Papers about solder preforms
by Dr. Ronald C. Lasky , Paul Socha , Carol Gowans
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. However, in many mixed
product technology (i.e. SMT and through-hole on the same board) products,
it makes sense to consider assembling the through-hole components with the
pin-in-paste (PIP) process. PIP has been successfully used for several decades
now; however in many cases it is not possible to print enough solder paste to
obtain an acceptable solder joint. In addition to this “solder starved” condition,
the large quantity of solder paste used to form the though-hole joint results in
excess residual flux. This residual flux can lead to difficulties in in-circuit testing
and potential surface insulation resistance concerns.
In light of the above need, solder preforms have been developed. These slugs of
solder typically come in the same sizes as 0402, 0603, and 0805 passive components.
The solder preforms are placed by the component placement machines
onto the solder deposit. This additional solder assures that an adequate solder
joint is formed with a minimum of solder paste and its residual flux.
Although PIP was an early application of solder preforms, more recently other
“solder starved” applications have emerged such as radio frequency (RF)
shields and connectors. In addition, the use of ultra thin stencils in the assembly
of miniaturized components can result in some other components being solder
starved and, hence are candidates for solder preforms.
This paper will cover the design and assembly techniques for using of solder
preforms in the “solder fortification™” needs described above. Several successful
applications will be presented. In some of these applications, defects were
reduced by 95% after implementing solder preforms.
Apex 2011, solder starvation, flux, PIP, pin-in-paste, through-hole, SMT, solder fortification, solder paste, solder preforms
[Permanent Link to this Paper ]
Posted on 11 Apr 2011
by Dr. Ronald C. Lasky , Carol Gowans
As early as the 1990s, people were predicting the end of through-hole components, but they are alive and well with the numbers of dual in-line packages (DIPs) and connectors still measured in the tens of billions per year. Many of these components are assembled by wave soldering; however, in mixed technology (SMT and through-hole on the same board) where the through-hole count is low, it is often advantageous to consider selective soldering or the pin-in-paste process (PIP). PIP is a process in which solder paste is printed over or near the PWB through-holes. The through-hole components are then placed and the solder joint is formed during the reflow process. PIP has the advantage of eliminating the wave soldering process step. In many cases it is difficult to print enough solder paste to make an acceptable through-hole solder joint. Solder preforms were developed to meet this need.
These solder preforms are typically shaped in the form of 0402, 0603, or 0805 passive components. The preforms are placed on the appropriate printed solder paste deposit by a component placement machine. Preforms come in tape & reel packaging.
Today solder preforms are also used in other “solder starved” applications such as radio frequency (RF) shields, connectors, and under QFN thermal pads. In all cases, the extra solder delivered by the preform is vital to the reliability of the assembled product.
In this paper, process, design, and assembly methods for solder fortification using preforms will be discussed. Four successful solder fortification examples will be presented along with the associated defect reductions.
solder preforms, pin-in-paste, solder fortification, solder starvation, mobile phone shields, QFN packages, flux
[Permanent Link to this Paper ]
Posted on 14 Oct 2011
by Karl Pfluke , Richard H. Short
The advent of Lead-Free Soldering presents many manufacturers with the need to Wave Solder using
Lead-Free Alloys . These alloys melt and are soldered at temperatures well above conventional SNPB processing temperatures. This creates several well-documented problems. This article offers a proven and practical alternative to the Lead-Free Wave Soldering Process.
lead-free, wave solder flux, pb-free, Rework, solder preforms, solder paste, solder reliability
[Permanent Link to this Paper ]
Posted on 1 Jan 2009
by Karl Pfluke , Richard H. Short
German version of Eliminate Lead-free Wave Soldering.
lead-free, wave solder flux, German language, pb-free, Rework, solder preforms, solder paste, solder reliability
[Permanent Link to this Paper ]
Posted on 1 Jan 2009
by Amanda Hartnett , Daniel Evans Jr., Don Beck, Seth Homer
High-power semiconductor devices, such as high-brightness LEDs, must be mounted using a robust die-attach material that can handle the temperature fluctuations generated by the chip and mechanical stresses due to CTE mismatches between the die material and substrate to which it is mounted. The selected material must also comply with current legislation, which restricts manufactured products containing numerous materials due to environmental concerns, including some that were historically popular in this application. Eutectic gold-tin (AuSn) materials meet these requirements, and process recommendations for their implementation will be presented.
Utilizing Palomar Technologies’ die bonder, AuSn solder preforms and solder paste will be placed/dispensed and reflowed using a Pulse Heat System (PHS). Evaluation methods comparing these means of eutectic die-attach to a pre- plated AuSn die will be discussed. Technical generalizations will be detailed to explain the derivation of test method as well as hypotheses of results.
gold-tin solder, LED, die bonder, solder preforms, solder paste, automated pick-and-place, eutectic die-attach, solder spread
[Permanent Link to this Paper ]
Posted on 14 Oct 2011
by Seth Homer , Dr. Ronald C. Lasky
According to Prismark Partners, the use of quad-flat no-leads (QFNs) is growing faster than any package type except for flip-chip CSPs. Prismark projects that by 2013, 32.6 billion QFNs will be assembled worldwide, which represents 15% of all IC packages.
However, QFNs can be a challenge to assemble, especially when it comes to voiding. In most QFN assembly processes, solder paste is used as a means of attachment. This approach can be problematic, as excessive voiding often occurs due to the lack of standoff on the component and the high flux content of the paste. The addition of a solder preform can reduce such voiding by increasing the solder volume of the joint without adding flux volume.
Adding preforms to an assembly process is very easy. Preforms are packaged in tape & reel for easy placement by standard pick and place machines, right next to your components. The focus of this paper will quantify the preform requirements and process adjustments needed to use preforms in a standard SMT process. In addition, experimental data showing void reduction using preforms will also be presented.
Apex 2012, solder preforms, flux, QFN packages
[Permanent Link to this Paper ]
Posted on 14 Oct 2011
by Steve Buerki, Amanda Hartnett
Paper Interview
Process and Reliability Advantages of AuSn Eutectic Die-Attach
This video requires Adobe Flash Player to play correctly. Download the player for free .
High-power semiconductor devices must be mounted using a robust die-attach material that can handle the temperature fluctuations generated by the chip and mechanical stresses due to CTE mismatches between the die material and the substrate it is mounted to. Traditionally, various die-attach products, such as metal-filled conductive epoxies, high lead-containing solders, and gold-silicon solders, have been sufficient to mount the chip and have it perform reliably for the life of the device it operates. However, the trend toward increasing heat generation, the demand for compact devices, the enactment of RoHS and REACH legislation, and the transition to GaAs chips, limit the use of conventional materials. The demand for high reliability in power devices, in light of these industry trends, has led engineers to evaluate various new materials for their die-attachment.
The use of a high temperature solder preform is proposed and demonstrated for use as a die-attach material in high power devices. The suggested solder preforms are eutectic gold-tin and may be implemented for high volume or lab quantity adoption using a Palomar Technologies’ die bonder. This equipment is capable of handling the complete die-attach process, including high-accuracy pick-and-place of substrates, eutectic gold-tin preforms, and components; eutectic die-attach; and pulsed-heat reflow using a computer controlled Pulse Heat Stage (PHS). Each of these steps is precisely controlled to offer a near void-free eutectic die-attach between the device and its substrate. This is critical for thermal and electrical stability in high power applications. When the substrates, preforms, and components are supplied in high volume packaging, the assembly line can be fully automated, which enables a reduction in the cost of ownership and improves process yields.
Assembly applications suited for this process include, but are not limited to, high-brightness LEDs, power amplifiers, LASER diodes, VCSELS, lid attach, MEMS, RF packages, IGBT modules and wafer scale packaging.
wafer scale packaging, pb-free, eutectic die-attach, automated pick-and-place, solder preforms, die bonder, AuSn solder
[Permanent Link to this Paper ]
Posted on 5 Nov 2009
by Paul Socha
Paul A. Socha, Indium Corporation, reviews the types of solder preforms and their uses. He offers 10 basic steps to determining if an assembly needs preforms. Solder preforms can be used on a mixed SMT and through-hole PCB or to fortify solder paste on a difficult joint. Most solder preforms can be flux coated. When incorporating preforms, be sure to consider possible effects on reflow, cleaning, and RoHS compliance.
solder preforms, solder paste, SMT, PCB assembly, through-hole, solder fortification
[Permanent Link to this Paper ]
Posted on 9 Mar 2010
by Karl Pfluke , Dr. Ronald C. Lasky , Ross B. Berntson
Surface mount assembly has dominated its through-hole predecessor since the early 1990s. The higher density and lower ultimate cost of SMT makes it a preferred assembly technology. However, the mechanical strength of through-hole connections continues to make through-hole the technology of choice in assembling connectors. This presentation will describe the primary methods currently used for through-hole connector assembly: 1) selective wave solder, 2) pin-in-paste (PIP)i reflow, 3) hand soldering and 4) solder preforms. We will show how solder preforms are an excellent alternative when PIP provides insufficient solder.
The wave solder method requires specialized equipment and processes to solder connectors. Pin-in- paste reflow evolved as a way to accomplish through-hole assembly without additional equipment or process steps. In the PIP method, the additional solder required to fill the though-hole barrel is deposited by overprinting the pad in the area of each connector pin, using standard SMT equipment. During reflow, the solder wicks to each pin forming the solder fillet.
This paper explains why pin-through-paste reflow methods based on overprinting solder paste have become more challenging due to an increasing use of Organic Solderability Preservative (OSP), fine- feature devices (e.g. fine pitch connectors) and densely populated PCB layout designs that conflict with requirements for successful use of step-stencils. This paper also shows an example where solder preforms were used to provide extra solder volume for each pin. This work demonstrates how solder preforms provide a viable manufacturing solution to ensure complete through-hole solder joints.
lead-free, pb-free, through-hole connectors, selective wave soldering, mixed technology, intrusive reflow, pin-in-paste, solder preforms
[Permanent Link to this Paper ]
Posted on 1 Jan 2009
