DFM/DFA analysis solution: how to cope with through-hole component defects


During PCB design, some common defects, such as TH component’s lead diameter, plated hole and pad mismatch, tend to occur on through-hole (TH) components. These defects should be found out and fixed as early as possible to avoid subsequent rework.


Common defects of TH component:

1. Clearance for plated holes and leads. When the gap C between the plated hole and the lead > 0.4mm, incomplete filling could happen, the porosity rate could increase and the soldering quality would be weaken.

2. Improper size matching of pad and component lead. Due to the uneven distribution of surface tension, when the pads are large and leads thin, the solder joints will be insufficient and shriveled; on the contrary, when the pads are small and leads thick, it also can cause the amount of solder being insufficient, lowering soldering quality.

3. Improper matching of pads and traces. When the pad and the printed trace partially (or the connecting piece) or the pad is close to the printed trace, the solder joints will be insufficient and shriveled, thus soldering quality would be weaken because the larger surface energy caused when the larger surface is soldered and most of the solder will be attracted to the surface of the trace.

4. When a hole in the pad is not concentric with the pad, the amount of solder will not be distributed evenly along the circumference of the pad and lead. Asymmetry soldering decreases soldering quality.

5. The TH diameter being too large leads to soldering leakage, components floating, pins not protruding from the board surface, overflowing tin, short, flux residue.

6. The TH diameter being too small leads to components couldn’t be inserted. It can also cause pin damage, poor penetration of tin, damaging plated TH wall while applying press-fit.

7. Flat lead plated hole design, as shown in picture below, the DIP flat pins are matched with the round holes on the PCB. Incomplete filling can easily happen thus decreasing soldering quality.


DFM/DFA solution to these common defects

Nowadays, DFM/DFA solution has been an efficient approach to optimizing the design of product for its manufacturing and assembly process, thus helping make a better product at lower cost. To these defects of TH component, Vayo Technology’s VayoPro-DFM Expert provides a 3D DFM/DFA analysis solution.

The software comes with 1500+ checking rules, including 300+ rules for fabrication process and 1200+ for assembly process. The checking items cover the component, pad, fiducial, testpoint, signal layer, silkscreen, etc. Besides, these rules are continuously innovated to follow the trends and demands. Vayo Technology also offers on-demand rule development service to meet different needs of clients.

What’s more, based on 3D component entity library of the software, upon the completion of DFM/DFA analysis, it would automatically generate a 3D DFM/DFA analysis report, more intuitively displaying the location of defects.

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