ALPHA® Exactalloy® Tape & Reel Preforms Help Eliminate Wave Soldering

Posted 10/18/2012 by cderama

A mixed technology process is one that uses both SMT and Wave soldering to produce a board assembly. Transitioning a mixed technology to an SMT-only process, or what we like to call the “elimination of wave,” is a value proposition demonstrating cost, reliability, and environmental benefits.  One of the most common methods to accomplish a transition from wave to surface mount technology is known as pin-in-paste or P-i-P.  Pin-in-Paste is a high-yield process that simultaneously reflows surface mount and through hole components - without the need for wave soldering. By eliminating the wave soldering step in the assembly process, pin-in-paste saves time, reduces production costs, and increases throughput.

 

Let’s discuss P-i-P in a little more detail.  Pin-in-Paste is an SMT method used for through hole components. It consists of overprinting solder paste at each pin location and then placing the through hole component directly through the paste and into the plated through hole.  During the reflow process, the overprinted solder paste becomes molten and is drawn back to the plated through hole and pad through capillary action from the plated features, and forms the final solder joint.

 

PiP is a very effective technique for eliminating wave, but it comes with a few challenges. Printing enough solder paste volume to fill a plated through hole can be very difficult especially when managing a thicker board or when there is limited space on the board. What’s more, excessive overprinting can generate random solder balls causing assembly reliability issues. ALPHA® Tape & Reel (T&R) Preforms can help resolve these issues.

Elimination of wave using Preforms

 Here is an example where preforms were used to generate more solder volume when overprinting was not possible. At the picture on the left, we see the required amount of overprint on the outermost pins and insufficient printing on the center row of pins. In the picture on the right, we can see how tape and reel preforms were placed into the inadequate print areas to increase the solder volume.

The power of ALPHA® Tape & Reel (T&R) Preform is that they are 100% alloy, and therefore can accurately and precisely increase the volume of solder in a joint. Here are some more advantages you can achieve when using ALPHA® T&R Preforms:

 They are an economical alternative for increasing solder volume when overprinting solder paste is not adequate.
 They are offered in a wide variety of tape and reel preform sizes to address most through hole applications.
 The implementation of T&R preforms into an existing SMT process is not complicated since the preforms are handled and placed just like standard chip cap components and require no special tooling.
ALPHA® Tape & Reel (T&R) Preforms provide higher reliability benefits:
 100% hole fill is routinely achieved.
 They can be used to reduce or eliminate overprinting of the solder paste.
 Reducing the overprint size can diminish the likelihood of the formation of random solder balls.

The power of the ALPHA® Tape & Reel (T&R) Preform is seen here. Take a look at this video and see how different sizes and quantities of preforms can produce different results-- In this case, small, large, or no fillet at all.

 Preform video

(Click the image to see video)

Alpha has developed a documented strategy that can help you quickly assess your board as a candidate for elimination of wave using ALPHA® Tape & Reel (T&R) Preforms. The document also contains a Fitness for Use process that will take you through the steps in implementing an Elimination of Wave Process and provide the necessary calculations for determining solder volumes. It’s called the ALPHA® Checklist for Success.  Contact your local Alpha sales partner to get your copy or simply download it from our web site and get started today.

 

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