Introduction: Sherlock Solder Models Solder fatigue calculations in Sherlock are accomplished using one of the many solder models available. The different solder models address the type of package that is used for an individual component. Knowing which solder model to select requires knowing and being able to identify the package type of a component. This document will outline which packages use each of the solder models as well as how to identify packages. Solder Models: The available solder models available are listed below: BGA CBGA CC CGA Die LCCC Leaded QFN Thruhole BGA Model The BGA model is used for all BGA (Ball Grid Array) Packages. These are IC packages that have a grid pattern on the bottom made of solder balls. These solder balls melt during reflow and solder the BGA package to the PCB. The BGA solder model is valid for wire bonded BGAs as well as flip chip BGAs. Figure 1: BGA (Ball Grid Array) Packages
CBGA Model The CBGA model is used for BGAs with a ceramic substrate. This package can look very similar to a normal BGA as the substrate is often covered with overmold and therefore it can be difficult to see if the substrate is ceramic. The datasheet will however indicate if the substrate is ceramic. CC Model The CC model is used for all leadless chip carrier packages. These packages can be used for a variety of functions from resistors and capacitors to ferrites and diodes. These components are terminated at opposite ends and then attached to a PCB by soldering the end caps to copper pads on the board. It is important that the correct material is attributed to the component depending on its application as this will affect the solder fatigue results. As CC components have no leads, the dimensions of the pads on the board are critical for determining the solder area. Figure 2: Various CC (Chip Carrier) Packages
CGA Model The CGA model is used for column grid array components. These components are like BGAs in appearance however instead of using solder balls as the interface between the component and the PCB, CGAs uses solder columns. Figure 3:CGA (Column Grid Array) Package Die Model The Die model is use when a die is attached directly to a PCB. Die attach material is used to glue the die to the PCB and then wirebonds are used to connect the die electrically to the PCB. The whole die can then be encapsulated to create a glob top to protect the die and wirebonds. Figure 4: Die Attached Package
LCCC Model The LCCC model is used for leaded ceramic chip carriers. These are IC components that have leadless pins around the sides of the components. The sides are often castellated, and solder is applied in these areas. Figure 5: LCCC (Leadless Ceramic Chip Carrier) Packages Leaded Model The leaded model is used for all leaded components regardless of the lead geometry. Lead geometry can take many forms such as C-Leads, J-Leads, L-Leads, Gullwing Leads and Stub Leads. It is important that for leaded parts the dimensions of the leads are correctly defined as the solder model uses these dimensions to determine the solder application area. Figure 6 (L to R): C-Lead, J-Lead, L-Lead, Gullwing & Stub Lead Packages
QFN Model The QFN model is used for quad flat no-leads packages as well as DFN (dual flat no-leads) packages. These are IC packages that have pins around the perimeter of the package. These pins can be along two parallel edges in the case of DFNs or all four edges for QFNs. The distinguishing feature that of a DFN or QFN is that is has a thermal pad, referred to as a flag, underneath the component. This is important as solder is applied to the flag and therefore must be accounted for in the solder model. This flag can also take the form of multiple smaller flags. If this is the case, the areas of these flags can be summed and entered as a single flag in the Parts Properties. Figure 7 (L to R:) DFN (Dual Flat No-Leads) & QFN (Quad Flat No-Leads) Package Thruhole Model The thruhole model is used for any components that are attached to the PCB using leads soldered into thruholes instead of surface mounting. Thruhole components can take many forms and provide different functions, however the solder applied is always the same and failure is a result of lead dimensions. Figure 8: Various Thruhole Components