Issue link: https://iconnect007.uberflip.com/i/1540425
74 PCB007 MAGAZINE I OCTOBER 2025 • 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 sep- arates from itself The three types of IP failure have their own inher- ent causes. We will discuss Type 1 in this column and Types 2 and 3 next month. Figure 2 shows a more pronounced view of Type 1 ICD. One can see the electroless copper deposit adhering to the elec- tro-deposited copper, not to the interconnect. because drill bits are remaining in the hole for an excessive amount of time? • The micro-etch in the electroless copper pre- plate line does not sufficiently roughen the copper surface to provide adequate anchor- ing sites for the copper deposit. • Excessive dwell time in the catalyst or inad- equate tin removal in the acceleration step leaves a barrier on the copper interconnect. Anything that weakens the bond between the copper deposit and the interconnect can cause separation. • Drag-in of cleaners into the various process tanks or poor rinsing due to insufficient dwell time. Rinse water quantity and/or quality can cause Type 1 ICDs. • Electroless copper deposit exhibits inherent stress. An excessively high deposition rate typically causes this. The primary cause of the stress is the amount of copper micro- inches deposited per minute. Operate the process within its designed parameters. Any change in the process that results in the electroless being deposited at a higher-than- normal rate can cause the Type 1 ICD. A good rule is that if the electroless copper pro- cess is designed to deposit 40–50 microinches in 30 minutes and the deposit is somewhere in the 70–100-microinch range, then there is a problem with the copper being deposited much too fast. This will cause the copper grains to "re-orient," leading to stress in the deposit. The stress can only be relieved by the deposit pulling away from the interconnect. Think about process control and understand all variables, both mechanical and chemical, that can cause the process to drift out of control. Next month, I'll discuss Type 2 and 3 ICDs. PCB007 Michael Carano brings over 40 years of electronics industry experience with special expertise in manufacturing, performance chemicals, met- als, semiconductors, medical devices, and advanced packag- ing. To read past columns, click here. Why is Type 1 the most common and often the most difficult to mitigate? Generally, it's because there is significant internal stress in the electroless copper deposit, causing it to pull away or separate from the interconnect post. So, ensure there is no drill smear remaining on the post. This will show as a separation. However, don't confuse smear with Type 1 ICD. Type 1, in its true fashion, is caused by several factors that may be interacting in such a way as to exacerbate the defect. Remember that the weakest bond breaks first. Generally, Type 1 ICDs can be attributed to the following: • "Invisible" drill smear not removed by the desmear process. Check parameters if using alkaline permanganate or plasma. Is the drill- ing process creating more smear than normal because of dull drill bits, faster in-feed rates, poor quality entry and back-up material, or F i g u re 2 : A m o re p ro n o u n c e d v i ew of Ty p e 1 I C D. ▼ T RO U B L E I N YO U R TA N K