liminfoSMD Code Reference
Free reference guide: SMD Code Reference
About SMD Code Reference
The SMD Component Reference is a searchable technical guide covering every aspect of surface-mount device (SMD) technology used in modern electronics. It includes detailed specifications for standard chip package sizes from 01005 (0.4 x 0.2 mm) through 2512 (6.3 x 3.2 mm), with Imperial-to-Metric conversions, recommended pad dimensions, power ratings, and maximum voltage for each size.
Beyond package dimensions, this reference provides complete reflow soldering profiles for both lead-free (SAC305) and leaded (Sn63/Pb37) processes, including preheat ramp rates, soak temperatures, peak reflow temperatures, and cooling rates. It also covers solder paste classification per IPC J-STD-005 with powder types (Type 3 through Type 6) matched to appropriate package sizes.
The reference includes comprehensive component marking guides for SMD resistors (3-digit, 4-digit, and EIA-96 codes), capacitors (MLCC and tantalum), diodes (polarity identification and common marking codes like T4 for 1N4148), transistors (SOT-23 pinouts), and ICs (pin 1 identification methods). PCB design sections cover IPC-7351 pad design density levels, thermal via placement, component spacing rules per IPC-2221, and common solder defect diagnosis.
Key Features
- Complete SMD package size table from 01005 to 2512 with Imperial/Metric cross-reference and power ratings
- Pb-free (SAC305) and leaded (Sn63/Pb37) reflow temperature profiles with zone-by-zone timing
- SMD resistor marking decoder supporting 3-digit, 4-digit, and EIA-96 code formats
- Capacitor, diode, transistor, and IC marking identification guides with common part number mappings
- IPC-7351 pad design guidelines with density levels A/B/C and recommended dimensions per package
- Thermal management reference including thermal via sizing, exposed pad design, and thermal resistance values
- Component placement spacing rules per IPC-2221 with minimum and recommended clearances
- Solder defect troubleshooting guide covering bridging, tombstoning, voids, cold joints, and solder balls
Frequently Asked Questions
What is the difference between Imperial and Metric SMD package codes?
Imperial codes (e.g., 0402) refer to dimensions in hundredths of an inch, while Metric codes (e.g., 1005) use tenths of a millimeter. Confusingly, some codes overlap: an Imperial 0402 (1.0 x 0.5 mm) is completely different from a Metric 0402 (0.4 x 0.2 mm). This reference includes both systems side by side to prevent mix-ups.
How do I read a 3-digit SMD resistor marking code?
The first two digits are significant figures, and the third digit is the multiplier (power of 10). For example, 103 means 10 x 10^3 = 10 kohm, and 4R7 means 4.7 ohm where R represents the decimal point. Four-digit codes work similarly but with three significant figures for higher precision (1% tolerance).
What is the recommended reflow peak temperature for lead-free solder?
For SAC305 (Sn96.5/Ag3.0/Cu0.5) lead-free solder, the recommended peak temperature is 245-250 degrees C, with an absolute maximum of 260 degrees C. The time above the liquidus temperature of 217 degrees C should be 60-90 seconds, and the total reflow cycle typically takes 4-7 minutes.
Which SMD package size is best for hand soldering?
0805 (2.0 x 1.25 mm) is the most commonly recommended size for beginners learning SMD hand soldering. The 0603 (1.6 x 0.8 mm) is also manageable with practice. For prototyping convenience, 1206 (3.2 x 1.6 mm) is the easiest to work with by hand, though it takes more board space.
How do I identify an unmarked SMD component?
Resistors typically have black or green bodies with visible markings, while MLCC ceramic capacitors are brown or yellow and usually unmarked. Use a multimeter: identical readings both ways indicates a resistor, one-way conduction suggests a diode, and very high resistance points to a capacitor. Inductors have coil shapes and very low DC resistance (under 1 ohm).
What solder paste type should I use for 0402 components?
For 0402 (1005 Metric) components, use Type 4 solder paste with particle size 20-38 micrometers. The stencil thickness should be 0.10-0.12 mm. For even smaller 0201 components, step up to Type 5 (15-25 micrometers) with a 0.08-0.10 mm stencil.
How do I prevent tombstoning in SMD assembly?
Tombstoning (Manhattan effect) occurs when uneven heating causes one end of a chip component to lift off the pad. Prevent it by ensuring balanced copper areas on both pads, aligning components perpendicular to the reflow oven conveyor direction, and using symmetrical pad designs per IPC-7351 guidelines.
What is the polarity marking on tantalum capacitors?
SMD tantalum capacitors mark the anode (positive) side with a bar or band. This is the opposite convention from aluminum electrolytic capacitors, which mark the cathode (negative) side. Always verify polarity before soldering, as reverse voltage on tantalum capacitors can cause thermal failure or fire.