JP5067283B2 - Component mounting method - Google Patents

Description

  According to the present invention, in a printed board on which an electronic component with a slag part is mounted, when a through via (Via) is provided in the footprint for mounting the slag part, solder does not protrude from the through via to the back surface of the printed board. It relates to the component mounting method.

  When an electronic component with a slag part is mounted on a printed board, the slag part is often soldered to the printed board for the purpose of heat dissipation or GND (grounding) reinforcement. Especially when the IC package has a slag part on electronic parts such as SOP (Small Outline Package), QFP (Quad Flat Package), QFN (Quad Flat Non-leaded package), LGA (Land Grid Array), etc. Is attached to the bottom of the package. A through via (Via) is disposed between the pad of the printed board to which the slag portion is solder-connected and the pad for the signal terminal, and is connected to a necessary net (wiring pattern) such as GND.

  8A and 8B are explanatory views of a conventional electronic component package (QFN). FIG. 8A is a description of the top surface of the package, FIG. 8B is a description of the side surface of the package, and FIG. It is. A package 1 of an electronic component such as an IC is provided with a plurality of signal terminals 2 provided on the side surface from the back surface of the package 1 and a slag portion 3 for heat dissipation of the electronic component and GND strengthening.

  FIG. 9 is an explanatory diagram of a conventional printed board. In FIG. 9, the conventional printed board 10 is provided with a through via 11, a signal terminal footprint 12, and a slag portion mounting footprint 13. Note that a dotted frame indicates the size of the package 1 of the electronic component to be mounted. The printed board 10 is a multilayer wiring board on which the electronic component package 1 is surface-mounted. The through via 11 is a penetrating wiring for connecting to a necessary net (wiring pattern) in the printed board 10. The through via 11 and the slag portion mounting footprint 13 are connected by a wiring pattern or a solid pattern. The signal terminal footprint 12 is a pad soldered to the signal terminal 2 of the electronic component package 1. The slag portion mounting footprint 13 is a pad that is solder-connected to the slag portion 3 of the electronic component package 1.

  FIG. 10 is an explanatory view of a downsized electronic component package (QFN) of a conventional example, FIG. 10 (a) is an explanation of the upper surface of the package, FIG. 10 (b) is an explanation of the side of the package, and FIG. It is an explanation of the back side. The electronic component package 1 is provided with a plurality of signal terminals 2 provided from the back surface to the side surface of the package 1 and a slag portion 3 for heat dissipation of the electronic component and GND strengthening. In the package 1, the shape of the slag portion 3 is hardly changed even when the package is small, and the gap with the signal terminal 2 is small.

  FIG. 11 is an explanatory diagram of a printed board on which a miniaturized electronic component package of a conventional example is mounted. In FIG. 11, since the gap between the slug portion 3 and the signal terminal 2 is small on the printed board 10 on which the conventional miniaturized electronic component package 1 is mounted, a space for arranging the through via 11 cannot be provided.

  FIG. 12 is an explanatory diagram of a printed board on which a miniaturized electronic component package of a conventional example is mounted. In FIG. 12, a through via 11 is disposed on a slag portion mounting footprint 13 in a printed board 10 on which a conventional miniaturized electronic component package 1 is mounted (see, for example, Patent Document 1). . As described above, when the through via 11 is arranged in the slag portion mounting footprint 13, the solder may flow out to the back surface of the printed board.

  In addition, in order to prevent the solder from flowing out to the back surface of such a printed board, there is one in which a solder resist is provided around the opening of the through via (for example, see Patent Document 2).

FIG. 13 is an explanatory diagram for disposing conventional non-through vias. In FIG. 13, the non-through via 21 is arranged in the slag portion mounting footprint 13 to prevent the solder from flowing out to the back surface. The arrangement of the non-through via 21 complicates the manufacturing process.
JP 2007-227484 A Japanese Patent No. 3639505

  The conventional device has the following problems.

  Miniaturization, thinning, and integration have led to the need for small, multi-pin electronic components, but when the component package is miniaturized, the gap between the slug portion and the signal terminal pad is shortened, and through vias are reduced. The space to arrange disappears.

Simply placing through vias in the pad of the slag part has caused a problem that the solder protrudes to the opposite surface through the through vias during component mounting. (If the solder protrudes on the back side, there is a risk that the discharged solder will short-circuit with nearby components, or if it protrudes on the first reflow surface, the solder mask metal mask will float on the second reflow surface Mounting quality may deteriorate due to excessive supply of solder.)
Further, it is possible to dispose a non-through via in the pad of the slag part and connect it to a necessary net, but the manufacturing cost of the printed board is expensive.

  The component mounting method on the printed board described here prevents solder from protruding to the back side of the printed board in a simple process by closing through vias in the line (process) for mounting the part on the printed board. With the goal.

  FIG. 1 is an explanatory diagram for closing a hole of a through via. In FIG. 1, 10 is a printed board, 11 is a through via, 12 is a footprint for a signal terminal, 13 is a footprint for mounting a slag part, and 14 is an adhesive (ink, a component for closing a hole). This component mounting method has the following means.

  A printed board 10 having a footprint 13 for mounting a slag portion and soldering the slag portion by solder printing and reflow soldering and a through via 11 provided in the footprint 13 for mounting the slag portion. In the component mounting method for mounting to the print board 10, the information printing ink or the component fixing adhesive in the step of mounting the component with the slag portion or the component that plugs the hole during the component mounting step, Through a step of closing the hole of the through via 11 before mounting the component, component mounting, solder printing, and reflow are performed. For this reason, the protrusion of the solder to the back surface of the printed board can be prevented with a simple process.

  Since the mounting via, solder printing, and reflow are performed by closing the through-via hole using the manufacturing process for mounting the component, it is possible to prevent the solder from protruding to the back surface of the printed board in a simple process.

  In the footprint of a printed board that is solder-connected to the slag portion of the electronic component package, a through via is provided in the footprint, and the through via is closed so that the solder does not enter. This prevents it from protruding on the back side. As a method of closing the through via, there is a method of filling the printed board with resin or copper in the process of manufacturing the printed board. However, since the number of steps increases, the cost of the printed board is generally increased. Therefore, in this mounting method, the through via is blocked in a line (process) for mounting the component on the printed board.

  For example, a method of filling a through via with a component fixing adhesive, a method of printing and filling a through via in a process of printing necessary information such as a lot number, or filling a hole in a component mounting process It is conceivable to add a hole filling process such as mounting of minute parts.

  Further, as in the case of ink used for printing, even if the through via is not completely buried, it can be prevented from protruding to the back surface of the solder if it becomes a barrier that blocks the solder on the periphery or the inner wall of the hole.

  For this reason, even if it does not use the expensive printed board which uses a non-penetrating via, it becomes possible to maintain the connection between a slag part and a printed board, and to mount without impairing manufacturing quality.

(1): Explanation of mounting of electronic component package Although it depends on the configuration of the mounting line of the printed board, there is usually an adhesive coating process after solder printing, and then component mounting, reflow, and appearance inspection are performed.

a) Explanation of printing on through-vias If there is a manufacturing information printing process in the component mounting process, printing is performed before solder printing. For example, when printing through vias in the manufacturing information printing process, printing is performed by spraying ink (no solder) as in an inkjet printer. However, if the through-via hole diameter is φ0.25 mm, printing is not possible. Print on a round shape with a diameter of about 0.5mm and cover at least the diameter of the through-via hole. However, the hole need not be completely filled, and ink may be applied to the entire circumference of the hole. Solder melts at about 200-220 ° C in the reflow process and travels along the copper foil surface of the slag part, but the ink is printed on the circumference of the through-via, so that the transmission of the solder can be blocked .

  In this case, the through vias are preferably arranged at the four corners in the slag part, and are arranged so that the land of the through via is in contact with the side of the slag part. Then, the solder is printed (for example, in a cross shape) so as not to reach the through via.

  By doing so, solder is not printed directly on the through via, and even if the solder is transmitted on the copper foil surface of the slag part, it is blocked by ink, and a sufficient joint area with the slag part on the component side can be taken. It becomes possible.

  Although it depends on the characteristics of the parts, it is desirable that 50% or more of the joining area of the slag portion is soldered.

b) Description of plugging holes with adhesives When closing holes with adhesives, solder printing is performed prior to the adhesive application process, but as with ink printing methods, solder printing is performed in a cross so as not to penetrate through vias. Thus, an adhesive can be applied to the through via even after solder printing. As in the case of printing with ink, when the diameter of the through-via is φ0.25mm, it is desirable to apply the adhesive at about φ0.5mm. However, since the amount of application varies, the through-via is provided at the four corners of the slag part. By arranging so that the land of the penetrating via is in contact with the side of the slag part, even if the application amount of the adhesive increases to about φ1 mm, excess adhesive is dispersed inside and outside the slag part. It is possible to minimize the reduction of the joint surface due to the adhesive.

  Further, the adhesive tends to swell at the center during application, and is preferably provided at the four corners for the same reason because it is crushed during component mounting.

FIG. 1 is an explanatory diagram for closing a hole of a through via, FIG. 1 (a) is an explanation before closing the hole of the through via, and FIG. 1 (b) is a block for closing the hole of the through via. It will be explained later. In FIG. 1A, the printed board 10 is provided with a through via 11, a signal terminal footprint 12, and a slug mounting footprint 13. Note that a dotted frame indicates the size of the package 1 of the electronic component to be mounted. In FIG. 1B, the through-via in the slag portion mounting footprint 13 is closed with a component fixing adhesive 14, printing ink 14, or microcomponent 14. Thereafter, component mounting, reflow, appearance inspection, and the like are performed.

  FIG. 2 is an explanatory view of a cross section of a printed board, FIG. 2 (a) is an explanation for closing a hole with an adhesive, ink, and the like, and FIG. 2 (b) is an explanation for closing a hole with a micro component. In FIG. 2A, a printed circuit board 10 is a multilayer (four layers in this example), and the upper surface of the through via 11 is closed with an adhesive or ink 14 or the like. Here, the hole is closed with the adhesive when there is an application process of the adhesive for fixing the component. Further, the hole is closed with ink when printing is performed before solder printing when there is a manufacturing information printing step. Thereby, it is possible to prevent the solder from protruding from the through via 11 on the back surface of the printed circuit board 10. In this example, the through via 11 is electrically connected to the intermediate wiring 15 in the third layer from the top.

  In FIG. 2B, the printed circuit board 10 is a multilayer board (four layers in this example), and the upper surface of the through via 11 is closed with a micro component 14 for filling a hole. Thereby, it is possible to prevent the solder from protruding from the through via 11 on the back surface of the printed circuit board 10. Since the hole-filling micro component 14 is performed in the component mounting process on the printed circuit board 10, the number of processes does not increase.

(2): Explanation to prevent the spread of adhesive and ink By performing solder resist or silk printing between the through via and the slag part (footprint for mounting the slag part), the adhesive of the through via can be applied when mounting components. Even if it is crushed, resist or silk printing becomes a wall, and it is possible to prevent the adhesive or the like from spreading to the solder joint portion of the slag portion.

  Here, the resist is applied in the manufacturing process of the printed board before mounting the electronic component. Silk printing is a process for displaying the number of a mounted component, a component name, and the like in a manufacturing process of a printed board before mounting an electronic component.

  FIGS. 3A and 3B are explanatory views of putting a resist and silk around the through via. FIG. 3A is an explanation before closing the hole of the through via, and FIG. 3B is an explanation after closing the hole of the through via. is there. In FIG. 3A, resist and silk printing 16 are performed around the through vias 11 at the four corners of the slag portion mounting footprint 13 of the printed board 10. In FIG. 3B, the through via in the slag portion mounting footprint 13 is closed with an adhesive 14 for component fixing, an ink 14 for printing, or a micro component 14. Thereafter, even if the adhesive 14 or the like is crushed when the component is mounted, it is possible to prevent the resist 14 or the silk printing 16 from becoming a wall and spreading the adhesive 14 or the like to the solder joint portion of the slag portion.

(3): Explanation of Arrangement Position of Through Vias The arrangement position of the through vias 11 in the slag portion mounting footprint 13 is such that the land of the through via 11 is in contact with the end face of the slag portion mounting footprint 13. Thus, the area of the solder joint portion can be increased.

  FIG. 4 is an explanatory view of the arrangement position of through vias, FIG. 4 (a) is an explanation when four through vias are used, FIG. 4 (b) is an explanation when two through vias are used, FIG. (C) is a partially enlarged view of FIG. In FIG. 4A, four through vias 11 are arranged in the slag portion mounting footprint 13 such that the lands of the through via 11 are in contact with the end surfaces of the four corners of the slag portion mounting footprint 13. Is. In FIG. 4B, two through vias 11 in the slag portion mounting footprint 13 are arranged diagonally so that the lands of the through via 11 are in contact with the end surfaces of the two corners of the slag portion mounting footprint 13. It is arranged at the position. In FIG. 4C, the through vias 11 are arranged such that the land of the through via 11 (part indicated by a thick dotted line) is in contact with the end face of the slag portion mounting footprint 13. Thus, by arranging the through vias 11 in the corners, the solder joint area at the center can be made as large as possible.

(4): Description of the metal mask shape a) Description of the metal mask shape The shape of the metal mask that prints solder on the footprint 13 for mounting the slag portion is that the solder is excessive if the opening is 100%. It is reduced to about several to 50% with respect to the pad shape (here, square) of the footprint 13 for use. Even at this time, an opening is formed so that solder is printed at a position away from the through via in a printed state.

  5A and 5B are explanatory diagrams of the shape of the metal mask, FIG. 5A is a description of a cross shape, FIG. 5B is a description of a square shape, and FIG. 5C is a description of a round shape. In FIG. 5A, the shape of the metal mask 17 for printing the solder on the slag portion mounting footprint 13 is a cross shape. For this reason, a cross-shaped solder is printed on the slag portion mounting footprint 13 away from the through via as shown in the figure. In FIG.5 (b), the shape of the metal mask 17 which prints the solder on the slag part mounting footprint 13 is a square shape. For this reason, the solder for mounting the slag part 13 is printed with a quadrangular solder at a position away from the through via (the apex is vertically and horizontally) as shown in the figure. In FIG.5 (c), the shape of the metal mask 17 which prints the solder on the slag part mounting footprint 13 is a round shape. For this reason, as shown in the figure, a round solder is printed on the slag portion mounting footprint 13 at a position away from the through via (center portion).

b) Explanation of slitting a metal mask When solder printing is performed over a large range, voids may occur during mounting and reflowing, resulting in poor bonding. In order to eliminate this bonding failure, a slit which is an air escape path is provided.

  6A and 6B are explanatory views of slitting a metal mask, FIG. 6A is a description of slitting in a cross shape, FIG. 6B is a description of slitting in a square shape, and FIG. 6C is a round shape. It is the explanation which puts a slit in. In FIG. 6A, diagonal cross-shaped slits 18 are inserted in a cross-shaped metal mask. For this reason, in the solder joint at the time of reflow, the diagonal cross-shaped slits serve as air escape paths and can prevent the generation of voids.

  In FIG. 6B, diagonal cross-shaped slits 18 are inserted in a rectangular metal mask. For this reason, the diagonal cross-shaped slits serve as air escape paths and prevent the generation of voids.

  In FIG. 6C, a plurality of slits 18 are inserted in a diameter direction in a round metal mask. For this reason, the plurality of slits in the diametrical direction serve as air escape paths and can prevent generation of voids.

c) Explanation of opening a plurality of holes By opening a plurality of holes as a metal mask, it is possible to supply solder to every corner of the pad of the slag portion mounting footprint 13, and the hole diameter to be opened The amount of solder can be adjusted by uniformly changing.

  7A and 7B are explanatory diagrams when a plurality of holes are opened in the metal mask. FIG. 7A illustrates a small opening example, and FIG. 7B illustrates a large opening example. In FIG. 7A, a small round opening is provided in the metal mask, and solder is printed in a plurality of small round shapes 17 on the pads of the slag portion mounting footprint 13. In the soldering at the time of reflow, the small round 17 solders are crushed and connected to each other. In FIG. 7B, a large round opening is provided in the metal mask, and the solder is printed in a plurality of large round shapes 17 on the pads of the slag portion mounting footprint 13. The amount of solder is larger than that of). In the solder joint at the time of reflow, the large round shape solder 17 is crushed and connected to each other.

It is explanatory drawing which plugs up the hole of the penetration via of the present invention. It is explanatory drawing of the printed circuit board cross section of this invention. It is explanatory drawing which puts a resist and silk around the penetration via of the present invention. It is explanatory drawing of the arrangement position of the penetration via of this invention. It is explanatory drawing of the metal mask shape of this invention. It is explanatory drawing which puts a slit in the metal mask of this invention. It is explanatory drawing at the time of opening a some hole in the metal mask of this invention. It is explanatory drawing of the electronic component package (QFN) of a prior art example. It is explanatory drawing of the printed board of a prior art example. It is explanatory drawing of the electronic component package (QFN) reduced in size of the prior art example. It is explanatory drawing of the printed circuit board which mounts the electronic component package reduced in size of the prior art example. It is explanatory drawing of the printed circuit board which mounts the electronic component package reduced in size of the prior art example. It is explanatory drawing which arrange | positions the non-through-via of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Printed board 11 Through-via 12 Signal terminal footprint 13 Footprint for mounting slag part 14 Adhesive (parts that block ink and holes)

Claims (4)

To mount a component with a slag part on a printed board having a footprint for mounting the slag part and soldering the slag part by solder printing and reflowing, and a through via provided in the footprint for mounting the slag part The component mounting method of
Wherein the step of providing the slag wall on the footprint for mounting the periphery of the through vias, more adhesive inks or parts for fixing the information printed, close the hole of the through vias before the component mounting step through the door, the component mounting method and performing parts tower No及 beauty reflow. 2. The component mounting method according to claim 1 , wherein the wall is formed by solder resist or silk printing . The component mounting method according to claim 1, wherein the through via is disposed so as to be inscribed in a corner of the footprint for mounting the slag portion.   The shape of the opening portion of the metal mask for performing the solder printing is smaller than the pad shape of the footprint for mounting the slag portion, and the opening is provided so as to be a position farthest from the through via. The component mounting method according to claim 1.

Images