Indium Corporation Blogs

It seems like a fairly simple thing to do.  What could be difficult about soldering a wire to a pad? 

Well, I hear three common complaints and expressions of frustration:

POSITIONING: Typically, in this process, a soldering iron is used. The first problem arises from trying to hold onto the soldering iron AND the wire to be joined to the prefluxed pad AND the solid-core solder wire you are using.  An extra hand would be nice! Some people use a system of fixtures or clips to hold the wire and the pad in the appropriate position. (see image and link, below)*.

COLD SOLDER JOINT: Another common complaint is that, after soldering, the wire easily pulls out of the solder joint.  This is due to the poor wetting of the solder to the wire and the pad - it never really "soldered".  A solution that I share is to pretin both the pad and the wire with the solder, using a flux.  To pretin the wire, I suggest melting some of the solder in a crucible or solder pot.  Dip the wire in the flux and then into the molten solder.  A teardrop should form on the end of the wire.  It can also be pretinned using the soldering iron. Next, pretin the pad. Both pretinned surfaces will have a coating of post-reflow flux residue.  If required, this residue can easily be removed using a suitable solvent.  Now that you have pretinned both surfaces, the pad should be heated with the soldering iron and, when the proper temperature is reached, the pretinned wire should be pressed to the pretinned pad.  The solder on both the pad and the wire will melt together and, when the heat is removed, the joint will be formed.  Usually this can be accomplished without adding additional flux.

INCONSISTENT VOLUME: A third issue is that the volume of solder in the joint is not uniform from piece to piece. If this is your concern, consider using a flux-coated solder preform. They can be produced with the exact solder volume, and the precise dimensions to fit onto the wire you are joining to the pad.  Similar to the process described above, when the pad and the wire are heated, the flux will be activated (removing the oxides) and the solder preform will melt, forming a consistent and perfect solder joint.

Please contact our technical support group with any questions you may have.  We are always ready to help you solve your soldering problem, whether it is large or small.

For more background, read these blog posts on hand soldering:

• soldering iron tip temperature
• hand soldering flux selection
• hand soldering tech support
• the importance of a clean soldering iron tip

 

Paul Socha

 

*Image: Harbor Freight sells a product called "Helping Hands" for (US) $6.99, as of this writing. Other companies offer similar products. Consider buying more clamps to hold the wire in place, freeing you to hold only the solder wire and the soldering iron.

It won't be long until we in the northern hemisphere are complaining about the snow and the cold, but right now, it is all about the heat! 

In particular about the heat that is needed to reflow high melting point (HMP) alloys.  These are generally high-Pb alloys that see very high operational temperatures. They are used for applications such as automotive under-hood or down-hole drilling equipment .

If you try and use a flux that is not formulated to withstand higher (greater than 220C) temperatures, your flux will burn off and char and never get a chance to really do its job.

So, the key is to use a flux that is specially formulated to activate at higher temperatures, like our 807HMP used in our flux cored wire.  It is ROL1 but has only 650 PPM of halogens.    (AUTHOR'S NOTE: After further testing via oxygen bomb, the flux classification for the CW-807 has been found to be ROL0. Added 11 June 2013).

You may also want to consider an alloy with a small amount of indium in it (such as Indalloy #164 which is 92.5Pb 5.0In 2.5Ag) since indium is well known for its thermal fatigue resistance.  This alloy works very well with the 807HMP.

Choosing the right alloy and the right flux are key to keeping your cool!

Carol

Folks,

Let's look in on Patty and her colleagues......

Sam Watkins, ACME New Hampshire site GM, had just finished meeting with his boss, ACME CEO Mike Madigan. He was embarrassed that these meetings always stressed him; Mike was an intimidating character. Still, why should he be nervous? Things were going really well. Profits were up at all sites since NMAC/I/O was implemented as their new profitability metric. Patty Coleman, who suggested this metric, visited all of the ACME sites with weaker NMAC/I/O and profits, and, after performing process audits, helped these sites get their acts together. Oh, and we can’t forget Pete Ortiz, who works for Patty. They seemed to have a terrific synergistic relationship. He was an integral part of this success story.

Sam started writing an email to Patty. He and Mike concluded that, building on the recent NMAC/I/O success, they need to make ACME a “copy exactly” company. They agreed that if they were implementing a copy exactly strategy they should do it with the most cost effective assembly equipment and materials. It seemed to both of them that that the lowest “cost of ownership” should be the most important metric in this strategy. Sam finished his note to Patty asking (ordering) her to implement this strategy. She was to present a plan to achieve this goal to Sam and Mike in 6 weeks. Her presentation was to include the recommended equipment and materials, a phase-in plan, the budget needed to achieve the goal, and the projected ROI of the endeavor.

Patty was in her office having lunch while reading Golf Digest and USA Today. She looked up at her laptop screen and saw Sam's email. Reading it energized her. She was happiest when working on a significant project. After digesting the contents she thought she would call The Professor and ask his advice. Sam and Mike had insisted that she put The Professor on a retainer as he had added so much value to ACME. Patty had to chuckle, it was hard to get him to send in his bill; he seemed little motivated by money.

The Professor would never tell her how many languages he spoke, so she was going to try a little French on him.  She and Rob had been studying it at home.

“Bonjour Professeur, comment ca va?” Patty cheerfully said as The Professor answered the phone.

“Très bien Patty. Comment sont Rob et vos fils? Ma femme et moi avons été inquiets au sujet de Rob. Est-ce le dos guérit bien?” The Professor replied with a Parisian accent. (Very well Patty. How are Rob and your sons? My wife and I have been worried about Rob. Is his back healing well?)

Patty sighed and thought, “Well that makes about 10 languages I have verified so far.”

“Rob is doing quite well. Word got around and my Lean Six Sigma Green Belt instructor, Jim Hall called and shared his thoughts with me about over doing it in exercise programs. Jim is a fitness instructor and a big believer in moderate exercise. Rob has promised me to tone it down a lot,” Patty answered.

“I’m relieved,” said The Professor, “Rob needs to be healthy to keep up with your sons.”

“But, I imagine you have some business to discuss,” the Professor went right to the point.

“Yes, Sam and Mike want me to head up implementing a copy exactly program with equipment and materials, and they are strongly suggesting that the equipment and materials have the lowest cost of ownership,” Patty summarized.

“Copy exactly can be very beneficial, if the materials and equipment are good choices,” The Professor answered thoughtfully.

“But I have real problems with ‘Lowest Cost of Ownership.’ It is a good metric to compare something like automobiles, but to compare equipment or materials that are used to generate a profit it can be misused.” he replied.

Patty felt she understood where he was going, but wanted to hear it from him.

“Can you give an example?” she asked.

The Professor answered, “Let’s say a man mow lawns for a living. He considers two lawn mowers for his business, one is a push mower that cuts a 20 inch path and costs $300. Assume he takes 3 years to pay off the loan to buy it. Maintenance is $150 per year and fuel is $1200 for a 30 week season. The other is a sit down lawn mower that costs $3000, with $500 maintenance per year and it uses $3,000 in fuel per year. It cuts a 50 inch path. Which has the lower ‘Cost of Ownership?’”

“That’s easy,” Patty said, “the 20 inch push mower.” “But clearly the lowest cost of ownership is meaningless,” she went on.

“Explain,” replied the professor.

Patty answered, “Well, the man is in business to optimize profit. Clearly he can mow more laws with the sit down mower. Let’s say with the push mower he can do 4 lawns a day and with the sit down mower he can do 10 lawns a day. We can also assume he gets $35 per lawn. So, for a New Hampshire 30-week lawn mowing year, he earns 4x7x30x$35 = $29,400 with the push mower and 10x7x30x$35 = $73,500 with the sit down mower. Let me make a spreadsheet to determine the profit in each case.”

Patty was one of those young people who could type so fast that it made The Professor’s head spin. In seconds she had a spreadsheet developed.

“Wow, with the push mower he only makes $27,950 and with the riding mower he makes $69,000!” Patty exclaimed.

“And the same is true in electronics assembly. The best equipment, solder paste, solder preforms, underfill, cored solder wire, and solder fluxes are the ones that help your company make the most profit. Not the ones that have the ‘lowest cost of ownership,’” The Professor summed up.

To be continued.....

Cheers,

Dr. Ron

image

Solder wire is generally used for manual soldering operations, including rework.  But, it can also be used in automated applications such as die-attach soldering.  Solder wire can be flux-cored, or solid with a separate flux used.

Each application can have different requirements for the wire.  For example, wire used in die-attach applications needs tight dimensional tolerances to insure an exact, repeatable amount of solder is deposited each time.  Reduced oxides are also critical to eliminate any "splattering" of the molten solder during the deposition process.

Wire can also be used for non-soldering applications. For example, indium (and indium alloys) wire are often used as a sealing material (particularly in cryogenic sealing applications) - more here) and as a thermal interface / management material.

Decades ago, 0.030" (0.76mm) diameter was the standard size, but today we are able to produce diameters as small as 0.001" (0.025mm) in tin silver (Sn Ag), tin silver copper (SAC) and gold tin (Au Sn) alloys.  Considering that a human hair is about 4X that size, that is a very small diameter!  Pure indium wire is limited to 0.010" (0.254mm), but alloys containing indium can be produced smaller than that.

The wide variety of diameters available in Au Sn make this alloy ideal for the complex applications in medical, aerospace, and other high reliability applications.  However, the Sn Ag and the Sn Ag Cu are used across a variety of standard applications that require lead-free materials.  Sn Ag is particularly good in soldering to Nitinol.

At first look, wire seems like a pretty simple product.  But specifying the right alloy, diameter, tolerances, and packaging can make all the difference.  It can help you achieve a repeatable process that gives you high yields, strong solder joints, and enhanced profitability.  For further information - contact me.

Carol Gowans

Jon major recently joined the Indium Corporation as a Product Manager for Solar back-end assembly products. I greeted him with this impromptu interview.

Jim: First of all Jon, welcome. It’s great to have you as a new addition to the team!

 

Jon: Thank you Jim – it’s an exciting time to be at Indium Corporation and a fantastic time to be a part of the growing solar industry. I am extremely enthusiastic about my new position and am looking forward to making a positive contribution to the solar industry.

 

Jim: I noticed it didn’t take you long to get up to speed. Your time in Silicon Valley must have helped.

 

Jon: Coming from the electronics industry with a focus on product development, new product introduction, manufacturing, and external partner management, I am excited that my past experiences can contribute both to the industry and to Indium Corporation. After joining Indium only a few weeks ago, not only am I getting used to Upstate NY weather, but I have been immersing myself in solar with the goal of gaining a comprehensive understanding of:

 

•       Both rigid and thin-film technologies

•       Technology trends

•       Global and regional markets (EU, China, US, North America)

•       Solar supply chain (Silicon, wafers, cells, module, equipment, inverters, integrators)

•       Equipment manufacturers, contract manufacturers, and how we can collaborate with them to move the industry forward

•       Our products and pricing

•       Our current and future customers

•       Our short and long term opportunities

•       Our competition

•       Our roadmap

•       Our strengths, weaknesses, and threats

•       Our manufacturing capabilities and our QA process

•       Our sales channels, value proposition, key differentiators

•       All Indium processes

 

Jim: I know you've got solar products on your mind. Let our readers know a little bit more about your role here at Indium?

 

Jon: As a Solar Backend Product Manager I will focus (officially) on the business development and growth of Indium’s Solar Back End product offerings.  Now that sounds great but what does it actually mean? I could cut and paste my official job description but I prefer to explain it in my own words. As I think about the first part of that statement, “business development and growth…”, I see my role as:

 

–      Know the market, the customers, the product, and the competition

–      Develop relationships with the Indium team, reps, partners, equipment manufacturers, and, of course, customers

–      Write valuable data sheets, publications, and sales literature

–      Listen to our customers' needs and provide solutions

–      Manage schedules and orders with minimal surprises

–      Build cross-functional collaboration (sales, distribution, marketing, engineering, R&D, QA, production, management)

–      Never let down partners or customers

–      Support all functions of the organization, both internal and external

–      Deliver above & beyond commitments

–      Make great bets – on technology, customers, and opportunities

–      Understand the product life-cycle

–      Ship high quality, consistent product

 

The second part of that statement “..of Indium’s Solar Back End product offerings” is fairly straightforward. Of course this means I will focus on Indium’s current back end products (tabbing ribbon, bus ribbon, metallization paste (or as I prefer to call it – “grid ink”), flux and flux cored wire). With a product development background, this also means I have an opportunity to work with customers, partners, and R&D to develop and bring new products to market that will advance the module assembly industry – very exciting for me personally.

 

Ultimately, I think of my role as both building awareness of Indium’s products and superior technical support available to our customers as well as helping to shape our growing industry.

 

Jim: Okay Jon, you’ve had a while to settle in and get familiar with our Solar Team’s past and present – what are you planning for the future of module assembly?

 

Jon: Regarding the future of module assembly it’s a bit early to know for sure but I am excited about our low-temperature bismuth-containing alloys. These low temperature, lead-free, bismuth-containing alloys reduce the soldering process temperatures, thus reducing thermal stresses. I’m also working with the Indium production team to further reduce our tabbing and bus ribbon yield strength. A lower yield strength will reduce mechanical stress on cells during the assembly process. This is crucial to minimizing the possibility of microcracks and cell breakage during the solar module assembly process.

 

In closing, having lived in California for the last 10 years, I am not 100% familiar with our Upstate New York climate, and especially not all the snow shoveling. I see in my future a solar powered driveway heater!

 

Jon can be reached at jmajor@indium.com

The following is an example of how a simple procedure like cleaning a soldering iron tip can make a world of difference in the quality of a solder joint. Eric Bastow responded to a customer after doing some testing in the lab – and confirming that a clean iron tip contributes to a clean solder joint:

 

“As I mentioned in our conversation, I did not think that a flux coated preform would fare any worse than a cored wire in a hand soldering application where charring is concerned. Rosin is rosin is rosin, regardless of whether it is within a cored wire or coating a solder preform. I did a quick experiment to see what would happen.

 

Using a Weller WS80 soldering station, set to an abusively high temperature of 850F/455C, I soldered some .250” square x .005” thick Sn63 preforms (folded-up as small as I could do by hand), flux coated with 1% NC9, to a nickel metallized FR4 test coupon. The contact time of the iron to the solder was ~5 seconds. The results look pretty good. The charred flux that you do see is flux that burnt to the iron and was transferred to the solder from the previous preform. I would anticipate this sort of appearance with a flux cored wire, as well, used under these conditions. I believe that with frequent cleaning of the tip, the amount of unsightly flux residue with be minimal, especially if a more appropriate iron temperature were used.” -Eric

 

The bottom image is what happens when you don't clean a soldering iron tip.

Soldering Basics

I’m really excited about a new option for those of us who are prototyping solar assemblies or evaluating new tabbing ribbon materials. I’ve been waiting for something like this – everything you need to solder solar cells together in one package. The turn around time is key too – you may recall an older post where I learned how quickly these materials shipped.

 

On the website where these kits are offered, the description reads:

“Tabbing ribbon kits come with everything you need to evaluate how Indium Corporation materials will work with your solar cells and assembly process. The kits can be used to:
- Evaluate which tabbing ribbon size is best for your design
- Determine which flux is best for your operation
- Experiment with new solder coating alloys
- Assemble a few solar panels”

 

The tabbing ribbon kits come in 3 flavors:

- Standard Sn/Pb/Ag (62Sn/36Pb/2Ag)

- Pb-Free (96Sn/4Ag)

- Low Temp Pb-Free (58Bi/42Sn)

 

I have a feeling the Low Temp Pb-Free kits are really going to be the most popular of the 3 that are offered though. Application temperature ranges will determine which kit to use, but all three versions of the kits are said to offer similar base copper sizes and tolerances:
“The ribbon itself is industry standard CDA 110 (99.9% Cu) core flat wire, coated with a precisely controlled layer of solder. Each ribbon is manufactured using our proprietary softening process so you can increase the yield of your stringing process.” Basically, this means that the softer tabbing ribbon will help eliminate the breakage of thinned cells during the heating/cooling cycle.

It also includes some matching bus ribbon to complete your panel build. If you’re trying to find the right flux, this kit serves dually as a flux evaluation kit as well. The kit is loaded with VOC-Free flux, rosin-based flux, and resin-based tabbing fluxes. I prefer GS-5454 as a flux for most tabbing operations, but you can see how the others stack up as well.

 

Let me know how you like the kit after you try it out!

~Jim

(jhisert@indium.com)

Soldering through-hole connectors can be a tedious task.  Connector Specifier recently highlighted an article by principal engineer, Paul Socha discussing how connected preforms can be used to streamline the soldering process.

Many through-hole connectors can be hand soldered successfully using solid or flux cored wire.  Others are more difficult for reasons including long pins, thick boards, or difficult-to-reach connections.  Connected (integrated) preforms relieve these issues by supplying custom preforms to match the application.  

To read the article and to learn more about connected preforms and how to design them for your needs, visit Connector Specifier. 

How hot are you setting your solder iron for hand soldering using solder wire or preforms? If you are cranking up the solder iron temperature because you have transitioned to lead-free solders, think again.

For both Sn63 and SAC solders, the suggested hand soldering temperature is 315°C. Using this temperature, the solder iron tip temperature is significantly hotter than the liquidus temperature of either alloy, although there is a 34° C differential or more between the liquidus temperature of these two alloys.

Hand soldering relies on the thermal conduction of heat from the solder iron tip to a solder alloy, relying on Fourier's law for thermal transfer. The hot temperature of the solder iron tip will quickly rise the solder temperature to its melting temperature at this setting. If the solder iron tip temperature is set higher you can quickly lose control of the solder quality.

One of the biggest issues associated with high temperature hand soldering has more to do with the flux than the solder alloy. Most solder fluxes, regardless of form (liquid, tacky, or flux core) are designed to withstand temperatures up to 350°C. Above these temperatures, they begin to decompose and blacken.

Solder alloy oxidation is also an issue associated with high temperature hand soldering. As a solder is exposed to high temperatures, the rate it oxidizes increases. Fluxes aid to remove surface oxides, but at high soldering temperatures, fluxes are quickly exhausted.

For optimal solder results, keep the solder iron tip temperature low.