"Dead bug" attachment of electronic components is a way of building functioning electronic circuits by soldering the parts directly together or by soldering miniature jumper wires between the component leads and the PCB lands instead of the traditional surface mount or through-hole soldering of components onto a PCB. The dead bug electronic component attachment was named because when you invert the IC and bend the legs out it will look like a dead bug.
There are numerous reasons why this method of electronic component attachment would be done as part of the PCB rework process:
- The component is nonstandard or you do not have a library design for the pad configuration of the component
- A board modification or re-spin takes too long from beginning to end
- A layout error and the package configuration does not match the board layout
- The device may be available in the time you need it, but not in the device package configuration of your design
- It is an easier and or less expensive method to test a concept before putting in the time and effort to get boards fabricated, thereby making it useful for prototyping
Several weaknesses are related to a dead bug attachment of a device to a PCB. Once the dead bug modification has been made, it is very difficult to modify or rework this part of the PCB. With the electronic component many times being encapsulated to provide mechanical rigidity, re-working the dead bug becomes very difficult. The dead bug component is not mechanically robust. While this may be a way to attach an electronic component for prototyping or experimentation in any real end-use operating environment, vibration, heat or physical handling may cause a disconnection to occur.
For RF or capacitive sensitive circuits, it is difficult to repeat exactly how a dead bug attachment was made. This attachment technique will get you by in the moment, but it will be difficult to exactly replicate with the same length of jumpers or glue. Finally, the dead bug technique is one that takes a highly-skilled soldering technician many hours, and in some cases (like the example presented in the embedded photos) it may only be able to be completed by the most skilled people. As the complexity for the circuit or components increase it makes it more and more difficult to keep all the connections straight and separated.
There are several things to keep in mind when performing a dead bug attachment of an electronic component. Solid wires should be used as they tend to keep their shape and bend more consistently than stranded wire. Make sure to stake the component so as not to break the small jumper wires found in the dead bug attachment. Usually this involves some form of gluing the component and/or jumper wires to the PCB. This will help to stabilize the connections during the testing phase of the development. In addition, make sure that the person completing the soldering is working from some type of print. This might include pin out information of the component package as well as pad definitions on the PCB. This will assist in any debugging and later troubleshooting.
Dead bug soldering of a component to another component or to a PCB is challenging work, but it may be a fast answer to the question of whether the circuit or the PCB functions according to the circuit designer’s wishes.