A package base includes a package base body and a bonding metal layer provided in a frame shape or a ring shape in plan view on the package base body, wherein the bonding metal layer contains a Ti—Ag—Cu-containing alloy and a metal belonging to Group 6 in the periodic table.

A soldering alloy includes an alloy composition consisting of 13-22 mass % of In, 0.5-2.8 mass % of Ag, 0.5-5.0 mass % of Bi, 0.002-0.05 mass % of Ni, and a balance Sn. A soldering alloy, a soldering paste, a preform solder, a soldering ball, a wire solder, a resin flux cored solder and a solder joint, each of which is composed of the soldering alloy. An electronic circuit board and a multi-layer electronic circuit board joined by using the solder joint.

A stretchable mounting board that includes a mounting electrode section electrically connected to stretchable wiring, and solder electrically connected to the mounting electrode section. The mounting electrode section has a first electrode layer on a side thereof facing the stretchable wiring and which includes bismuth and tin, and a second electrode layer on a side thereof facing the solder and which includes bismuth and tin. A concentration of the bismuth in the first electrode layer is lower than a concentration of the bismuth in the second electrode layer, and the concentration of the bismuth in the second electrode layer is constant along a thickness direction thereof.

A batch soldering method includes providing a first passive device, arranging the first passive device on a first metal region of a substrate with a region of first solder material between the first passive device and the substrate, providing a semiconductor die, arranging the semiconductor die on a second metal region of the substrate with a region of second solder material between the semiconductor die and the substrate, and performing a common soldering step that simultaneously forms a first soldered joint from the region of first solder material and forms a second soldered joint from the region of second solder material. The common soldering step is performed at a soldering temperature such that one or more intermetallic phases form within the second soldered joint, each of the one or more intermetallic phases having a melting point above the second solder material and the soldering temperature.

Implementations of the disclosure are directed to a lead-free mixed solder powder paste suitable for low temperature to middle temperature soldering applications. The lead-free solder paste may consist of: an amount of a first solder alloy powder between 44 wt % and 83 wt %, the first solder alloy powder comprising Sn; an amount of a second solder alloy powder between 5 wt % to 44 wt %, the second alloy powder comprising Sn, where the first solder alloy powder has a liquidus temperature lower than a solidus temperature of the second solder alloy powder; and a remainder of flux. The solder paste may be used for reflow at a peak temperature below the solidus temperature of the higher solidus temperature solder powder but above the melting temperature of the lower solidus temperature one.

An electronic component module includes a substrate including a first main surface and a second main surface, and using a side near the second main surface as a mounting side, an external terminal by a solder ball made of first solder, on the second main surface, and a first electronic component mounted by using second solder, on the first main surface, and a melting point of the first solder is higher than a melting point of the second solder.

Systems and methods describe herein provide a solution to the technical problem of creating a wearable electronic devices. In particular, these systems and methods enable electrical and mechanical attachment of stretchable or flexible electronics to fabric. A stretchable or flexible electronic platform is bonded to fabric using a double-sided fabric adhesive, and conductive adhesive is used to join pads on the electronic platform to corresponding electrical leads on the fabric. An additional waterproofing material may be used over and beneath the electronic platform to provide a water-resistant or waterproof device This stretchable or flexible electronic platform integration process allows the platform to bend and move with the fabric while protecting the conductive connections. By using flexible and stretchable conductive leads and adhesives, the platform is more flexible and stretchable than traditional rigid electronics enclosures.

A solder joint which is used in power devices and the like and which can withstand a high current density without developing electromigration is formed of a Sn—Ag—Bi—In based alloy. The solder joint is formed of a solder alloy consisting essentially of 2-4 mass % of Ag, 2-4 mass % of Bi, 2-5 mass % of In, and a remainder of Sn. The solder alloy may further contain at least one of Ni, Co, and Fe.

A joint structure, in which an electronic component and a wiring substrate are joined to each other, includes: a base material of the electronic component; a base material of the wiring substrate; and a joint portion that includes at least an electrode of the electronic component and an electrode of the wiring substrate, and that joins the base material of the electronic component and the base material of the wiring substrate. The joint portion includes a material having an absorption coefficient of 2×10{circumflex over ( )}5 cm.sup.−1 or more for light of a wavelength of 250 to 1000 nm. The base material of at least one component of the electronic component and the wiring substrate consists of a material having an absorption coefficient of 1.5×10{circumflex over ( )}5 cm.sup.−1 or less for the light of a wavelength of 250 to 1000 nm.

A method for interconnecting a first conductor and a second conductor includes forming a layer of substantially pure copper on the first conductor, applying a copper sintering material to the first conductor, the second conductor, or both, and interconnecting the first conductor and the second conductor by sintering the copper sintering material so as to form a copper-copper interface that includes the layer of substantially pure copper, the second conductor, and the copper sintering material.