JP2005340230A - Method of manufacturing printed circuit board and part package - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a printed circuit board and a part package which obtains solderability of high reliability without being affected by the warpage of the part or a substrate. <P>SOLUTION: A spacer 33 provided on the substrate 21 to increase the coating quantity of soldering paste 26 is formed by using a material which performs a degradation sublimation and dissipates during reflow heating of the solder paste 26. Thus, the warpage of the part 28 or the substrate 21 during reflow processing is absorbed in a gap formed by the vanishing of the spacer 33. The generation of a non-solder improper part is prevented, and a reliable solder junction 26A is obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a printed wiring board for surface mounting and a method for manufacturing a component mounting body in which an electronic component is mounted on the printed wiring board. More specifically, a bonding material such as solder paste is applied by screen printing, and the component is subjected to reflow processing. The present invention relates to a printed wiring board to which solder is soldered and a method for manufacturing a component mounting body.

  Conventionally, mounting of surface mounted multi-terminal electrical / electronic components (hereinafter simply referred to as components) such as SOP (Small Outline Package), QFP (Quad Flat Package), and connectors on a printed wiring board has been carried out on the printed wiring board. A solder paste is preliminarily printed on a land, and a component is mounted thereon, and then soldered in a reflow furnace.

  As shown in FIG. 6A, a substrate 1 constituting a printed wiring board has a plurality of lands 3 for connecting parts made of copper or the like formed on the surface of an insulating base 2 made of, for example, thermosetting or thermoplastic resin. The region other than the land 3 is covered with the solder resist 4. In the solder paste printing and coating process, as shown in FIG. 6B, a screen mask 5 having an opening 5 a corresponding to the land 3 formation position is superimposed on the mounting surface (land 3 formation surface) of the substrate 1. Solder paste 6 is supplied onto the screen mask 5 and filled in the openings 5a of the screen mask 5 by the movement of the squeegee 7 in the direction of the arrow in the figure. Then, by removing the screen mask 5 from the substrate 1, a predetermined amount (thickness) of the solder paste 6 is supplied onto the land 3.

  The supply amount of the solder paste 6 to the land 3 is determined in consideration of the height variation of the component terminals.

  For example, as shown in FIG. 7A, in a terminal protruding type component 8A in which a terminal 9 such as a QFP or a connector protrudes from the component main body, if the terminal 9 has a height H variation, the solder paste 6 on the land 3 If the amount is small, there is a possibility that an unsoldered defective portion F1 may occur in the soldering process in the reflow furnace as shown in FIG. 7B. Normally, the solder paste 6 is composed of a mixture of a solder component and a flux component, and the capacity of the solder joint portion 6A formed after the reflow process is reduced to about half the height of the applied solder paste 6. Therefore, a good solder joint portion 6A can be obtained if there is a solder amount that can absorb the height variation H of the terminal 9 at the time of mounting. However, if the solder amount is so small that the height variation H cannot be absorbed, the land 3 and the terminal An unsoldered defective portion F1 that cannot be (or is insufficiently) electrically connected to 9 occurs.

  Further, the supply amount of the solder paste 6 to the land 3 is determined in consideration of the amount of warp due to the heat of the component or the board during reflow.

  For example, as shown in FIG. 8A, even if the solder amount is sufficient to absorb the height variation of the component terminal 9, the substrate 1 is warped by heating during reflow, and depending on the warp amount, the terminal 9 may be soldered. There is a case where the unsoldered defective portion F2 is generated as shown in FIG. 8B without being properly joined to the portion 6A.

  As shown in FIG. 9A, the IC chip 11 is mounted on the interposer substrate 10 so as to be substantially flush with the lower surface of the component main body (interposer substrate 10) (or to be pulled inwardly on the lower surface of the component main body). 9) Even in the LGA (Land Grid Array) type surface mount component 8B in which the terminals 12 are arranged in a grid, the interposer substrate 10 or the substrate 1 is warped during reflow as shown in FIGS. 9B and 9C. A similar unsoldered portion F2 may occur.

  As described above, it is preferable that the supply amount of the solder paste is large enough to absorb the variation in the height of the component terminals and the amount of warpage of the component or the substrate during reflow.

  However, the amount of solder paste that can be supplied to the substrate is mainly determined by the thickness of the screen mask 5, but if this screen thickness is increased, it affects other components mounted on the substrate. In particular, for fine pitch components, bridges due to an excessive amount of supplied paste, and unsoldability of solder paste may deteriorate, and unsoldering due to an excessive amount of paste may occur. Even for small-sized square chips, tombstones due to an excessive amount of paste and unsoldering due to an excessive amount of paste can occur.

  Also, depending on the type of printed wiring board, components that are surface-mounted with a relatively small amount of (thin) solder paste and components that are surface-mounted with a relatively large amount of (thick) solder paste are mixed. However, when manufacturing such a component mounting body, it is difficult to supply solder paste with different coating thicknesses on a single substrate.

  In order to solve such a problem, among the positions on the mounting surface where the solder paste is applied using a screen mask, around the position where the amount of solder paste applied should be increased, the height corresponding to the increased amount of application is increased. There is a technique of providing a spacer (see, for example, Patent Document 1 below).

  As shown in FIG. 10A, after a spacer 13 having a height corresponding to the amount of solder paste to be increased is formed on the solder resist 4 of the substrate 1 by, for example, screen printing, the spacer as shown in FIG. 10B. 13 is a method of increasing the supply amount of the solder paste 6 without increasing the plate thickness of the screen mask 5 by printing the solder paste 6 on the land 3 with the screen mask 5 superposed on the land 13. As a result, as shown in FIGS. 11A and 11B, it is possible to supply a large amount of solder paste 6 that can absorb the height variation H of the component terminal 9, and in the component 8A where the height variation of the terminal 9 is relatively large. In the reflow process, a good solder joint portion 6A is obtained, which can contribute to improving the joint reliability of the component 8A.

JP-A-10-303535 JP 2001-60642 A

  However, a component that is advantageous for improving the bonding reliability by interposing the spacer 13 is a component 8A having a relatively large height variation of the terminal 9, that is, a terminal protruding type surface mounting such as SOP, QFP, connector, etc. The component 8A, which is a component 8B in which the terminals 13 are arranged so as to be drawn almost in the same plane as the lower surface of the component main body or inward from the lower surface of the component main body, like a package component such as an LGA shown in FIG. 12A. In FIG. 12, since the warp amount of the interposer substrate 10 at the time of reflow is significant, the lower surface of the component is warped against the upper surface of the spacer 13 as shown in FIG. There is a problem in that a portion where the unsoldered defective portion F2 is generated is generated. The same problem occurs due to the warp of the substrate 1.

  In particular, in recent years, parts have become larger (longer sides) and thinner, and parts such as LGA whose terminal surface is the same as or lower than the lower surface of the component body can be used during reflow. The occurrence of unsoldered defective parts due to the warpage of components or printed wiring boards in the above-mentioned has become obvious, which is a cause of lowering of soldering reliability.

  The present invention has been made in view of the above problems, and it is an object of the present invention to provide a printed wiring board and a method for manufacturing a component mounting body that can obtain highly reliable solderability without being affected by warping of components and boards. To do.

  In solving the above problems, the printed wiring board of the present invention has a surface as a component mounting surface, and increases the amount of bonding material applied among the positions of the mounting surface where the bonding material is applied using a screen mask. In a printed wiring board provided with a spacer having a height corresponding to the increasing coating amount around the power position, this spacer is formed using a material that disappears or melts during reflow heating of the bonding material. It is a feature.

  The component mounting body manufacturing method of the present invention is a component mounting body manufacturing method in which a component is mounted on a mounting surface of a printed wiring board via a bonding material, and the bonding material is applied out of the mounting surface positions. Around the position where the amount should be increased, a step of forming a spacer having a height corresponding to the increased coating amount using a material that disappears or melts during reflow heating of the bonding material, and screens the bonding material on the mounting surface. There are a step of applying by a printing method and a step of reflow heating the bonding material after the components are mounted on the mounting surface to cause the spacers to disappear or melt.

  In the present invention, the spacer provided around the position where the coating amount of the bonding material should be increased is formed by using a material that disappears or melts during reflow heating of the bonding material, so that the component or the printed wiring board is reflowed. Even if warpage occurs, the warpage of the component or the printed wiring board is absorbed within the gap between the printed wiring board and the component formed by disappearance or melting of the spacer. Generation of solder is prevented, and a highly reliable solder joint is obtained.

  The spacer can be formed using a material that decomposes and sublimates by heat treatment and disappears, or a material that softens and melts by heat treatment. As the sublimation temperature or melting temperature of the spacer, the one having a melting point or lower of the bonding material used is used.

  Furthermore, in order to effectively avoid the occurrence of a non-solder defective portion due to the warp of the component, it is preferable to set the height of the spacer higher than the warp amount of the component during reflow heating of the bonding material.

  According to the present invention, the spacer provided on the substrate in order to increase the coating amount of the bonding material is formed using a material that disappears or melts during the reflow heating of the bonding material. Can be absorbed by the gap between the substrate and the component formed by the disappearance or melting of the spacer, and the terminal surface is the same as the lower surface of the component or the LGA type of which is retracted inward. Even in the case of a surface-mounted component, it is possible to suppress the occurrence of unsoldered defective portions and obtain highly reliable solderability.

  Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment]
1 to 4 show a first embodiment of the present invention.
Here, FIG. 1 is a process sectional view for explaining a method of manufacturing a printed wiring board 20 having a spacer according to the present invention, FIG. 2 is a sectional view for explaining a printing process of a solder paste (joining material) 26, and FIG. FIG. 4 is a cross-sectional view for explaining a reflow soldering process for the component 28.

  First, with reference to FIG. 1, the manufacturing method of the printed wiring board 20 which has the spacer which concerns on this invention is demonstrated.

  First, the substrate 21 shown in FIG. 1A is prepared. This printed wiring board 21 has a plurality of lands 23 for connecting parts made of copper, aluminum or the like formed on the surface of an insulating base 22 made of, for example, thermosetting or thermoplastic resin. The region is covered with a solder resist 24.

  The solder resist 24 has a formation thickness equal to or greater than that of the land 23, but may be less than the formation thickness of the land 23. The solder resist 24 may be omitted as necessary.

  Next, as shown in FIG. 1B, the mounting surface (land 23 forming surface) of the substrate 1 is covered with a spacer forming resin 33A by a method such as spin coating.

  The spacer forming resin 33 </ b> A is made of a photosensitive material that decomposes and sublimates at a temperature lower than the reflow temperature (melting point) of the solder paste (joining material) 26. For example, when SnAg-based lead-free solder (melting point: 220 to 230 ° C.) is used as the solder paste 26, a material is used in which the spacer forming resin 33A decomposes and sublimates at about 200 ° C. and disappears. As the spacer forming resin 33A having such characteristics, for example, a modified silicone resin having an acrylic skeleton can be cited, and can be appropriately selected according to the type (melting point) of the solder paste to be used.

  Although the thickness of the spacer forming resin 33A can be arbitrarily set, the thickness of the spacer forming resin 33A affects the supply amount of the solder paste 26, and therefore is determined in consideration of the warping amount of the component or the substrate at the time of reflow. It is preferable to do this. For example, the spacer forming resin 33A is formed with such a thickness that the height of the spacer 33 formed through the subsequent photolithography process is higher than the warping amount of the component or the substrate during reflow.

  Subsequently, as shown in FIG. 1C, a predetermined mask 34 is placed on the spacer forming resin 33A, exposed, and subjected to development processing, and the spacer forming resin 33A is patterned. As a result, as shown in FIG. 1D, a spacer 33 having a predetermined thickness is selectively formed on the solder resist 24 around the land 23.

As described above, the printed wiring board 20 of the present embodiment is manufactured.
In the above example, the spacer forming resin 33A is provided with photosensitivity, and the spacer 33 is formed by the photolithography technique. However, the present invention is not limited to this. For example, the spacer 33 can be patterned by using a spacer-forming resin having no photosensitivity so that only the formation portion of the land 23 is selectively opened by laser processing or the like.

  Next, a component mounting method on the printed wiring board 20 configured as described above will be described.

  FIG. 2 shows a printing process of the solder paste 26 on the substrate 21. In the printing application process of the solder paste 26, as shown in the figure, a screen mask 25 having an opening 25a corresponding to the formation position of the land 23 is superimposed on the mounting surface of the substrate 1. Solder paste 26 is supplied on the screen mask 25 and filled in the openings 25a of the screen mask 25 by moving the squeegee 27 in the direction of the arrow in the figure. Then, by removing the screen mask 25 from the substrate 21, a predetermined amount (thickness) of the solder paste 26 is supplied onto the land 23.

  In the example of FIG. 2, there are a position where the spacer 33 is provided on the same substrate 21 and a position where the spacer 33 is not provided. The position where the spacer 33 is provided is compared with the position where the spacer 33 is not provided. The application amount (thickness) of the solder paste 26 is increased by an amount corresponding to the formation thickness of the spacer 33.

  That is, in the illustrated example, a surface mount component that requires a relatively large amount (thick) solder paste 26 and a surface mount component that requires a relatively small amount (thin) solder paste 26 on the substrate 21. Is a printed wiring board for a component mounting body. For example, relatively large LGA, connector, QFP, SOP, etc. are supported as the former surface mounting parts, and the latter surface mounting parts are, for example, small chips, fine pitch BGA, QFP, etc. Parts with high demands for avoiding bridging failures are available.

  It is assumed that the screen mask 25 has flexibility and is superimposed on the mounting surface of the substrate 21 with high alignment accuracy with respect to the formation position and non-formation position of the spacer 33. As the screen mask 25, for example, a metal screen made of stainless steel or the like is applied, but of course not limited thereto.

  FIG. 3 shows a process of mounting the component 28 on the substrate 21. In the illustrated example, the IC chip 31 is mounted on the interposer substrate 30, and the terminals 29 are arranged so as to be substantially flush with the lower surface of the component main body (interposer substrate 30) (or so as to be drawn inwardly on the lower surface of the component main body). In this example, the LGA type surface mounting components 28 are arranged in a grid shape, and are mounted on a substrate region in which the amount of supplied solder is increased by interposing a spacer 33. Of course, a terminal protruding type surface mount component such as SOP or QFP is also applicable as the component 28, but here, the LGA type component will be described as an example.

  The interposer substrate 30 is an organic substrate, and an IC chip 31 is flip-chip mounted or wire bonded mounted on the interposer substrate 30 and sealed with a mold resin as required. However, the component configuration is not particularly limited, and the terminal surface is a component. All parts located on the same side as the lower surface of the main body or on the inner side thereof are included.

  The terminal 28 of the component 28 after mounting is in contact with the solder paste 26. In this state, by loading the substrate 21 into a reflow furnace (not shown), a reflow soldering process of the component 28 with a predetermined temperature profile is performed.

  FIG. 4A shows a state in which the spacer 33 is decomposed and sublimated by heating just before the solder reflow temperature. As described above, since the spacer 33 is formed using a material that decomposes and sublimates at a temperature lower than the melting temperature of the solder material constituting the solder paste 26, the spacer 33 is sublimated and disappears before the solder paste 26 is reflowed. . As a result, as shown in FIG. 4A, a gap S is formed between the component lower surface and the substrate 21 upper surface.

  When the solder reflow temperature is exceeded, the solvent component of the solder paste 26 volatilizes, the solder component melts, and the flux component is pushed away to the surroundings without impairing the wettability of the solder. After cooling, the terminals 29 of the component 28 and the lands 23 of the substrate 21 are mechanically and electrically connected via a solder joint 26A as shown in FIG. 4B.

  At this time, as shown in FIG. 4B, even if the warpage C occurs in the component 28 or the substrate 21 or both of them (in the figure, only the component 28 is warped), it is formed by the disappearance of the spacer 33. Since the warp is absorbed in the range of the gap S, it is possible to avoid the occurrence of an unsoldered defective portion between the terminal 29 and the land 23.

  Therefore, according to the present embodiment, the spacer 33 provided on the substrate 21 in order to increase the coating amount of the solder paste 26 is formed using a material that disappears by decomposition sublimation during reflow heating of the solder paste 26. Therefore, even if warpage C occurs in the component 28 or the substrate 21 during reflow, the warpage C can be absorbed in the gap S between the substrate 21 and the component 28 formed by the disappearance of the spacer 33. As a result, it is possible to effectively prevent the occurrence of an unsoldered defective portion, obtain good solderability, and manufacture a component mounting body 35 (FIG. 4B) provided with a highly reliable solder joint portion 26A. .

  In particular, according to the present embodiment, it is effective for LGA type surface mounting components in which the terminal surface is the same as or lower than the lower surface of the component main body, but SOP, QFP, connector, Of course, it is also effective in preventing the occurrence of unsoldered defective parts due to variations in the height of the component terminals and warping of the component body, even for surface-mounted surface-mount components such as electric field capacitors, inductors, and network resistors.

[Second Embodiment]
FIG. 5 shows a second embodiment of the present invention. In the figure, the same reference numerals are given to portions corresponding to those in the first embodiment described above, and detailed description thereof will be omitted. Here, FIG. 5A shows the printing application process of the solder paste 26, FIG. 5B shows the mounting process of the component 28, and FIG. 5C shows the reflow process.

  In the present embodiment, the spacer 43 provided on the substrate 21 in order to increase the application amount of the solder paste 26 is formed using a material that is melted by high-temperature softening of the solder paste 26 by reflow heating.

  The spacer 43 can be formed by using the same photolithography technique as that in the first embodiment as long as the material for forming the spacer 43 has photosensitivity. Otherwise, screen printing, laser processing techniques, etc. can be used.

  As a material for forming the spacer 43, a material that melts (softens) at a temperature equal to or lower than the reflow temperature (melting point) of the solder paste 26 is used. For example, when SnAg-based lead-free solder (melting point 220 to 230 ° C.) is used as the solder paste 26, a material is used in which the spacer 43 is softened and the coat thickness is reduced at about 200 ° C. A material that softens and spreads and is safe to contact with solder is desirable. In order to avoid contact with the solder, it is effective to secure a distance from the land portion, or to provide a through hole or groove in the substrate, and pour softened resin there.

  As a material for forming the spacer 43 having such characteristics, for example, “T693 / R3901” manufactured by Nagase Chemtech, “CNB837-44” manufactured by Dexter, and “RE9101” manufactured by Kester can be used. Among these, “T693 / R3901” manufactured by Nagase ChemteX Corporation is a resin containing naphthalenediglycidyl ether as a main ingredient and tetrahydrophthalic anhydride as a curing agent.

  The thickness of the material for forming the spacer 43 can be arbitrarily set. However, since the thickness of the material for forming the spacer 43 affects the supply amount of the solder paste 26, the amount of warpage of the component or the substrate during reflow is taken into account. Is preferably determined. For example, the spacer 43 is formed with such a thickness that the height of the spacer 43 is higher than the warping amount of the component or the substrate during reflow.

  When the spacer 43 made of such a material is interposed between the substrate 21 and the component 28 and the reflow process is performed, the spacer 43 is softened and thinned before or after the solder is melted. . As a result, a gap having a size corresponding to the height of the reduced spacer 43 is formed between the substrate 21 and the component 28, and warpage occurring in the component 28, the substrate 21, or both within the gap ( FIG. 5C shows that the substrate 28 is warped). Thereby, generation | occurrence | production of the unsoldering defective part between the terminal 29 and the land 23 can be avoided.

  As shown in FIG. 5C, the melted spacer 43 ′ may be left around the solder joint portion 26 </ b> A to reinforce the solder joint portion 26 </ b> A or perform an outside air blocking action by coating. The durability and reliability of the solder joint portion 26A can be improved.

  As described above, according to the present embodiment, the spacer 43 provided on the substrate 21 in order to increase the coating amount of the solder paste 26 is formed using a material that is melted during reflow heating of the solder paste 26. Therefore, even if warpage occurs in the component 28 or the substrate 21 at the time of reflow, the warpage can be absorbed in the gap between the substrate 21 and the component 28 formed by melting of the spacer 43. The component mounting body 45 (FIG. 5C) including the solder joint portion 26 </ b> A having a high reliability can be manufactured by effectively preventing the occurrence of a defective solder portion and obtaining good solderability.

  As mentioned above, although each embodiment of this invention was described, of course, this invention is not limited to these, A various deformation | transformation is possible based on the technical idea of this invention.

  For example, in the first embodiment described above, a surface mounting component that requires a relatively large amount (thick) solder paste 26 and a relatively small amount (thin) solder paste 26 are required on the substrate 21. The printed wiring board for the component mounting body in which the surface mounting components are mixedly mounted has been described as an example. However, the present invention is not limited to this, and only the surface mounting components requiring a relatively large amount of solder paste 26 are mounted. The present invention is also applicable to a printed wiring board for a component mounting body.

It is process sectional drawing explaining the manufacturing method of the printed wiring board 20 by the 1st Embodiment of this invention. 7 is a cross-sectional view of a main part for explaining a printing process of the solder paste 26. FIG. FIG. 10 is a cross-sectional view of the main part for explaining the mounting process of the component 28. It is principal part sectional drawing explaining a reflow process. It is process sectional drawing explaining the manufacturing method of the component mounting body by the 2nd Embodiment of this invention. It is process sectional drawing explaining the manufacturing method of the conventional printed wiring board. It is principal part sectional drawing explaining generation | occurrence | production of the un-solder defective part resulting from the height variation of a component terminal. It is principal part sectional drawing explaining generation | occurrence | production of the un-solder defective part resulting from the curvature of a board | substrate. It is principal part sectional drawing explaining generation | occurrence | production of the unsoldering defective part resulting from the curvature of components. It is process sectional drawing explaining the manufacturing method of the conventional printed wiring board using a spacer. It is principal part sectional drawing explaining the advantage when using the conventional spacer. It is principal part sectional drawing explaining a problem when using the conventional spacer.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 20 ... Printed wiring board, 21 ... Board | substrate, 22 ... Insulation base material, 23 ... Land, 24 ... Solder resist, 25 ... Screen mask, 26 ... Solder paste, 28 ... Component, 29 ... Terminal, 30 ... Interposer board, 31 ... IC chip, 33, 43... Spacer, 35, 45.

Claims (8)

The surface is the mounting surface of the component, and the position corresponding to the increasing coating amount is increased around the position of the mounting surface where the bonding material is applied using a screen mask. In the printed wiring board provided with a spacer,
The printed wiring board, wherein the spacer is formed using a material that disappears or melts during reflow heating of the bonding material. The printed wiring board according to claim 1, wherein the spacer is formed using a material that is decomposed and sublimated by heat treatment. The printed wiring board according to claim 1, wherein the spacer is formed using a material that is softened and melted by heat treatment. The printed wiring board according to claim 1, wherein a height of the spacer is set to be higher than a warping amount of the component after the reflow heating of the bonding material. A component mounting body manufacturing method in which a component is mounted on a mounting surface of a printed wiring board via a bonding material,
A spacer having a height corresponding to the increasing application amount is used around the position of the mounting surface where the application amount of the bonding material should be increased, using a material that disappears or melts during reflow heating of the bonding material. Forming, and
Applying the bonding material to the mounting surface by a screen printing method;
And a step of reflow-heating the bonding material after the component is mounted on the mounting surface to eliminate or melt the spacer. The method for manufacturing a component mounting body according to claim 5, wherein the spacer is formed using a material that decomposes and sublimates by heat treatment and disappears. The method of manufacturing a component mounting body according to claim 5, wherein the spacer is formed using a material that is softened at a high temperature by heat treatment. The method for manufacturing a component mounting body according to claim 5, wherein a height of the spacer is set higher than a warping amount of the component after the reflow heating of the bonding material.

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