Surface mount technology method and magnetic carrier system

A method of soldering one or more components to a substrate includes providing a substrate and applying an amount of solder material to the top planar surface of the substrate. One or more electrical components are mounted to the solder material in a predetermined position and orientation. A carrier is provided having one or more magnets embedded therein. The substrate is positioned above the carrier such that each of the one or more magnets is positioned directly below a corresponding electrical component. A carrier cover is positioned above the substrate and the electrical components. The solder material is heated to a predetermined temperature for a predetermined amount of time during which each of the magnets exerts a magnetic force on a corresponding electrical component to maintain its orientation relative to the substrate. The magnets reduce the occurrence of tombstoning of the electrical components during heating of the solder material.

BACKGROUND

The present disclosure generally relates to Surface Mount Technology methods and, more particularly, to a surface mount technology method including the use of a magnetic carrier system.

Surface Mount Technology (SMT) is a method commonly used to mount electrical components directly onto the surface of a substrate, such as a printed circuit board (PCB). In SMT methods, various areas on the surface of the PCB are covered with a solder paste material. The electrical components are mounted on said areas covered with the solder paste material. The PCB undergoes a reflow process wherein the PCB, the solder paste, and the electrical components mounted thereto is placed into a reflow oven and subjected to controlled heat. During reflow, the solder paste is melted causing it to create permanent solder joints between the electrical components and the PCB. However, during reflow the electrical components may shift or rotate such that they are not in the intended position relative to the PCB. For example, the electrical components may experience component shift, in which the electrical components shift in a direction transverse to the PCB surface, and/or the electrical components may experience tombstoning in which the component rotates upwards such that one end is no longer in contact with the solder paste. Component shift and tombstoning each often lead to defects in the electrical and mechanical connection between the PCB and the respective electrical component, which results in a faulty product. Therefore, there is a need to improve the SMT method to prevent, or at least reduce the occurrence of, component shift and tombstoning during reflow.

SUMMARY

In one embodiment there is a method of soldering one or more components to a substrate, the method includes providing a substrate having a top planar surface and a bottom planar surface and applying an amount of solder material to at least a portion of the top planar surface of the substrate. The method further includes mounting one or more electrical components on the solder material, each of the one or more electrical components having a position and orientation relative to the substrate, and providing a carrier having a top carrier surface and a bottom carrier surface, and one or more magnets disposed between the top and bottom carrier surfaces. The method further includes positioning the substrate above the carrier such that the bottom planar surface of the substrate is above the top carrier surface and each of the one or more magnets is positioned directly below a corresponding electrical component of the one or more electrical components. The method further includes positioning a carrier cover above the top planar surface of the substrate such that there is a gap between the carrier cover and the one or more electrical components, and heating the solder material to a predetermined temperature for a predetermined amount of time to cause the solder material to melt. The method further includes during heating of the solder material, exerting, by each of the one or more magnets, a magnetic force on a corresponding electrical component of the one or more electrical components to maintain the orientation of the corresponding electrical component relative to the substrate while the solder material melts.

In some embodiments, the magnets are configured to prevent tombstoning of the one or more electrical components during the heating step. In some embodiments, the one or more magnets includes a first magnet and a second magnet positioned adjacent to the first magnet, wherein the one or more electrical components includes a first electrical component corresponding to the first magnet and a second electrical component corresponding to the second magnet, and the magnetic force exerted by the first magnet does not affect the position or orientation of the second electrical component corresponding to the second magnet. In some embodiments, the gap between the carrier cover and the one or more electrical components is about 10 micrometers.

In some embodiments, each of the one or more magnets disposed within the carrier have a maximum operating temperature that is greater than the predetermined temperature that the solder material is heated to during the heating step. In some embodiments, each of the one or more magnets disposed within the carrier have a maximum operating temperature of at least 350 degrees Celsius. In some embodiments, each of the one or more magnets disposed within the carrier have a magnetic force between about 336*10−6N to about 865*10−6N. In some embodiments, the heating step includes positioning the substrate having the one or more electrical components mounted thereto via the solder material, the carrier and the carrier cover in a reflow oven and operating the reflow oven to cause the solder material to melt.

In another embodiment there is a method for soldering one or more electrical components to a substrate comprising an amount of solder material coupling the one or more electrical components to the substrate. The method includes positioning a carrier below the substrate, the carrier including one or more magnets embedded therein, each of the one or more magnets positioned directly below a corresponding electrical component of the one or more electrical components. The method includes positioning a carrier cover above the substrate and spaced from the substrate such that there is a gap between the carrier cover and the one or more electrical components, and heating the solder material to a predetermined temperature for a predetermined amount of time to cause the solder material to melt. During heating of the solder material each of the one or more magnets exerts a magnetic force on a corresponding electrical component of the one or more electrical components to maintain the orientation of the corresponding electrical component relative to the substrate while the solder material flows about the corresponding electrical component.

In some embodiments, the magnets are configured to prevent tombstoning of the one or more electrical components during the heating step. In some embodiments, the magnets are configured to prevent the one or more electrical components from shifting in a direction that is transverse to the top planar surface of the substrate during the heating step. In some embodiments, the gap between the carrier cover and the one or more electrical components is about 10 micrometers. In some embodiments, each of the one or more magnets embedded within the carrier have a maximum operating temperature that is greater than the predetermined temperature that the solder material is heated to during the heating step. In some embodiments, each of the one or more magnets embedded within the carrier have a maximum operating temperature of at least 350 degrees Celsius. In some embodiments, each of the one or more magnets embedded within the carrier have a magnetic force between about 336*10−6N to about 865*10−6N. In some embodiments, the heating step includes positioning the substrate having the one or more electrical components mounted thereto via the solder material, the carrier and the carrier cover in a reflow oven and operating the reflow oven to cause the solder material to melt.

In another embodiment, there is a substrate assembly for assembling an electronic device, and the substrate assembly includes a substrate including a plurality of layers alternating between conductive layers and non-conductive layers, wherein the conductive layers comprise signal traces, the substrate having a top planar surface and an opposing bottom planar surface, a plurality of electrical components each mounted to the substrate via an amount of solder material, and a carrier having a top carrier surface and a bottom carrier surface, the carrier including a plurality of magnets embedded between the top and bottom carrier surfaces. Each magnet of the plurality of magnets exerts a magnetic force on a corresponding electrical component of the plurality of electrical components to maintain an orientation of the corresponding electrical component relative to the substrate.

In some embodiments, the plurality of magnets are configured to prevent tombstoning of the plurality of electrical components. In some embodiments, the plurality of magnets includes a first magnet and a second magnet positioned adjacent to the first magnet, wherein the plurality of electrical components includes a first electrical component corresponding to the first magnet and a second electrical component corresponding to the second magnet, and the magnetic force exerted by the first magnet does not affect the position or orientation of the second electrical component corresponding to the second magnet. In some embodiments, each magnet of the plurality of magnets embedded within the carrier have a magnetic force between about 336*10−6N to about 865*10−6N.

DETAILED DESCRIPTION

The present subject matter will now be described more fully hereinafter with reference to the accompanying Figures, in which representative embodiments are shown. The present subject matter can, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to describe and enable one of skill in the art.

Referring toFIG.1, there is shown a substrate assembly, generally designated100, in accordance with an exemplary embodiment of the present disclosure. The substrate assembly100may include a substrate102, one or more electrical components104, and one or more other electrical components105coupled thereto. The substrate assembly100illustrated inFIG.1may represent an assembly of the substrate102, the one or more electrical components104, and the one or more other electrical components105prior to soldering the electrical components104,105to the substrate102. In some embodiments, the substrate102may be a mechanical base support for a semiconductor device package (not shown) and an electrical interface (or electrical circuit) that provides access to the electrical components104,105coupled thereto. For example, the substrate102may include an electrical circuit106(shown inFIGS.2A-2B) including plurality of metal layers and/or traces disposed within the substrate102, including one or more layers for routing signals such as, but not limited to, input/output signals, power signals, and ground signals using conductive (e.g., copper) traces. In some embodiments, the plurality of layers of the substrate alternate between conductive and non-conductive layers. The conductive layers may include one or more signal traces. The electrical circuit106may be positioned between a top planar surface110and a bottom planar surface111(shown inFIG.2A) of the substrate102.

The one or more electrical components104may be components that are, according to conventional soldering methods, prone to certain assembly related defects, and the one or more other electrical components105may be components that are not prone to or have a significantly low chance of experiencing certain assembly related defects. For example, a distinction between the electrical components104and the other electrical components105is that the other electrical components105are less prone to reflow tombstoning and/or shift defects than the electrical components104in a conventional SMT process. This may be dependent upon the relative size and/or weight of the components104,105and/or the manner in which said components are coupled to the substrate102. For example, the electrical components104may be SMT components that are mounted to the substrate102according to an SMT method prior to reflow. The electrical components104may have a size and/or weight that is significantly lesser than the size and/or weight of the other electrical components105. For example, the electrical components104may be resistors and/or capacitors and the other electrical components105may be semiconductor dies.

In some embodiments, the electrical components104are components having a length and width that is less than or equal to an existing SMD package type, which is often abbreviated using an SMD package type size code. The SMD package type size codes referenced herein are in the imperial system. For example, the electrical components104may be components having a size that is equivalent to or less than SMD package type 0201, where the length is 0.6 mm and the width is 0.3 mm, and/or the SMD package type 01005, where the length is 0.4 mm and the width is 0.2 mm. However, it will be understood that other components having a size that is greater than the examples provided above may also be considered as electrical components104. For example, the electrical components104may be any component that has a weight and/or size that would result in the forces from the surface tension caused by a solder material to be larger than the gravitational forces relating to said components size and/or weight.

In some embodiments, the electrical components104are SMT components and the other components105are not SMT components. The one or more electrical components104may include, resistors, capacitors, SMT diodes, transistors and the one or more other electrical components105may be any other electrical component. For example, the other electrical components105may include, but are not limited to, semiconductor dies (e.g., NAND memory dies, controller dies, application-specific integrated circuit (ASIC) dies, or other integrated circuit (IC) dies). In some embodiments, the one or more other electrical components105may include SMT components as well. The one or more other electrical components105will not be discussed in further detail, however, it should be understood that the one or more other electrical components105are any electrical component to which the method(s) of the present disclosure, as discussed in more detail below with reference toFIGS.4-8, may not be directed to. Put another way, the method(s) of the present disclosure include positioning magnets below certain electrical components (e.g., electrical components104) in order to prevent, or at least reduce, the occurrence of component shift and/or tombstoning during reflow of the substrate assembly100. As such, the other electrical components105may be characterized as electrical components coupled to the substrate102that have no magnets positioned below them during reflow, according to the method(s) of the present disclosure.

In some embodiments, the electrical components104may be mounted to the substrate102at predetermined locations for soldering. For example, the electrical components104may be arranged on the substrate102at locations that correspond to the locations where electrical connections will be established. Said electrical connections may correspond to locations at the top surface110of the substrate102where portions of the electrical circuit106are exposed to allow for electrical connections between the electrical components104and substrate102to be formed. In some embodiments, a solder material (e.g., a solder paste) is used to mount the electrical components104to the substrate102at the desired locations and to form the electrical connection, following reflow soldering.

Referring toFIGS.2A-2B, there is illustrated an electrical component104coupled to substrate102according to an SMT method prior to reflow. The dimensions of SMT components may be defined by one or more industry standards such as, but not limited to, the joint electron device engineering council (JEDEC) standards. There may be portions of solder material108applied to the top planar surface110of the substrate102(seeFIG.2A). The solder material108may be a solder paste including a combination of a powder made up of metal solder particles and a flux material. The flux material may be a sticky flux that has adhesive characteristics. The solder material108, while a paste, may flow like a fluid when a sufficiently large load or stress is applied to it. The solder material may be any conventional solder material known to those skilled in the art. In some embodiments, the solder material108is in direct contact with at least a portion of the electrical circuit106of the substrate102. For example, the solder material108may be in direct contact with the portions of the electrical circuit106exposed at the top planar surface110of the substrate102.

In some embodiments, the electrical components104are mounted directly onto the solder material108thereby coupling the electrical components104to the substrate102(seeFIG.2B). InFIG.2B, the solder material is a paste, as described above, that has not been heated to a temperature to cause the solder paste to melt and/or solidify (e.g., the eutectic temperature). Put another way, the solder material108illustrated inFIGS.2A-2Bhas not been subjected to soldering (e.g., reflow soldering) yet. As such, the solder material108, may act as an adhesive that is coupling the electrical components104to the substrate102. For example, the flux included in the solder paste mixture, may act as a temporary adhesive that holds the electrical components104in place relative to the substrate102. In this manner, the electrical components104are coupled to the substrate102and held in the intended positions relative to the substrate102prior to soldering. The electrical components104may be coupled to the substrate102via the solder material108, however, it should be understood that the electrical components104are not fixedly coupled to the substrate102. For example, while the solder material108may act as an adhesive keeping the electrical components104in place, there is no permanent solder joint formed that fixedly couples the electrical components104to the substrate102.

Although a single electrical component104is illustrated inFIGS.2A-2B, it will be understood that one or more of the electrical components104illustrated inFIG.1, may be coupled to the top planar surface110of the substrate102in generally the same manner as what is depicted inFIGS.2A-2B. In some embodiments, each of the electrical components104is mounted to the substrate102, prior to soldering, in generally the same manner as what is illustrated and described above, with reference toFIGS.2A-2B.

Referring toFIG.3, there is shown an illustration of an electrical component10offset from an intended orientation relative to a substrate12due to reflow soldering.FIG.3is provided to facilitate better understanding of the systems and methods of the present disclosure and it will be understood thatFIG.3illustrates an electrical component10undergoing a conventional method of reflow soldering. InFIG.3, the electrical component10is a surface mount capacitor coupled to the substrate12via two volumes of solder material14disposed at opposite ends of the electrical component10. As discussed above, in conventional systems and methods of soldering, including reflow soldering, the electrical component10may be displaced and/or rotate relative to the substrate12due to the heating of the solder material14. As the solder material14is subjected to controlled heat, the solder material14undergoes a “wetting” process in which the solder material14transitions to a molten fluid state. In the fluid molten state, the solder material14may spread along portions of the electrical component and form bonds with the metal of the substrate12and electrical component10. However, during wetting, the solder material14may spread unevenly causing the electrical component10to shift and/or rotate relative to the substrate12resulting in defects such as, but not limited to, component shift and tombstoning. Such instances may be characterized as poor wetting of the solder material14.

Poor wetting of the solder material may result in an unbalanced distribution of forces on the electrical component10, as illustrated inFIG.3. InFIG.3, the forces are represented as moment forces (τ), also referred to as moment or torque. The moment forces τ are calculated about a pivot point N located at the bottom left corner of the electrical component10. In order to decrease the risk of rotation of the electrical component10(e.g., reduce the risk of tombstoning) it may be desirable to balance the moment force about the pivot point N τN.

The individual moment forces may be calculated as follows:
τG=GL*cos(α+β)/(2*cos α)whereτGis the moment force cause by gravity,L is the length of the electrical component10in meters,G is the gravitational constant,α is the angle formed between the bottom surface of the electrical component10and a line extending from pivot point N to the center of gravity of the electrical component10, andβ is the angle of the bottom surface of the electrical component10relative to the horizontal.
τST1=(γsoldersin θ1)n1WcapHcapwhereτST1is the moment force caused by the solder material14at the pivot point N,γsolderis the surface tension of the solder material14,θ1is the contact angle of the respective solder material14,n1is the fraction of the solder height at the terminal with the pivot point N,Wcapis the width of the electrical component10in meters, andHcapis the thickness of the electrical component10in meters.
τST2=(γsoldersin θ2)n2WcapHcapwhereτST2is the first moment force caused by the solder material14on the tipping side of the electrical component10(e.g., the solder material14on the right inFIG.3),γsolderis the surface tension of the solder material14,θ2is the contact angle of the respective solder material14,n2is the fraction of solder height on the tipping side,Wcapis the width of the electrical component10in meters, andHcapis the thickness of the electrical component10in meters.
τST2′=(γsoldercos θ2)n2WcapLwhereτST2′is the second moment force caused by the solder material14on the tipping side of the electrical component10.γsolderis the surface tension of the solder material14,θ2is the contact angle of the respective solder material14,n2is the fraction of solder height on the tipping side,Wcapis the width of the electrical component10in meters, andL is the length of the electrical component10in meters
TST2″=(γsoldercos θ2)n2*2TWLwhereTST2″is the third moment force caused by the solder material14on the tipping side of the electrical component10,γsolderis the surface tension of the solder material14,θ2is the contact angle of the respective solder material14,n2is the fraction of solder height on the tipping side,TWis the terminal width of the electrical component10in meter. In some embodiments, the third moment force τST2″may be disregarded for some resistors (e.g., surface mount resistors), andL is the length of the electrical component10in meters
τBuoyancy=ρVg*LwhereτBuoyancyis the moment force caused by buoyancy,ρ is the density of the solder material14in kg/m3,g is gravitational acceleration, andL is the length of the electrical component10in meters

The total moment force τNabout pivot point N may be calculated as follows:
τN=(n1sin θ1−n2sin θ2)γsolderWcapHcap+ρVg*L−(n2cos θ2)γsolder(Wcap+2TW)L−GL/2*(cos β−sin β tan α)wheren1is the fraction of the solder height at the terminal with the pivot point N,θ1is the contact angle of the respective solder material14,n2is the fraction of solder height on the tipping side,θ2is the contact angle of the respective solder material14,γsolderis the surface tension of the solder material14,Wcapis the width of the electrical component10in meters,Hcapis the thickness of the electrical component10in meters,ρ is the density of the solder material14in kg/m3,g is gravitational acceleration,L is the length of the electrical component10in meters,TWis the terminal width of the electrical component10in meters,G is the gravitational constant,β is the angle of the bottom surface of the electrical component10relative to the horizontal, andα is the angle formed between the bottom surface of the electrical component10and a line extending from pivot point N to the center of gravity of the electrical component10

Decreasing the total moment force TN may reduce the risk that the electrical component tilts or rotates about the pivot point N. The total moment force τNabout the pivot point N of the electrical component N may be decreased by increasing or decreasing the various moment forces as calculated above. For example, increasing the moment force τGcaused by gravity (e.g., increasing G and/or L, decreasing a and/or H/L) may decrease the total moment force τN. Furthermore decreasing τST1/τST2and/or increasing τST2′may also decrease the total moment force. This may be accomplished by decreasing the contact angles θ1and/or θ2of the solder material14, which may be accomplished by decreasing the volume V of the solder material14and/or by shortening the length of the solder material14along the substrate12. Furthermore, increasing the terminal width TW, decreasing n1/n2, and/or increasing the length L and decreasing the height H of the electrical component10in order to optimize the torque surface tension. It will be understood that although what is illustrated inFIG.3is a conventional system and method for reflow soldering the moment forces, as described above, may apply to the electrical components104of the exemplary systems and methods discussed herein.

Referring toFIG.4, in some embodiments, there is a carrier112and a carrier cover114configured to prevent, or at least reduce the occurrence of component shift and/or tomb stoning of the electrical components104during soldering. The carrier112may include one or more magnets116configured to exert a magnetic force on the electrical components104in order to maintain the orientation of the electrical components104during soldering. It will be understood that the magnetic force exerted by the one or more magnets116may be factored into the calculations for the total moment force τNdiscussed above. For example, the magnetic force may decrease the total moment force τNthereby preventing, or at least reducing the risk of component shift and/or tombstoning. The carrier cover114may define an opening118extending through the thickness of the carrier cover114and one or more plates120extending across the opening118. The plates120may be configured to prevent tombstoning of the electrical components104during soldering. For example, the plates120may act as a physical barrier or stop that prevents the electrical components104from rotating relative to the substrate102by a predetermined amount. Put another way, in an instance where the electrical components104rotate relative to the substrate102, the maximum angle of rotation may be restricted by the plates120.

Referring toFIGS.5A-5B, the substrate102, and the electrical components104mounted thereon may be positioned between the carrier112and the carrier cover114and subjected to controlled heating for soldering. The carrier112may include a top carrier surface122and a bottom carrier surface124opposite the top carrier surface122. In some embodiments, each of the magnets116is disposed between the top and bottom carrier surfaces122,124. In some embodiments, each of the magnets116is embedded within the carrier112between the top and bottom carrier surfaces122,124. In some embodiments, the substrate102is mounted on the carrier112such that the bottom planar surface111of the substrate102and the top carrier surface122abut one another. In some embodiments, the carrier112has a thickness as measured in a direction perpendicular to the top and bottom carrier surfaces122,124of about 3 mm. The thickness of the carrier112may be greater than the thickness of the magnets116. In some embodiments, the carrier112may be a substrate having a plurality of layers. In some embodiments, the plurality of layers may alternate between conductive and non-conductive layers. The conductive layers may include signal traces. In some embodiments, the magnets116embedded in the carrier112substrate may receive an electrical current transmitted via one or more of the conductive layers such that the magnets116generate a magnetic force.

The plates120of the carrier cover114may be positioned directly above the electrical components104. In some embodiments, there is a gap formed between the carrier cover114and the electrical components104. For example, the plates120may be offset from the electrical components by a distance D. In this manner, the plates120may not abut the electrical components104while they are in their original position and/or orientation and may act as a barrier preventing the electrical components from rotating beyond a maximum angle. The distance D may be dependent upon the angle of rotation for an electrical component104at which tombstoning would occur. For example, the distance D may be less than a change in height caused by the rotation of the electrical component104that result in tombstoning. The change in height caused by the rotation of the electrical component104that would result in tombstoning may be referred to herein as the “tombstoning value”. In some embodiments, the distance D is dependent upon a maximum contact angle θ1, θ2of the solder material108. For example, as the contact angle θ1, θ2of a respective solder material108increases a moment force exerted by the respective solder material108on the electrical component104may increase. As such, the distance D may be less than a distance (e.g., the tombstoning value) that would result in a moment force exerted by the respective solder material108from overcoming the moment force of gravity and/or the moment force caused by the magnet116. In some embodiments, the distance D is about 10 micrometers. In some embodiments, the tombstoning value may be dependent upon the size of the electrical component104. For example, and as provided below in Table 1, some ranges of tombstoning values for electrical components104characterized by different SMD package types are provided below. It will be understood that the distance D may be less than the tombstoning values provided below.

TABLE 1Tombstoning Value Ranges by SMD Package TypeElectrical Component Size byTombstoning Value RangeSMD Package Type Code(micrometers)020140-50040250-600603 Cap60-70080570-80

The one or more magnets116may be positioned between the top carrier surface122and the bottom carrier surface124. In some embodiments, each of the one or more magnets116is positioned within the carrier112such that each magnet116may exert a magnetic force on a corresponding electrical component104. For example, each of the one or more magnets116may be positioned within the carrier112such that each of the magnets116are positioned directly below a corresponding electrical component104. There may be a single magnet116positioned directly below each of the electrical components104when the substrate102is positioned above the carrier112. In some embodiments, a magnet116being directly below a corresponding electrical component104refers to the magnet116being positioned in a generally central position relative to the electrical component104. For example, each electrical component104has an intended position relative to the substrate102that may be represented by a continuous surface area on the surface of the substrate102. Each magnet116corresponding to a respective electrical component104may be positioned so that it is centered within and below that surface area. Put another way, a vertical axis A extending through the geometric center and/or center of gravity of the electrical component104may extend through the geometric center of the magnet116as well.

As discussed above, each of the magnets116may be configured to prevent tombstoning and/or component shift of the electrical component104that the magnet116is positioned directly below. For example, the magnetic force exerted by a magnet116may be sufficient to overcome any shift of the electrical component104in a direction transverse to the top planar surface110of the substrate102and/or rotation of the electrical component104relative to the substrate102. In some embodiments, the amount of the magnetic force exerted by a magnet116may be greater than or equal to a force required to cause the total moment force τNto be less than or equal to zero. For example, the magnetic force exerted by a magnet116in combination with the force of gravity may be large enough to overcome the moment forces exerted on the electrical component104by the solder material108. In some embodiments, the magnetic force exerted by a magnet116in combination with the force of gravity must be great enough to overcome any surface tension force from the solder material108. In some embodiments, the magnetic force exerted by each of the one or more magnets116is between about 336*10−6N to about 865*10−6N.

In some embodiments, by exerting a magnetic force on the electrical components104, via corresponding magnets116during soldering the wetting of the solder material108on opposite ends of the electrical component104may occur more evenly when compared to conventional systems and methods. In some embodiments, by exerting a magnetic force in combination with the force of gravity on the electrical component104that is great enough to overcome the surface tension forces exerted by the solder material108, the wettability of the solder material108contacting the opposing ends of the electrical component104(e.g., the terminal ends) may be optimized. For example, the surface tension of the solder material108in combination with the magnetic force exerted by the magnets116may reduce the occurrence of component shift during soldering thereby creating a balanced moment force exerted on the terminal ends of the electrical component104by the solder material108. In this manner, the magnets116may reduce the risk of tombstoning and/or component shift when compared to conventional systems and methods.

The recommended magnetic force may be calculated based on the following equation:
Fmagnet+Fgravity>Ftension1cos θ1+Ftension2cos θ2where,Fmagnetis the magnetic force exerted by the magnet116,Fgravityis the force of gravity,Ftension1is the force exerted by the surface tension of the solder material108at one terminal end of the electrical component104,θ1is the contact angle of the respective solder material14,Ftension2is the force exerted by the surface tension of the solder material108at the opposite terminal end of the electrical component104, andθ2is the contact angle of the respective solder material14

Some examples of recommended magnetic forces based on the dimensions and mass of the electrical component104, and the surface tension of the solder material108are provided below in Table 2.

TABLE 2Examples of recommended magnetic forceDimensionsLengthWidthThicknessWeightSurface TensionRecommend(μm)(μm)(μm)(mg)(N/m)Fmagnet/N6003002500.350.5670.00033710005003501.80.00054916008004504.20.000865

In some embodiments, each magnet116has a maximum operating temperature that is greater than the temperature required for soldering. In this manner each of the magnets116may be configured to exert a magnetic force on a corresponding electrical component104that is sufficient to maintain the orientation of the electrical component104during soldering. In some embodiments, each of the magnets116has a maximum operating temperature of at least 350 degrees Celsius. In some embodiments, each of the magnets116include cobalt. In some embodiments each of the magnets116are Chinese Fir Cobalt magnets. In some embodiments, each of the magnets116are Samarium Cobalt magnets. In some embodiments, each of the magnets116may be generally the same size and/or exert generally the same magnetic force as one another.

Referring toFIG.6, in some embodiments, each of the magnets116is spaced from each other magnet116such that the magnetic force exerted by any one magnet116does not affect the position and/or orientation of an adjacent electrical component104. For example, there may be a first magnet116apositioned directly below a first electrical component104aand a second magnet116bpositioned directly below a second electrical component104b. The magnetic force exerted by the first magnet116amay affect the position and/or orientation of the first electrical component104awhile not affecting the position and/or orientation of the second electrical component104b. Similarly, the magnetic force exerted by the second magnet116amay affect the position and/or orientation of the second electrical component104bwhile not affecting the position and/or orientation of the second electrical component104b.

Referring toFIG.7, there is a flowchart illustrating a method, generally designated200, of soldering one or more electrical components to a substrate in accordance with an exemplary embodiment of the present disclosure. The method200may include the step202of providing a substrate with electrical components mounted thereto. For example, substrate102may be provided, having a top planar surface110and a bottom planar surface111. An amount of solder material108may be applied to the top planar surface110of the substrate102. One or more electrical components104may be mounted on the solder material108such that each of the electrical components104has a position and orientation relative to the substrate102. The method200may include the step204of positioning the substrate above a carrier having magnets embedded therein. For example, carrier112, having a top carrier surface122and a bottom carrier surface124, may be provided. The one or more magnets116may be embedded therein between the top and bottom carrier surfaces122,124. The substrate102may be positioned above the carrier112such that the bottom planar surface111of the substrate102is above the top carrier surface122of the carrier112. Each of the one or more magnets116may be positioned directly below a corresponding electrical component104of the one or more electrical components.

The method200may include the step206of positioning a carrier cover above the substrate and the electrical components. For example, the carrier cover114may be positioned above the top planar surface110of the substrate102such that there is a gap (e.g., the gap having a distance D inFIG.5B) between the carrier cover114and the one or more electrical components104. The method200may include the step208of heating the solder material while a magnetic force is exerted on the electrical components by the magnets. For example, the substrate102, carrier112, and carrier cover114(as shown inFIG.5A) may be heated along with the solder material108to a predetermined temperature for a predetermined amount of time to cause the solder material108to melt. During the heating of the solder material108, each of the magnets116may exert a magnetic force on a corresponding electrical component104to maintain the orientation of said electrical component104relative to the substrate102while the solder material melts. In some embodiments, heating the solder material includes positioning the substrate102having the one or more electrical components104mounted thereto via the solder material108, the carrier112and the carrier cover114in a reflow oven and operating the reflow oven to cause the solder material to melt.

In this manner, the carrier112and the magnets116embedded therein may prevent or at least reduce the occurrence of component shift and/or tomb stoning by exerting a magnetic force on the electrical components104while the solder material108melts. Furthermore, the carrier cover114may also ensure that tomb stoning does not occur by providing a physical barrier preventing rotation of the electrical components104beyond a predetermined amount, as discussed above with reference toFIGS.5A-5B. In some embodiments, the carrier cover114may not be positioned above the substrate102and the electrical components104mounted thereto during soldering. For example, the method200may not include step206of positioning the carrier cover above the substrate102.

It will be appreciated by those skilled in the art that changes could be made to the exemplary embodiments shown and described above without departing from the broad inventive concepts thereof. It is understood, therefore, that this invention is not limited to the exemplary embodiments shown and described, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the claims. For example, specific features of the exemplary embodiments may or may not be part of the claimed invention and various features of the disclosed embodiments may be combined. The words “right”, “left”, “lower” and “upper” designate directions in the drawings to which reference is made. Unless specifically set forth herein, the terms “a”, “an” and “the” are not limited to one element but instead should be read as meaning “at least one”. As used herein, the term “about” may refer to +/−10% of the value referenced. For example, “about 9” is understood to encompass 8.1 and 9.9.

Further, to the extent that the methods of the present invention do not rely on the particular order of steps set forth herein, the particular order of the steps should not be construed as limitation on the claims. Any claims directed to the methods of the present invention should not be limited to the performance of their steps in the order written, and one skilled in the art can readily appreciate that the steps may be varied and still remain within the spirit and scope of the present invention.