JP5538352B2 - Flow palette - Google Patents

Description

  Embodiments of the present invention relate to a flow pallet.

  In manufacturing a printed wiring board, mounting components are soldered to the front and back surfaces of the board. On the front surface of the substrate, an insertion component in which the lead reaches the back surface through the through hole is also mounted. Soldering of the lead reaching the back surface is generally performed by flow soldering. At this time, a flow pallet is used to support and convey the substrate while masking the mounted components on the back surface of the substrate.

  The flow pallet is provided on the periphery of the board installation part to prevent warpage and soldering, and the board installation part made of a rectangular plate-like member provided with openings according to the board design (flow soldering part) Reinforcing material. In general, the substrate installation part is manufactured by cutting a laminated plate containing glass fiber reinforced resin into a predetermined size, and the reinforcing material is attached to the periphery of the substrate installation part using components such as screws.

  Since it is used in the soldering process, the flow pallet is required to have high heat resistance, and the warpage generated under a high temperature environment is required to be as small as possible. In order to form an opening according to the design of the substrate, the flow pallet is also required to be easy to cut. Currently, the cost required for the flow pallet occupies a relatively large proportion of the manufacturing cost of the printed wiring board. If the number of parts of the flow pallet and the number of manufacturing steps can be reduced without impairing the heat resistance and the cutting workability, the flow pallet will be cheaper. This also leads to a reduction in the manufacturing cost of the printed wiring board.

JP 2003-62686 A JP 2011-23691 A JP 2003-179339 A

  The problem to be solved by the present invention is to provide a flow pallet having high heat resistance and excellent cutting workability.

The flow pallet of the embodiment includes a substrate installation portion on which a substrate is installed, and a reinforcing material that extends from the substrate installation portion and surrounds the periphery. The substrate holding portion and the reinforcing member are integrally formed by a glass-containing phenolic resin at a deflection temperature under load 300 ° C. or higher containing less than 200 mesh graphite powder, der Rukoto 98 wt% 325 mesh or less of the graphite powder Features.

The perspective view of the base material of the flow pallet concerning one Embodiment. The top view of the base material of the flow pallet concerning one Embodiment. The side view from the A direction in FIG. The side view from the B direction in FIG. The figure explaining the dimension of a pallet sample. The figure explaining the measurement location of the curvature of a pallet sample. The figure explaining the measurement location of the surface resistance value of a pallet sample.

  Hereinafter, embodiments will be described in detail with reference to the drawings.

  As shown in the perspective view of FIG. 1, a flow pallet 10 according to an embodiment is integrally formed with a substrate installation portion 11 made of a rectangular plate-shaped member and a reinforcing material 12 surrounding the periphery of the substrate installation portion. It is a thing. When used in the soldering process, the board installation section 11 is provided with an opening according to the design of the board, and a board fixing component is attached.

  The reinforcing material 12 exists at the peripheral edge over all of the opposing long side and the opposing short side in the board installation portion 11, and prevents warping of the pallet and soldering. A conveying portion 13 extends from the side surface of the reinforcing member 12 at the two opposing long sides. The conveying unit 13 engages with a conveyor claw of the soldering apparatus, whereby the pallet is held on the conveyor. Note that reference numeral 14 attached to a part of the short side indicates a reference plane for positioning in the X direction when processing the pallet.

  FIG. 2 is a top view of the flow pallet shown in FIG. As shown in FIG. 2, the outer shape of the flow pallet of the embodiment is a rectangular shape having a long side L1 and a short side W1. As shown in FIG. 1, the reinforcing material 12 is present on all the peripheral edges of the long side and the short side of the substrate installation portion 11, thereby forming a rectangular recess in the flow pallet. The top surface of the recess is a rectangle with a long side L2 and a short side W2, and the bottom surface is a rectangle with a long side L3 (<L2) and a short side W3 (<W2).

  3 and 4 are side views from the A direction and the B direction, respectively. As shown in FIGS. 3 and 4, the flow pallet has a height D1, and the position of D3 from the top surface and D2 from the bottom surface corresponds to the top surface of the transport unit. Each dimension in the flow pallet 10 may be appropriately determined as follows according to the size of the board to be installed, the specifications of the soldering device to be used, and the like.

  The outer long side L1 is determined according to the substrate size, and generally, the outer long side L1 is about 100 to 500 mm. As for the thickness ((L1-L2) / 2) of the reinforcement part 12, 5-10 mm is common. Accordingly, the long side L2 of the upper surface (rear surface) of the recess can be set within the range of (L1-10) mm ≦ L2 ≦ (L1-20) mm. Further, the long side L3 of the bottom surface of the recess is designed to be about 1 to 2 mm smaller than the long side L2 of the top surface. By providing such a taper, the releasability after pallet forming is improved.

  The outer short side W1 is a dimension within the specification range of the soldering apparatus and is determined according to the substrate size. Generally, the outer short side W1 is about 100 to 400 mm. The thickness of the reinforcing portion 12 is generally 5 to 10 mm, and the width of the conveying portion is generally 5 mm on one side. The short side W3 on the bottom surface of the recess is preferably smaller by about 1 to 2 mm than the short side W2 on the top surface. By providing such a taper, the releasability after pallet forming is improved. If the positioning part is too large, the molded pallet will not easily come off the mold. The size W4 of the positioning part is generally 20 to 100 mm.

  The height D1 is generally 11 to 22 mm. The distance D2 from the lower surface to the conveying unit is generally selected from 6, 8, 10, 12 mm, and the distance (height of the reinforcing portion) D3 from the upper surface to the conveying unit is generally 5 to 10 mm. is there.

  The flow pallet of this embodiment is a molded body of glass-containing phenol resin, and has a deflection temperature under load of 300 ° C. or higher. The deflection temperature under load is obtained according to JIS [7191]. Since it has super heat resistance that can withstand the solder flow temperature (250 to 300 ° C.), the flow pallet according to this embodiment does not decrease in strength even when exposed to high temperatures, and can be used continuously in the flow solder process. Since long-term thermal stability at a high temperature (250 ° C.) is also excellent, the occurrence of warpage is suppressed even after continuous use.

  Such a flow pallet can be manufactured by putting a molding material into a mold and heat-curing it. As the molding material, a glass-containing phenol resin is used, and a solid type (particulate) having a self-reactive functional group is preferable. Since a self-reactive functional group exists, it can be cured as it is by heating in a mold. Examples of such a phenol resin include a resole resin.

  The glass-containing phenol resin contains a glass component in a state suitable for molding using a mold in an amount of about 40 ± 5 mass% of the whole. When the content of the glass component is too small, the resulting molded article has sufficient heat resistance and is likely to warp. On the other hand, when there is too much content of a glass component, the molded object obtained becomes a brittle thing in addition to the machinability falling. For example, a molded body obtained by curing a resin containing about 80% by mass of a glass component as a whole cannot be easily cut.

When the flow pallet has a certain degree of conductivity, the influence of static electricity in the flow soldering process can be reduced, and the production yield of the printed wiring board can be increased. If the resistance value of the flow palette is about 1 × 10 ⁴ to 1 × 10 ¹¹ Ω, the influence of static electricity is sufficiently reduced. For example, after processing the opening according to the design of the substrate into the substrate installation portion, the conductive property can be imparted to the flow pallet by applying a conductive coating to the surface. When a molding material containing conductive powder is used, a flow palette having desired conductivity can be obtained more easily.

  For example, graphite powder can be used as the conductive powder. The graphite powder preferably has a moisture content of 0.3% by mass or less determined by weight measurement before and after drying. The size of graphite powder particles (Tyler mesh) is preferably 28 mesh or less, and the representative particle size can be selected as appropriate. The representative particle size mainly refers to the size of the existing particles. For example, graphite powder having a typical particle size of 100 to 200 mesh, graphite powder having a typical particle size of 100 to 325 mesh, graphite powder having a typical particle size of 325 mesh or less, and the like can be used.

Content of electroconductive powder can be suitably selected according to the kind, particle diameter, etc. Here, content of electroconductive powder refers to the ratio (mass%) of electroconductive powder with respect to the sum total of glass-containing phenol resin and electroconductive powder. The content necessary for obtaining a pallet having a resistance value in the range of 1 × 10 ⁴ to 1 × 10 ¹¹ Ω exceeds 16% by mass in the case of graphite powder having a typical particle size of 100 to 200 mesh, for example. In the case of 100 to 325 mesh graphite powder, the content is 11.5 to 11.8% by mass. A graphite powder having a smaller particle diameter can achieve a resistance value in the above-described range with a smaller content. In the case of graphite powder of 200 mesh or less and 98% by mass of graphite powder of 325 mesh or less, a resistance value in the above range can be achieved with a content of about 5.8 to 6.5% by mass.

  In molding the flow pallet of this embodiment, first, a molding material is put into a predetermined mold. What is necessary is just to select a metal mold | die suitably according to the shape, dimension, etc. of a printed wiring board. The glass-containing phenol resin which is a molding material is preferably in the form of particles as described above, and may have a particle diameter of 140 μm or more. In addition, the particle diameter here refers to the particle diameter calculated | required with the microscope etc. When a molding material having a particle size of about 140 μm or less is used, a molded product having no variation in characteristics depending on the location can be obtained. For example, the particles having a particle diameter of 140 μm or more may be removed by sieving or the like, but it is preferable that the particle diameter of the molding material is 140 μm or less by fine pulverization by selecting a pulverizer or the like. In particular, when blending conductive powder such as graphite powder, it is advantageous in that a uniformly mixed molding material can be obtained.

The molding machine is not particularly limited, and can be appropriately selected according to the mold size and the like. The heat curing conditions may be, for example, 170 to 200 ° C. for 200 to 400 seconds, the initial pressure may be 80 to 150 kgf / cm ² , and the curing pressure may be 150 to 200 kgf / cm ² .

  The pallet taken out from the mold after heat curing is preferably left on a surface plate with a metal plate placed on the substrate installation surface. By leaving in this way, the stability of the shape is enhanced.

  When the flow pallet of this embodiment is used in a soldering process, an opening corresponding to the board design (flow soldering part) is provided in the board installation part. Since the molded body is formed by curing a glass-containing phenol resin containing a glass component of about 40 ± 5% by mass, the pallet of this embodiment can be easily cut.

  Further, in the pallet of this embodiment in which the reinforcing material is integrally formed with the substrate installation portion, it is not necessary to fix the reinforcing material to the substrate installation portion by screwing as in the conventional case. Since the molding material is a molded body obtained by putting a molding material into a predetermined mold and heat-curing, the pallet of this embodiment can be easily manufactured.

  After providing the opening, a component for fixing the substrate is attached to the substrate installation portion, and the flow pallet of this embodiment is used with flow solder. Since it has super heat resistance that can withstand the solder flow temperature (250 to 300 ° C.), the flow pallet of this embodiment is used well in the soldering process, and warpage exceeding the allowable range does not occur even after continuous use. In addition, the pallet according to the present embodiment has a relatively smooth surface due to the molded body. When used in the soldering process, the flow pallet of this embodiment also has an advantage that the soldering material is less likely to adhere and the frequency of cleaning with a solvent can be reduced.

  A specific example of the flow pallet is shown below.

  A particulate glass-containing phenolic resin was prepared as a molding material. Content of the glass component in a glass containing phenol resin is 40 mass%. The glass-containing phenol resin used here is KM-2000 (manufactured by Kyocera Chemical).

A 200 ton molding machine was prepared, 1520 g of the molding material was placed in a mold, and heat-cured at a set temperature of 180 ° C. The initial pressure was set to 100 kgf / cm ² and the curing pressure was set to 170 kgf / cm ² . After 310 seconds, the sample was taken out from the mold, and the pallet sample of the example was obtained. A top view of the fabricated sample is shown in FIG. FIG. 5B is a diagram for explaining a cross-section along W11 in FIG. Each dimension in the figure is as follows. As shown in the drawing, in the pallet sample, the peripheral edge of the substrate installation portion 21 is surrounded by an integrally formed reinforcing material 22.

L11: 380mm, L12: 200mm, W11: 300mm
W12: 250mm, D11: 16mm, D12: 6mm
When the deflection temperature under load of the pallet sample was measured according to JIS [7191], it was confirmed to be 300 ° C. or higher.

  About the obtained sample, the curvature of the initial stage (before an acceleration test) was investigated. For the measurement, Mitutoyo image measuring device QV404 was used to measure 10 points (a1 to a10) shown in FIG. 6 and compared with 3 reference points (std). The difference (mm) from the reference point at each measurement location is summarized in Table 1 below. The range 1 is the difference between the maximum value and the minimum value among the five locations of the measurement points a1 to a5, and the range 2 is the difference between the maximum value and the minimum value among the five locations of the measurement points a6 to a10. is there.

Moreover, the commercially available pallet was prepared and the curvature was similarly investigated and it was set as Comparative Examples 1-7. The results are summarized in Table 2 below. In the pallet of the comparative example, the reinforcing material is screwed to the board installation portion. The board | substrate installation part in the pallet of Comparative Examples 1-6 cuts and processes the laminated body of glass fiber reinforced resin, glass mat or glass cloth, and an epoxy resin. The board | substrate installation part in the comparative example 7 is a product made from an epoxy resin.

  It turns out that the curvature before the acceleration test of the pallet sample of a present Example is comparable as a commercial item. When used in the flow soldering process, the pallet sample of this example has no problem.

Next, the pallet sample was accommodated in a thermostat, and after a durability acceleration test at 260 ° C. for 1 hour, the warpage was similarly examined. For the same commercial pallet as described above, a durability acceleration test was performed in the same manner to examine warpage after the test. The results are shown in Table 3 and Table 4 below.

  The pallet samples of the examples were confirmed to have sufficient durability without increasing warpage even after an accelerated test at 260 ° C. for 1 hour. Compared to commercial products, it has no inferiority and rather good characteristics. The warpage after leaving the same sample at 260 ° C. for 30 hours was 3 mm or less.

  Next, graphite powder was blended with the same glass-containing phenolic resin as described above to prepare a molding material. The physical properties of the graphite powder used are as follows.

Water content: 0.3% by mass or less Fixed carbon: 99.0% by mass or more
Ash content: 0.3% by mass
Maximum particle size: 74μm
Typical particle size: 98% or more is 325 mesh or less Particles of glass-containing phenol resin were finely pulverized by a pulverizer and sieved to separate particles having a particle size of 140 μm or more. Graphite powder was added here and mixed uniformly with a stirrer. The content of the graphite powder was 6% by mass of the total of the glass-containing phenol resin and the graphite powder.

  A pallet sample was formed in the same manner as described above except that a molding material containing graphite powder was used. The dimensions of the pallet sample are the same as described above.

About the obtained pallet sample, several surface resistance values were measured. The measurement locations were 13 locations (b1 to b13) shown in FIG. 7, and the resistance value between the two points was measured using a Mitsubishi Chemical Corporation high resistivity meter Hiresta-UP. The results are shown in Table 5 below.

As shown in Table 5 above, the surface resistance value in the pallet sample of the example is 1.11 × 10 ⁵ Ω at the minimum and 1.70 × 10 ⁹ Ω at the maximum, and the average value is 1.35 × 10 6. ⁸ Ω.

Commercially available pallets similar to those described above were prepared, and the surface resistance values at 13 locations were measured in the same manner as Comparative Examples 1 to 7. The results are summarized in Table 6 below.

A pallet sample molded using a molding material containing graphite powder has a resistance value of 1 × 10 ⁴ to 1 × 10 ¹¹ Ω, similar to a commercially available product, so that the influence of static electricity can be sufficiently reduced. it can. When such a pallet is used, a printed wiring board can be manufactured with a high yield.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 ... Flow pallet; 11 ... Board | substrate installation part; 12 ... Reinforcement material; 13 ... Conveyance part 14 ... X direction reference plane at the time of a process, 21 ... Substrate installation part;

Claims (2)

A substrate installation portion on which the substrate is installed; and a reinforcing material extending from the substrate installation portion and surrounding the periphery, wherein the substrate installation portion and the reinforcement material have a deflection temperature under load of 300 ° C. containing graphite powder of 200 mesh or less. or more is integrally formed by a glass-containing phenolic resin, flow pallets 98 mass% of the graphite powder is characterized in der Rukoto 325 mesh or less. The flow pallet according to claim 1, which has a resistance value of 1 x 10 ⁴ Ω or more and 1 x 10 ¹¹ Ω or less.

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