 39 are provided at the same positions as the mounting positions of the BGAs 31 and 32. That is, depletion portions 38 and 39 having the same size as the occupied area of the BGA 31 on the surface shown in FIG. 5 are provided in the prepreg layers 34 and 35. However, in the prepreg layers 34 and 35, prepreg pieces are formed in regions where the through holes 50 and 51 penetrate. The through holes 50 and 51 are formed so as to make holes in the prepreg pieces. Plated bodies 41 and 42 are provided in the through holes 50 and 51. The plated bodies 41 and 42 electrically connect the BGA 31 on the front surface and the BGA 32 on the back surface. As shown in the second embodiment, the through holes 50 and 51 can be formed even if the depletion portions 38 and 39 are provided in the prepregs 34 and 35. The depletion portions 38 and 39 effectively absorb the stress caused by the difference in thermal expansion between the BGAs 31 and 32 and the laminated substrate 30. That is, the strain applied to the solder balls 40 of the BGAs 31 and 32 can be absorbed, and the connection reliability between the BGAs 31 and 32 and the multilayer substrate 30 is improved.

  FIG. 7 is an explanatory view of a side cross section showing a modification of FIG. In FIG. 6, the prepreg layers 34 and 35 are provided with depletion portions 38 and 39. However, in FIG. 7, the depletion portions are filled with a flexible resin and deformed as resin portions 43 and 44. Yes. This resin has a softer property than prepreg and uses a resin having high adhesiveness. The elastic modulus is characterized by being smaller than the elastic modulus of the prepreg. Such a resin effectively absorbs stress caused by the difference in thermal expansion between the BGAs 31 and 32 and the laminated substrate 45. That is, the strain applied to the solder balls 40 of the BGAs 31 and 32 can be absorbed, and the connection reliability between the BGAs 31 and 32 and the laminated substrate 45 is improved.

  As described above, the connection reliability between the BGA and the multilayer substrate can be improved by sandwiching the flexible layer in the multilayer substrate. In the first and second embodiments, the size of the depletion portion or the resin portion in the prepreg layer and the size of the BGA are completely the same. However, in order to solve the problem of improving the connection reliability, it is sufficient that they are almost the same. In addition, the size of the BGA on the front side and the size of the BGA on the back side are completely the same. However, if the positions are aligned, connection reliability can be improved even if the sizes are slightly different. It is. Furthermore, although the case where the number of BGAs on the front surface and the BGA on the back surface is one has been described as an example, there may of course be a plurality of BGAs.

Next, the manufacturing process of the printed board shown in FIG. 3 will be described. The printed board of FIG. 3 can be made by the following steps.
[A] A hole is made in the prepreg. The place where the hole is made is a place where the BGA is mounted at the same front and back positions.
[B] A prepreg having a hole is stacked on the core material.
[C] and [b] are bonded by heating and pressing with a laminating press.
[D] Laminate an insulating layer.
[E] BGA is laminated through solder balls.

Then, the manufacturing process of the printed board shown in FIG. 4 is demonstrated. The printed board of FIG. 4 can be made by the following steps.
[A] A hole is made in the prepreg. The place where the hole is made is a place where the BGA is mounted at the same front and back positions.
[B] Fill the hole opened with [a] with resin.
[C] A prepreg having a resin portion is overlaid on the core material.
[D] [c] is bonded by heating and pressing with a laminating press.
[E] Laminate an insulating layer.
[F] BGA is laminated through solder balls.

  The manufacturing process of the printed board shown in FIGS. 6 and 7 is the same process. Note that this embodiment can also be applied to a build-up substrate (a printed substrate in which an insulating layer and a wiring layer are stacked by a build-up method in which thin films are stacked from below).

  In the present embodiment, there is provided a printed board structure that can absorb the strain caused by the difference in thermal expansion coefficient even when the BGA is mounted at the same position on the front and back sides. As a method for absorbing strain caused by the difference in thermal expansion coefficient, a layer including a depletion portion or a flexible resin portion capable of absorbing strain is sandwiched between superimposed layers of a printed board. The layer absorbs the stress generated by the thermal expansion difference between the BGA and the printed wiring board, and relaxes the stress applied to the solder ball. Such a stress relaxation effect can suppress the occurrence of cracks in the solder balls and can improve the reliability when the BGA is mounted at the same front and back positions. Therefore, high-density mounting is possible by increasing the area on which the BGA can be mounted on the printed board.

FIG. 1 is a diagram for explaining a conventional printed board on which a BGA is mounted. FIG. 2 is a plan view showing a first printed board according to the present invention on which a BGA is mounted. FIG. 3 is an explanatory view of a side cross section showing a first printed board according to the present invention on which a BGA is mounted. FIG. 4 is an explanatory view of a side cross section showing a modification of the first printed board described in FIG. FIG. 5 is a plan view showing a second printed board according to the present invention on which a BGA is mounted. FIG. 6 is an explanatory view of a side section showing a second printed board according to the present invention on which a BGA is mounted. FIG. 7 is an explanatory view of a side cross section showing a modification of the second printed board described in FIG.

Explanation of symbols

10, 25, 30, 45 Laminated substrate 11, 12, 31, 32, 101, 102 BGA
13, 33 Core material layers 14, 15, 34, 35 Prepreg layers 16, 17, 36, 37 Insulating layers 18, 19, 38, 39 Depletion parts 20, 40, 103 Solder balls 21, 22, 43, 44 Resin part 41 , 42 Plated body 50, 51 Through hole 100 Printed board

Claims (8)

A laminated substrate;
A first BGA mounted on the front side of the multilayer substrate;
A second BGA mounted on the back surface of the multilayer substrate;
The printed board, wherein the mounting position of the first BGA and the mounting position of the second BGA are plane-symmetrical with respect to the multilayer substrate. The laminated substrate is
The printed board according to claim 1, comprising a core material layer in the center and symmetrically having prepreg layers on both sides thereof. The prepreg layers are all
The printed circuit board according to claim 2, further comprising a depletion portion at a position overlapping the mounting position of the first BGA and the mounting position of the second BGA. In the depletion part,
The printed board according to claim 3, filled with a resin having an elastic modulus lower than that of the prepreg layer. The laminated substrate is
One or a plurality of through holes are provided in the mounting position of the first BGA and the mounting position of the second BGA,
The prepreg layers are all
The printed circuit board according to claim 2, further comprising a depletion portion at a position overlapping the mounting position of the first BGA and the mounting position of the second BGA except for a region portion through which the one or more through holes penetrate. In the depletion part,
The printed board according to claim 5, filled with a resin having an elastic modulus lower than that of the prepreg layer. A step of making a hole in the prepreg membrane;
Laminating a prepreg film with holes on both sides of the core material layer;
A step of forming a prepreg piece in a region portion through which one or a plurality of through holes penetrates in the hole formed in the prepreg film;
A step of further laminating another insulating layer on both sides of the prepreg layer comprising the prepreg film and the prepreg piece;
Passing through one or more through holes;
And a step of mounting both sides of the BGA so as to overlap the holes formed in the prepreg film. Between the step of forming the prepreg piece and the step of laminating the other insulating layer,
The printed board manufacturing method according to claim 7, further comprising a step of filling a hole formed in the prepreg film with a resin having an elastic modulus lower than an elastic modulus of the prepreg layer except for a region portion where the prepreg piece is formed. Method.

Images