JP2012104659A - Electronic component mount substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable electronic component mount substrate which reduces breaking in a solder joint part caused by influence of heat strain due to heat generated by an electronic component mounted on a surface of a substrate in which a wiring pattern is formed and suppresses inclination of the electronic component during solder joint.SOLUTION: In an electronic component mount substrate 3, an electronic component 2 is mounted on a surface of a substrate 1 in which a wiring pattern 4 is formed by solder joint. In the electronic component mount substrate 3, a heat resistant tape 6 is disposed at a position on the substrate 1, which is located between the substrate 1 and the electronic component 2 and excludes a solder joint part.

Description

  The present invention relates to an electronic component mounting board in which an electronic component is mounted on a surface of a substrate on which a wiring pattern is formed by solder bonding.

Conventionally, when an electronic component is mounted on a printed circuit board, a method of joining the electronic component to a wiring pattern formed on the substrate by soldering using a tin-lead eutectic solder has been employed. It was. This tin-lead eutectic solder has a low melting point and is flexible, so there is a good balance between elongation and strength. The difference in thermal expansion coefficient between the printed circuit board and the electronic component terminals during soldering Can absorb the stress caused by. Moreover, since it deteriorates itself (coarse particle size), it prevents rapid breakage or breakage and acts as a kind of buffering agent, thus giving the soldered joint high reliability.

  However, lead is a metal harmful to the human body. For this reason, research and development of lead-free solders that do not contain lead have been promoted in response to increasing international demands to protect the global environment and avoid the use of harmful substances.

  Currently, the most commonly used lead-free solder is a ternary tin-silver-copper alloy. As this typical composition, Sn-3.5Ag-0.7Cu, Sn-3.0Ag-0.5Cu, etc. are put into practical use. In addition, ternary Sn-Ag-Bi, Sn-Cu-Ni (Ni is a trace additive), quaternary Sn-Ag-Cu-Bi, quinary Sn-Ag-Cu- Lead-free solder such as Bi-Ge has been announced.

  However, it is known that these lead-free solder materials have a smaller effect of absorbing the stress than lead-containing solder. For this reason, when the temperature rises during energization, the stress generated due to the different coefficients of thermal expansion between the substrate and the electronic component cannot be completely absorbed, and minute plastic strain is accumulated. If such stress or plastic strain occurs, the solder cannot withstand when the strength and rigidity of the solder decrease at high temperatures.

  For this reason, in electronic component mounting boards, thermal distortion occurs due to heat generated from itself and surrounding components each time it is used, and the stress generated due to the difference in thermal strain between each member also reaches the solder part. . For this reason, in lead-free solder, plastic strain accumulates every time heat is generated, and cracks are generated inside the joint at a certain point in time, and as the use continues further, the crack grows and breaks the joint. There is a problem that the electrical connection cannot be maintained.

  In addition, lead-free solder has less fatigue test data accumulation than conventional solder, and it is difficult to predict the service life. There is also a problem that the reliability of a product joined by solder cannot be guaranteed. In order to solve this problem, reliability has been increased by increasing the cost, such as improving the mechanical properties of lead-free solder, optimizing the amount and position of solder joints, selecting the materials used, or changing to an expensive board material with low thermal distortion. There is a reality that maintains sex.

That is, in the temperature range of about −60 to 150 ° C., the cause of the breakdown that occurs when thermal strain occurs is that the substrate 1 and the electronic component 2 appear due to different thermal expansion coefficients as shown in FIG. There is one warp. For example, a ferrite sintered body often used in a chip resistor exhibits an elastic coefficient of about 100 to 200 GPa and a thermal expansion coefficient of about 5 to 10 × 10 ⁻⁶ / ° C.

  On the other hand, there are many types of substrates 1 such as a metal or glass base impregnated with resin and a paper base base impregnated with resin. However, the elastic modulus is almost in the range of 5 to 250 GPa and the thermal expansion coefficient is in the range of 15 to 25 × 10 −6 / ° C. In such a component configuration, when the temperature shifts to a high temperature or low temperature, stress is generated due to the difference in thermal expansion coefficient between the electronic component and the substrate, but the elastic coefficient of the substrate is clearly smaller than that of the electronic component, that is, soft. The deformation amount of the substrate 1 is remarkably larger than the deformation of the electronic component 2. As a result, the substrate 1 is warped in a concave shape and a convex shape on the electronic component 2 side at high temperature and low temperature, respectively. When the substrate 1 is warped, stress concentrates at a position near the corner portion of the electronic component in the solder fillet, and large stress is locally generated.

  This is due to the characteristic that the lead-free solder 5 has less stress relaxation capability than conventional solder and accumulates strain. The accumulated strain eventually develops into a crack, and the crack expands at every temperature cycle, and finally reaches the surface of the solder fillet. Thus, even if locally, when high stress is generated, it leads to the tearing of the entire fillet, which is a big problem.

  As a result of various studies on this problem, in order to increase the fatigue resistance of the solder fillet and prevent the solder fillet from being destroyed, it is most important to increase the thickness of the solder 5 in the gap 7 between the electronic component 2 and the substrate 1. It turns out to be effective. This is because the stress generated between the electronic component 2 and the substrate 1 is uniformly distributed, and the amount of plastic strain accumulated in the stress concentration portion during use is reduced. It has also been found that this tendency does not change even if the materials, sizes, and thickness dimensions of the electronic component 2 and the substrate 1 are varied, and generally an effect of reducing plastic strain can be obtained.

  However, it is not easy to increase the gap distance between the electronic component 2 and the substrate 1. This is because, at the time of joining, the solder 5 is solidified while maintaining the melt shape immediately before being melted and solidified, but at this time, the electronic component 2 is settled by its own weight. When the solder is melted, a force (wetting force) that wets the electrode surface of the electronic component is generated, so that the surface of the solder 5 is surface tensioned, and the solder 5 enters the gap between the substrate and the electronic component (metal wiring pad). Capillary phenomenon occurs. A solder fillet is formed by the balance between these forces and the weight of the electronic component.

  Among these, the force acting in the direction of floating the electronic component 2 and increasing the gap distance from the substrate 1 is a capillary force due to a capillary phenomenon between the substrate 1 and the electronic component 2. On the other hand, the surface tension appearing on the surface of the solder 5 and the wetting force appearing at the interface between the solder 5 and the metal work to draw the molten solder to the fillet side. Since the capillary force for floating the electronic component 2 is very small as compared with the surface tension and the wetting force, the general electronic component 2 is joined at a position where it almost contacts the substrate 1. Further, since the position of the electronic component 2 is determined by a delicate balance of forces, the variation is large, which is one factor that reduces the reliability. In particular, in a large-sized electronic component 2 that tends to have a short fatigue life, its own weight increases and the gap distance tends to be short, which adversely affects the fatigue life.

  However, the force acting in the direction of floating the electronic component 2 is small, and it is difficult to increase the gap distance unless a force is directly applied to the electronic component 2 itself at the time of soldering. Further, the gap distance can be adjusted by lifting the electronic component 2 at the time of soldering. For example, in the joining process by automatic control using an auto-feeder and a reflow process, the wiring of the numerous boards 1 There is a problem that it is difficult to individually lift the electronic components 2 corresponding to the pattern 4 and the component arrangement pattern.

  Furthermore, in the solder joint, when the solder 5 is melted, there is a phenomenon called so-called self-alignment in which the electronic component moves due to the surface tension appearing on the surface of the solder 5 and the wetting force appearing on the interface between the solder 5 and the metal. . This self-alignment attracts molten solder and electronic components to their original positions when the component placement position by the feeder or the solder paste application position by mask printing deviates from the ideal position in the solder joining process. Work.

  That is, if a force is applied to or fixed to the electronic component 2 in order to increase the gap distance between the electronic component 2 and the substrate 1, the function for correcting misalignment by self-alignment will not work. The overall reliability will be greatly reduced.

  In addition, there is a problem in that the function of correcting misalignment by self-alignment itself is difficult to function stably. This occurs because the respective solder pastes cannot be precisely arranged in the same environment, such as the amount of paste printed, the positional relationship with electronic components and wiring patterns, and the heating conditions. For example, since the heating at the time of soldering cannot be performed uniformly for all the electronic components, the respective solders 5 on the side end of the electronic component 2 are in a state where the temperature rise and the melting timing are shifted. For this reason, when the solder is melted, a complicated force due to the self-alignment works, and the electronic component 2 is tilted without being kept horizontal at the time of soldering. Further, in the case where it is remarkable, the inclination of the electronic component 2 becomes 90 ° and may rise.

  Therefore, in Patent Document 1 below, when the electrode formed on the outer edge of the element and the land formed on the substrate surface are joined by the solder layer, the thickness of the portion of the electrode facing the land is determined. There has been proposed a method for making the thickness substantially uniform or increasing the thickness of the portion of the electrode facing the land as the distance from the edge portion of the element increases.

  Moreover, in the following Patent Document 2, an electronic component having a first electrode formed at an end portion is mounted on a mounting substrate, and the second electrode formed on the mounting substrate and the first electrode are combined. An electronic component mounting structure has been proposed in which a first spacer made of a resin containing an inorganic filler is disposed between the electronic component and the mounting substrate when electrically connected by solder.

  Furthermore, in the following Patent Document 3, an electronic component mounted on a circuit board, the corridor board, a substrate electrode provided on the circuit board, and a component electrode provided on the electronic component are electrically connected. A solder layer to be connected, and the circuit board has a convex part in contact with the electronic component at a site where the electronic component is mounted, and the height of the convex part is higher than that of the substrate electrode. Circuit devices have been proposed.

JP 2005-183468 A Japanese Patent Laid-Open No. 11-163510 JP 2008-60182 A

  However, in the conventional method for controlling the thickness of the electrode of the element corresponding to the land, the thickness of the electrode can be increased even if the gap between the substrate and the element is increased by increasing the thickness of the electrode of the element. Since the amount is limited and the effect of increasing the thickness of the solder portion where stress is concentrated is small, there is a problem that the effect of improving the life is small. In addition, it is difficult to control the thickness of the electrodes, and the manufacturing process becomes complicated, and there is a problem that a great deal of cost is required for setting conditions in the process.

  Further, in the conventional method of arranging a resin member made of an epoxy resin containing a silica filler between a chip component and a printed board, a resin member serving as a spacer is directly connected to the printed board, so that a new stress is applied. There is a problem of becoming a source. In addition, since the resin member is formed of an ambiguous blended resin, an additional installation step for arranging the substrate and the resin member is necessary in the manufacturing process, which increases the manufacturing cost.

  Furthermore, in the conventional method of providing a convex part for contacting an electronic component on the circuit board by combining solder resist, circuit board electrode, silk ink, or a combination thereof on the circuit board, There is a problem that a large increase in the gap distance is difficult and a sufficient life improvement effect cannot be expected. Incidentally, the gap distance between the electronic component and the substrate is determined by the capillary force and surface tension of the molten solder in the gap and the weight of the electronic component, but is generally 15 μm to 35 μm in a commonly used electronic component. However, in the method using resist or silk screen printing, the increase in the gap distance is about 20 μm at the maximum, and no effect is recognized in view of manufacturing variations.

  The present invention has been made in view of such circumstances, and reduces breakage of a solder joint portion caused by the influence of thermal distortion due to heat generation of an electronic component mounted on a surface of a substrate on which a wiring pattern is formed. An object of the present invention is to provide a highly reliable electronic component mounting board by suppressing the inclination of time.

  In order to solve the above problems, the invention according to claim 1 is an electronic component mounting board in which an electronic component is mounted on a surface of a board on which a wiring pattern is formed by solder bonding. A heat-resistant tape is disposed between the electronic component and a position excluding the solder joint.

  The invention according to claim 2 is the invention according to claim 1, wherein the heat-resistant tape includes a base material mainly composed of polyimide and an adhesive mainly composed of silicon or acrylic on one side of the base material. It is characterized by being formed by applying an agent.

  Further, the invention according to claim 3 is the invention according to claim 1 or 2, wherein the heat-resistant tape has a thickness dimension of 50 μm or more and a width that abuts on a surface area of 50% or more of the electronic component. It is characterized by being formed in dimensions.

  According to a fourth aspect of the present invention, there is provided a method for manufacturing an electronic component mounting board in which an electronic component is mounted on a surface of a board on which a wiring pattern is formed by solder bonding, and the heat-resistant tape is attached to the board and the electronic device. The wiring pattern and the electronic component are solder-bonded after being disposed between the components.

  The invention according to claim 5 is the invention according to claim 4, wherein the heat-resistant tape is located at a position excluding the wiring pattern, and the solder joint between the substrate and the electronic component is provided. A paste-like solder is disposed on the wiring pattern at a position where the electronic component is mounted after being disposed at a position other than the position, and the wiring pattern and the electronic component are soldered together. Is

  According to this invention of Claims 1-3, since the board | substrate has arrange | positioned the heat resistant tape in the position except the said solder joint part between the said board | substrate and the said electronic components, the said Using the heat-resistant tape as a spacer, the gap distance between the substrate and the electronic component can be increased. As a result, the thickness of the solder fillet formed at the solder joint between the substrate and the electronic component can be increased, resulting from a difference in thermal expansion coefficient between the substrate and the electronic component due to heat generation during energization. Stress can be evenly distributed to reduce plastic strain accumulation.

  In addition, since the heat-resistant tape is used as a spacer between the substrate and the electronic component, when the solder having a melting point of about 220 ° C. is melted at the time of soldering, the substrate and the electronic component become 240 to 240 ° C. Even when heated to a high temperature of about 260 ° C., there is no decrease in adhesion function or strength, and a stable increase in gap distance can be exhibited. As a result, the heat-resistant tape can be easily used as a spacer between the substrate and the electronic component.

  Further, since the heat resistant tape is soft and has a small elastic modulus, it does not cause a new stress on the substrate and the electronic component due to heat generated during soldering and heat generated during energization. Thereby, it does not become a factor which reduces the reliability of a product.

  According to invention of Claim 2, since the said heat-resistant tape has apply | coated the adhesive which has a silicon | silicone or an acrylic as a main component on the single side | surface of the base material which has a polyimide as a main component, the said heat-resistant tape is the said It can be affixed to either the substrate or the electronic component as a spacer. Thereby, when soldering the wiring pattern formed on the substrate and the electronic component, the heat-resistant tape is not displaced or detached, and it is easy to mount a plurality of the electronic components. In addition to being able to solder, existing manufacturing processes can be used without adding new equipment and processes, and an increase in manufacturing costs can be prevented.

  In addition, since the heat-resistant tape is attached to only one of the substrate and the electronic component, the heat-resistant tape serves as a spacer to support the electronic component in the vertical direction and increase the gap distance. There is no power on the parts. As a result, when the solder is melted at the time of soldering, the self-alignment that occurs due to the surface tension that appears on the solder surface and the wetting force that appears at the interface between the solder and metal can act as a position offset correction function. Reliability can be improved.

  According to the invention described in claim 3, the heat-resistant tape has a thickness dimension of 50 μm or more, and the heat-resistant tape is formed to have a width dimension that abuts on a surface area of 50% or more of the electronic component. Therefore, the gap distance between the substrate and the electronic component can be greatly increased, the electronic component can be stably supported, and self-alignment during soldering works unevenly on the two solder fillets. Therefore, the inclination of the electronic component can be suppressed. Thereby, as the gap distance between the substrate and the electronic component is increased, the electronic component can be solder-bonded in a state where the electronic component is kept horizontal, and high heat fatigue resistance can be obtained.

In addition, since the heat-resistant tape is widely installed with respect to the surface area of the electronic component, the heat-resistant tape is used for the solder to the gap portion when the wiring pattern of the substrate or the supply amount of the solder is inappropriate. Intrusion and generation of solder balls can be avoided, and the failure rate during soldering can be reduced.
Also,

  According to the invention described in claim 4, after the heat-resistant tape is disposed between the substrate and the electronic component, the wiring pattern and the electronic component are soldered to each other. And the thickness of the solder fillet can be easily increased by soldering. As a result, an electronic component mounting board in which stress due to the difference in coefficient of thermal expansion between the substrate and the electronic component due to heat generation upon energization is uniformly dispersed and the accumulation of plastic strain is reduced can be manufactured.

  According to the invention described in claim 5, after the heat-resistant tape is disposed at a position excluding the wiring pattern and at a position excluding the solder joint between the substrate and the electronic component, the paste In order to solder-bond the wiring pattern and the electronic component, the heat-resistant tape can be adhered in a stable state. it can.

  In addition, in order to attach the heat-resistant tape in advance to either the substrate or the electronic component, use a reflow process facility that automatically performs pasted solder placement, component installation, and reflow. Can do. Furthermore, the heat-resistant tape can be applied only to components that are particularly fragile among the electronic components, and the heat-resistant tape can be used while being minimized. Thereby, it is possible to manufacture an electronic component mounting board in which the reliability of the entire product is improved while suppressing the manufacturing cost.

1 shows an embodiment of an electronic component mounting substrate of the present invention, (a) is a schematic cross-sectional view of a state in which solder and heat-resistant tape are arranged on the substrate, and (b) is a solder joint after mounting the electronic component on (a). It is the cross-sectional schematic of the state which carried out. It is the cross-sectional schematic which shows the conventional electronic component mounting board. (A) And (b) is a microscope picture which shows the result of having carried out the temperature cycle test by soldering the 2012 size electronic component to the test board | substrate by one Embodiment of this invention. (A) And (b) is a microscope picture which shows the result of having carried out the temperature cycle test by soldering the 2012 size electronic component to the test board by the conventional method. (A) And (b) is a microscope picture which shows the result of having carried out the temperature cycle test by solder-joining the 3216 size electronic component to the test board | substrate by one Embodiment of this invention. (A) And (b) is a microscope picture which shows the result of having carried out the temperature cycle test by soldering a 3216 size electronic component to a test board by the conventional method.

  As shown in FIG. 1B, in one embodiment of the electronic component mounting substrate 3 according to the present invention, a heat-resistant tape 6 is formed between the electronic component 2 and the substrate 1 on which the wiring pattern 4 is formed on one side. In addition, the wiring pattern 4 of the substrate 1 and the terminal portion of the electronic component 2 are joined together by solder 5 so as to be roughly configured.

  Here, a rigid substrate having a thickness of 0.02 to 0.05 mm is used as the substrate 1. From the type of composition, a paper phenol substrate in which paper is impregnated with phenol resin, and a paper epoxy substrate in which paper is impregnated with epoxy resin A glass composite substrate in which cut glass fibers are laminated and impregnated with an epoxy resin, a glass epoxy substrate in which an epoxy resin is impregnated on a glass fiber cloth (cloth), and the like are used.

  The wiring pattern 4 is formed by using copper as a main component and printing the wiring pattern 4 on one surface of the substrate 1. The heat-resistant tape 6 is formed by applying a base material mainly composed of polyimide and an adhesive mainly composed of silicon or acrylic to one side of the base material. The heat-resistant tape 6 has a thickness dimension of 50 μm and a width dimension that makes contact with the surface area of 50% of the electronic component 2.

  The solder 5 is a paste-like lead-free solder. This lead-free solder is a ternary tin-silver-copper alloy. And as the composition, there are Sn-3.5Ag-0.7Cu, Sn-3.0Ag-0.5Cu, and the like. In addition, ternary Sn—Ag—Bi, Sn—Cu—Ni (Ni is a trace additive), quaternary Sn—Ag—Cu—Bi, quinary Sn—Ag—Cu -There are lead-free solders such as Bi-Ge.

A method of manufacturing the electronic component mounting board having the above configuration will be described.
First, as shown in FIG. 1A, paste-like lead-free solder 5 is disposed at a joint position with the terminal portion of the electronic component 2 on the wiring pattern 4 formed on the substrate 1. And it sticks with the adhesive agent of the 50-micrometer-thick heat-resistant tape 6 in the position between this solder 5 and the position except the wiring pattern 4, and arrange | positions. The heat-resistant tape 6 is cut to a size that contacts 50% of the surface area of the electronic component 2. When the heat-resistant sheet 6 having a thickness of 50 μm is disposed on the substrate 1, the height of the paste-like lead-free solder 5 disposed on the wiring pattern 4 is higher than the thickness of the heat-resistant tape 6. Arrange.

  Next, the electronic component 2 is disposed on the paste-like solder 5 disposed on the heat-resistant tape 6 and the wiring pattern 4, and is put into a reflow furnace and heated. In the reflow furnace, the paste-like solder 5 is melted, and the terminal portion of the electronic component 2 and the wiring pattern 4 of the substrate 1 are joined. Further, when the solder 5 is melted, the electronic component 2 is lowered in the vertical direction by its own weight because of the difference in the height dimension of the solder 5 and the thickness dimension of the heat-resistant tape 6. At that time, since it is supported by the heat-resistant tape 6, the distance of the gap portion 7 between the substrate 1 and the electronic component 2 is maintained to be equal to or greater than the thickness dimension of the heat-resistant tape, and a solder fillet having an increased thickness is formed.

  Furthermore, when the electronic component 2 descends in the vertical direction when the solder is melted, a strong surface tension is generated in the molten solder 5, and a capillary phenomenon occurs in the lower part of the electronic component 2 and its electrode part. A self-alignment phenomenon occurs in which the solder joint is pulled and moved, and the displacement of the electronic component 2 is corrected. This self-alignment phenomenon corrects the displacement of the electronic component 2 by moving the electronic component 2 most greatly when the electronic component 2 is disposed only on the solder 5 when the solder is melted. In addition, when the heating at the time of melting the solder is not uniformly transmitted to the electronic component 2, a complicated force due to self-alignment acts on the electronic component 2, and the electronic component 2 tends to tilt. Since the heat-resistant tape 6 is in contact with 50%, the inclination of the electronic component 2 is suppressed and the level can be maintained.

  Moreover, when affixing to the board | substrate 1 side, according to the condition of the electronic component 2 or the wiring pattern 4 of the board | substrate 1, while cutting the heat-resistant tape 6 according to the magnitude | size of each electronic component 2, and each electronic component 2 Must be arranged as appropriate. Therefore, by introducing an automatic labeling machine, it is possible to automate mass production regardless of the number of heat-resistant tapes 5 disposed.

  In addition to the method of affixing the heat-resistant tape 6 on the substrate 1 side, there are a method of affixing on the electronic component 2 side or a method of affixing on each of the substrate 1 and the electronic component 2. Further, when the heat-resistant tape 6 is affixed to each of the substrate 1 and the electronic component 2, the amount of increase in the gap distance can be increased, so that the heat fatigue resistance of the solder joint can be further increased.

Example 1
Whether or not the electronic component mounting board manufactured by the above configuration is possible with conventional manufacturing equipment and manufacturing conditions will be described by a test conducted by the inventors.

  In this test, a commercially available heat-resistant tape 6 having a thickness of 50 μm (manufactured by YT130 series / ACE GLOBAL LTD) was prepared, and the heat-resistant tape 6 was arranged on the substrate 1 and the electronic component 2. The soldering was performed using conventional soldering equipment and manufacturing conditions. In addition, several types of electronic components 2 to be mounted were prepared and soldered together.

  As a result, both the method of arranging the heat-resistant tape 6 on the substrate 1 and the method of arranging the heat-resistant tape 6 on the electronic component 2 were able to be soldered satisfactorily using conventional soldering equipment and manufacturing conditions. Thus, it was confirmed that self-alignment was exhibited without problems when soldering.

  Further, as a result of measuring the gap distance between the substrate 1 and the electronic component 2 after soldering, the distance of the gap portion 7 increased by an average of 50 μm regardless of the size of the electronic component 2. And it was confirmed that the variation width of the gap distance is smaller than that of the conventional manufacturing method, and the variation of the inclination amount of the electronic component 2 is small (high flatness). Further, it was confirmed that the shape and appearance of the solder fillet and the familiarity between the solder 5 and the wiring pattern 4 and the terminal portion of the electronic component 2 were good.

  That is, it has been found that the manufacturing method of the present invention uses the manufacturing equipment and manufacturing process used when manufacturing the conventional electronic component mounting board 3.

(Example 2)
Next, the heat fatigue resistance due to the temperature cycle of the electronic component mounting board manufactured by the above configuration will be described by a test conducted by the inventors.
This test was performed using two test electronic component mounting boards manufactured by the manufacturing method of the present invention and two test electronic component mounting boards manufactured by a conventional manufacturing method.

  The configuration of the test electronic component mounting substrate used in this test and the temperature cycle conditions are as follows.

<Implementation 1>
Electronic parts: 2012 size
Substrate: Glass composite (CEM-3)
Solder: Lead-free solder (ternary tin-silver-copper alloy)
Heat-resistant tape: 50μm YT130 series (manufactured by ACE GLOBAL LTD)
Temperature cycle: Low temperature -55 ° C, high temperature 125 ° C, hold for 15 minutes each

<Comparison 1>
Electronic parts: 2012 size
Substrate: Glass composite (CEM-3)
Solder: Lead-free solder (ternary tin-silver-copper alloy)
Heat-resistant tape: None Temperature cycle: Low temperature -55 ° C, high temperature 125 ° C, hold for 15 minutes each

<Execution 2>
Electronic parts: 3216 size
Substrate: Glass composite (CEM-3)
Solder: Lead-free solder (ternary tin-silver-copper alloy)
Heat-resistant tape: 50 μm (YT130 series / ACE GLOBAL LTD)
Temperature cycle: Low temperature -55 ° C, high temperature 125 ° C, hold for 15 minutes each

<Comparison 2>
Electronic parts: 3216 size
Substrate: Glass composite (CEM-3)
Solder: Lead-free solder (ternary tin-silver-copper alloy)
Heat-resistant tape: None Temperature cycle: Low temperature -55 ° C, high temperature 125 ° C, hold for 15 minutes each

  Embodiments 1 and 2 above are test electronic component mounting boards manufactured by the manufacturing method of the present invention, and comparisons 1 and 2 are test electronic component mounting boards manufactured by a conventional manufacturing method. Each test electronic component actual measurement substrate is held for 15 minutes on the low temperature side of −55 ° C., then held for 15 minutes on the high temperature side of 125 ° C., and again held for 15 minutes on the low temperature side of −55 ° C. A temperature cycle test was conducted.

The results will be described with reference to the micrographs of FIGS.
First, FIG. 3A is an enlarged view of the solder fillet portion after 300 cycles of the temperature cycle test using the test electronic component mounting substrate of Example 1, and FIG. 1 is an enlarged view of a fillet portion after 450 cycles of a temperature cycle test using the test electronic component mounting board of No. 1; As can be seen from the test results shown in FIGS. 3A and 3B, the solder fillet is not broken.

  Next, FIG. 4 (a) is an enlarged view of the solder fillet portion after 300 cycles of the temperature cycle test using the test electronic component mounting substrate of Comparative 1, and FIG. Using the electronic component mounting substrate for test of Example 1, the fillet portion after performing the temperature cycle test for 450 cycles is enlarged. In the test result of FIG. 4A, a crack is recognized inside the gap 7 between the substrate 1 and the electronic component 2. Further, in the test result of FIG. 4B, a crack is generated from the gap portion 7 between the substrate 1 and the electronic component 2 to the solder fillet portion, and the solder joint portion is broken.

  FIG. 5A is an enlarged view of the solder fillet portion after 300 cycles of the temperature cycle test using the test electronic component mounting substrate of the second embodiment, and FIG. 2 is an enlarged view of a fillet portion after 450 cycles of a temperature cycle test using the test electronic component mounting board of No. 2; In the test result of FIG. 5A, cracks are recognized near the corners of the electronic component to which the solder 5 is joined. Further, in the test results of FIG. 5B, cracks are recognized from the vicinity of the corners of the electronic parts to which the solder 5 is bonded to the solder fillets, but breakage of the solder bonding is not recognized.

  Further, FIG. 6A is an enlarged view of the solder fillet portion after 300 cycles of the temperature cycle test using the test electronic component mounting substrate of Comparative 2, and FIG. 2 is an enlarged view of a fillet portion after 450 cycles of a temperature cycle test using the test electronic component mounting board of No. 2; In the test result of FIG. 6A, cracks are recognized near the corners of the electronic component to which the solder 5 is bonded. Further, in the test result of FIG. 6B, a crack is generated from the gap portion 7 between the substrate 1 and the electronic component 2 to the solder fillet portion, and the solder joint portion is broken.

  That is, it was found from this test that the fatigue life can be extended by soldering with the manufacturing method of the present invention rather than the electronic component actual measurement board soldered with the conventional manufacturing method. This does not depend on the size of the electronic component 2, and the fatigue life can be extended even with a relatively large electronic component 2 that is difficult to maintain its life.

  According to the electronic component mounting substrate 3 according to the above-described embodiment, since the substrate 1 has the heat-resistant tape 6 disposed at a position excluding the solder joint between the substrate 1 and the electronic component 2, By using 6 as a spacer, the gap distance between the substrate 1 and the electronic component 2 can be increased. As a result, as can be seen from the test results of Example 2, the thickness of the solder fillet formed at the solder joint between the substrate 1 and the electronic component 2 can be increased, and the substrate 1 and the electrons due to heat generation during energization can be increased. The stress due to the difference in thermal expansion coefficient with the component 2 can be evenly distributed to reduce the accumulation of plastic strain.

  Further, since the heat-resistant tape 6 is used as a spacer between the substrate 1 and the electronic component 2, when the solder having a melting point of about 220 ° C. is melted at the time of soldering, the substrate 1 and the electronic component 2 become 240 Even when heated to a high temperature of about ˜260 ° C., there is no decrease in adhesion function or strength, and a stable increase in gap distance can be exhibited. As a result, the heat-resistant tape 6 can be easily used as a spacer between the substrate 1 and the electronic component 2.

  Furthermore, since the heat-resistant tape 6 is soft and has a low elastic modulus, the substrate 1 and the electronic component 2 are not stressed by heat at the time of soldering and heat generation at the time of energization. Thereby, it does not become a factor which reduces the reliability of a product.

  Further, since the heat-resistant tape 6 has an adhesive mainly composed of silicon or acrylic applied to one side of a base material mainly composed of polyimide, the heat-resistant tape 6 is applied to either the substrate 1 or the electronic component 2. Adhering or adhering to each other can be used as a spacer. Thereby, as can be seen from the test results of Example 1, the heat-resistant tape 6 is not displaced or detached when the wiring pattern 4 formed on the substrate 1 and the electronic component 2 are solder-bonded. When mounting a plurality of electronic components 2, soldering can be easily performed, and existing manufacturing processes can be used without adding new equipment and processes, preventing an increase in manufacturing costs. be able to.

  Since the heat-resistant tape 6 is attached to only one of the substrate 1 and the electronic component 2, the heat-resistant tape 6 serves as a spacer, supports the electronic component 2 in the vertical direction, and increases the gap distance. 2 does not reach force. As a result, when the solder is melted at the time of soldering, the self-alignment that occurs due to the surface tension that appears on the solder surface and the wetting force that appears at the interface between the solder and metal can act as a position offset correction function. Reliability can be improved.

  Further, since the heat-resistant tape 6 has a thickness dimension of 50 μm or more and the heat-resistant tape 6 is formed to have a width dimension that makes contact with the surface area of 50% or more of the electronic component 2, the substrate 1 and the electronic component 2 The gap distance of the electronic component 2 can be greatly increased, the electronic component 2 can be supported stably, and the inclination of the electronic component 2 due to the non-uniform self-alignment of the solder joints acting on the two solder fillets can be reduced. Can be suppressed. Thereby, as the gap distance between the substrate 1 and the electronic component 2 is increased, the electronic component 2 can be solder-bonded in a horizontal state, and high heat fatigue resistance can be obtained.

  In addition, since the heat-resistant tape 6 is widely installed with respect to the surface area of the electronic component 2, the heat-resistant tape 6 has an inappropriate supply amount and supply position of the wiring pattern 4 and the solder 5 of the substrate 1, and various factors during manufacture. Therefore, it is possible to avoid the intrusion of the solder 5 into the gap portion and the generation of solder balls that occur when the joining environment fluctuates due to various factors, and the failure occurrence rate during solder joining can be reduced.

  And before arrange | positioning the paste-like solder 5 on the wiring pattern 4 of the position in which the electronic component 2 is mounted, it is a position except the wiring pattern 4, and solder joining between the board | substrate 1 and the electronic component 2 Since the heat-resistant tape 6 is disposed at a position excluding the portion and the wiring pattern 4 and the electronic component 2 are soldered together, the heat-resistant tape can be adhered in a stable state, and the substrate 1 and the electronic component 2 can be adhered. Thus, an electronic component mounting board in which the thickness of the solder fillet is increased can be manufactured by soldering.

  In addition, in order to attach the heat-resistant tape 6 to either the substrate 1 or the electronic component 2 in advance or to each, a reflow process facility that automatically performs pasted solder placement, component installation, and reflow is used. Can be used. Further, the heat-resistant tape 6 can be applied to only the fragile parts among the electronic parts 2 and the heat-resistant tape 6 can be manufactured to the minimum. Thereby, it is possible to manufacture an electronic component mounting board in which the reliability of the entire product is improved while suppressing the manufacturing cost.

In addition, in the said embodiment, although demonstrated only when the thickness dimension used the heat resistant tape 6 of 50 micrometers, it is not limited to this, For example, if it is the heat resistant tape 6 of about 50 micrometers-200 micrometers, it can respond. It is.
Moreover, in the said embodiment, although demonstrated only when the board | substrate 1 in which the wiring pattern 4 was formed in the single side was used, it is not limited to this, For example, the board | substrate 1 in which the wiring pattern 4 was formed in both surfaces But it is possible.

  It can be used for a substrate on which a wiring pattern is formed.

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Electronic component 3 Electronic component mounting board 4 Wiring pattern 5 Solder 6 Heat-resistant tape 7 Gap part

Claims (5)

In an electronic component mounting board in which electronic components are mounted on the surface of the board on which the wiring pattern is formed by soldering,
An electronic component mounting substrate, wherein the substrate is disposed between the substrate and the electronic component, and a heat-resistant tape is disposed at a position excluding the solder joint portion.   The heat-resistant tape is formed by applying a base material mainly composed of polyimide and an adhesive mainly composed of silicon or acrylic on one side of the base material. Electronic component mounting board.   4. The heat-resistant tape according to claim 1, wherein the heat-resistant tape has a thickness dimension of 50 μm or more and a width dimension that abuts on a surface area of 50% or more of the electronic component. Electronic component mounting board. An electronic component mounting board manufacturing method for mounting an electronic component on a surface of a board on which a wiring pattern is formed by solder bonding,
A method of manufacturing an electronic component mounting board, comprising: arranging the heat-resistant tape between the substrate and the electronic component; and solder-bonding the wiring pattern and the electronic component.   After the heat-resistant tape is disposed at a position excluding the wiring pattern and at a position excluding the solder joint between the substrate and the electronic component, the paste-like solder is mounted on the electronic component. 5. The method of manufacturing an electronic component mounting board according to claim 4, wherein the wiring pattern and the electronic component are solder-bonded to each other on the wiring pattern at a certain position.