BOOK_CONTENT
From Solders and Soldering: Materials, Design, Production, and Analysis for Reliable Bonding, Fourth Edition

10.1 Introduction

In Sec. 5.7, we discussed the preplacement of flux and solder in the joint before heat application. The methods used are judged by their quantity control. The importance of solder quantity per joint is further explored in Sec. 10.3. Obviously, the economy of the process and the production size are additional selection factors. Finally, surface topography has a direct impact on the final assembly process.

A flat surface contour is easiest for most assembly techniques, while a rounded surface profile can cause mating-part slippage during assembly. Table 10.1 lists the most common solder-preplacement methods and rates them in these important issues.

Table 10.1: Common Solder Preplacement Methods

Method

Quality control

Contour outline

Process cost

Application comments

Paste or cream

Good

Best

Medium

Good on any surface and contour; tacky paste can hold parts together

Solder preform

Best

Flat

Medium

Need conforming surfaces and must juggle three parts

Hot dip coating

Poor

Rounded

Low

May not pick up enough solder in coating

Fused plating

Very good

Rounded

High

Normally limited amount of solder in coating

Electroplating

Very good

Flat

Medium

Has unpredictable aging solderabil-ity potential

To summarize, flat surfaces are ideal for part assembly unless they have unique shapes designed into them. When a truly level exterior is not possible, a slight curvature is also acceptable. The use of a tacky paste or flux will help to hold the parts together during assembly.

10.2 Precoated Solder on the Joint Surfaces

There are two ways of supplying solder to the...

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Products & Services
Solder
Solders include low melting point metal alloys usually in wire, powder, preform or paste forms. Solders are metal alloys with low melting points that are used to join metals together.
Brazing and Soldering Services
Brazing and soldering services use welding techniques and related processes to fabricate parts and join components.
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.
Filler Alloys and Consumables
Filler metal alloys and consumables used in welding, brazing or soldering include items in rod sheet, wire spool, coated stick, weld stud, powder, preform or paste forms.
Fluxes
Fluxes are chemical compositions used in soldering, brazing and welding. They clean the metal’s surface, assist with heat transfer, and remove unwanted oxide films.

Topics of Interest

11.1 The Role of Quality Control in Soldering Quality control and inspection are an integral part of making reliable solder joints. Their primary function is the continuous monitoring of all the...

6.1 Heating in Soldering The Heat Profile In Chap. 5, we covered the reasons for heating in soldering. We also went into the details of preheating and the sensitivity of certain materials such as...

Although many have predicted the demise of through-hole components, they are alive and well with tens of billions assembled each year. In many cases these components are assembled by wave soldering.

Although many have predicted the demise of through-hole components, they are alive and well with tens of billions assembled each year. In many cases these components are assembled by wave soldering.

Surface mount technology (SMT) adds components to a printed circuit board (PCB) by soldering component leads or terminals to the top surface of the board. SMT components have a flat surface that is...