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Understand Wire Bonding and Die Shear Testing

Wire bonding, as shown in Fig. 1, and die shear strength training are inextricably intertwined. Die shear strength is a demanding aspect of wire bonding to assure top quality and reliability to comply with Mil STD 883, Rev. G or Rev. F. In particular, wire bonding and die shear strength testing play prominent roles for small IoT and wearable PCB applications.

IoT devices require more and more electronics functionality placed on extremeley small printed circuit boards (PCBs) like rigid and rigid-flex circuits. To comply with the reduced real estate, bare chips or dies without space consuming packages are placed directly on the small board or a substrate on the board. These die attach or bare chips can be such types as chip on board (CoB) or flip chip and other types.

There is considerably more to know, you can read more on our most recent blog on this subject.

In the meantime, here are some tips and hints to get you better acquainted.

  • The PCB industry is rapidly moving to both microelectronics/wire bonding and conventional SMT manufacturing on the same product line.
  • The new technology trend puts extra challenges on the EMS Provider. It’s best to rely on experience in these instances.
  • Now, you are dealing with metallization between the die and the media, as well as differences in media which can be adhesive, solder or epoxy. Plus, you are now dealing with the media and the substrate.
  • It’s critical you have assurances a die or bare chip is solidly attached so die integrity compromised.
  • Get a handle on a shear strength test and how it is performed to check integrity of the metallization between die and adhesive and adhesive and the substrate.

A number of different die shear strength testers are available on the market for EMS Providers performing IoT PCB assembly and wire bonding. There are variances among these different testers. However, the main points to be made here is each has a so-called “push gate” and a die contact tool. The push gate is applied at the side of a die to assure the die remains in its position. The die contact tool then uniformly distributes force to the edge of the die to determine the validity of the joint.