SMD - Surface Mount Devices - color codes.

Using SMD or surface mount components is often regarded as difficult and to be avoided at all costs - but that is a great waste.
Not only are surface mount devices relatively easy to solder they also open up a world of sophisticated devices for you to use - from accelerometers to high performance microcontrollers.
Prototyping and soldering these devices might use a different technique from the normal soldering style - but it is not difficult. All you need is a good soldering iron and a steady hand.
This page summarises my views and techniques on using these components. It is aimed at the hobbyist who might want to assemble a few projects using some surface mount devices and does not want to turn it into a major production.

SMD Codes.
SMD devices are, by their very nature, too small to carry conventional semiconductor type numbers.  Instead, a somewhat arbitrary coding system has grown up, where the device package carries a simple two- or three-character ID code.  Identifying the manufacturers' type number of an SMD device from the package code can be a difficult task, involving combing through many different data books.  To identify a particular SMD device, first identify the package style and note the ID code printed on the device.  Now look up the code in the alphanumeric listing which forms the main part of this book by clicking on the first character shown in the left-menu.  Unfortunately, each device code is not necessarily unique. For example a device coded 1A might be either a BC846A or a FMMT3904. Even the same manufacturer may use the same code for different devices.

If there is more than one entry, use the package style to differentiate between devices with the same ID code.  This compilation has been collected from R P Blackwell G4PMK, manufacturers' data and other sources of SMD device ID codes, pinout and leaded device equivalent information.  The entries under the Manufacturer column are not intended to be comprehensive; rather they are intended to provide help on locating sources of more detailed information if you require it.

ID Code Variations
Many manufacturers use an extra letter as their own identification code. If the device is from Philips it will sometimes have a lower case 'p' (or sometimes 't') added to the code; Siemens devices usually have a lower case 's'.
For example, if the code is 1A, according to the table there are a number of possibilities:
· 1A BC846A Phi ITT N BC546A
· 1A FMMT3904 Zet N 2N3904
· 1A MMBT3904 Mot N 2N3904
· 1A IRLML2402 IR F n-ch mosfet 20V 0.9A

This has been a problem in the past, however recently manufacturers have been adding lower case letters which clarify the code.
Many recent Motorola devices have a small superscript letter after the device code, such as SAC . (This smaller letter is merely a month of manufacture code.)  Many devices from Rohm Semiconductors which start with G have direct equivalents found in the rest of the
number. For example GD1 is the same as D1 which is a BCW31.  Some devices have a single colored letter (usually on extremely small diode packages). Color, if significant, is shown in small type after the code letter.

An 'L' suffix usually indicates a low-profile package, such as an SOT323 or SC70.

Reverse joggle devices do present a few problems. They often have an 'R' in the type number. A reverse package is one where the lead has been bent up instead of down. So it's a mirror image of a conventional device. Identification is usually possible from the code number, but some manufacturers use the same code. In these cases, it's a case of looking at the device with a magnifying glass. The leads of most normal packages come out closer to the circuit board side of the device; conversely a reverse joggle package will have them coming out closer to the 'top' of the device.  Sometimes a series of devices, derived from the same die, have related type (not code) numbers. Often an 'R' will indicate a reverse joggle package, and/or a 'W' indicates a smaller package variant, such as SOT343.  Sometimes similarities are also found in the code numbers. Recently some manufacturers have used a symbol or lower case letter to indicate the country of manufacture.  These have been ignored in the alphabetical ordering. For example:

· '67' is the code for a BFP67 (SOT143 package) ,
· '67R' is the code for the reverse joggle variant BFP67R (SOT143R),
· 'W67' is the code for a SOT343 package version.

'Z-S' and 'ZtS ' are both 2PC4081Q devices made by Philips; the first made in Hong Kong and the second in Malaysia; this appears in the codebook classified under ZS.

Leaded equivalent device and information
Where possible, the listing gives the part number of a conventional wire-leaded device with equivalent characteristics. If the leaded device is well-known then no more information is given. If the device is less common, some additional information will sometimes be given. Where no exact leaded equivalent exists, a brief device description is given, which may be sufficient to allow substitution with another device.  When describing device characteristics, some terms are implied from the type of device. For example, a voltage specified for a rectifier diode is usually the maximum PIV (peak inverse voltage) of the diode, but for a zener diode the operating (zener voltage) will be given.  Normally, where a voltage, current or power is specified, these will be limiting values. For example, a device specified as NPN 20V 0.1A 1W is a NPN transistor with a Vce (max) of 20V, maximum collector current of 100mA and a maximum total power dissipation of 1W. Some of the transistors are types with integrated resistors; in the list, a base resistor means a resistor connected in series with the base. When two resistor values are given, the first is the series base resistor and the second the resistor between base and emitter.

Digital Transistors (dtr)
These are transistors with built-in resistors.  Some have one resistor between base and emitter, others in series with the base. Many others have both.  To keep things simple, the series resistor is called R1 and the base emitter resistor is called R2. If both are present, then two values are given, R1 first. So 4k7 + 10k means that R1 (the base resistor) is 4k7 and R2 (the resistor between base and emitter) is 10k.

SMD Ceramic Capacitor Coding

SMD ceramic capacitors are sometimes marked with a code, consisting of one or two letters and a digit. The first letter if present is a manufacturer code (i.e K for Kemet, etc.), the second letter the mantissa and the digit the exponent (multiplier) of the capacitance in pF. For example S3 is a 4.7nF (4.7 x 10³ pf) capacitor from an unknown manufacturer, while KA2 is a 100 pF (1.0 x 10² pF) capacitor from Kemet.

SMD Electrolytic Capacitor Coding

SMD electrolytic capacitors are often marked with their capacitance and working voltage, e.g.

10 6V is 10 µF 6V . Sometimes a code is used instead, which normally consists of a letter and 3 digits. The letter indicates the working voltage and the 3 digits (2 digits and multiplier) give the capacitance in pF.

The band or stripe indicates the positive terminal. For example, a capacitor marked A475 is a 4.7m F 10V unit. 475 = 47 x 105 pF = 4.7 x 106 pF = 4.7m F.

SMD Resistor Coding SMD Resistors are usually coded with a numerical equivalent of the familiar three band colour code. In the same way as wire ended components, precision resistors (1% or better) may be marked with a four digit code. The first two (or 3) digits are the first two (or 3) digits of the resistance in ohms, and the third (or 4th) is the number of zeros to follow - the 'multiplier'. Resistances of less than 10 ohms have a 'R' to indicate the position of the decimal point. Some examples will make this clearer:

Three Digit Examples Four Digit Examples

330 is 33 ohms - not 330 ohms.    1000 is 100 ohms - not 1000 ohms

221 is 220 ohms.     4992 is 49900 ohms, or 49.9 kohm

683 is 68000 ohms, or 68 kohm.    16234 is 162000 ohms, or 162 kohm

105 is 1000000 ohms, or 1 Mohm

8R2 is 8.2 ohms 0R56 or R56 is 0.56 ohms.

SOD-123 Package Diodes

Colour-coded SOD-123 diodes. Devices marked with letter/number codes

HP diodes appear to follow a regular coding scheme. Although this is not always followed, it may help in identifying diodes and package styles if used with caution.  Not all HP diodes follow this scheme, so beware.  The general type number scheme is: HSMX-123#HSM stands for HP Suface Mount, I suppose.  X is either S for a schottky diode or P for a PIN diode. # is a letter for a SOT323 package and a number for a SOT23 device. It denotes the internal arrangement - single, common anode pair, quad, etc. The digit of the code marked on the package itself usually corresponds to the package style (#) number.

SOD-80 Package Diodes

The SOD-80 package, also known as a MELF, is a small glass cylinder with metal ends.

Code marked devices Marked 2Y4 to 75Y (E24 series) BZV49 series 1W zener diodes (2.4 - 75V) Marked C2V4 TO C75 (E24 series) BZV55 series 500mW zener diodes (2.4 - 75V) The cathode end is indicated by a coloured band.