JP7334285B2 - Multi-component leadless stack - Google Patents

Description

The present invention relates to electronic components and methods of manufacturing electronic components. More specifically, the present invention relates to electronic components and methods of manufacturing electronic components, in particular stacks of electronic components including at least one multilayer ceramic capacitor (MLCC) and preferably additional passive or active electronic components. related to integrated leadless electronic components. Electronic components may be used for external lead or lead frame connection or for direct leadless connection of electronic components so that they may subsequently be connected to electronic circuits by various secondary connection materials and processes. It has improved terminations. More specifically, the present invention relates to a microphonic noise-suppressed, leadless, stackable stack of electronic components comprising electronic elements, preferably comprising at least one multilayer ceramic capacitor. .

In general, the method and materials used to form the conductive termination are very important for reliable performance. When the electronic component is subsequently assembled into an electronic circuit, in-use performance is directly related to the conductive termination. Historically, lead (PB) based solders have been used to mount electronic components to electronic circuit boards and to connect external leads to electronic components. Very recently, the use of hazardous substances in electrical and electronic equipment has been regulated by the European Regulations on the Use of Specified Hazardous Substances as a typical example, and the use of lead (Pb) in solder has been restricted. Alternatives are being explored.

For example, US Pat.
C) describes the use of a tin (Sn) based solder containing 10-30% antimony (Sb) to contact the components. However, this described solder has a liquidus below 270°C. For comparison, high concentration lead solders such as Sn10/Pb88/Ag2 have a liquidus of about 290°C. It is widely recognized in the industry that a melting point at least 30° C. higher than any subsequent processing temperature is desirable to ensure the reliability of external lead connections. Since Sn, Ag, Cu based solders, referred to in the art as SAC solders, are now the common choice for bonding in lead-free circuits, the ability to achieve high melting points is of great importance. became. SAC solder typically has a temperature of about 260°C, which is higher than older Pb-based alternatives such as Sn63/Pb37, which has a melting point of 183°C.
must be reflowed at °C. The material that contacts the external leads, ie, the material that forms the terminals, must be able to withstand temperatures well above this so as not to melt or partially melt causing serious reliability problems. A temperature at least 30° C. above the melting point of the SAC solder is desirable. Due to the material compatibility and high processing temperatures involved in semiconductor technology, alloys of gold/germanium, gold/silicon and gold/tin have been developed for attaching dies to substrates. Due to the small difference in coefficient of thermal expansion (CTE) between the die and its bonding surface, these alloys provided high temperature performance and high strength with tensile strength in the range of 20,000 psi and shear strength in the range of 25,000 psi. . However, these materials also require higher processing temperatures due to their high melting points, generally above 350°C. Its high processing temperature has prevented its widespread use in the electronics field. Tin and indium have been added to combinations of Zn, Al, Ge and Mg to form high temperature lead free solders. However, powders of zinc and aluminum tend to form an oxide film on the surface, resulting in poor wettability with subsequent solder, making them unsuitable for practical use. Solders with tin, zinc, cadmium, and aluminum are available, but their alloys have a wide plasticity range of 50-175°C, except for eutectic alloys, which limits their use to very specific applications outside the electronics sector. and is usually used in the form of eutectic alloys. Alloys of cadmium, zinc and silver are suitable for soldering aluminum. Solders with liquidus temperatures above 450° C. are referred to as "hard solders" and are typically used in structural applications rather than electrical applications. Therefore, a method of forming a lead-free high temperature adhesive for a capacitor that maintains its integrity above 260° C. and is inexpensive to manufacture has not yet been realized.

The following patents describe transitional liquid phase sintering (TLPS) materials and processes for the formation of conductive bonds. Patent Document 2 describes coating two bonding surfaces, one with Sn and the other with Pb, and bonding the two bonding surfaces by raising the processing temperature to about 183° C., which is slightly lower than the melting point of Sn. ing. The transitional liquid phase sintering method (TLP
The formulation according to S) combines the material of TLPS with a cross-linked polymer to produce a conductive adhesive with improved conductivity as a result of the formation of an intermetallic interface between metal surfaces by the TLPS process. US Pat. No. 5,300,003 discloses two bonding surfaces, one of which is sprayed with a low melting point material, the bonding surfaces are sprayed with a matching high melting point material, heated to the melting point of the low melting point material, and bonded together. It is described to join

US Pat. No. 5,300,000 describes the use of SnBi or SnIn to solder discrete components such as resistors to printed circuit boards using the TLPS process. US Pat. No. 6,300,000 describes mounting an electronic module to a substrate using Ag/Sn/Bi coated on two adhesive surfaces. US Pat. No. 6,200,403 describes depositing materials on two bonding surfaces, the substrate and the bump surface of the flip chip, and raising the temperature until diffusion between the materials occurs to produce a TLPS compatible alloy. US Pat. No. 6,200,000 describes the use of TLPS in the formation of semiconductor devices that are bonded to packages and other components and conductive surfaces containing SiC. US Pat. No. 5,300,001 discloses placing a TLPS compatible material on the bonding surface, reflowing the material with a relatively low melting point, followed by a hot aging treatment to terminate the diffusion process, and to connect the two devices to be bonded together by microelectronics. It is described as a micro-electro-mechanical system (MEMS) device for circuits. US Pat. No. 5,300,009 describes using TLPS to bond a heat spreader made of copper, black diamond, or a composite of copper and black diamond to a silicon die. Although these patents and patent applications describe the processing of TLPS for bonding components to substrates, the use of TLPS to form the terminations of electronic components or to connect electronic components to leadframes has been described. did not teach anything about

According to recent developments, US Pat. No. 6,300,007 describes a high temperature diffusion bonding process for welding leads to internal electrodes of laminated ceramic components. The TLPS material is plated by introducing heat to the surfaces of the bonding surfaces that are to be joined together to initiate the diffusion process. In this case, contact between the component and the leadframe is required over the surface to facilitate diffusion. This limits the application to joining surfaces that can form cohesive lines, and the application cannot accommodate components of different lengths that are connected to the leadframe. Additionally, 70 to achieve a welded joint.
High temperatures in the range 0-900° C. are described. Achieving these high temperatures requires careful process design, such as a preheating stage, to avoid thermal shock damage to the multilayer ceramic component, and even then it is not suitable for all materials.

None of the other lead-free bonding techniques disclosed in the art are suitable. Solders are alloys of two or more metals with a single melting point, which is always lower than the melting point of the metal with the highest melting point, generally lower than 310° C. depending on the alloy. . The solder is reworkable, meaning that the solder can be reflowed many times, thereby providing a means to remove or replace defective components. Solder also creates a metallurgical bond by forming a metal-to-metal interface with the surfaces to which it joins. As the solder wets the surfaces to be joined, the solder effectively flows outward and spreads over the surface area to be joined.

MLCCs are used in a variety of applications. Generally, MLCC or ML
A stack of CCs is mounted on the board as individual components. A particular problem with MLCCs is that they tend to crack when subjected to stress such as substrate warpage. In order to avoid cracking due to such stress, the MLCC is mounted between lead frames of each polarity, and the lead frames are then mounted on the substrate by soldering or the like. Leadframes are considered essential in the field and reduce the stress associated with board warpage to M
A great deal of effort has gone into designing leadframes that can withstand such stresses without transmitting to the LCC. Determining lead frame designs and materials is particularly difficult due to differences in thermal expansion coefficients, equivalent series resistance (ESR), inductance, and other parasitic suppression requirements. Although there is a desire to remove the leadframe, those skilled in the art have been unable to do so, as any substrate warpage would be transferred directly to the MLCC, effectively insuring the MLCC against damage.

Multilayer ceramic capacitors or MLs fabricated with polarized dielectrics such as barium titanate
CC is prone to microphonic noise. Microphonic noise is believed to be caused by electrostriction, also called the piezoelectric effect, which is the movement of ceramics that occurs in the presence of an applied electric field. When an electric field is applied, the movement of the ceramic is amplified by the substrate on which the component is mounted, ultimately producing audible noise. Reeds reduce microphonic noise. The use of leadless capacitors, especially leadless capacitor stacks mounted on substrates, enhances microphonic noise, which is highly undesirable, especially for portable devices such as mobile phones. Accordingly, it is desirable to eliminate or suppress microphonic noise while enjoying the benefits of leadless capacitors, particularly leadless stacks of at least one capacitor.

In spite of constant efforts, suitable electronic components consisting of multilayer ceramic capacitors and other stacked electronic elements have not yet been realized. There is a continuing need for lead connections with improved reliability for high temperature applications, especially lead-free electronic components with minimal or no microphonic noise, especially including multilayer ceramic capacitors.

U.S. Patent No. 6,704,189 U.S. Pat. No. 5,038,996 U.S. Patent No. 5,853,622 U.S. Patent No. 5,964,395 U.S. Pat. No. 5,221,038 U.S. Pat. No. 6,241,145 U.S. Patent Application Publication No. 2002/0092895 U.S. Patent Application Publication No. 2006/0151871 U.S. Patent Application Publication No. 2007/0152026 U.S. Patent No. 7,023,089 U.S. Patent Application Publication No. 2009/0296311

An object of the present invention is to provide an ML that can be connected by reflow without damaging the connection of metal external leads and lead frames during connection to a lead frame or subsequent assembly to an electronic circuit.
It is an object of the present invention to provide an improved method of forming metallic external terminals suitable for use as leadless stacks of electronic devices containing CCs.

Another object of the present invention is to provide an improved termination suitable as a leadframe connection or leadless termination that can withstand subsequent solder reflow processes to electronic circuits without damaging the termination or lead connection interconnect. to provide a method.

Another object of the present invention is to provide an improved termination suitable as a leadframe connection or leadless termination that can withstand subsequent solder reflow processes to electronic circuits without damaging the termination or lead connection interconnect. to provide a method.

Another object of the present invention is that preferably at least one electronic element is an MLCC that can be mounted without a lead frame, and the warping of the substrate does not cause the expected stress of cracking the electronic element, especially the MLCC. The object is to provide an electronic component comprising a stack of devices.

Another object of the present invention is the advantage of having an initially low process temperature but then a high melting point temperature without the use of prohibited materials such as lead and cadmium, or costly materials such as large amounts of gold. forming terminations or interconnects in electronic components with

A feature of the present invention is the ability to provide a leadless stack of electronic devices, preferably including at least one MLCC, with minimal microphonic noise propagation.

These and other advantages can be realized with an electronic component that preferably comprises a stack of electronic elements including at least one multilayer ceramic capacitor, each multilayer ceramic capacitor having a respective first electrode and a respective first electrode. It includes first electrodes and second electrodes that are alternately laminated with a dielectric interposed between adjacent second electrodes. The first electrode terminates on the first side and the second electrode terminates on the second side. a first transitional liquid phase sintered conductive layer on a first side and in electrical contact with each first electrode; a second transitional liquid phase sintered conductive layer on a second side and in electrical contact with each second electrode; make electrical contact.

Further provided is another example method of forming an electronic component:
Each electronic element has a first side and a second side, at least one electronic element of the electronic elements being a multilayer ceramic capacitor, each multilayer ceramic capacitor adjacent to each first electrode and each first electrode. a first electrode and a second electrode stacked alternately with a dielectric interposed therebetween, the first electrode terminating on a first side of the capacitor and the second electrode terminating on the second side of the capacitor; comprising an electronic element that terminates on two sides;
stacking the electronic elements such that each first side is parallel and each second side is parallel;
forming a first layer of a first component of the transitional liquid phase sintering conductive layer;
forming a second layer of the first component of the transitional liquid phase sintering conductive layer;
contacting the first layer and the second layer with a second component of the transitional liquid phase sintered conductive layer;
heating to a first temperature sufficient to form a first transitional liquid phase sintered conductive layer comprising the first component and the second component such that the first transitional liquid phase sintered conductive layer forms the first forming a second transitional liquid phase sintered conductive layer including a first component and a second component in electrical contact with one electrode, wherein the second transitional liquid phase sintered conductive layer electrically contacts the second electrode; contacting and thereby forming a stack capacitor.

Further provided is another example method of forming a multilayer ceramic capacitor stack:
A plurality of electronic elements, at least one of which is a multilayer ceramic capacitor, each multilayer ceramic capacitor comprising:
including first electrodes and second electrodes alternately stacked with a dielectric interposed between each first electrode and a second electrode adjacent to each first electrode, the first electrodes having a first polarity terminating on a first side of the multilayer ceramic capacitor and the second electrode having a second polarity and terminating on a second side of the multilayer ceramic capacitor;
forming a stack of electronic elements;
forming a first transitional liquid phase sintered conductive layer in electrical contact with an adjacent electronic device; and forming a second transitional liquid phase sintered conductive layer in electrical contact with a second electrode of the adjacent electronic device. Form,
Including.

Yet another example provided is an electronic component stack. The stack includes at least one multilayer ceramic capacitor, the multilayer ceramic capacitor having: first electrodes and second electrodes arranged in parallel with each other with a dielectric interposed between adjacent first electrodes and second electrodes; The first electrode has a first polarity and terminates on the first side of the multilayer ceramic capacitor and the second electrode has a second polarity and terminates on the second side of the multilayer ceramic capacitor. Contains two electrodes. A first transitional liquid phase sintering compatible material is on the first side and electrically contacts each first electrode. A second transitional liquid phase sintering compatible material is on the second side and electrically contacts each second electrode. An electronic element is further provided, the electronic element comprising: a first external termination including a third transitional liquid phase sintering compatible material on the first external termination and a fourth transitional liquid phase sintering compatible material on the second external termination and a second outer termination comprising a material. first
A metallurgical bond is created between the transitional liquid phase sintering compatible material and the third transitional liquid phase sintering compatible material.

Yet another embodiment provided is a stacked electronic component comprising at least two electronic elements, each electronic element including a first external termination and a second external termination. consists of a stack containing A transitional liquid phase sintering adhesive is provided between and in contact with each first outer termination of adjacent electronic elements.

Yet another embodiment provided is stacked electronic components. The stacked electronic component includes an MLCC, the MLCC having a first external termination of the capacitor and a second external termination of the capacitor.
Includes external termination. At least one electronic element is adjacent to the MLCC and forms a stack with the MLCC, each electronic element including a first element external termination and a second element external termination, the electronic elements being resistors, varistors, inductors, diodes, fuses. , overvoltage discharge devices, sensors,
Selected from switches, electrostatic discharge suppressors, semiconductors, and integrated circuits. A transitional liquid phase sintering adhesive is provided in electrical contact with the first capacitor outer termination and the first element outer termination between the first capacitor outer termination and the first element outer termination.

Yet another embodiment provided is a method of forming an electronic device comprising: forming an MLCC including: a first capacitor external termination and a second capacitor external termination; a first device external termination and a second device forming an electronic component including an external termination; and stacking the MLCC and the electronic component with a TLPS junction between the first capacitor external termination and the first component external termination.

1 is a schematic side view of an embodiment of the invention; FIG. 1 is a schematic cross-sectional view of an embodiment of the invention; FIG. 1 is a schematic cross-sectional view of an embodiment of the invention; FIG. 1 is a schematic side view of an embodiment of the invention; FIG. 1 is a schematic cross-sectional view of an embodiment of the invention; FIG. 1 is a cross-sectional schematic exploded view of an embodiment of the present invention; FIG. 1 is a schematic cross-sectional view of an embodiment of the invention; FIG. 1 is a schematic cross-sectional side view of an embodiment of the present invention; FIG. 1 is a schematic cross-sectional side view of an embodiment of the present invention; FIG. 1 is a schematic cross-sectional view of an embodiment of the invention; FIG. FIG. 2 is a schematic side view of a stacked electronic device; 1 is a schematic side view of an embodiment of the invention; FIG. 1 is a graphical representation of an embodiment of the invention; 1 is an electron micrograph of a cross-section of a coupon bonded according to an embodiment of the invention; 1 is an electron micrograph of a cross-section of a coupon bonded according to an embodiment of the invention; 1 is an electron micrograph of a cross-section of a coupon bonded according to an embodiment of the invention; 1 is an electron micrograph of a cross-section of a coupon bonded according to an embodiment of the invention; 4 is a graphical representation of the advantages of the present invention; 4 is a graphical representation of the advantages of the present invention; 4 is a graphical representation of the advantages of the present invention; 4 is a graphical representation of the advantages of the present invention; 4 is a graphical representation of board warpage test results; 4 is a graphical representation of board warpage test results; 1 is an electron micrograph of a shear overlap joint of two coupons with plated surfaces; Figure 2 depicts two coupons joined with TLPS paste according to an embodiment of the present invention; 4 is a graphical representation of board warpage test results; 4 is a graphical representation of board warpage test results; 1 is a schematic cross-sectional view of an embodiment of the invention; FIG. 1 is a schematic cross-sectional view of an embodiment of the invention; FIG. 1 is a schematic cross-sectional view of an embodiment of the invention; FIG. 1 is a schematic cross-sectional view of an embodiment of the invention; FIG. 1 is a schematic side view of an embodiment of the invention; FIG. 1 is a schematic top view of an embodiment of the invention; FIG. 1 is a schematic top view of an embodiment of the invention; FIG. 1 is a schematic side view of an embodiment of the invention; FIG. Figure 3 is a schematic bottom view of an embodiment of the invention; 1 is a schematic side view of an embodiment of the invention; FIG. 1 is a schematic top view of an embodiment of the invention; FIG. Figure 3 is a schematic bottom view of an embodiment of the invention; 1 is a schematic side view of an embodiment of the invention; FIG. 1 is a schematic side view of an embodiment of the invention; FIG.

The present invention provides an electronic device with improved bonding to external leads or lead frames, or improved bonding between electronic elements in a stack of electronic elements used as leadless electronic components, at least one of which is preferably an MLCC. The present invention relates to an electronic component composed of an element. Furthermore, the stack significantly reduces the propagation of microphonic noise.

The electronic elements are preferably selected from the group consisting of MLCCs, resistors, varistors, inductors, diodes, fuses, overvoltage discharge devices, sensors, switches, electrostatic discharge suppressors, semiconductors and integrated circuits. The diode may be a light emitting diode. More preferably, the electronic element is selected from the group consisting of MLCCs, resistors, varistors, inductors, diodes, fuses, overvoltage discharge devices, sensors, switches, electrostatic discharge suppressors.

The present invention relates to the use of transitional liquid phase sintering (TLPS) adhesives for forming terminations and attaching external leads to electronic devices. This improved termination has the advantage of accommodating electronic elements of different lengths as well as different surface finishes. Furthermore, since no solder balls are formed, electronic devices can be stacked on top of each other with only TLPS interposed between the electronic devices without the gaps normally required for cleaning as in soldering techniques. . If the electronic element is an MLCC, the TLPS can be directly bonded to the internal electrode of the electronic element and the termination can be formed at a low temperature. In some embodiments, high density terminations can be created by forming an improved outer lead adhesive bond using a thermal compression bonding process.

Solder is an alloy whose composition does not change after the first reflow. Solder has a unique melting point and can be melted over and over again. The most common solder is 60% Sn4
0% Pb. Solders are the material of choice in electronics to provide mechanical and electrical interconnects between electronic devices and circuit boards. Solder is well suited for use in mass production assembly processes. The physical properties of solder can be changed simply by changing the proportions of metals used to form the solder alloy. References to solder in this context mean an alloy of at least two metals that can be melted over and over again.

Conductive epoxy adhesives are typical cross-linked polymers, which are typically filled with conductive fillers of silver or gold flakes or gold particles to create a conductive epoxy polymer bond. Unlike solder, conductive adhesives are cured only once and cannot be reworked. When the metal particles come into contact with each other, they form serpentine conductive paths in the epoxy to provide an electrical connection between two or more components. Conductive epoxies, solders, and epoxy solders have temperature limits below 315°C.

Another material, polymer solder, is used for metallurgical bonding between two or more compatible metals. Polymeric solder is generally a combination of solder, a cross-linked polymer and an epoxy. The solder provides electrical conductivity and bulk that provides mechanical strength to the bond, while the epoxy forms a polymeric bond thereby providing additional mechanical strength and improving the temperature performance of the solder itself. Polymer solders should preferably not be used for microphonic noise reduction techniques.

Bonding by transitional liquid phase sintering (TLPS) is distinguished from solder. Prior to high temperature exposure, TLPS materials are mixtures or alloys of two or more metals, thereby distinguishing the material's thermal history. The TLPS material has a low melting point before exposure to high temperatures, but increases its melting point after exposure to high temperatures. The first melting point comes from the lower melting point metal or an alloy of two lower melting point metals. 2
The second melting point is the melting point of the intermetallic compound formed when a lower melting point metal or alloy forms a new alloy with a higher melting point thereby producing an intermetallic compound with a higher melting point. The TLPS material forms a metallurgical bond between the metal surfaces to be joined. Tin/lead solder or lead (P
b) Unlike free solder, TLPS does not spread when it forms an intermetallic bond. Rework of the TLPS system becomes very difficult due to the high secondary flow temperature. Transient liquid phase sintering is a process that describes the metallurgical state that results when two or more TLPS compatible materials are brought into contact with each other and the temperature is raised to a temperature sufficient to melt the low melting point metal. is a terminology given to At least one of a family of low melting point metals such as tin (Sn) and indium (In) are selected for the TLPS process or interconnect, and a family of high melting point metals such as copper (Cu) and silver (Ag). A second metal is selected from When Sn and Cu are brought into contact with each other and the temperature is raised, Sn and Cu
forms an intermetallic compound of CuSn, resulting in a melting point higher than that of metals with low melting points. In the case of In and Ag, when the In is heated sufficiently, it melts and actually diffuses into the Ag, thereby forming a solid solution with a higher melting point than In itself. TLPS is used when referring generally to the process, and TLPS compatible materials are used when forming a metallurgical bond between two or more LPS compatible metals. TLPS provides an electrical and mechanical interconnect that is relatively low temperature (<300
°C) and have a second remelting temperature >600°C. The above temperature is T
Determined by different combinations of LPS compatible metals. TLPS is generally utilized in connection with the processes and materials used to form metallurgical bonds or interconnects with TLPS.

TLPS bonding can be performed at a relatively low initial process temperature of 157°C. Once T
Once the LPS bonding process is complete, the resulting bond has a melting temperature much higher than the initial process temperature, typically 300° C. or higher, in a large set of materials.
It is common to have a secondary melting point above 50°C. TLPS differs from conventional solder in that the solder is formed by melting two or more metals together to form an alloy with specific properties. Such specificity can be altered simply by adding additional metals to the alloy or by changing the proportions of the metals that make up the alloy. The solder alloy is then remelted and solidified to join the two or more surfaces. TLPS is not initially an alloy material like a solder alloy. TLPS is a metallurgical process based on interdiffusion and sintering of two or more metals, especially at the interface between two surfaces. Once the TLPS interface is created, it cannot be melted again at low temperatures. Once the sintering or diffusion process is complete, the high remelting temperature of TLPS often prohibits rework of the assembly. Such high temperatures would cause irreversible damage. The TLPS process is accomplished by contacting a low melting point metal such as indium or tin with a high melting point metal such as silver or copper and raising the temperature to a point where the low melting point metal melts and diffuses or sinteres into the high melting point material. . Diffusion or sintering speed is a function of time and temperature and is different for different metal combinations. The result is a solid solution with a new melting temperature approaching that of the refractory metal.

A second fashion consists of high melting point metals such as silver, copper, aluminum, gold, platinum, palladium, beryllium, rhodium, nickel, cobalt, iron, molybdenum, etc., and forms a diffused solid solution. Generate.

It is very important to use a flux-free process to remove potential voids in the joint. Since TLPS is a sintering-based process, the bond lines are uniform and void-free. The flux necessary for the solder is trapped in the joint and then burns out, leaving voids. In the semiconductor industry, especially in the die attach process, these voids create hot spots within the integrated circuit (I/C), causing premature failure and reliability problems. TLPS is a sintering process and uses no flux to address this issue. When the two metals are brought into contact and heat is applied, the low melting point metal diffuses into the high melting point metal forming a solid solution over the bonding surface area. In order to form a solid and uniform bond line, it is essential that the bonding surfaces are flat and coplanar, and that the entire bonding surface is in close contact. The required planarity of the bonding surfaces also limits the application of this technique. This is because there are many instances where it is not planar enough to make a good bond.

The TLPS-compatible metal particle cores can be combined with a liquid carrier material to form a paste that can be applied between two non-planar and non-uniform surfaces, plated, sintered thick film, and/or plated. After applying a mixed surface treatment technique such as sintered thick film, it is heated to the melting temperature of the metal with the lowest melting point and held at that temperature long enough for the bond to form. Single-metal particle cores eliminate the need to include multiple metals in the paste, eliminating the need for metal ratio considerations. Furthermore, silver, a metal with a high melting point of about 960°C, is used as a core particle to produce a single particle, and then the single particle is coated with a metal shell of a low melting point metal such as indium, which has a melting point of 157°C. Is possible. The advantage of using indium is that it melts and diffuses into the silver. If this bimetallic particle of silver and indium is placed between two silver-coated surfaces respectively, indium diffuses to the silver surface and also to the silver core to form a solid solution connection. Other metals with low melting points such as indium that can be considered as bimetallic single particles include tin, antimony, bismuth, cadmium, zinc, gallium, tellurium, mercury, thallium, selenium, polonium, lead, Metals with high melting points such as silver, copper, aluminum, gold, platinum, palladium, beryllium, rhodium, nickel, cobalt, iron and molybdenum can also be considered as possible combinations.

Indium powder was mixed with flux and solvent to form a paste that was applied between two coupons with a base metal of copper overplated with Ni and overplated with approximately 5 microns (200 μin) of silver. to form a metallurgical bond of TLPS. This sample was prepared by applying an indium paste to the surface of a coupon having a plated surface as described above, then bringing the two coupons in contact with each other and heating to 150°C, holding for 5 seconds, and then increasing the temperature to 320°C. Raise and hold for 60 seconds. The bond strength of the samples thus made exhibits a tensile force in the range of 85-94 pounds corresponding to a shear stress of 4,177 psi, with an average of 7 pounds achieving a peel force in the range of 5-9 pounds. . This strength is comparable to that of SnPb solder, which has a shear strength of about 3000 psi and a peel strength in the range of 7-10 pounds. One major difference is that AgIn junctions can withstand secondary melting temperatures above 600°C. These results suggest that the In paste used to bond the two silver-plated coupons is at least as strong, if not stronger, than current SnPb solders, and even more so when compared to SnPb solders. much higher second
Having a melting temperature makes it suitable for high temperature connection applications and still provides a lead-free material.

The method of bonding the leadframe to the structure generally involves coating one of the two bonding surfaces with a high melting point metal and the other bonding surface with a low melting point metal. The coating process may consist of vapor deposition or plating. A second method is to sandwich a preform film consisting of a low melting point metal or an alloy of two or more low melting point metals between two planes coated with a high melting point metal such as Ag, Cu, Au. The third method is to produce a paste consisting of particles of a high melting point metal such as copper, add particles of an alloy of two low melting point metals such as Sn—Bi, and mix to clean the bonding surface and form a mixed paste. to create a dual-purpose liquid that acts as a liquid component for the metal particles to be used.

If sufficient diffusion of the two metals is not completed within the prescribed cycle time and if the maximum second reflow temperature is not reached, the bonding process enters a second heating process. In this case, the joint or assembly is exposed to a temperature above the melting point of the low melting point material for a period of 15 minutes to 2 hours. This time and temperature can be varied to set the desired second reflow temperature determined by the second assembly process or final environmental application requirements. In the case of indium/silver TLPS, a second melting temperature above 600° C. can be achieved.

The bond is made by heating the assembly to a temperature sufficient to melt the low melting point metal and holding for a time sufficient to form a mechanical bond, such as 5 to 30 seconds. During a subsequent second heating process, the joint is subjected to a temperature sufficient to diffuse the indium and silver and held for a sufficient time to produce an alloy having a second higher reflow temperature.

In addition to applying a paste to form a TLPS alloy bond between suitable surfaces, TLP
The S-alloy joint may be formed by a preform. In simplest terms, the preform may be a thin foil of low melting point TLPS component. Alternatively, the preform may be produced by molding a paste and drying to remove the solvent. The resulting solid preform may be placed between surfaces to be bonded. In this case it is necessary to add a suitable binder to the paste to add strength after drying. In any case, it is important that the preform is malleable so that it can conform to the bonding surface.

An interconnect material comprised of a single metal such as indium and contained in a paste is utilized to form a bond to a surface coated with a refractory metal such as silver. Diffusion of indium into silver produces a low temperature transitional liquid phase which then reacts to produce a higher temperature bond. This bond formation is important for increasing the diffusion speed of the low-melting paste.
It is desirable to add other metals to the paste to achieve desirable properties in the final connection, such as void reduction and homogeneous phase. However, it is important to maintain the high diffusivity of the low melting point material. Therefore, if one or more metals are required in addition to the low melting point metal, it is preferable to incorporate these metals by coating with metal powder prior to forming the paste. Coating the metal with the lowest melting point over the metal with the higher melting point is preferred to maintain an active surface. The coating also has the desirable effect of reducing the diffusion distances between the different metallic elements of the paste, making the preferred phases easier as opposed to simply incorporating one or more additional metal powders into a single metallic paste. can be formed.

It is preferred not to include alloys. The alloy reduces the spreading activity of the paste. The coated metal powder is preferably formed using plating prior to incorporation into the paste.

Conductive adhesives are generally crosslinked polymers filled with silver or gold particles that cure or crosslink at a specific temperature range, typically 150° C., to form a mechanical bond to the materials to be connected. do. Their conductivities are created by metal particles trapped inside a polymer matrix and in close contact with each other, forming a conductive path from one particle to another. Because the binders are organic in nature, they typically exhibit relatively low temperature capability in the range of about 150°C to about 300°C. Conductive epoxies cannot be reworked once cured. Unlike TLPS bonding, exposure to high temperatures and corrosive environments can degrade the polymer bonds and oxidize the metal particles, degrading electrical properties. Both the electrical and mechanical performance of the interconnect are compromised, resulting in increased ESR and reduced mechanical strength.

Polymer solders are conventional solder systems based on Pb/Sn alloys or Sn/S
b, which are combined with a cross-linked polymer that acts as a detergent. This cross-linked polymer is also capable of forming cross-linked polymer bonds, such as epoxy bonds, which are produced during the melting phase of metals to form solder alloys and mechanical polymer bonds. An advantage of polymer solders is that the polymer bond provides additional mechanical bond strength at temperatures above the melting point of the solder, thus allowing solder joints to have higher temperatures in the range of about 5 to 80°C above the melting point of the solder. Can provide operating temperature. Polymer solders bond commercial solder alloys in the same paste as the cross-linked polymer and are hardened by heating or the like, as well as metallurgical bonds as well as mechanical bonds. Provides bond strength. However, the upper temperature limit and bond strength have so far been increased solely by the physical properties of the materials. The practical upper limit remains at 300°C, whereas the TLP
Bonds produced by S can achieve higher temperatures.

TLPS technology is particularly suitable for providing a mechanically and electrically conductive metallurgical bond between two relatively planar bonding surfaces. Metals commonly used in TLPS processes are selected from two families of metals. The first family is indium, tin, lead, antimony, bismuth, cadmium, zinc, gallium, tellurium, mercury, thallium, selenium, TLPS
The paste can form the terminations of electronic elements or components, which can then be connected to electronic circuits by other methods and/or materials. A metallurgical metal compound bond is formed in a lead-free state, which has improved bond strength at elevated temperatures compared to other types of materials such as lead-free solders. A TLPS junction may be created by one or more electrodes embedded within the electronic device or via other materials connected to these electrodes. TLPS bonds do not need to overlap the edges of the part.

The use of TLPS in paste form allows bonding of non-uniform surfaces. More specifically, TLPS in paste form can be used to join two textured surfaces without sticking or creating a continuous contact line. This is particularly advantageous compared to plated surfaces that are subsequently diffusion bonded, which require the surfaces to be coherent and continuous lines of contact during the process. This allows electronic elements of different lengths to be combined in a stack or stacked in a leadframe. Because TLPS does not form solder balls, stacked devices can be stacked on top of each other, have their ends oriented in the same direction, and require no cleaning as is required for conventional bonding using solder. No gap occurs.

Since TLPS paste does not flow like conventional solder, there is no need to build solder dams in the leadframe. This provides significant manufacturing advantages.

TLPS paste can be used when bonding two or more electronic devices to each other or within a common leadframe. In the case of lead frames, electronic elements of different lengths can be connected,
Since solder balls do not occur, there is no need to provide a gap between the electronic elements to clean the solder balls. The resulting stack is therefore thinner than one assembled by conventional solder. TLPS excludes solder balls.

Thermocompression bonding with TLPS paste is used to densify the bond, thereby forming a more reliable bond than relying solely on temperature. Both mechanical and electrical properties are improved by thermocompression bonding.

TLPS can be used to form junctions directly to internal electrodes or external terminations. In MLCCs, internal electrodes can be refractory metals. A low melting point metal is coated on the edges and sheets of the MLCC or a high melting point metal layer such as the outer surface of the coupon. When the low melting point metal is heated, it can intermingle with the internal electrode and alloy, whereby the external metal forms a metallurgical bond directly to the internal electrode.

Low temperatures are particularly preferred for forming an initial bond between the transitional liquid phase sintering conductive adhesive and the electronic device. After formation of the initial bond, an isothermal aging treatment is performed to form a high temperature bond capable of withstanding high temperatures. The reflow temperature occurs during the process of connecting electronic components to a circuit using a secondary connection process and is the melting temperature of the element with the highest melting point and the melting of the alloy formed during the heating process to form the initial joint. lower than temperature. This is preferred over SAC type solders which require reflow at about 260°C.

Additionally, the transitional liquid phase sintering process can use a two-step reflow, in which the conductive metallurgical bond is formed in the first step from 5 seconds to 5 minutes, depending on the metals used in the TLPS alloying process. and a low temperature in the range of 180°C to 280°C. In a second step a portion thereof, for example but not limited to 5 to 6
Isothermal aging is performed using a temperature range of 200° C. to 300° C. for a relatively long time of 0 minutes. The short time required to form the initial bond is well suited for automated processing.
Alternatively, a single-step process can be performed, in which TLPS applies a temperature of, for example, 250° C. to 325° C. between the external leads and the electronic element, for example, 10 seconds to 3 seconds.
Hold for 0 seconds to form a terminal or conductive metallurgical bond. 175°C to 210°C
, can be used for longer periods of time, for example 10 to 30 minutes. This is particularly useful when the electronic components themselves are temperature sensitive.

Generally, the terminations are preferably heated by heating to a temperature in the range of, but not limited to, 190° C. to 220° C. for, but not limited to, 10 to 30 minutes using a one-step sintering process. It is formed by creating an electrically conductive metallurgical bond. second
is at least 80°C above the first melting temperature. Metallic bonding has a secondary melting temperature above 450° C., making this technology a viable option for low temperature process lead (Pb) free solutions suitable for use in subsequent high temperature applications. However, this type of process is more suited to the batch-type processes typical of semiconductor processing and some PCB processing, and is less useful for high volume vertical termination and external lead connections to electronic devices, including multilayer ceramic capacitors. Furthermore, treating TLPS in this manner may result in a high degree of porosity, particularly with high levels of organic content.

The desired interconnected joints can be achieved by processing the TLPS material using a two-step process. The first step is a relatively short process time of 30 seconds or less and 225
C. to 300.degree. C. to form a strong conductive bond. The second step is the sintering step, in which the part is exposed to temperatures of 200° C. to 250° C. or less for 5 minutes to 30 minutes to complete the alloying process. These two steps meet the requirements of high volume in-line assembly and enable subsequent batch sintering processes. but,
Similar to the single step process described above, this often results in unnecessarily high porosity.

A high degree of porosity is acceptable in many applications. However, under harsh environments such as high humidity circuit board mounting processes, water and other chemicals can penetrate the bond and cause the bond to fail. Accordingly, a preferred embodiment of the present invention uses a thermocompression bonding process to form low porosity terminations in transitional liquid phase sintered joints. The process is performed in a single step at temperatures ranging from 225° C. to 300° C. with short process times of 15 to 30 seconds, with the added advantage of ease of automation. At low temperatures of less than 30 seconds for one step and when the leads are used in combination with thermocompression bonding, it is possible to form strong joints for applications connecting external leads to electronic devices.

In addition, thermocompression bonding is also the preferred method of processing when polymer solders are used because polymer solders assist in forming a high-density metallurgical bond between contact surfaces. The advantage of thermocompression bonding is 2.
A higher strength connection can be achieved by forming a stronger bond for subsequent connection processes. a compressive force of 0.5 to 4.5 kilograms/cm ² (7.1 to 64 psi);
More preferably, a compressive force of 0.6 to 0.8 kilograms/cm ² (8.5 to 11 psi) is sufficient here as an illustration to illustrate thermocompression. About 0.63 kilograms/cm ² (9 psi) is a particularly suitable pressure for illustrative purposes.

TLPS materials include refractory materials selected from silver, copper, aluminum, gold, platinum, palladium, beryllium, rhodium, nickel, cobalt, iron, molybdenum, or mixtures thereof in any combination, which are suitable for the TLPS process. Suitable for use. Lead (Pb)
Free TLPS materials preferably use either silver or copper as the high melting point component and preferably indium, tin, or bismuth as the low melting point component.

Further TLPS materials include low melting point materials selected from tin, antimony, bismuth, cadmium, zinc, gallium, indium, tellurium, mercury, thallium, selenium, polonium or mixtures or alloys of any two or more thereof.

TLPS materials are compatible with finishes including silver, tin, gold, copper, platinum, palladium, nickel, or combinations thereof, and are used as finishes on either lead frames, component bonds, or internal electrodes2. An electrically conductive metallurgical bond is formed between the two surfaces. Suitable materials for external leads or leadframes include, but are not limited to, beryllium copper, Cu194 and Cu.
Phosphor bronzes such as 192, copper, copper alloys, and leadframes made of ferrous alloys such as, but not limited to, 42 alloy and Kovar.

Heating may be done by any method known in the art, but convective, radiant and inductive heating are most preferred.

The present invention will be described with reference to the drawings disclosing essential but non-limiting components. The same elements are numbered the same in the various drawings.

An embodiment of the present invention will now be described with reference to the schematic cross-sectional side view of FIG. In FIG. 1 the electronic device 1 includes external terminations 2 which are TLP's to the internal electrodes of the MLCC or functional elements of the electronic device.
They are integrally and electrically contacted through S-junctions, which will be more readily understood by the discussion below. A particular advantage of this embodiment is that at least one and preferably MLCCs, resistors, varistors, inductors, diodes, fuses, overvoltage discharge devices,
Bonding a stack of electronic elements, preferably selected from the group consisting of sensors, switches, electrostatic discharge suppressors, semiconductors, and integrated circuits, such that each end is in electrical contact with external terminations formed by TLPS bonding. and the ability to form leadless mounted electronic elements or stacks of leadless electronic elements that can be connected to contact pads 4 of an electronic circuit board 5 using a secondary connection material 3 such as a solder fillet. be. Such electronic devices with many terminations formed by TLPS bonding can be individually or stacked and connected to circuits in a leadless manner. However, the higher secondary melting temperature of TLPS joints allows a wider range of secondary connecting materials to be considered, thereby allowing TLP
S-joints are preferred over polymer solders. Element 1A is an additional electronic component as described above or in the case of a leadless stack, representing a sacrificial chip that absorbs warpage. The size of the sacrificial tip is preferably large enough to accommodate warping, but not larger than necessary. A sacrificial chip 35-60 thousandths of an inch thick is sufficient. A sacrificial chip is an element that physically replaces an electronic element, but does not provide any electronic function to the electronic component.

A leadless stack of electronic components is conveniently designated as an MLCC in the present invention and is shown in schematic cross-sectional side view in FIG. In FIG. 2, a leadless stack is formed by applying and reacting a suitable TLPS paste or preform 18 between the external terminations 7 of adjacent electronic devices. The preforms described herein are preferably malleable so that the preform conforms to adjacent surfaces. Heating causes the low melting point metal of the preform to diffuse into the outer termination thereby forming a metallurgical bond. The preform may contain a refractory metal, preferably of the same metal as the outer termination, and when heated the low melting point metal diffuses into the refractory metal of the preform, thereby reducing the refractory metal of the preform. and external terminations to ensure proper electrical conductivity between the external terminations of adjacent electronic devices. The external terminations are formed by co-firing a thick film of paste or by curing a conductive adhesive, and are thereby represented schematically as internal electrodes 9, 10 and a dielectric 11 separating the internal electrodes. forming electrical contact with the functional elements of the electronic device to which it is applied.

The external termination may consist of multiple layers to facilitate TLPS bonding. An embodiment of the invention is shown in the schematic cross-sectional view of FIG. In FIG. 3, the external termination consists of multiple layers, the first layer 7' being in direct contact with the functional elements of the electronic device represented schematically as internal electrodes 9, 10 of the MLCC. The first layer is in direct contact with the termination layer 7, which can conform to the preform 18 to form a TLPS bond there. A solder or plated layer 26 is provided to wrap the termination layer and preform to facilitate secondary connection to a circuit board, particularly to improve solderability. The solder or plated layer may include flexible non-metals, as described elsewhere herein.

In the inventive case described here, the TLPS joint functions as an electrical and mechanical bond. Electrical bonding in the prior art relies on the decomposition temperature of the polymer, usually an epoxy, to limit its performance as a conductive adhesive. It is generally not possible to use solder to join electronic devices in a leadless stack. This is because solder tends to compromise the electrical and/or mechanical integrity of the stack during secondary connection to the circuit board by reflow. The use of leads in the prior art, or overcoming mechanical failure due to substrate warpage by reducing CTE mismatch, is limited due to weakening of the interconnects used during thermal cycling. Combinations of lead materials and MLCC types have been developed to reduce these stress problems and provide reliable performance, but they have resulted in other limitations. For example, a 42 alloy was used to reduce stress, but unnecessarily increased the ESR of the resulting stack. Leadless stacks fabricated using TLPS to bond electronic components to fired and plated terminations are highly resistant to cracking due to substrate warpage, yet their performance is comparable to that of individual electronic components. The robustness of this ingenious joint against its mechanical performance is confirmed by its comparison with . Because TLPS can form a continuous, highly conductive metallurgical interconnect layer between electronic components, it can achieve a lower ESR than the leaded stack fabricated with 42 alloy leads. The same number and type of electronic components can be formed in a lower profile stack because leadless stacks do not require crimping associated with the stack.
The low profile stack coupled with the relatively low forming temperature of the TLPS junctions allows other components and additional circuitry to be added to the stack. If the leadless stack is to be used in a very mechanically demanding application, a mechanical absorbing component with no electrical function can be attached to the bottom of the stack.

The use of TLPS terminations to form conductive bonds to external leads is illustrated in FIG. are connected by TLPS8 between

In FIG. 5, the TLPS external termination 12 is connected to the internal electrodes 9, 10 of the multilayer ceramic capacitor.
direct contact with Alternating planar internal electrodes of alternating polarity are separated by dielectrics 11 and alternate internal electrodes directly contact opposing external terminations 12 formed by TLPS. This configuration has the added advantage of avoiding the processing costs associated with forming other connection materials on electronic components. Using the TLPS external termination, the embodiment of FIG.
LPS bonding can form external terminations that are stacked and coupled by similar embodiments, thereby providing a leadless stack of electronic components, preferably including at least one MLCC, as shown in FIG.

An embodiment of the invention is shown in schematic exploded cross-section in FIG. In FIG. 6, the electronic device is represented as an MLCC, schematically illustrated as a monolith, comprising alternating layers of internal electrodes 9, 10 separated by a dielectric 11, with adjacent internal electrodes terminating at opposite ends. , diagrammatically represent the functional elements of the electronic device. at least one electronic element is preferably an MLCC,
resistors, varistors, inductors, diodes, fuses, overvoltage discharge devices, sensors,
With at least one additional element selected from the group consisting of switches, electrostatic discharge suppressors, semiconductors, and integrated circuits. In one embodiment, the internal electrode or functional element is a TLPS bonded refractory metal. A preform 302 is applied to the edge of the monolith to form an external termination. The preform consists of a core having a layered structure in which a high melting point metal 303 forms an interface with a low melting point metal 304 . With the electronic component laminated and the preform connected to the electronic component, the low melting point metal 304 diffuses into the internal electrode and diffuses into the high melting point metal 303, thereby representing the preform and internal electrode. A metallurgical bond is formed with the functional element of the electronic device. A preform of refractory metal may form the leadframe. In another embodiment, a low melting point metal may be formed on the electronic element as an external termination.

During formation of a TLPS bond, the diffusion of the low melting point metal depends on its reactivity as well as the time and temperature of the bond formation process. While avoiding alloys to achieve a high degree of reactivity, it is desirable to select the individual metals and their thicknesses with reference to phase diagrams to eliminate the possibility of secondary phase formation.

FIG. 7 shows an embodiment with a single electronic component, schematically illustrated as an MLCC. TLPS terminations 14 join external leads 15 to functional elements of the electronic device, schematically illustrated as internal electrodes 9, 10 in FIG. This embodiment reduces failures occurring in this overlap region as mechanical stress is eliminated.

FIG. 8 shows a cross-sectional view of an electronic component, in this case an electronic element schematically illustrated as a multilayer ceramic capacitor 100 with TLPS terminations 102 contacting external leads 104 through conductive interconnects. Edge 106 does not have a continuous adherence line between the conductive connection and the external lead. A particular advantage is that the two surfaces of the external lead and conductive interconnect need not form a continuous bond line when bonded.

FIG. 9 represents one embodiment of the present invention. In FIG. 9, two electronic elements 200, 200', schematically illustrated as MLCCs, are positioned between leadframes 206, with the understanding that many electronic elements and combinations of electronic elements are stacked. shown in Each electronic element has a TLPS termination 202 that only partially covers the edge 108 of the electronic element. This allows for minimal or no spacing between the surfaces of the electronic elements. The TLPS termination 202 may be preformed as a composite or layered structure and inserted between parts, followed by a single heating step or multiple heating steps. Alternatively, external terminations can be formed in direct electrical contact with internal electrodes or functional elements of the electronic device.

Although diffusion-driven bonding processes have been used successfully between planes such as those found in die attach, there are applications where it is impractical to create such planes. In such cases, a high temperature solution is needed that allows bonding of non-uniform bonding surfaces that can fill gaps and voids between the bonding surfaces to be bonded. Metals commonly used in TLPS technology are selected from two metal families. The first family consists of metals with low melting points and the second family consists of metals with high melting points. When a metal of the low melting point metal family contacts a metal of the high melting point metal family and is exposed to heat, the low melting point metal diffuses into the high melting point metal and sinters to produce an alloy with a lower melting point than the high melting point metal. This process is called transitional liquid phase sintering (TLPS), and the formation of a solid solution of TLPS allows interconnects to be made at secondary reflow temperatures that are relatively low, but higher than the melting point of the refractory metal. can.

FIG. 10 shows an embodiment of the present invention and presents a schematic side view of stacked electronic elements in which the two electronic elements 20, 21 have different widths. Termination 22 of TLPS is external lead 2
Different length electronic elements can be accommodated in proper contact with 3 . In this way, parts of different lengths up to 0.10 inch can be connected in the same stack. However, the difference in length preferably does not exceed 0.010 inches. It is often desired to join multiple uneven surfaces having surface metals applied with mixed technologies such as plated silver, sintered silver, or other TLPS compatible metals. there is One surface to be joined is electroplated with silver or the like as described in FIG. 10 and the bonding surface is covered with a thick film silver paste and then sintered. A single component low melting point metal such as indium paste is then placed between the two surfaces to be bonded, each having a silver coating or other compatible TLPS high melting point metal. The paste functions to fill gaps between uneven surfaces of electronic elements of different sizes. The assembly is then heated to the melting point of indium, 157° C., or to the melting point of another suitable low melting point metal other than indium, held at the liquidus temperature for 5 seconds to 15 minutes, cooled, and then solidified. be. The resulting joining interconnect material has a secondary reflow temperature above the melting point of the low melting point material. An optional insulating layer 70 placed between adjacent elements in the stack provides protection against arcing between external leads. Insulating layers are more preferred for high voltage applications above 200 volts and above 250 volts. Insulating layers are realized by a variety of polymer conformal coatings based on various chemical families including acrylics, polyurethanes, polyimides, epoxies, parylenes (para-xylenes), and silicones. The TLPS termination may contain inert fillers 112 .

TLPS pastes or preforms can be modified by including inert fillers therein.
useful for one purpose. The first purpose is to reduce costs due to the use of expensive metals, and the second purpose is to make direct electrical and metallurgical connections to the non-terminated portions and exposed internal electrodes of electronic devices. be. Replacing portions of the refractory metal components with inert materials or low cost conductive materials in particular can reduce costs when gaps are filled as described with respect to FIG. Particularly preferred fillers for use in place of refractory metals are non-metals such as ceramics and glasses with melting points above 300°C or refractory polymers with glass transition temperatures (T _g )>200°C. One example is a thermosetting polymer such as polyimide.
The first of two particular advantages of replacing a refractory metal with one of these non-metals is that T
The active low melting point metal of the LPS is not depleted by diffusion during formation of the TLPS junction. A second advantage of inert fillers is that when selected from a family of glasses with low melting points, the glass inside the TLPS paste or preform mix is bonded to the exposed glass frit of the MLCC ceramic body, where the glass is non-terminated and exposed. is to form It is also possible to coat these non-metals with low-melting-point metals by methods such as spraying and plating.

FIG. 11 shows a schematic side view of a stack of two electronic components 30,31, which are connected to external leads 32,33 using conventional solder 34. FIG. In this case, at least 0.254 mm (0.01 mm) between components for post assembly cleaning to remove solder balls.
0″) gap G is required.

FIG. 12 shows an embodiment of the invention in schematic side cross-sectional view, in which electronic components 31 and 32 are connected to external leads 32 and 33 using TLPS 35 . In this case a gap of less than 0.254 mm between the parts, since no solder balls are formed and therefore no cleaning is required;
Alternatively, no gap is preferred. Eliminating the gap reduces the overall stack height and reduces the vertical space required for the electronic components. Moreover, the space savings are even greater for stacks of two or more pieces.

It is highly desirable to form bonds of minimal porosity, such bonds exhibiting the following properties: Form intimate contact or pull between uneven surfaces with gaps within 0.015 inches. 5 Lbs. for peel test. /inch, tensile strength, high shear conductivity, low initial process temperature ranging from 150°C to 225°C, secondary reflow temperature above 300°C.

28-31 show schematic cross-sectional views of representative MLCC structures suitable for use with microphonic noise reduction structures used in stacks, particularly leadless stacks, as shown, MLCCs are herein referred to as It further comprises a microphonic noise reducing structure 19, such as a non-metallic compliant layer or shock absorbing conductor, as described elsewhere in . In FIG. 28 internal electrodes 9 and 10 of opposite polarity terminate in opposite external terminations 2 . Coplanar conductors 401, 402 are provided which terminate in opposite outer terminations. As shown, top conductor 401 provides shielding with capacitive overlap for adjacent internal electrodes of opposite polarity, while bottom conductor 401' is of the same polarity as the adjacent electrode and is normally terminated, thus Bottom conductor 401' does not function as a shield electrode. The top conductor 402 is of the same polarity as the adjacent electrode and is normally terminated so that the top conductor 402 does not function as a shield electrode, whereas the bottom shield electrode 402' is capacitive with the adjacent inner electrode of opposite polarity. Provide overlap. For the purposes of the present invention, the shield electrode is defined as the outermost conductor that provides capacitive coupling as represented by conductors 401, 402' shown in FIG.

FIG. 29 shows in cross-sectional schematic view an embodiment of an MLCC used in stacks, particularly leadless stacks, as described herein, wherein the capacitive structure of FIG. It has an additional conductor, a floating conductor 404 parallel to but outside the main conductive layer represented by the assembly of planar electrodes 401,402. For the purposes of the present invention, a floating electrode with all internal conductors inside the floating electrode is referred to as an external floating electrode. For purposes of the present invention, a floating electrode is a conductor that is not terminated.

FIG. 30 shows in cross-sectional schematic view an example of an MLCC used in a stack, particularly a leadless stack, as described herein. In FIG. 30, coplanar internal electrodes 40
8, 410 terminate in opposite outer terminations 2 so that the coplanar inner electrodes have opposite polarities. An internal floating electrode 412 between adjacent layers of coplanar internal electrodes provides a capacitive overlap region 414 . For the purposes of the present invention, floating electrodes with at least one internal conductor outside the floating electrode are referred to as internal floating electrodes. As shown, FIG. 30 has two capacitive overlap regions. As will be appreciated by those skilled in the art, the floating electrode forms an opposing electrode to the terminal contacting electrode to achieve two capacitive overlap regions in series.

FIG. 31 shows in cross-sectional schematic view an example of an MLCC used in a stack, particularly a leadless stack, as described herein. In FIG. 31, the active plane consists of coplanar floating electrodes 416 which are coplanar with the terminated internal electrodes 9,10. Internal electrode is external termination 2
, but coplanar floating electrodes are not themselves terminated. Coplanar internal floating electrodes 412 between adjacent active planes provide a plurality of capacitive overlap regions 414 .

FIG. 32 shows in schematic side view a portion of an electronic device 701 of the present invention. In FIG. 32,
Non-metallic compliant layer 50 in which the microphonic noise reduction structure is laminated to the conductive metal layer 504
2. The outer terminations 2 of the electronic element 1, at least one of which is preferably an MLCC, are electrically contacted to the conductive metal layer 504 by TLPS interconnects 506 extending through gaps forming via holes 508 in the non-metallic compliant layer 502. . Optionally, additional electronic components may be stacked on top of the lowest electronic components and connected by TLPS interconnects 118, such as preforms, as described elsewhere herein. The conductive metal layer is electrically and mechanically connected to the contact pads 4 of the electronic circuit board 5 by a secondary connecting material 3 such as a solder fillet. that the mechanical energy that causes microphonic noise is reduced by the non-metallic compliant layer and by reducing the size of the solder fillet as the non-metallic compliant layer is not wetted by the solder thereby reducing the transmission of vibrational energy; It can be estimated without being bound by theory. Non-metallic compliant layers can be very thin at lower limits defined by layering manufacturability, but become too thin and difficult to handle in a large scale manufacturing environment. The thinnest non-metallic compliant layer is 25.4 μm
(0.0001 inch) thickness, more preferably at least 0.0254 mm (0.00
1 inch) to a thickness not exceeding 0.062 inch, preferably 0.3
A thickness not exceeding 81 mm (0.015 inch) is suitable for practicing the invention.

FIG. 33 shows in schematic top view one embodiment of the present invention. In FIG. 33, an electronic element 1 or stack of electronic elements is connected by one or more microphonic noise reduction structures, preferably to the corners of the external termination 2, thereby providing multiple electrical and mechanical connections to the contact pads 4 on the circuit board 5. A physical connection is realized by a secondary connection material 3 such as a solder fillet. The overall solder fillet connection area can be further reduced by using more than one microphonic noise reduction structure per terminal, and the microphonic noise reduction structures can be positioned to minimize microphonic noise.

A schematic top view of FIG. 34, a schematic side view of FIG. 35, and a schematic bottom view of FIG. 36 illustrate one embodiment of a microphonic noise reduction structure formed from common circuit board materials. Figures 34-36
, the microphonic noise reduction structures are manufactured from standard circuit board materials such as FR4, perfluoroelastomer, polyimide, Kapton, PEEK, yttria stabilized zirconia or electronic _grade ceramics such as _Al2O3 (aluminum oxide). circuit board 340. Conductor traces 342 are electrically connected to solder pads 344 to which electronic devices are electrically connected as described in connection with FIGS. Solder mask 346, as a non-metallic compliant layer over solder pads 344, contains gaps between the solder pads and can be used to electrically and mechanically connect external terminations of electronic devices to the solder pads. Limited surface area. Via hole 3 penetrating the circuit board
48 allow electrical conductivity to conductive solder pads 350 on the opposite side of the circuit board to the electronic device. A vibration-absorbing elastomer 352 inhibits the transmission of vibrations, thereby isolating microphonic noise into the microphonic noise-reducing structure. Optional mechanical solder pads 354 may be provided to ensure proper adhesion in connecting the microphonic noise reduction structure to the subsequent substrate of the electronic device. The mechanical mounting pads can be positioned so that they are not directly beneath the electrical contact pads that connect the electronic elements of the microphonic noise reduction structure. Conductor traces and solder pads are separated by a sufficient distance to avoid arcing between them.

FIG. 37 shows, in schematic side view, one embodiment of the present invention, having at least one electronic noise reduction structure, preferably implemented by TLPS thereon, as shown in FIGS. 34-36 and described in connection therewith. Device 1, preferably comprising a stack of electronic devices, with external terminations adhered to solder pads 344 with a solder mask in between. Solder pads 350 are in electrical contact with contact pads 4 on electronic circuit board 5 . Optional mechanical solder pads 354 are mechanically connected to dummy traces 355, which may not be conductive or electrically connected.

An embodiment of the present invention will now be described with reference to FIGS. 38-40, in which a microphonic noise reduction structure is shown in the form of a blocking pad with two electronic elements 1 mounted thereon for illustrative purposes. ing. At least one of the electronic elements is preferably an MLCC. The number of electronic elements is not particularly limited and may be a row of individual electronic elements or a stack of electronic elements. FIG. 38 is a schematic top view of a microphonic noise isolation pad 600, FIG.
is a schematic bottom view, and FIG. 40 is a schematic side view. 38-40, a strip circuit board 340 is connected to a conductive metal layer by TLPS interconnects extending through via holes in the non-metallic compliant layer 502. In FIGS. As noted above, the solder pads 350 on the opposite side of the electronic device from the microphonic noise isolation pads are electrically contacted to the solder pads by electrical traces and via holes. A solder mask or non-metallic compliant layer is between the external termination of the electronic device and the conductive metal layer, thereby suppressing microphonic noise. Preferably, the microphonic noise blocking pads are used in pairs with different polarities.

One embodiment of the invention is described with reference to FIG. 41, and as described elsewhere herein,
A microphonic noise reduction structure is implemented in the form of a shock absorbing conductor 702 between the electronic element 1 and the external termination 2 in electrical contact. The shock-absorbing conductor has a shape consisting of offset mounting tabs with spaces in between that connect to at least one flexible stress relief portion 706 so that vibrations can be absorbed. The shock absorbing structure may have an open shape such as a "C", "S" or "Z", or a closed shape such as a circle or square. The non-metallic compliant layer 704 can be included as a preform or filler within the interstitial region of the shock absorbing conductor to further dampen mechanical vibrations thereby further reducing microphonic noise. The shock absorbing structure may be made of any ferrous or non-ferrous conductive material suitable for the practice of the present invention, 42 alloy, kovar, invar, phosphor bronze, or alloys with copper. The lower limit of the thickness of the impact absorbing structure is determined by conductivity and manufacturability. In one embodiment, the preform is coated with a conductor onto it to allow a thickness approaching the number of atomic layers required for electrical conductivity. at least 25.4 μm (
0.0001 inch), preferably 0.0254 mm (0.001 inch) to 0
. Thickness not exceeding 127 mm (0.005 inch) and more preferably 0.0635
A thickness not exceeding 0.0025 inch (mm) is suitable for practicing the invention. the height or offset height of the shock absorbing structure measured perpendicular to the circuit board is preferably at least 0.001 inch and not more than 0.005 inch; More preferably it does not exceed 0.0025 inches.

Substrates or circuit boards are suitable for practicing the invention, such as FR4, Polyimide, Kapton, PE
Any standard PCB material including electronic grade ceramics _{such as EK, yttria stabilized zirconia or Al2O3 (} aluminum oxide) or yttria stabilized zirconia is not particularly limited. Considering different design forms use ferrous alloys such as 42 alloy, Invar or Kovar, or non-ferrous materials such as copper, phosphor bronze, beryllium copper.
Particularly preferred non-metallic compliant layers are FR4, perfluoroelastomer, polyimide, Kapton,
Selected from electronic grade ceramics such as PEEK, yttria stabilized zirconia or Al ₂ O ₃ (aluminum oxide).

The slump test is based on visual observation, preferably by magnification, to inspect the part after processing to see if the MLCC has moved or flowed within the leadframe.
Slumping indicates that the reflow process compromises the integrity of the bond to the leadframe. Failure is indicated by visual movement of the MLCC within the leadframe, ie, loss of joint integrity.

(Example 1: Mechanical robustness of polymer solder)
The case size mounted on a common lead frame is 5.6 mm × 5.1 mm (0.22
68 identical stacks were fabricated, each with two MLCCs of 0.20 inch). The stacks were divided into equal sets of 34 each. In set 1, 91.5w
A lead frame was attached to each MLCC using 1 mg of Sn/Sb solder containing t% Sn and 8.5 wt% Sb. In set 2, 1 mg of Sn obtained by Henkel 10048-11A polymer solder containing 91.5 wt% Sn and 8.5 wt% Sb
A lead frame was attached to each MLCC using /Sb polymer solder. 26 each part
It was passed through a solder reflow oven at 0° C. three times, and the number of chips that flowed in each pass was measured.
Table 1 shows the results. A cumulative number of defective parts is recorded for each pass.

The results in Table 1 show that set 1 failed 4 parts in the first pass and 1 additional part failed in subsequent passes, whereas set 2 failed none. I didn't. The polymer solder therefore has added mechanical strength at elevated temperatures compared to the solder of the control sample.

(Example 2: Improved mechanical robustness of TLPS)
Similar stacks were fabricated with silver or tin plated leadframes and Ormet3
28 using a Cu-based transitional liquid phase sintering adhesive. The sample showed no slumping (flowing) or detachment of external leads. Later US Patent Nos. 6 and 7
04,189, and the stack was placed in the furnace with a 30 g weight hanging over the MLCC and hanging below the stack. The temperature was increased to about 260°C with a dwell time of 10 minutes at each temperature of at least 10°C. The parts were then inspected for defects in flow and/or external lead disconnection. Tin plated outer lead frame failure 360°C
However, the first failure was detected at 630° C. for the silver plated leadframe, demonstrating ultra-high temperature mechanical performance for TLPS.

(Example 3: Temperature performance of polymer solder)
A stack of 120 J-leads was fabricated using the same MLCC, the same J-leads, and the thermocompression process. The samples were divided into 30 groups, each with Henk
Bonded using various volumes of 91.5/8.5 Sn/Sb solder available as el92ADA1OODAP85V EU 2460 and Henke for set 3
A polymer solder available as 120048-11A was used with the same solder composition for set 4. The samples were then sent to various soldering ovens and passed through the ovens three more times at different temperatures. The samples were then inspected part by part. The results are shown in FIG. No slumping was detected in the polymer solder and the samples showed improved high temperature robustness in the range tested. Polymer solders are not resistant to temperatures above 350°C.

Example 4 Polymer Solder Durability to High Speed Secondary Assembly Processes
A J-lead stack was fabricated using identical MLCCs, identical J-leads, and a thermocompression process. Control sample is Henkel92ADA100DAP85V EU 246
0 was made using 91.5/8.5 Sn/Sb solder. set 5
was made using a polymer solder containing the same solder composition available as Henkel 20048-11A. The samples were then attached to FR4 boards using standard solder and placed in an IR reflow oven using a faster temperature ramp rate than that recommended for leadframe soldering. Inspected for slumping or poor lead frame contact. The samples containing the Sn/Sb solder had 9 out of 15 failures, while the polymer solder had 0 out of 15 failures, demonstrating increased robustness for high speed assembly. The parts were subjected to the same high speed assembly.

(Example 5: thermocompression bonding)
Figures 14 and 15 are TLPS Ag/Sn/B available as the Ormet 701 series.
2 is a photomicrograph demonstrating bonding using Cu/Sn/Bi, available as the Ormet 280CE series, using an IR reflow process to bond between coupons of silver-plated phosphor bronze using an IR reflow process. Significant areas of voids are shown. FIG. 16 is a micrograph showing the state of TLPS Cu/Sn/Bi after the thermocompression bonding process, and FIG. 17 is a micrograph showing the state of Cu/Sn/Bi after the thermocompression bonding process. A fine microstructure is observed in both examples. A thermocompression bond is accomplished in a very short time of less than 5 minutes at 2-10 pounds of pressure.

Coupons were made in a manner similar to Example 4. A 30 gram weight was suspended from the device to stress the thermocompression bond. The joint was subjected to an elevated temperature. 850
No defects were observed despite heating to °C.

Cu/Sn/Bi TLPS available as Ormet 701 and 10/88/2 S
Observations of lead bonding using n/Pb/Ag solder show that the TLPS stays where it is placed while the solder flows upon heating. Solder requires the use of a solder dam and resist when used to attach external leads, while TLPS does not. This is a great manufacturing advantage.

Ormet 701 Cu/Sn/Bi TLPS is used to bond coupons of matte plated tin phosphor bronze under various conditions with and without post cure using thermocompression bonding. The results are compared with 91.5Sn/8.5Sb solder. In FIG. 18, sample A1 was heated at 180° C. for 20 seconds without post-sintering, and sample B1 was heated at 180° C. for 1
It was heated for 5 seconds and post-sintered at 210° C. for 20 minutes. Sample C1 was heated at 180° C. for 20 seconds and post-sintered at 210° C. for 30 minutes. Sample D1 was heated at 190° C. for 20 seconds and was not post-sintered. Sample E1 was heated at 190°C for 20 seconds and heated at 210°C for 15 seconds.
A minute post sintering was performed. Sample F1 was heated at 190° C. for 20 seconds and post-sintered at 210° C. for 30 minutes. Sample G1 was heated at 200° C. for 20 seconds and was not post-sintered. Sample H1 was heated at 200° C. for 20 seconds and post-sintered at 210° C. for 15 minutes. Sample I1 was heated at 200° C. for 20 seconds and post-sintered at 210° C. for 30 minutes. Sample J
1 was heated at 200° C. for 10 seconds and was not post-sintered. Sample K1 was heated at 230° C. for 10 seconds and was not post-sintered. Sample L1 was heated at 210° C. 91 .
A 5Sn/8.5Sb solder was used to reproduce the 30 minute post-sintering. These examples demonstrate that the initial bond can be formed at relatively low temperatures and that the bond strength can be significantly increased with post-sintering.

(Example 6)
A set of experiments similar to Example 5 were performed using Ormet 280CE Ag/Sn/Bi on silver plated coupons. The results are shown in the bar graph of FIG. In this example, the outer leads, as measured by the maximum pull to failure (in Kg), exhibit shear strength exceeding that of the solder even though no post cure was used in the thermocompression bonding process.
The samples were in each case preheated at a first temperature for a first period of time, then ramped to a second temperature over 3 seconds and held at the second temperature for a period of time. In FIG. 19, sample A2 was preheated at 140° C. for 10 seconds and the temperature was increased to 300° C. and held for 20 seconds. Sample B2 was preheated to 140°C for 10 seconds and the temperature was increased to 300°C and held for 10 seconds. Sample C2 was preheated to 140°C for 10 seconds and the temperature was increased to 300°C and held for 5 seconds. Sample D2 was preheated to 140°C for 3 seconds and the temperature was increased to 300°C and held for 20 seconds. Sample E2 was preheated to 140°C for 3 seconds and the temperature was increased to 300°C and held for 10 seconds. Sample F2 was preheated to 140°C for 3 seconds and the temperature was increased to 300°C and held for 5 seconds. Sample G2 was preheated at 140°C for 10 seconds and the temperature was 280°C.
and held for 20 seconds. Sample H2 was preheated to 140°C for 10 seconds and the temperature was increased to 280°C and held for 10 seconds. Sample I2 was preheated to 140°C for 10 seconds and the temperature was increased to 280°C and held for 5 seconds. Sample J2 was preheated to 140°C for 3 seconds and the temperature was increased to 280°C and held for 20 seconds. Sample K2 was preheated to 140°C for 3 seconds and the temperature was increased to 280°C and held for 10 seconds. Sample L2 is 140°C
for 3 seconds and the temperature was raised to 280° C. and held for 5 seconds. Sample M2 is 14
It was preheated at 0°C for 10 seconds and the temperature was increased to 260°C and held for 20 seconds. Sample N
2 was preheated to 140° C. for 10 seconds and the temperature was increased to 260° C. and held for 10 seconds. Sample O2 was preheated to 140°C for 10 seconds and the temperature was increased to 260°C and held for 5 seconds. Sample P2 was preheated to 140°C for 3 seconds and the temperature was increased to 260°C and held for 20 seconds. Sample Q2 was preheated at 140°C for 3 seconds and the temperature was increased to 260°C for 10 seconds.
held for seconds. Sample R2 was preheated to 140°C for 3 seconds and the temperature was increased to 260°C and held for 5 seconds. Sample S2 was preheated to 140°C for 10 seconds and the temperature was increased to 240°C and held for 20 seconds. Sample T2 was preheated at 140°C for 10 seconds and the temperature was 24°C.
Raised to 0° C. and held for 10 seconds. Sample U2 was preheated to 140°C for 10 seconds and the temperature was increased to 240°C and held for 5 seconds. Sample V2 was preheated to 140°C for 3 seconds and the temperature was increased to 240°C and held for 20 seconds. Sample W2 was preheated to 140°C for 3 seconds and the temperature was increased to 240°C and held for 10 seconds. Sample X2 is 3 at 140°C
seconds and the temperature was raised to 240° C. and held for 5 seconds. Sample Y2 is 140°C
for 10 seconds and the temperature was raised to 220° C. and held for 20 seconds. Sample Z2 was preheated to 140°C for 10 seconds and the temperature was increased to 220°C and held for 10 seconds. Sample AA2 was preheated to 140°C for 10 seconds and the temperature was increased to 220°C and held for 5 seconds. Sample BB2 was preheated to 140°C for 3 seconds and the temperature was increased to 220°C and held for 20 seconds. Sample CC2 was preheated at 140°C for 3 seconds and the temperature was increased to 220°C for 1
It was held for 0 seconds. Sample DD2 was preheated to 140°C for 3 seconds and the temperature was increased to 220°C and held for 5 seconds. The results of Example 6 demonstrate the time-temperature effect for the TLPS process without post-sintering.

(Example 7: TLPS termination)
TLPS Cu/Sn/Bi, available as Ormet 701, was cured to the MLCC of the nickel-based metal electrode to terminate directly to the nickel inner electrode. Average capacity is 0.3
At 2 μF it was shown that a bond with a continuous conductive path was formed to the internal electrode, similar to the standard high burnout termination material.

(Example 8: temperature resistance test)
To test the bond strength of the adhesive, a load test was performed according to US Pat. The suspended parts and weights were subjected to elevated temperatures until the external lead wires detached and the failure was detected. The results are shown in FIG. 20, where the polymer solder exhibited significantly better bond strength than the 88Pb/10Sn/2Ag solder as a function of temperature. Figure 20
, set 6 was joined using 88Pb/10Sn/2Ag solder. set 7
nickel/tin leads were bonded with a conductive adhesive. Set 8 was bonded to nickel/gold leads using a conductive adhesive. Set 9 was bonded to the nickel/silver leads using a 95Sn/5Ag solder dot in the center with conductive adhesive on the nail head.

A similar sample is MIL-STD-202G, Method 211, Test Con
Subjected to a shear strength test performed according to dition A, Pr edure 3.1.3, a load was applied in the axial direction of the capacitor terminals and force was applied until the device failed. The results are shown in FIG. In FIG. 21, set 10 used dots of Sn95/Ag5 polymer solder that were reflowed and then joined to silver plated nail heads with conductive adhesive and subjected to a post-reflow cure. Set 11 is Sn
Using 95/Ag5 solder, set 12 was bonded to the silver-plated lead wires using a conductive adhesive. Conductive epoxies exhibited poor shear holding strength of less than 3 lbs, demonstrating inadequate handling strength for processing.

The original sample was a 30°C sample suspended from external lead wires at temperatures in excess of 400°C.
It can withstand gram weights. The conductive adhesive alone withstood temperatures in excess of 400° C. but exhibited poor shear holding power at room temperature as shown in FIG. This is unacceptable for the processing and handling of the parts after bonding, which is commonly done during the bonding of subcomponents and electronic devices.
Shear testing showed acceptable shear strength in excess of 3 lbs at room temperature.

(Example 9)
A case size 2220, 0.47 μF rated, 50 V MLCC with C0G dielectric ceramic based on calcium zirconate and nickel internal electrodes was fabricated by processes well known in the prior art. These MLCCs were terminated using a copper thick film paste containing a glass frit. Samples were made by two different types of electroplating. Nickel plating was applied to the fired copper terminations, followed by copper plating on one case and silver plating on the other. All plated layers were made a minimum of 5 microns (200 μinch) thick. Or
A leadless stack was fabricated using a met CS510. The stack was fabricated with a thin bead of TLPS paste applied along the top surface of the plated terminations to be bonded. Thus, a four-chip stack was assembled with the Ormet CS510 along the ends of adjacent capacitors. These stacks were clamped into one assembly and heated to a peak temperature of 330°C using a Heller reflow furnace under a nitrogen atmosphere and 90 degrees above 300°C.
held for seconds. The substrate bending performance of these leadless stack samples is AEC-Q20
A single M
Compared to LCC. Bending was applied at a speed of 1 mm/sec with a capacitance loss of 2% recorded as failure. The samples were connected to a test circuit board using reflowed tin-lead (SnPb) solder. These results are shown in Figures 22 and 23 as Weibull graphs for copper and silver plated parts, respectively. Although the stack performance is slightly inferior to the single MLCC, the bend failure for leadless stacks made with both types of plating is well above the 3 mm minimum required by the AEC for the C0G type MLCC.

(Example 10)
A case size 2220, 0.50 μF rated, 500 V MLCC with X7R dielectric ceramic based barium titanate and nickel internal electrodes was fabricated by processes well known in the prior art. These MLCCs were terminated using a copper thick film paste containing a glass frit. The samples were then electrolytically nickel (minimum 50 µin) and tin (minimum 100 µin).
inches). A leadless stack of two MLCCs is O
It was manufactured by applying a thin bead of TLPS paste along the top surface of the plated termination which was bonded using rmet CS510. These stacks were clamped into one assembly and heated to a peak temperature of 330°C using a Heller reflow furnace under a nitrogen atmosphere for 30 minutes.
0° C. or higher was held for 90 seconds. The substrate bending performance of these leadless stacks is AEC-Q
It was compared to a single MLCC by bending to 10 mm using the test method described in 200-005 Rev A. Bending was applied at a speed of 1 mm/sec with a capacitance loss of 2% recorded as failure. The samples were connected to a test circuit board using reflowed tin-silver-copper (SAC) solder. These results are shown in FIG. 26 as a Weibull graph. The leadless stack performance is similar to a single MLCC, and both well exceed the 2 mm minimum required by the AEC for X7R-type MLCCs. FIG. 27 shows the bending of a single chip under certain bending conditions versus the bending of a two-chip leadless stack under certain bending conditions, and the magnitude of the bending distribution well over 6 mm.
A further comparison between leaded stacks can be seen in Example 11, which shows the high temperature performance of a control group of leaded stacks interconnected with SnSb solder and TLPS (CS510
) to the high temperature performance of a leaded stack interconnected using

(Example 11)
Table 2 shows the high temperature performance of the TLPS material CS510 for a control group made with standard Cu/Ni/Sn terminations, tin lead finish, and caps with capacitor stacks and leadframes terminated with standard SnSb solder. along with the high temperature performance of The test group used a variety of capacitor terminations, including metallization and various leadframe surface finishes, as well as non-terminated capacitors and interconnects using CS510TLPS to make electrical and mechanical connections between the internal electrodes and the leadframe. The results are shown. It can be seen from Table 2 that the control group failed in the temperature range of 230 to 235°C when heated and hung with a 30 gram weight. Samples made using the Ormet CS510 included unterminated capacitors and did not fail when reaching the 600° C. test limit regardless of the type of metallization on the capacitor terminations. The only exception was the test group with tin on both the termination and the leadframe surface which showed failures in the 420-450°C range.

(Example 12)
FIG. 25 presents a comparison of embodiments of the present invention, comparing two plated coupons shown in FIG. In FIG. 24, two copper coupons, one nickel-plated and then silver-plated, and the second copper coupon are nickel-plated and then silver-plated and then indium-plated. The two coupons are then placed face to face and heated to initiate diffusion of the indium. After processing, the two coupons were shear tested and pulled until a bond failure occurred. The results demonstrate that an intimate contact surface between the joints is essential to ensure maximum bond strength and uniform diffusion. FIG. 24 arrows indicate isolated contact points within the bonding area where diffusion occurred. The surface area of the bond is 3.81 x 3.81 mm (0.1
50" x 0.150" square or 14.52 mm ² (0.0225 in ² ) and a bond shear strength of 266 psi. However, the contact surface area is estimated at 20%. This clearly demonstrates the need for intimate contact between the mating surfaces to maximize bond strength.

25 is the coupon shown in FIG. 24 plated with 2.5 microns (100 microinches) of nickel and 5 microns (200 microinches) of silver and bonded to a second coupon using indium paste. indicates the same type of coupon as . 100% surface coverage
was uniformly coated with a shear strength of 9000 psi. The difference between bonding two non-planar surfaces and using indium paste to bond two non-planar surfaces is demonstrated because the assembly, processing and shearing methods are exactly the same.

Although the invention has been described with reference to preferred embodiments, it is not so limited. Those skilled in the art may recognize additional embodiments and modifications not specifically mentioned herein, but which fall within the scope of the claims appended hereto and forming an integral part of this application.

Claims (5)

a first conductive metal layer and a second conductive metal layer;
a first non-metallic compliant layer comprising a gap formed on the first conductive metal layer;
an electronic element comprising a first external termination having a first polarity and a second external termination having a second polarity;
a transitional liquid phase sintering adhesive in electrical contact with the first outer termination and the first conductive metal layer;
including
The electronic component, wherein the transitional liquid phase sintering adhesive extends through the gap. The electronic component of Claim 1, wherein said first non-metallic compliant layer is selected from the group consisting of FR4, perfluoroelastomer, polyimide, Kapton® , PEEK, and electronic grade ceramics. 3. The electronic component according to claim 1, wherein said first non-metallic flexible layer includes a via hole having said gap. 4. The electronic component of claim 1, 2 or 3, wherein the first non-metallic compliant layer comprises strips and the gaps exist between the strips. The electronic component according to any one of the preceding claims, wherein said first non-metallic compliant layer has a thickness of at least 25 µm to no more than 1.575 mm.