Protective element and protective circuit including the same

Abstract

To provide a protective element which prevents falling of a cap in a heat treatment step at the time of surface mounting, and prevents a mold resin from intruding into a cap protecting a fuse element in mold treatment after the surface mounting.SOLUTION: A protective element includes an insulation substrate, a plurality of fuse electrodes provided on one surface of the insulation substrate, a fuse element which is mounted on the one surface of the insulation substrate and electrically connects the plurality of fuse electrodes, an operation flux with which the surface of the fuse element is coated, a cap which is provided on the one surface, and covers and protects the fuse element and the operation flux, and a gas releasing part for exhausting the gas generated from the operation flux at the time of surface mounting from the inside of the cap, where the gas releasing part is formed of a through hole penetrating the insulation substrate in a plate thickness direction.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a protection element for electrical and electronic devices and a protection circuit including this protection element.

Background Art

[0002] Conventionally, there is a surface-mounted protection element used in a protection circuit of a secondary battery, which includes a plurality of fuse electrodes provided on the surface of an insulating substrate, a fuse element electrically connecting the plurality of fuse electrodes, and a cap that covers and protects the fuse element and the operating flux and prevents the blown fuse element from scattering (for example, Patent Document 1).

[0003] In the protection element of Patent Document 1, a through hole is provided in the cap of the protection element so that the cap does not fall off due to the operating flux gasifying during the fusing operation and the internal pressure in the cap rising.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, for dust and waterproof measures and space saving in a battery pack in a protection circuit on which various elements such as protection elements are mounted, for example, it is conceivable to use a mold resin to completely seal the circuit pattern of the protection circuit and the protection element mounted thereon. By sealing the protection element in this way, it seems that the cap can be fixed to the insulating substrate and there is no need to provide a through hole in the cap.

[0006] However, if the through-hole in the cap is eliminated and the fuse element or the like is sealed inside the cap, during the heat treatment process when the protection element is surface-mounted, there will be no escape path for the gas generated from the operating flux, and the internal pressure inside the cap may increase, leading to the risk of the cap falling off or deforming.

[0007] Therefore, if one attempts to provide a through-hole in the cap as in Patent Document 1 to enable the evacuation of air inside the cap, then when the protection circuit is sealed with a molding resin, the molding resin may flow into the cap through the through-hole, potentially inhibiting the normal fusing operation of the fuse element.

[0008] Therefore, the main object of the present invention is to provide a protection element that is less likely to have the cap fall off or the like during the heat treatment process at the time of surface mounting, and in which the molding resin is less likely to penetrate into the cap that protects the fuse element during the molding process after surface mounting.

Means for Solving the Problems

[0009] That is, the protection element according to the present invention is a protection element surface-mounted on a mounting substrate, and includes an insulating substrate, a plurality of fuse electrodes provided on one surface of the insulating substrate, a fuse element mounted on one surface of the insulating substrate and electrically connecting the plurality of fuse electrodes, an operating flux applied to the surface of the fuse element, a cap provided on the one surface and covering and protecting the fuse element and the operating flux, and a gas escape portion for exhausting the gas generated from the operating flux during surface mounting from inside the cap. The gas escape portion is formed by a through-hole penetrating the insulating substrate in the plate thickness direction.

[0010] For a protection element configured in this way, since it is provided with a gas escape portion, the air inside the cap can be exhausted, and the risk of the cap falling off or deforming due to the flux-derived gas during the heat treatment process at the time of surface mounting can be reduced. Furthermore, since the through-holes of the gas escape portion are formed so as to penetrate the insulating substrate in the thickness direction thereof, the outlet of the gas escape portion can be opened to the other surface of the insulating substrate. If this is the case, by mounting the protection element so that the distance between the insulating substrate and the mounting substrate becomes close and narrowing the space formed therebetween, in the molding process, it is possible to prevent the molding resin from reaching the outlet of the through-hole. And, since it becomes difficult for the molding resin to enter the cap, it is possible to reduce the risk such as the fusing of the fuse element being inhibited.

[0011] The through-hole may preferably open around a mounting region which is a region on one surface of the insulating substrate where the fuse element is mounted. If this is the case, since the inlet of the gas escape portion is not covered by the fuse element, in the heat treatment process during surface mounting, gas can be efficiently exhausted.

[0012] Furthermore, the through-hole may preferably open around a fuse electrode region which is a region on one surface of the insulating substrate where the fuse electrode is mounted. If this is the case, the distance between the inlet of the gas escape portion and the fuse element can be taken, and it becomes difficult for this inlet to be covered by the fuse element, and gas can be efficiently exhausted in the heat treatment process during surface mounting. Also, when the through-hole is provided in the electrode, risks such as solder entering the through-hole due to the high wettability of the electrode and blocking the through-hole, or reaching the internal space of the protection element and inhibiting the normal fusing of the fuse become high. However, with the above configuration, such risks can be reduced.

[0013] Furthermore, it further includes a mounting electrode provided on the other surface of the insulating substrate, electrically connected to the fuse electrode, and soldered to the mounting substrate, and the through-hole may preferably open around a mounting electrode region which is a region on the other surface where the mounting electrode is provided. In this case, since the outlet of the gas escape portion is not provided in the mounting electrode region that is soldered during surface mounting, the through hole is not blocked by solder, and in the heat treatment process, the gas in the cap can be more reliably exhausted.

[0014] If the gas escape portion has two or more through holes, the exhaust efficiency can be improved, but it is conceivable that one through hole functions as an intake hole and the other through hole functions as an exhaust hole. In this case, in the molding process, there is a risk of sucking up the molding resin together with the gas through the intake hole. Therefore, it is preferable that there is only one through hole forming the gas escape portion. In this case, since the inside of the cap and the outside can be configured not to communicate with each other except through the through hole, it is possible to prevent the molding resin from being sucked up in the molding process.

[0015] The protection circuit according to the present invention includes a mounting substrate on which the above-described protection element is surface-mounted, and is characterized in that the protection element is sealed with a molding resin. With such a protection circuit, the action and effect of the above-described protection element can be exerted, and the protection element can be packaged with a molding resin, so that the dustproof and waterproof functions can be improved, and the cap can be more firmly fixed by the protection element, reducing the risk that the cap falls off during the fusing operation and the fused fuse element scatters. Further, if the cell and the protection circuit board are closely adhered and molded, the volume can be reduced, and the protection circuit can be made more space-saving.

[0016] Furthermore, in such a protection circuit, it is preferable that the through hole is not blocked by the molding resin that has entered between the other surface of the insulating substrate and the mounting surface of the mounting substrate. In this case, since the molding resin is not sucked up into the cap in the molding process, the fusing operation of the fuse element is more reliably guaranteed.

Effect of the Invention

[0017] According to the present invention configured as described above, in the heat treatment process during surface mounting, the cap is less likely to fall off or the like, and in the molding process after surface mounting, a protective element can be provided in which the molding resin hardly penetrates into the cap that protects the fuse element.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0019] Hereinafter, a protective element 100 according to an embodiment of the present invention will be described with reference to the drawings.

[0020] [First Embodiment] The protective element 100 of the present embodiment is mounted on a small electronic device such as a smartphone, and is for protecting a secondary battery 220 such as a battery pack included in the small electronic device from overcurrent and overvoltage. This protective element 100 is a so-called surface mount type that is mounted on a mounting substrate 210 in a protection circuit 200 of the secondary battery 220 included in the small electronic device.

[0021] Specifically, as shown in FIGS. 1 to 3, this protection element 100 includes an insulating substrate 1, a fuse electrode 2, an intermediate electrode 3, a mounting electrode 4, a fuse element 5, an operating flux 6, a resistance element 7 (heater), and a cap 8.

[0022] As shown in FIGS. 1 to 3, the insulating substrate 1 is a thin plate having a substantially rectangular shape in plan view and is made of an insulating material such as ceramics or alumina.

[0023] As shown in FIGS. 2 to 3, the fuse electrode 2 is made of a sintered silver alloy formed on one surface which is the upper surface of the insulating substrate 1. Here, a pair of fuse electrodes 2 having an elongated shape are provided along the long side direction of the insulating substrate 1.

[0024] As shown in FIGS. 2 to 3, the intermediate electrode 3 is made of a sintered silver alloy formed on one surface of the insulating substrate 1. Here, the intermediate electrode 3 having an elongated shape is provided between the pair of fuse electrodes 2 along the long side direction of the insulating substrate 1.

[0025] As shown in FIGS. 2 to 3, the mounting electrode 4 is made of a sintered silver alloy formed on the other surface which is the bottom surface of the insulating substrate 1. Here, four mounting electrodes 4 are provided inside each side of the insulating substrate 1 in a bottom view. The mounting electrode 4 is soldered to the mounting substrate 210.

[0026] Among the four mounting electrodes 4, two arranged along the long side of the insulating substrate 1 are electrically connected to the fuse electrode 2 arranged on one surface which is the back side surface across the insulating substrate 1 via a plurality of vias. One of the remaining two mounting electrodes 4 is electrically connected to the end of the intermediate electrode 3 arranged on the one surface via a via, and the remaining one mounting electrode 4 is electrically connected to the mounting electrode 4 connected to the intermediate electrode 3 via a resistance element 7 described later.

[0027] As shown in FIGS. 2 to 3, the fuse element 5 is joined so as to straddle the surfaces of a pair of fuse electrodes 2 and the intermediate electrode 3, and is composed of a soluble conductor that electrically connects the pair of fuse electrodes 2 and the intermediate electrode 3. The fuse element 5 is a fusible alloy material and is composed of, for example, a Pb-free solder mainly composed of a low melting point metal such as Sn.

[0028] As shown in FIGS. 2 to 3, the operating flux 6 is applied to the surface of the fuse element 5 and is, for example, a coating material in which chemical agents such as an activator and a thixotropic agent are blended in a modified rosin resin. By applying the operating flux 6, oxidation of the fuse element 5 is prevented and the wettability of the fuse element 5 during the fusing operation is improved.

[0029] As shown in FIGS. 2 to 3, the resistance element 7 is laminated on the other surface of the insulating substrate 1 and is arranged so as to be able to heat the operating flux 6 laminated on one surface. Note that the resistance element 7 may be laminated on one surface of the insulating substrate 1. The resistance element 7 is composed of a thick film resistor electrically connected to the mounting electrode 4. In the resistance element 7 of the present embodiment, in a bottom view, the entire body is insulated and covered by a glass coat 71 further laminated on the other surface of the insulating substrate 1. In the present embodiment, a resistance element functioning as a heater is provided on the other surface (bottom surface) of the protection element 100, but this may be provided on one surface (upper surface) of the protection element.

[0030] As shown in FIGS. 1 to 3, the cap 8 is fixed to one surface of the insulating substrate 1 and is a lid for covering and protecting the fuse element 5 and the operating flux 6. This cap 8 is preferably a super engineering plastic having chemical resistance and heat resistance, and for example, LCP (liquid crystal polymer) or the like is used. The cap 8 has a substantially rectangular parallelepiped shape with one side open, and the open end thereof is fixed to the insulating substrate 1 using an adhesive resin 8a. In the cap 8 of the present embodiment, the open end, which is the adhesive portion with the insulating substrate 1, is configured to be substantially flush, and the entire periphery of the end of this open end is configured to be adhesively fixed to one surface of the insulating substrate 1 without play. In the plan view of FIG. 2, the region indicated by hatching is the cap adhesion region to which the adhesive resin 8a for adhering the cap 8 adheres.

[0031] The fuse element 5 and the operating flux 6 are accommodated in an internal space S surrounded by one surface of the insulating substrate 1 and the cap 8. This internal space S has a size sufficient for the fuse element 5 to aggregate on the fuse electrode 2 during the fusing operation. The cap 8 of the present embodiment is not provided with holes.

[0032] The protection element 100 configured as described above is fixed to the mounting surface of the mounting substrate 210 of the protection circuit 200 with solder as shown in FIG. 1. More specifically, a circuit pattern (not shown) is formed on the mounting substrate 210, which is a printed circuit board, and each mounting electrode 4 of the protection element 100 is electrically connected to a plurality of pads provided at predetermined positions of the circuit pattern.

[0033] In this mounted state, the other surface of the insulating substrate 1 of the protection element 100 and the mounting surface of the mounting substrate 210 of the protection circuit 200 are arranged to be substantially parallel to each other. In the present embodiment, the distance between these two surfaces is configured to be a short distance (here, about 0.060 ± 0.020 mm) so that the space sandwiched by these two surfaces becomes as narrow as possible.

[0034] Note that the distance between these two surfaces is preferably set to a distance that can prevent the mold resin from entering the space between the two surfaces in the mold processing step described later. Incidentally, as described above, at least the mounting electrode 4 and the glass coat 71 are laminated on the other surface. The other surface of the insulating substrate 1, the surface of the mounting electrode 4, and the surface of the glass coat 71 are configured to be substantially flush.

[0035] Thus, the surface mounting process of mounting the protection element 100 on the mounting substrate 210 of the protection circuit 200 includes, for example, a solder printing process of applying solder paste to the pads of the mounting substrate 210 with a printer, a mounting process of mounting the protection element 100 on the pads on which the solder is printed, and a reflow process of melting the solder in a reflow furnace to bond the mounting substrate 210 and the protection element 100.

[0036] In the protection circuit 200 of the present embodiment, the protection element 100 mounted on the mounting substrate 210 and the circuit pattern provided on the mounting substrate 210 are entirely sealed with a molding resin.

[0037] The process of molding the protection circuit 200 is performed by setting the protection circuit 200 in a mold processed into a desired package shape and filling and curing the molten molding resin in the mold, as shown in FIG. 5. Here, although the molding process by the so-called transfer method is described as an example, the protection circuit 200 may be mold-sealed by a compression method.

[0038] Furthermore, the protection element 100 according to the present invention further includes a gas escape portion that exhausts the gas generated by overheating the operating flux 6 from the internal space S of the protection element 100 in the reflow process.

[0039] As shown in FIGS. 1 to 3, the gas escape portion is formed by a through hole 11 that penetrates the insulating substrate 1 in the plate thickness direction. The through hole 11 of the present embodiment has a substantially cylindrical shape, and its hole diameter (diameter) is configured to be about 0.150 mm to 0.500 mm. Note that the through hole 11 may have a substantially elliptical column shape or a polygonal column shape. The through hole 11 only needs to be able to function as an exhaust hole in the reflow process.

[0040] In this embodiment, one through-hole 11 is formed in the insulating substrate 1 itself by a drill or the like. When the opening on one surface side of this through-hole 11 is an inlet 11a and the opening on the other surface side is an outlet 11b, the inlet 11a and the outlet 11b of this embodiment are arranged in a substrate region where no electrodes or the like are provided on each surface of the insulating substrate 1. Note that the through-hole may be integrally formed when the insulating substrate 1 is molded by die pressing.

[0041] More specifically, when a region where the fuse electrode 2 and the intermediate electrode 3 are laminated on one surface of the insulating substrate 1 is defined as a fuse electrode region, the inlet 11a is provided around this fuse electrode region. The fuse electrode region of this embodiment includes a region sandwiched by the fuse electrode 2 and the intermediate electrode 3. That is, the inlet 11a is provided while avoiding the fuse electrode 2 and the intermediate electrode 3.

[0042] When a region where the fuse element 5 is mounted on one surface of the insulating substrate 1 is defined as a mounting region, the inlet 11a is provided around this mounting region. The mounting region is a portion of the one surface that is covered by the fuse element 5 in a plan view of the protection element 100. That is, the inlet 11a is provided while avoiding the fuse element 5.

[0043] Further, the inlet 11a is inside the cap 8 and opens at a position where the adhesive resin 8a for adhering the cap 8 to the insulating substrate 1 does not adhere. More specifically, the inlet 11a of this embodiment opens within a region surrounded by the above-described cap adhesion region.

[0044] When a region where the mounting electrode 4 is provided on the other surface of the insulating substrate 1 is defined as a mounting electrode region, the outlet 11b is provided around this mounting electrode region. This mounting electrode region is also a region where solder applied to the mounting substrate can adhere when the protection element 100 is surface-mounted. That is, the outlet 11b is provided while avoiding the mounting electrode 4 and the solder for mounting the protection element 100.

[0045] Moreover, the outlet 11b is disposed inside at a predetermined distance from the outer edge of the insulating substrate 1 in a bottom view. This predetermined distance is preferably set to be longer than the distance that the mold resin that tries to enter the gap between the insulating substrate 1 and the mounting substrate 210 from the outer edge of the insulating substrate 1 can reach in the mold treatment step. After surface mounting on the mounting substrate, this outlet 11b is covered by the mounting surface in a bottom view. That is, the space between the other surface of the insulating substrate 1 and the mounting substrate 210 is configured not to be filled even after the mold treatment, and the through hole 11 that opens here is configured not to be blocked by the mold resin.

[0046] In this way, the through hole 11 of the present embodiment is disposed at a position where the fuse element 5, solder, the adhesive resin 8a, and the mold resin do not adhere to and block the hole.

[0047] [Effect] With respect to the protection element 100 according to the present embodiment configured in this way, since it is provided with a gas escape portion, the air in the internal space S can be exhausted. Thereby, in the heat treatment step at the time of surface mounting, the risk that the internal pressure in the cap 8 increases due to the gas derived from the flux and the gas expanded by heat, and the cap 8 falls off or deforms can be reduced.

[0048] Since the opening on the internal space S side of the gas escape portion is not covered by the fuse element 5, the risk that the through hole 11 is blocked by the fuse element 5 can be reduced in the heat treatment step at the time of surface mounting, and the gas can be efficiently exhausted.

[0049] Since the opening on the mounting substrate side of the gas escape portion is not provided in the mounting electrode region that is soldered at the time of surface mounting, the through hole 11 is not blocked by the solder, and the gas in the internal space S can be more reliably exhausted in the heat treatment step.

[0050] Since the outlet 11b of the through hole 11 of the gas escape portion is provided on the other surface of the insulating substrate 1 and is configured to be covered by the mounting surface of the mounting substrate after surface mounting, the risk that the molding resin enters the internal space S through this through hole 11 and inhibits the fusing of the fuse element 5 can be reduced.

[0051] Since the through hole 11 is configured to open into a narrow space sandwiched between the other surface of the insulating substrate 1 and the mounting surface of the mounting substrate after surface mounting, in the subsequent molding process, the molding resin can be prevented from reaching the outlet 11b of the through hole 11, and the risk of the molding resin entering the internal space S can be further reduced.

[0052] By the way, if there are a plurality of through holes 11 that communicate the internal space S of the protection element 100 with the outside, it is conceivable that gas can enter and exit by some holes functioning as intake holes and other holes functioning as exhaust holes. In this case, there is a risk that the molding resin will be sucked up from the intake hole in the molding process. On the other hand, in the protection element 100 of this embodiment, since there is only one through hole 11 that communicates the internal space S with the outside, it is possible to prevent the molding resin from being sucked into the cap in the molding process.

[0053] The protection element 100 of this embodiment can be packaged with a molding resin after surface mounting, so the dustproof and waterproof functions are improved, and the cap 8 can be fixed more strongly by the protection element 100, so the risk that the cap 8 falls off during the fusing operation and the melted fuse element 5 scatters can be reduced. Also, since the cap 8 is made of a material having chemical resistance and heat resistance, it can withstand the filling of the molding resin injected while being heated and pressurized, and can maintain the space for the fuse element to fuse normally. Also, if the cell and the protection circuit board are brought into close contact and molded, the volume can be reduced, and the space of the protection circuit can be saved.

[0054] [Second Embodiment] As shown in FIG. 6, the protection element 100 according to the second embodiment further includes an adhesive resin intrusion prevention portion 12 in addition to the configuration included in the above-described embodiment. The adhesive resin intrusion prevention portion 12 is for preventing the above-described adhesive resin 8a from flowing on the upper surface of the insulating substrate 1 and entering the through-hole 11.

[0055] The adhesive resin intrusion prevention portion 12 is in a bank shape surrounding the entire circumference of the inlet 11a on the upper surface of the insulating substrate 1. The height of the adhesive resin intrusion prevention portion 12 from the upper surface is preferably such that the adhesive resin 8a having fluidity during the thermosetting of the adhesive resin for fixing the cap cannot naturally overcome it. The adhesive resin intrusion prevention portion 12 of the present embodiment is an insulating material laminated by printing around the through-hole 11 in the insulating substrate 1 provided with the through-hole 11 in advance.

[0056] The adhesive resin intrusion prevention portion 12 can reduce the risk of the through-hole 11 being sealed by the adhesive resin 8a, and in the heat treatment process, the gas in the internal space S can be more reliably exhausted.

[0057] [Other Embodiments] The gas escape portion may have a plurality of through-holes.

[0058] The shape of the through-hole of the gas escape portion is not limited to that of the above-described embodiment. The through-hole may be a bent exhaust passage formed inside the insulating substrate or an exhaust passage having different hole diameters at the inlet and the outlet. The through-hole only needs to penetrate the upper surface and the bottom surface of the insulating substrate in the thickness direction.

[0059] In the above-described embodiment, the inlet 11a of the through-hole 11 was provided while avoiding the region where the fuse electrode 2 and the fuse element 5 are provided, but the through-hole may open into the region where the fuse electrode or the like is provided. Also, a part of the inlet of the through-hole may be provided in the region where the fuse electrode or the like is provided. The through-hole only needs to be configured to be able to exhaust the air inside the cap.

[0060] [Operation of the protection element] As shown in FIG. 3, the protection element 100 is connected in series to the secondary battery 220 in the protection circuit 200, and cuts off the circuit by melting the fuse element 5 when an overcurrent or an overvoltage is applied.

[0061] Specifically, when an overcurrent is applied to the secondary battery 220 of the protection circuit 200, the protection element 100 operates in an overcurrent mode in which the fuse element 5 is melted by self-heating generated by the energization resistance, thereby cutting off the circuit.

[0062] On the other hand, when an overvoltage is applied to the secondary battery 220 of the protection circuit 200, the protection element 100 energizes the resistance element 7 and melts the fuse element 5 using the heat generated from the resistance element 7, thereby operating in an overvoltage mode in which the circuit is cut off. Specifically, this protection circuit 200 includes detection means 230 that detects the voltage applied to the secondary battery 220 and switches the on / off of the current flowing through the resistance element 7 of the protection element 100. This detection means 230 is configured using a voltage detection IC and an FET. When the detection means 230 detects an overvoltage, it turns on the current flowing through the resistance element 7, and thereby the fuse element 5 is melted by the heat of the resistance element 7.

Explanation of reference numerals

[0063] 100 ··· Protection element 1 ··· Insulating substrate 2 ··· Fuse electrode 3 ··· Intermediate electrode 4 ··· Mounting electrode 5 ··· Fuse element 6 ··· Actuating flux 7 ··· Resistive element 71 ··· Glass coat 8 ··· Cap 11 ··· Through-hole 11a ··· Inlet (one opening) 11b ··· Outlet (the other opening) 12 ··· Adhesive resin intrusion prevention part S ··· Internal space 200 ··· Protection circuit 210 ··· Mounting substrate 220 ··· Secondary battery 230 ··· Detection means

Claims

1. A protection element surface-mounted on a mounting substrate, comprising: an insulating substrate; a plurality of fuse electrodes provided on one surface of the insulating substrate; a fuse element mounted on one surface of the insulating substrate and electrically connecting the plurality of fuse electrodes; an operating flux applied to the surface of the fuse element; a cap provided on the one surface to cover and protect the fuse element and the operating flux; a gas escape portion for exhausting gas generated from the operating flux during surface mounting from inside the cap; and the gas escape portion is formed by a through hole penetrating the insulating substrate in the plate thickness direction. A protection element.

2. The protection element according to claim 1, wherein the through hole opens around a mounting region which is a region where the fuse element is mounted on one surface of the insulating substrate.

3. The protection element according to claim 2, wherein the through hole opens around a fuse electrode region which is a region where the fuse electrodes are mounted on one surface of the insulating substrate.

4. Further comprising a mounting electrode provided on the other surface of the insulating substrate, electrically connected to the fuse electrode, and soldered to the mounting substrate, The protection element according to claim 1, wherein the through hole opens around a mounting electrode region which is a region where the mounting electrode is provided on the other surface.

5. The protection element according to claim 1, wherein there is only one through hole forming the gas escape portion.

6. A protection circuit comprising a mounting substrate on which the protection element according to claim 1 is surface-mounted, wherein the protection element is sealed with a molding resin.

7. The protection circuit according to claim 6, wherein the through hole is not blocked by the molding resin that has entered between the other surface of the insulating substrate and the mounting surface of the mounting substrate.

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