Why the package matters as much as the part number
Two parts can share the same electrical function and die, yet behave very differently in production. The package determines the footprint on the PCB, the thermal path, the pin count available, whether the board can be reworked, and what inspection equipment is required. When you specify or substitute a component, the package is not a detail — it is part of the specification.
Through-hole (THT): the original form factor
Through-hole parts have leads that pass through the board and are soldered on the far side.
- DIP (dual in-line package) — two parallel rows of pins on a 2.54 mm pitch. Still common for prototyping, sockets, and older or low-volume designs.
- TO-220, TO-247, TO-3P — power packages, usually bolted to a heatsink. Common for regulators, rectifiers and MOSFETs handling meaningful current.
- Axial and radial — resistors, capacitors and diodes with wire leads.
THT remains the better choice where mechanical strength matters, where the part must be socketed, or where hand assembly and rework dominate. It costs board area and limits density.
Surface mount (SMD / SMT): the default today
Surface-mount parts are soldered directly to pads on the board surface. They dominate new designs because they are smaller, cheaper at volume, and compatible with reflow assembly.
- Chip components — resistors, capacitors and inductors in 0402, 0603, 0805 and 1206 body sizes. The size code describes the body, not the value.
- SOT-23, SOT-89, SOT-223 — small transistor and regulator outlines; SOT-223 is often used where a little more dissipation is needed.
- SOP / SOIC, SSOP, TSSOP, MSOP — small-outline packages with pins along two sides, typically on 1.27 mm, 0.65 mm or 0.5 mm pitch. SOP and SOIC remain the most repairable surface-mount options.
- QFN and DFN — no leads; contacts sit under the body edges, often with an exposed thermal pad underneath. Excellent thermal and footprint efficiency, but the pad must be soldered correctly and the joint is hard to inspect visually.
- QFP, LQFP, TQFP — pins on all four sides, from around 32 to over 200 pins. Common for microcontrollers and logic.
- BGA — a grid of solder balls underneath the package. High pin count with a small footprint, but inspection depends on X-ray, and rework requires dedicated equipment.
Choosing between them
- Board space and pin count. If the design is dense or the pin count is high, surface mount is effectively the only answer; QFN and BGA are the most area-efficient.
- Thermal load. QFN packages with an exposed pad, or power packages such as TO-220, are the usual answers. A BGA soldered to a properly designed ground plane also conducts heat well.
- Assembly and rework capability. SOP and SOIC can be reworked with basic tools; QFN needs hot-air or reflow control; BGA generally needs X-ray and a rework station. If your line cannot inspect or rework a package, avoid it.
- Inspectability. Visible solder joints (SOP, QFP, THT) are easier to accept at goods-in and after assembly than hidden joints (BGA, QFN thermal pads).
- Cost and availability. The same die is often offered in several packages. Availability of a specific package can decide a substitution, and package variants are not always interchangeable even when the die is identical.
A note on pitch and naming
Pitch is the centre-to-centre distance between adjacent pins, and it is stated in millimetres or sometimes in mils. Two parts can share a family name and still differ in pitch and body width, so always confirm the full suffix in the part number rather than the family alone. Where a manufacturer offers the same device in multiple packages, the package code is part of the ordering code — mixing them up is one of the most common sourcing errors.
Checking availability by package
At YILUDA TECH every listed part is 100% original, new and unused, held in stock at our Shenzhen warehouse and shipped worldwide by DHL, FedEx or UPS. Because the ordering suffix determines the package, the fastest way to confirm what is available is to send the exact part number with a request for quote, along with the quantity and destination.
You can browse the full inventory, or start from a manufacturer such as Samtec for interconnect, Panasonic for passives, or Texas Instruments for analogue and power devices.