The use of solder preforms can significantly simplify the effective attachment of components to an electronic package, reducing assembly time and subsequent costs while increasing reliability. Preforms are designed to deliver precise amounts of a specific solder type to a predetermined location for a solder joint. There are a wide variety of solder preform materials and shape options. This article will provide an overview of our solder preform capabilities and answer common questions we see regarding this product line.
What is a Solder Preform?
Simply put, a solder preform is a quantity of solder that is presented in a manufactured shape suitable for the application for which it was intended. Preforms can be made from any of approximately 250 different solder alloy combinations.
Standard or traditional shapes include:
- Squares
- Rectangles
- Discs
- Washers
- Frames
- Custom shapes as defined by the user
The purpose of a solder preform is to ensure a precise amount of solder is deposited consistently in the component assembly process. Using solder preforms not only helps ensure the quality and performance of your package (whether designed to be hermetic or not) but also improves efficiency of your electronic package assembly. Preforms also eliminate the need for uncontrolled use of flux and post soldering cleaning when used in a controlled atmosphere.
Solder preforms are used commonly for sealing packages and lids, but they are also used in a number of other applications including:
- Die attach
- Thermal interfaces
- PCB assembly
- Connectors and cable assembly
- And a variety of other electronic applications
Is a Solder Preform Right for Me?
A number of factors go into determining whether or not a solder preform would be beneficial to your application and manufacturing processes.
Do you have a strict quality requirement for precise volume of solder? If so, you know that excess solder can result in solder bridged components and subsequent package failure. Not enough solder can result in voiding, poor attachment and hermetic seal leaks. Precisely manufactured solder preforms can eliminate those issues.
Are you manufacturing high volume components from relatively complex designs and strict quality considerations? These are sweet spots for the use of a solder preform, especially if there is automation in your manufacturing process.
Are labor costs a consideration? Hand soldering a complex assembly is labor intensive and, consequently, will increase manufacturing costs.
Selecting the Right Alloy
The primary driver for solder material selection is the operating environment the package will be used in. Here are a few things to consider:
- What are the maximum and minimum temperatures the module will be exposed to?
- What is the potential for thermal and mechanical shock?
- How flat are the components to be joined?
- Does the assembly need to be hermetic?
- Are any surface treatment applied to the components if so what are they?
Your solder material of choice will also impact the dimensional limits that can be manufactured. The primary defining dimension limits when considering manufacturing of solder preforms and design are material thickness, wall thickness and overall size.
Your solder preforms shape and size also have an impact on material choice. Some alloys, Indium for example, are extremely fragile and challenging to manufacture. (Indium is a very low temperature solder and is generally selected only when assemblies cannot be exposed to high temp solder).
The table below shows some of the most common alloys.
