Integrated® Preforms are connected units of solder that can be placed in an application to provide the sole solder for the joint. They can also be used to add to the volume of solder, when used in conjunction with solder paste - to fortify the joint. Integrated Preforms are available in most alloys that are currently incorporated in common solder pastes.
The only difference between connected preforms and separate preforms is that the Integrated (connected) Preforms are attached to one another and can be placed in the application as one multiple unit of solder. Connecting each individual solder preform is a small strand of solder that is designed so narrow that it will separate during reflow (to prevent bridging).
When manually reworking boards to add additional solder to joints becomes too large of a task, Integrated Preforms can be incorporated prior to reflow so any rework is not necessary. In through-hole applications, the connected preform can be placed on the component and then inserted into the holes of the board that have solder paste placed on top of them. There is no need to flux the Integrated Preform because the flux vehicle in the paste will provide the fluxing.
When used as a stand-alone connected preform, or with solder paste to fortify the joint, Integrated Preforms can be reflowed using the same temperatures and profiles as for the paste by itself.
To learn more about Integrated Preforms and solder fortification®, plan to attend the presentation of a paper on this topic at Apex 2011 (Las Vegas, NV, 10-14 April) given by Dr. Ronald C. Lasky (see sidebar →), Indium Corporation Sr. Technologist and Instructional Professor, Thayer School of Engineering, Dartmouth College.
The next post in this series will address the various shapes of Integrated Preforms and how they are packaged.