Issue link: https://iconnect007.uberflip.com/i/1526666
46 PCB007 MAGAZINE I SEPTEMBER 2024 It has been well documented that, with a very expensive and complex printed circuit board, thermal and mechanical excursions oen find weaknesses. A lack of robustness and poor pro- cess control oen leads to the exploitation of those weaknesses. An interconnect defect (ICD) oen goes undetected until the printed circuit board reaches the final assembly stage or undergoes multiple thermal cycles, including intercon- nect stress tests or thermal shock. It is impossi- ble to rework the ICD defect. But unlike voids, if detected in time, the panels can be repro- cessed. However, ICDs are not always detected by Quality Control, mainly because the ICDs are rarely catastrophic failures. Rather, con- stant thermal cycling or the high tempera- tures of assembly operations cause a weak- ened interconnect to separate. Many engineers expect that performing one or two solder floats on plated coupons removed from panels will provide a sufficient QC check. Unfortunately, Interconnect Defect: The Three Degrees of Separation for the reasons cited, this oen allows the problem to go undetected, much to the cha- grin of many. The Three Degrees of Separation ICD is categorized as three types of inter- plane (IP) separation: • Type 1: Separation of the electroless copper deposit from the interconnect • Type 2: Separation of the electrolytic copper deposit from the electroless copper deposit but the electroless remains on the post • Type 3: Cohesive failure of the electroless whereby the electroless copper deposit separates from itself Note: ere is oen a fourth type that I will present in a future edition of this column. However, let's try to understand the insidious nature of ICDs, also referred to as IP separa- tion. Trouble in Your Tank by Michael Carano, IPC CONSULTANT 46 PCB007 MAGAZINE I SEPTEMBER 2024