Surface Mount Electronic Transformer

Transformers (and inductors) can be classified in several ways: by power rating, by type of application, by type of construction, by industry, and others. “Surface mount electronic transformers” refer to a type of construction that permits attachment of surface mount transformers to a printed circuit board (PCB). Historically, transformers and other circuit devices have been mounted on PCBs using “pin-thru” technology. Transformer wires are terminated to pin type terminals. Holes are drilled in the PCB’s copper circuitry to accommodate the transformer pins. The transformer pins are inserted through these holes and then soldered to the copper circuitry. Engineers have developed solder pastes, adhesives, and assembly processes that permit attaching transformer terminals to PCBs without using holes. Flat areas (known as pads) on the transformer terminals are soldered directly to copper circuitry surfaces hence the term surface mount transformer. This process eliminates the need to drill holes for the pins, thereby reducing the cost to manufacture a PCB.

Surface mount electronic transformers (and inductors) are usually wound on surface mount bobbins, but are also available as toroidal coils. The toroidal coil is mounted on a “header” equipped with surface mount terminals. The bobbins (or headers), used with surface mount transformers, come in a variety of materials: plastics, phenolic, glass, Teflon and others. Most of these are molded. Some are fabricated. Some bobbins and headers are “self leading”. The winding wire is also used to form the surface mount terminal by looping the wire under a pre-formed flat edge thereby forming a reasonably flat terminal area.

Surface mount electronic transformers (and inductors) are available in a variety of shapes. Surface mount electronic transformers shapes include pot cores (round), “RM” (square pot cores), “EP”, “E”, “EI”, “EEM”, “EFD”, “U”, “UI”, “ER”, and some others including custom shapes. Surface mount transformers in these shapes are usually only available in the smaller sizes. Designers are adapting more shapes and larger sizes to surface mount transformer applications. Designers have mechanical concerns about the larger sizes. The weight of the larger sizes may exceed the weight that soldered surface mount pads can safely handle under vibration. Over time, designers hope to develop surface mount transformers (and inductors) in larger sizes.

Like other electronic transformers, surface mount electronic transformers (and inductors) can use a variety of core materials: laminated or taped wound silicon steel alloys, nickel-iron alloys, cobalt alloys; powdered irons and nickels; ferrite; air core; and/or core materials processed for square loop or round loop properties; and others.

Butler Winding can make (and has made) surface mount electronic transformers (and inductors) in a wide variety of materials and sizes. Butler Winding can also do a variety of custom transformers. Butler Winding’s upper limits are 40 pounds of weight and 2 kilowatts of power. We have experience with foil windings, litz wire windings, and perfect layering. For toroids, we can (and have done) sector winding, progressive winding, bank winding, and progressive bank winding. Butler winding has a variety of winding machines, bobbin/tube and toroid. That includes two programmable automated machines and a taping machine for toroids. Butler Winding has vacuum chamber(s) for vacuum impregnation and can also encapsulate. To ensure quality, Butler Winding purchased two programmable automated testing machines. Most of our production is 100% tested on these machines. For more information on Butler Winding’s capabilities, click on our “capabilities” link.

Need More Technical Information about Electronic Transformers in general

More information is available on other web pages included in this web site. Saturation and the volt-second product are discussed in the “pulse transformer” web page. An equivalent circuit for a transformer is included in the “power transformers” web page. The “inverter transformer” and “push pull” web pages include some discussion about magnetic “bipolar” and “unipolar” operating modes. There are web pages for various types (applications) of electronic transformers (and inductors). Click on one of the available links.

Also, feel free to contact Butler Winding and ask for technical or engineering assistance.