Packaging - Shock-n-vibration sensitivity assessment from Marcelo Chirai July 7, 2016 Pin-in-Paste Hole Fill We are about to implement Pin-in-Paste technology.How can we ensure proper plated hole fill during the screen printing process? Will the process require using a different solder paste than the one we use for pure SMT assemblies?R. L. Experts Comments Paste-in-hole processes are somewhat more complex than traditional SMT from a process control standpoint, but with good engineering practices and the properly optimized stencil, it can be avery controllable process for many users. The key is doing some math on the front end and determining how much paste will be needed to fill the space between the barrel of the through-hole and the lead of the component. Since paste is generally about 50-55% metal by volume, you will generally find that you need to overprint the pad area to ultimately deliver enough solder to the solder joint. Various stencil design techniques will work; contact your solder paste and/orstencil supplier for more detailed pointers.As for picking the right paste for paste-in-hole applications, many standard solder pastes may drop into this type of process without any issues. However, there are two additional solder paste performance requirements for paste selection in paste-in-hole versustraditional SMT. These include coalescence behavior and anti-dripping behavior. The coalescence behavior becomes more of an issue than usual due to the likelihood of overprinting onto the solder mask on the top side of the board. The anti-dripping requirements stem fromthe fact that some pastes can drip off the bottom of the component lead upon heating, resulting in less solder than expected for the solder joint. This can be avoided by selecting a solder paste that was designed not to drip in a paste-in-hole application. Brian SmithGeneral Manager - Electronic Assembly AmericasDEK InternationalMr. Smith has been supporting customers in the electronics assembly industry since 1994. His expertise is focused on solder paste printing and reducing soldering defects. He holds a BS in Chemical Engineeringand an MBA in Marketing. He has authored several papers in trade magazines and at industry conferences. He is an SMTA Certified Process Engineer. To ensure proper plated hole fill during the screen printing process you must have the proper volume of solder paste. Here's an example of the formula you can use:H=Hole diameterD=Lead diameterT=Board thicknessL=Width of lead in the X direction (For square lead)W=Width of lead in the Y direction (For square lead)Pi =3.14Hole Volume (HV)=(3.14)(H/2)(H/2)(T)Lead Volume (LV)=(3.14)(D/2)(D/2)(T) (For round leads)Lead Volume (LV)=(L)(W)(T) (For square or rectangular leads)Annular Ring Area(RA)=(3.14)(L/2)(L/2)-(3.14)(H/2)(H/2)Solder volume (SV)=HV-LVPrint Volume (PV)=(2)(SV) (50%) Print Area (PA)=(F)(PV)/stencil thicknessF=Inspection Factor.7=no fillet.9=fillet on both sider0.8=fillet on primary side1.0=large fillet on both sides Joe KarcewskiProduct ManagerAPS-Novastar, LLCJoe Karcewski has been a Process Engineer for 16 years in the industry. He is a certified IPC-A-610 trainer and is presently working at APS-Novastar as a Product Manager for Soldering Systems includingSelective Soldering systems. The best solution for the Pin-in-Paste process is the ProFlowR enclosed head system.The main reason for this is that ProFlow allows independent control of paste pressure and, therefore, the ability to control the amount of paste