SOLDER PREFORMS
Preform Alloys
Solder preforms come in standard shapes such as squares, rectangles, washers, and discs. Typical sizes range from 0.010″(0.254mm) up to 2″(50.8mm), though smaller and larger sizes, as well as custom shapes, are also available. Dimensions can be held to tighter tolerances to assure volume accuracy.
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Selecting Alloys
A wide assortment of alloys is available in liquidus temperatures that range from 47°C to 1,063°C. Alloys can be indium-containing, gold-containing, lead-free, fusible or standard lead, as well as many others.
Choose a Safe Melting Margin
A general rule is to select an alloy that melts at least 50°C higher than the operational temperature of the part being soldered.
Ensure Material Compatibility
Consider the materials being soldered and what solder is most compatible. For example, tin-based solders will scavenge the gold from gold-plated parts, forming brittle intermetallics, so indium-based solders are generally recommended in these cases.
Consider Preform Shape
It is important to consider the shape of the final preform in the alloy selection process, as metals and alloys have unique characteristics that effect malleability.
Evaluate Operating Conditions
The operating environment of the completed assembly is also an important consideration. Will it operate in very high or very low temperatures, and/or be subjected to vibration?
Dimensional Specifications
The location of the solder joint and the required solder volume dictate the preform’s size and shape. Once flat dimensions (diameter, length, and width) are set, adjust thickness to achieve the needed volume. For through-hole connections, add 10-20% to the calculated volume to achieve a good fillet, while pad-to-pad joints should have about 5% less surface area than the pad.
Each solder preform should have a specified burr tolerance. Adhering to standard tolerances helps avoid extra costs and delays. Indium Corporation offers an extensive library of preform sizes and shapes, or we can create custom setups for your application. Choosing an existing preform size can help save setup time.
| Width/Length or Diameter | Typical Tolerances |
|---|---|
| Up to .100″ (2.54mm) | ± .002″ (± .051mm) |
| Over .100″ (2.54mm) | ± .005″ (± .127mm) |
| Thickness | Typical Tolerances |
|---|---|
| Up to .001″ (.025mm) | ± .0002″ (± .005mm) |
| .001″ (.025mm) to .002″ (.050mm) | ± .0003″ (± .0076mm) |
| >.002″ (.050mm) to .010″ (.254mm) | ± .0005″ (± .0127mm) |
| > .010″ (.254mm) to .020″ (.508mm) | ± .0010″ (± .0254mm) |
| > .020″ (.508mm) to .050″ (1.27mm) | ± .0025″ (± .0635mm) |
| > .050″ (1.27mm) | ± 5% |
| Burr Tolerances (Discs, Squares & Rectangles) | Typical Tolerances |
|---|---|
| < .050″ (1.27mm) | .002″ (.050mm) |
| > .050″ (1.27mm) to .500″ (12.7mm) | .003″ (.076mm) |
| > .500″ (12.7mm) | .005″ (.127mm) |
| Burr Tolerances (Washers & Frames) | Typical Tolerances |
|---|---|
| < .100″ (2.54mm) | .003″ (.076mm) |
| When thickness ≥ 2/3 of I.D. | .005″ (.127mm) |
Solder Preform Recommendations
Packaging
There are a variety of packaging options, including tape and reel. To minimize excessive handling, exposure to air, and subsequent oxidation, solder preforms should be packaged according to the quantity used during a typical work shift.
Storage
Keep in the original container, closed securely, in 55% RH or less and at temperatures below 22°C. Solder preforms can also be stored in an inert atmosphere, such as a nitrogen dry box.
Shelf Life
The shelf life of solder preforms is dependent on the alloy composition. Pb-free alloys and alloys with less than 70% lead content have a shelf life of 1 year from the date of manufacture (DOM). Alloys with more than 70% lead content have a shelf life of 6 months from the DOM.
Related Applications
Alloys are prevalent in all of our applications, and our engineers and chemists have developed numerous variations, categorized based on how they serve different needs.
Semiconductor Packaging & Assembly
Critical semiconductor packaging ensures functionality and
Thermal Management
Thermal solutions for HPC ensuring reliability and optimal
High-Temperature Soldering
Offering high-temperature soldering materials for critical applications in harsh
Related Markets
Our preform alloys are the foundations of the preforms used in a variety of markets, including:
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