JP5446132B2 - Method for manufacturing planting pin and printed wiring board with pin - Google Patents

Description

  The present invention relates to a planting pin for planting a printed wiring board for a semiconductor package, and a method of manufacturing a printed wiring board with a pin in which the planting pin is planted.

  In Patent Documents 1 to 3, a technique for forming a solder fillet 7 by soldering a planting pin to a printed wiring board for a semiconductor package to be planted is known. In Patent Document 1, a disk-shaped nail head is installed at one end of a rod-shaped portion of a planting pin, and the tip joint surface of the nail head is formed into a spherical convex surface and soldered to an external electrode pad of a printed wiring board with a solder fillet. It was attached. However, in Patent Document 1, it is considered that the solder fillet does not reach the upper surface of the nail head, so that the solder fillet has a weak force for holding the nail head.

  In order to hold the nail head strongly, it is desirable to form a solder fillet in which the solder rises and spreads until the rod-shaped portion is reached on the entire surface of the nail head's rod installation surface where the rod-shaped portion of the planting pin is installed, If the amount of solder is increased in order to realize this state, as shown in FIG. 5, an excessive solder fillet 7 starts to rise from the rod installation surface 1d of the planting pin 1 to the rod-shaped portion 1a. There is a problem that the solder fillet 7 touches the socket into which the rod-shaped portion 1a is inserted. Therefore, Patent Documents 2 and 3 disclose a technique in which the solder fillet 7 climbs up to the bar installation surface 1d on the upper surface of the nail head 1b, and the solder fillet 7 that has climbed up does not touch the bar-shaped portion 1a. It had been.

The known literature is described below.
JP 63-316464 A JP 2001-217341 A JP 2001-291790 A

  However, as in Patent Documents 2 and 3, if the entire surface of the bar mounting surface 1d on the top surface of the nail head 1b of the planting pin 1 is coated with solder so as not to spread, variation in soldering conditions as shown in FIG. As a result, only one end of the bar installation surface 1d is supported by being wetted with solder, and the other end of the bar installation surface 1d is not supported because the solder is not wetted. In that case, there is a problem that the nail head 1b starts to be peeled off from the solder fillet 7 on the rod installation surface 1d side which is not wet with solder. As described above, there is a problem that it is difficult to solder the nail head 1b so as to be firmly supported by the solder fillet 7 while preventing the solder from excessively entering the rod-shaped portion 1a.

In order to solve this problem, the present invention provides a planting pin in which a nail head is formed at the tip of a rod-shaped portion, and the tip joint surface of the nail head of the planting pin is a pinned printed wiring board. A planting pin that is soldered to an external electrode pad, and a resist film that can be removed by a solvent or a flux cleaning solution is formed at least in the vicinity of the nail head of the rod-shaped portion , and the resist film is formed on the photosensitive ink. the resist film der Rukoto obtained by curing by ultraviolet irradiation is implanted pin characterized.

The present invention also relates to a planting pin for soldering a tip joint surface of a nail head formed at the tip of a rod-like portion to an external electrode pad of a printed wiring board with a pin, and at least the nail head of the rod-like portion A printed wiring board with a pin mounted with a planting pin on which a resist film that can be removed by a solvent or a flux cleaning solution is mounted, and the rod- like shape is formed by the resist film of the planting pin A step of wrapping and soldering the tip joint surface of the nail head and the surface to which the rod-like portion is connected with a solder fillet while preventing the solder from spreading to the part, and the resist film of the planting pin It is a manufacturing method of the printed wiring board with a pin characterized by having the process of removing with a solvent or a flux washing | cleaning liquid.

  In the present invention, by forming a resist film on the rod-shaped portion of the nail head of the planting pin, when the nail head is soldered to the external electrode pad with the solder fillet, the solder fillet excessively spreads on the rod-shaped portion. Therefore, it is possible to firmly bond the nail head of the planting pin to the external electrode pad with a solder fillet made of a large amount of solder. There is an effect to be obtained.

<First Embodiment>
A first embodiment of a printed wiring board with pins of the present invention will be described in detail with reference to FIGS. As shown in FIG. 1, the planting pin 1 of the present invention comprises a rod-shaped portion 1a and a disk-shaped nail head 1b connected to the tip thereof. The rod-shaped portion 1a of the planting pin 1 is connected perpendicularly to the rod installation surface 1d of the nail head 1b, and the tip joint surface 1c of the nail head 1b far from the rod-shaped portion 1a is connected to the external electrode pad 2 of the printed wiring board 100. The printed wiring board 100 with a pin is manufactured by soldering. Fig.1 (a) is the top view which observed the pin 1 for planting from the axial direction of the rod-shaped part 1a, FIG.1 (b) is a pin for planting from the side surface perpendicular | vertical to the axial direction of the rod-shaped part 1a. 1 is a cross-sectional view of the printed wiring board 100 and 1 observed. A resist film 1e is formed on the surface of the rod-shaped portion 1a having a predetermined height or more in the vicinity of the rod installation surface 1d. The solder fillet 7 covers the rod installation surface 1d and further reaches the rod-shaped portion 1a, but the solder is repelled by the resist film 1e and does not rise above it.

  As shown in FIG. 2, the printed wiring board 100 with pins includes, for example, a copper wiring pattern 3 and an epoxy resin material or polyimide resin material having a thickness of 50 μm to 200 μm, or an epoxy resin material containing glass fiber or polyimide containing glass fiber. This is a printed wiring board 100 in which an insulating resin layer 4 made of an insulating resin containing glass fibers such as a resin material is laminated. On the upper main surface 101 of the printed wiring board 100, external electrode pads 5 for connecting the bumps 11 of the semiconductor element 10 to be mounted are formed by openings of the solder resist 6 having a thickness on the wiring pattern 3 of about 10 μm to 40 μm. Yes. On the lower main surface 102, external electrode pads 2 for connecting the planting pins are formed by openings of solder resist 6 having a thickness of about 10 μm to 40 μm on the wiring pattern 3. External electrode pads 5 and 2 are formed by forming a nickel plating layer having a thickness of about 3 μm and a gold plating layer having a thickness of about 0.03 μm to 1 μm on the surface exposed from the opening of the solder resist 6 of the wiring pattern 3. .

  The external electrode pad 5 is precoated with a precoat solder having a solid phase point of 235 ° C. or lower as a preparation for soldering the bumps 11 of the semiconductor element 10. This precoat solder is remelted when the bumps 11 of the semiconductor element 10 are soldered to the external electrode pads 5. That is, Sn—Ag—Cu solder having a solid phase point of about 217 to 227 ° C., Sn—Bi—Ag solder having a solid phase point of about 213 ° C., SnPb solder, or the like is precoated. The solid phase point of this precoat solder is more preferably 230 ° C. or lower. The external electrode pads 5 and 2 are formed with an aqueous organic rust preventive film using a water-soluble preflux made of an imidazole compound or a benzimidazole compound instead of a metal plating layer such as nickel-gold. And 2 can be formed.

The operation of forming the pin grid array structure by soldering the planting pins 1 to the external electrode pads 2 of the printed wiring board 100 is performed before the semiconductor element 10 is soldered to the printed wiring board 100, so that the subsequent semiconductor It is necessary to solder using solder that can withstand the soldering temperature of the element 10. Therefore, the soldering of the nail head 1b of the nail head 1b of the planting pin 1 to the external electrode pad 2 has a solid phase point and a liquid phase point higher than the soldering temperature of the semiconductor element 10 to the printed wiring board 100. Solder with the solder you have. That is, since the solid phase point of the solder for mounting the semiconductor element 10 is 230 ° C. or less, the planting pin 1 is a solder having a solid phase point of 240 ° C. or more and a liquid phase point of 270 ° C. or less, and the nail head 1b. Is soldered to the external electrode pad 2 of the printed wiring board 100. The solder composition is binary or ternary solder in which Pb is 80% or more and the rest is other elements, for example, Pb is 80% and Sn is 20%, or Pb is 82% and Sn is 18%. Alternatively, solder having 80% Pb and 10% Sn and 10% Sb, or solder having 82% Pb, 10% Sn, and 8% Sb can be used. Pb-free high-temperature solder can also be used.

  When the liquid phase point of the solder for soldering the nail head 1b of the planting pin 1 to the external electrode pad 2 of the printed wiring board 100 exceeds 270 ° C., there is a problem that the soldering temperature deteriorates the insulating resin layer 4. When the solid phase point is less than 240 ° C., the solder fillet 7 is bonded to the tip bonding surface 1 c of the nail head 1 b of the solder fillet 7 by heat treatment when the bump 11 of the semiconductor element 10 is later soldered to the external electrode pad 5. There arises a problem that the strength of the portion deteriorates and falls off. Therefore, the nail head 1b of the planting pin 1 is soldered to the external electrode pad 2 of the printed wiring board 100 using solder having a solid phase point of 240 ° C. or higher and a liquid phase point of 270 ° C. or lower.

  The material of the planting pin 1 is, for example, a nickel-based alloy or copper alloy such as Kovar, Alloy 42, Alloy 194, etc., which is molded with a metal mold, nickel-plated on the surface, and covered with electrolytic gold plating as a base. desirable. For example, the nickel plating thickness is 4.0 μm and the gold plating thickness is 0.3 μm. Since the object of plating is a minute pin, the nickel gold plating film is formed by electrolytic barrel plating or electroless plating.

  The cross-sectional shape of the rod-shaped part 1a of the planting pin 1 is a circle, and the diameter is, for example, 0.3 mm. The diameter 0.3 mm of the rod-shaped part 1a is suitable when the pin pitch of the PGA package, which is the main application of the printed wiring board 100 with pins, is 1.27 mm. The nail head 1b of the planting pin 1 has a disc shape, and a rod installation in which one surface of the disc is a tip joint surface 1c formed in a spherical convex surface and the other surface of the disc is formed in a flat shape. Surface 1d.

  The diameter of the disk of the nail head 1b is determined according to the size of the external electrode pad 2 of the printed wiring board 100 to which it is soldered. The size of the external electrode pad 2 is the land diameter when the external electrode pad 2 is formed by a land not covered with the solder resist, and the external electrode pad 2 is formed by the opening of the solder resist 6 covering the land. In this case, the diameter of the opening is about 1.0 to 1.1 mm, and the diameter of the nail head 1b is set to 0.75 mm. The thickness of the disk of the nail head 1b is, for example, 0.15 mm. At the outer peripheral edge of the disk, which is the portion where the tip joint surface 1c of the nail head 1b and the rod installation surface 1d are connected, the direction of the tip joint surface 1c is changed gently, and there is no sudden inflection point. It connects with the surface of the installation surface 1d. The direction of the surface is gently changed until the tip joint surface 1c is connected to the rod installation surface 1d. As described above, the surface of the outer peripheral edge of the nail head 1b is gently connected to the rod installation surface 1d without changing the direction of the surface, so that the solder fillet 7 is connected to the outer peripheral edge of the disk at that portion. To get on easily.

(Procedure for forming resist film on rod-shaped part)
Below, the manufacturing method which forms the resist film 1e in the surface formed in the rod-shaped part 1a more than predetermined | prescribed height from the rod installation surface 1d like FIG. 1 is demonstrated using FIG. 3 and FIG.
(Step 1) First, photosensitive ink containing a solvent component is applied to the entire surface of the planting pin 1 by a method such as dipping, spraying or electrodeposition. This photosensitive ink uses a photosensitive resist that contains an ultraviolet curable component such as acrylate, can be developed with an alkali or a solvent, and can be peeled off with a solvent, an amine, a strong alkali, or the like. In addition, it is desirable to use a material having excellent heat resistance that does not deform with respect to heating by solder reflow, such as a heat-resistant dry film resist for forming wafer bumps, as the photosensitive resist.
(Step 2) By volatilizing the solvent component contained in the photosensitive ink by spraying hot air on the planting pin 1 applied with the photosensitive ink or by performing a drying process such as irradiating infrared rays, A resist coating film of 10 μm or more and 50 μm or less is formed.

  (Step 3) Next, as shown in FIG. 3A, the planting pin 1 is held in such a manner that the bar installation surface 1d of the nail head 1b is supported by the thin metal plate holding plates 20 from both sides. Ultraviolet rays 31 are radiated from the light source 30 to both sides of the rod-shaped portion 1 a protruding from the holding plate 20. As a result, the nail head 1b and the rod-shaped portion 1a corresponding to the thickness of the holding plate 20 are shielded from the irradiation of the ultraviolet rays 31, and only the photosensitive ink of the rod-shaped portion 1a irradiated with the ultraviolet rays 31 is photocured. A resist film 1e is formed to protect the solder from getting wet during the attaching process. Then, the root of the rod-shaped portion 1a from the rod installation surface 1d to the height at which the resist film 1e starts is wetted with the solder together with the rod installation surface 1d with a large amount of solder. A large amount of solder is formed with the solder fillet 7 at the bottom of the nail head 1b of the lower end joint surface 1c and the upper bar installation surface 1d of the nail head 1b and the base part of the bar 1a up to the resist film 1e. The nail head 1b is firmly held by surrounding. By holding firmly with a large amount of solder in this manner, an effect of preventing the solder fillet 7 from peeling off from the tip joint surface 1c of the nail head 1b can be obtained.

  The holding plate 20 that supports the nail head 1b of the planting pin 1 to form the resist film 1e is, for example, as shown in a plan view on FIG. 4, a front view on the lower left of FIG. 4, and a side view on the right of FIG. In addition, a metal plate having a gap 21 at the center is used. The gap 21 is formed in a slit having a width narrower than the diameter of the nail head 1b of the planting pin 1 and wider than the diameter of the rod-shaped portion 1a. The planting pin 1 is installed with the rod-like portion 1a facing downward, the rod-like portion 1a inserted into the gap 21 downward, and the rod installation surface 1d of the nail head 1b in contact with the surface of the holding plate 20. The planting pin 1 is sequentially installed in the gap 21 with the rod-shaped portion 1a facing downward, and each time the holding plate 20 is moved in the direction of the gap 21, the new planting pin 1 is moved to the position of the new gap 21. The rod-shaped part 1a is inserted into and installed. Further, the holding plate 20 tilts the surface of the holding plate 20 so as to lift up the end portions on both sides parallel to the gap 21. The nail head 1b is shielded from the ultraviolet rays by shielding the ultraviolet rays 31 with the surfaces lifted by the edge portions on both sides of the holding plate 20.

  Moreover, static electricity of the planting pin 1 is removed by performing static elimination air blow from above the nail head 1b of the planting pin 1 installed on the holding plate 20, and an unexpected electrostatic force acts on the planting pin 1. Make sure there is nothing. Furthermore, if the holding plate 20 is vibrated and there is the planting pin 1 overlapping in the gap 21, the planting pins 1 are aligned by removing the overlapping of the planting pins 1. Then, the planting pin 1 is sucked by sucking air from below the holding plate 20, and the rod installation surface 1 d of the nail head 1 b is brought into close contact with the holding plate 20. The planting pins 1 are arranged in such a manner, and ultraviolet light 31 is applied to the rod-like portion 1a from which the planting pins 1 protrude downward from the holding plate 20, and a light source such as a laser, a metal halide lamp, or a high-pressure mercury lamp. By irradiating from 30, the photosensitive ink of the rod-shaped part 1a is photocured to form a resist film 1e. Here, in order to shorten the exposure processing time, it is desirable that the light source 30 such as a high-pressure mercury lamp has a high output.

Further, it is not always necessary to irradiate the entire surface of the lower bar-shaped portion 1a from the holding plate 20 with the ultraviolet rays 31, but the bar-shaped portion 1a near the holding plate 20 is irradiated with the ultraviolet rays 31 in a ring shape, and the photosensitive ink in that portion is discharged. The ring-shaped resist film 1e may be formed by photocuring. The ring-shaped resist film 1e can be used as a barrier to prevent the progress of solder wetting. As described above, the ultraviolet ray 31 may be irradiated only to the minimum region of the rod-shaped portion 1a. For example, by scanning and irradiating the bar-shaped part 1a near the holding plate 20 for planting pins with ultraviolet laser light, the photosensitive ink of only that part can be photocured to form the resist film 1e. it can.
(Process 4)
Next, the film of the photosensitive ink that has not been irradiated with the ultraviolet ray 31 and has not been photocured is selectively removed by development processing. For development, a weak alkali such as sodium carbonate or a solvent is used, and methods such as dipping and spraying are used.

(Soldering pins for planting)
The tip joint surface 1c formed on the spherical convex surface of the nail head 1b of the planting pin 1 is soldered to the external electrode pad 2 of the printed wiring board 100 with molten solder. This soldering can be performed by heating and melting the solder paste installed on the external electrode pad 2 and pressing the nail head 1b of the planting pin 1 against the molten solder, or the tip first. It is possible to install the molten solder on the joint surface 1c and press the molten solder against the external electrode pad 2 for soldering.

  At the time of this soldering, the surface of the external electrode pad 2 of the printed wiring board 100 is directed upward, and the planting pin 1 is externally attached with the tip joint surface 1c of the nail head 1b facing downward from above the surface. Solder to the electrode pad 2. At that time, the spherical convex tip joint surface 1 c is brought into contact with the external electrode pad 2 of the printed wiring board 100 or soldered with a narrow gap of 40 μm or less between the external electrode pad 2. Since the tip joint surface 1c is a spherical convex surface, the surface other than the tip point that is closest to the external electrode pad 2 is spaced apart from the surface of the external electrode pad 2 by a predetermined distance and forms an inclined surface. . Therefore, when bubbles exist in the molten solder between the external electrode pad 2 and the tip joint surface 1c, the bubbles rise along the inclination of the tip joint surface 1c and are discharged out of the molten solder. There is an effect that bubbles are not mixed in the solder between the external electrode pad 2 and the tip joint surface 1c, and a strong solder fillet 7 is formed. The space between the tip joint surface 1c of the nail head 1b and the external electrode pad 2 is filled with solder of the solder fillet 7, and the shape of the solder fillet 7 is gentle from the outer peripheral edge of the disk of the nail head 1b. It is formed in a shape that extends to the outer peripheral edge of the external electrode pad 2 in the shape of the base of the slope mountain. The solder fillet 7 further wets and spreads on the bar installation surface 1d on the upper surface of the nail head 1b, and wraps the nail head 1b from above and below. On the other hand, in the rod-shaped portion 1a, the resist film 1e serves as a barrier against rising of the solder and protects the rod-shaped portion 1a so that the solder does not rise any further, so that the solder fillet 7 is not excessively spread over the rod-shaped portion 1a. There is.

(Removal of resist film)
Next, the solder film and the flux on the surface of the printed wiring board 100 are also removed, and the resist film 1e is removed with a solvent or a dedicated flux cleaning solution to complete the printed wiring board 100 with pins. During surface mounting of the planting pin 1 by solder, since the resist film 1e is present on the shaft portion of the planting pin 1, the solder does not get wet excessively. By attaching, the entire surface of the tip joint surface 1c and the rod installation surface 1d of the nail head 1b is covered with the solder fillet 7, and the effect of increasing the reliability of joining of the connecting portion of the planting pin 1 by the solder fillet 7 can be achieved. is there.

  In the above, the tip joint surface 1c of the nail head 1b of the planting pin 1 is formed as a spherical convex surface. However, the tip joint surface 1c can also be formed in a planar shape parallel to the flat rod installation surface 1d. is there. Further, the shape of the nail head 1b is not limited to a disk, and the nail head 1b with the solder fillet 7 can be similarly formed by using a nail head 1b having a polygonal outer periphery or a nail head 1b having a rectangular outer periphery. The bonding strength to the external electrode pad 2 can be improved.

<Second Embodiment>
In the second embodiment, the thermosetting resist film 1e is formed on the rod-shaped portion 1a as follows.
(Step 1) As shown in FIG. 4, the planting pin 1 having the nail head 1b formed at the tip of the rod-shaped portion 1a is inserted into the gap 21 of the holding plate 20 so that the rod-shaped portion 1a protrudes downward. .
(Step 2) Next, by lowering the holding plate 20 to near the liquid surface of the thermosetting resist solution, the rod-shaped portion 1a is placed in the liquid of the thermosetting resist solution by the nail head 1b. Immerse it close and apply the resist solution to the rod-shaped portion 1a.
(Step 3) The holding plate 20 is pulled up from near the liquid surface of the resist solution, moved into a hot air drying furnace, and the thermosetting resist solution adhering to the rod-shaped portion 1a of the planting pin 1 is thermally cured. A resist film 1e is formed.
(Step 2-1) Instead of the above steps 2 and 3, the resist film 1e can be formed by performing the following step 2-1. That is, the resist solution is applied to the rod-shaped portion 1a by dispensing the resist solution from the lower portion of the holding plate 20 to the rod-shaped portion 1a by jet or spray. Then, the resist solution is cured to form a resist film 1e.
(Step 4) The planting pin 1 thus formed with the resist film 1e is soldered to the external electrode pad 2 of the printed wiring board 100 at the tip joint surface 1c of the nail head 1b.
(Step 5) Next, the resist film 1e is removed with a solvent or a dedicated flux cleaning solution, and the printed wiring board 100 with a pin is completed, which also serves as flux removal of the solder and the surface of the printed wiring board 100.

  According to the present embodiment, the resist solution for forming the resist film 1e is not limited to the photosensitive ink, and an inexpensive thermosetting material can be selected. Therefore, the resist solution 1e is formed on the rod-shaped portion 1a. There is an effect that the manufacturing cost of the standing pins 1 can be reduced.

  The material for forming the resist film 1e is not limited to a photosensitive ink or a thermosetting resist material. For example, a thermoplastic resin material is heated and melted to adhere to a portion near the nail head of the rod-shaped portion 1a. The resist film 1e may be formed.

It is the top view and side sectional view of the structure which soldered the pin for planting of embodiment of this invention to the printed wiring board. It is sectional drawing of the printed wiring board with a pin of embodiment of this invention. It is a figure which shows the manufacturing method which forms a resist film in the rod-shaped part of the planting pin of the 1st Embodiment of this invention. It is the top view, front view, and side view which show the arrangement | positioning relationship of a holding plate and the planting pin in the manufacturing method which forms a resist film in the rod-shaped part of the planting pin of embodiment of this invention. It is the top view and sectional side view which show the 1st state which soldered the pin for planting of a prior art to the printed wiring board. It is the top view and side sectional view which show the 2nd state which soldered the pin for planting of a prior art to the printed wiring board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Planting pin 1a ... Rod-shaped part 1b ... Nail head 1c ... Tip joint surface 1d ... Bar installation surface 1e ... Resist film 2, 5 ... External electrode pad 3 ... Wiring pattern 4 ... Insulating resin layer 6 ... Solder resist 7 ... Solder fillet 10 ... Semiconductor element 11 ... Bump 20 ... Holding plate 21 ... Gap 30 ... Light source 31 ... UV light 100 ... printed wiring board 101 ... upper main surface 102 ... lower main surface

Claims (2)

A planting pin in which a nail head is formed at the tip of a rod-shaped part, and a tip joining surface of the nail head of the planting pin is soldered to an external electrode pad of a printed wiring board with a pin A resist film that can be removed by a solvent or a flux cleaning liquid is formed at least in the vicinity of the nail head of the rod-shaped portion , and the resist film is obtained by irradiating a photosensitive ink with ultraviolet rays and curing the resist film. planting for the pin, characterized in der Rukoto. A planting pin for soldering a tip joint surface of a nail head formed at the tip of a rod-like portion to an external electrode pad of a printed wiring board with pins, and at least in the vicinity of the nail head of the rod-like portion, a solvent or A method of manufacturing a printed wiring board with pins on which a planting pin on which a resist film that can be removed by a flux cleaning solution is formed is mounted, and the solder spreads on the rod-like portion by the resist film of the planting pin The soldering fillet wraps and solders the tip joint surface of the nail head and the surface to which the rod-shaped portion is connected, and the resist film of the planting pin is removed with a solvent or a flux cleaning solution. The manufacturing method of the printed wiring board with a pin characterized by having the process to do.