BOOK_CONTENT
From Microvias: For Low Cost, High Density Interconnects

2.5 Solder Resist Materials and Processes

IPC-T-50b defines a solder resist (mask) as a coating material used to mask or to protect selected areas of a printed circuit board (PCB) from the action of an etchant, solder, or plating. A somewhat more useful working definition for a solder resist is as follows: a coating that masks off a printed circuit board surface and prevents those areas from accepting any solder during reflow or wave soldering processing (see Fig. 2.25).


Figure 2.25: Major features of solder resist on a PCB.

The prime function of a solder resist is to restrict the molten solder pickup or flow in those areas of the PCB, holes, pads, and conductor lines that are not covered by the solder resist. PCB designers, however, often expect more functionality out of the solder resist than just a means to restrict the solder pickup. Table 2.26 lists the functions of a solder resist.

TABLE 2.26: Functions of Solder Resists

Reduce solder bridging and electrical shorts

Reduce the volume of solder pickup to obtain cost and weight savings

Reduce solder pot contamination (copper and gold)

Protect printed circuit board (PCB) circuitry from handling damage, i.e., dirt, finger prints, etc.

Provide an environmental barrier

Fill space between conductor lines and pads with material of known dielectric characteristics

Provide an electromigration barrier for dendritic growth

Provide an insulation or dielectric barrier between electrical components and conductor lines or via interconnections when components are mounted directly on top of the conductor...

Copyright The McGraw-Hill Companies, Inc. 2001 under license agreement with Books24x7

Products & Services
SMT Manufacturing Equipment
Surface mount technology (SMT) manufacturing equipment is used to populate printed circuit boards (PCB). This includes soldering machines, ovens, component placement, paste depositors and screen and stencils.
Resistor, Capacitor Networks
Resistor, capacitor networks (RC networks) are integrated circuits (ICs) that contain resistor-capacitor arrays in a single chip.
Micro Connectors and Nano Connectors
Micro connectors and nano connectors exhibit contact pitches of 0.05'' (micro) and 0.025'' (nano), respectively.
Edge Connectors
Card edge connectors are edge-on connectors designed for single-sided or double-sided printed circuit boards (PCBs).
Relay Sockets
Relay sockets are devices that accept relays, electromechanical switches in which the variation of current in one electric circuit controls the flow of electricity in another circuit.

Topics of Interest

2.6 Machining and Routing Laminate machining consists of the mechanical processes by which circuit boards are prepared for the vital chemical processes of image transfer, plating, and etching. Such...

Solder mask or solder resist is like varnish or lacquer that is applied to the outside or top and bottom layers to form a permanent protective coating for the copper traces of a printed circuit board.

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OVERVIEW The manufacturing steps involved in coating an electronic part or assembly are numerous; each is essential to the performance and reliability of the end product. Among these steps are:...

Wave soldering is a widely applied mass soldering method for electronic boards. Wave soldering or flow soldering uses a molten solder bath with a traveling wave. Printed circuit boards are positioned...