Solder Preform

• High thermal conductivity (33W/mK)
• Higher melting point than SAC alloys (221C)
• Low tensile stress, so suitable for large die (5800psi)
• Excellent thermal cycling properties (-55 to 125C)

1.  Preform (a specially-shaped solder piece) with TACflux® used to hold the preform and die in place
2.  Solder paste, which holds the die in place with no extra materials added 
3.  Soft solder die-attach wire, a fluxless type of solder wire, which is melted onto the substrate metallization under an inert cover gas, and the die directly mounted onto the molten solder pool, then allowed to cool.

上来扫尘了！前段时间生了个大胖小子，所以从怀孕到破腹产，见识了很多美国先进的医疗器械，联系到平时销售工作中了解到的客户成品，有些感慨“原来成品长这个摸样, 是这样使用的”！幸运也好，或是有些“不幸”吧，成品用在了我身上。

在电子制造加工行业(Electronic Assembling Industry)，亚洲很多工厂都是在做high volume, low mix 的产品，特别是computers, consumer devices & communication发面。 美国和西欧的工厂，更多是做high mix, low volume, 比如说医疗器械。

医疗器械的产品，直接涉及到生命安全，而且大部分都是long life span的，所以对可靠性(reliability)的要求十分高。 这也使很多加工医疗器械产品的工厂对焊接材料的选择和测试要求很严格，特别是对焊锡膏(solder paste)。

大件的没有和人体直接接触的医疗器械板子，很多都还是在用有铅SnPb焊接材料，比如说我这次生产前使用的超声波测试仪，监视宝宝心跳和我宫缩的测试仪，都应该还是有铅板子。不过很多医疗器械的客户们都在密切关注着2014年RoHS2对这方面的要求；客户们也在密切做准备，评估无铅材料，来应对届时的变化需求。

和人体有直接接触的医疗器械，很多都已经是无铅了。 前段时间有个客户生产一种一次性心跳读数器heart rate reading device，板子的形状像一个很小的婴儿鞋子，只有成人手掌的1/4大小左右，而且十分薄。当时就使用了我们的SAC305 焊锡膏和solder preforms (预成型焊片)。据说这种携带型小仪器可以扣在衣服上读病人的心跳，读出的数据直接通过wi-fi传送到医院的数据中心进入系统；医生和医院就可以随时随地远程收集病人的数据……

世界人口在不断地增多，也在不断地老龄化(aging population)，这使对医疗器械的需要在增加。这应该是一个有前景的大行业，也希望大家都能享受到这些科技进步带来的便利，益寿连年。

Cheers!



Pic: Google Image

PS: 还是那句我喜欢的话“生命在于运动（一下）”。和身边很多孕妇朋友相比，我才发现原来自己从小坚持和热爱运动在怀孕和生产过程中帮了那么大忙，生之前那一天我妈妈还在感慨说我走路一小时都还是健步如飞的，哈哈：-）

Recent test results show that solder fluxes handle high reflow temperatures (>450°C), providing better-than-expected visual results of flux residue!  

Solder fluxes have not traditionally been used with AuSn, AuGe, or AuSi eutectic solder, because their peak reflow temperatures were very close to or above the flux activation range. An average flux activates at approximately 125°C and is not recommended for temperatures in excess of 350°C. Although AuSn solder melts at 280°C, peak reflow temperatures are recommended to be >300°C, nearing the maximum suggested temperature of flux. AuGe and AuSi alloys melt at 356°C and 363°C respectively, which exceed the documented flux activation range.

Since these alloys contain ≥80% gold and are resistant to oxidation, flux is not always necessary. Other methods have conventionally replaced the flux function, such as mechanical scrubbing, or forming gas purging. If these technologies are not available, or assembly speed is priority though, a flux may be required.

So I, along with my fellow engineer, Brandon Judd, sought out to test some of our best fluxes with Au alloys at these high temperatures. The result: Not all, but a few of these fluxes work extremely well up to temperatures as high as 450°C!!!

The reflow profiles used tested the extreme abilities of our fluxes:

·         Peak temperature 410°C

·         Nitrogen Purge

·         Time above liquidus: 137 seconds

·         80AuSn solder preforms 0.249” square x 0.002”

Some fluxes did what we expected- they charred and burned. They simply were not designed for this environment. 

Others, such as our TacFlux010® were very resilient at these temperatures. 

For more information about these test results, please contact myself or Brandon.

Happy Testing!!

Amanda

Solder starvation

• weak solder joint strength
• open solder joints
• intermittent short circuits
• reduced first-pass yields
• increased inspection
• increased rework
• field failures
• damage to your company's brand & image
• reduced sales and profits

• The single-thickness stencil is designed for the majority of smaller components, starving the few larger components of solder volume.
• High-use interfaces, such as connectors and USB ports, require extra solder - to assure their solder joints survive the constant use in the field.
• Smaller, more tightly compacted circuit boards don't allow for deposition of enough solder paste.

• You can add solder just where you need it without overprinting solder paste or working with step stencils.
• Preforms deliver precise, repeatable volumes of solder.
• Preforms can be added during your existing SMT process with existing pick & place equipment.
• Preforms eliminate the need for rework or hand soldering at the end of the process.

Power amplifiers and transistors come in many shapes and sizes. The performance requirements vary as well. Attaching them can be a critical aspect of your design.

Both Pb and Pb-free alloys can be manufactured as a solder preform with a flux coating.(Learn more)  Selecting the right alloy and flux coating can be crucial to meeting your void criteria.  

A high-tech SOLDERING solution might include NanoFoil®, which effects a solder joint while minimizing heat exposure to your components.

There are also thermal interface materials such as the HEAT-SPRING® which utilize the unique properties of indium to create a superior thermal connection, similar to a solder joint.

There are many different attachment methods available, contact me with your design parameters and we can find your solution.  

Folks,

Many people have been infatuated by the price of gold in recent months, but the price of silver has also skyrocketed. In 2000 silver was about $3.00 per troy oz. In the eight years that followed, its price grew to $15/oz. Today it is trading at over $41/oz! This price is almost an all time high, except for the time when the Hunt brothers tried to corner the silver market in 1980. The aberration of their efforts jolted the silver price to just short of $50/oz, but it settled down to $11 or so after the Hunts came under margin call and other pressures.

Unfortunately, the dramatic price increase today, does not appear to be an aberration. Although we may hope that it will soon drop to more historic levels, we may not have reason to expect that it will.

Although not as dramatic, tin and copper have experienced significant prices increases as well. The price of tin has doubled in the last year to $15/pound and copper has increased from about $3/lb to $4.50.  These metals are obviously key ingredients in critical electronic materials such as solder pastes, solder bar, and solder preforms.

In addition, oil, which is used for most organic electronic materials such as PWB resins, flip chip underfill, and epoxy fluxes, has increased to $110/bbl - approaching its all time high of $145/bbl.

All of these price increases have a significant impact on the electronic materials supply chain. Although we are used to price decreases in the cost of our mobile phones and PCs, at this point in time, the price of the materials that go into these devices will be increasing.

As one materials supply chain executive commented at APEX, “It’s not like we can be clever and somehow work around the price increase of silver and these other materials, we have to pass it on to our customer, or go out of business.”

At the time of writing, the price of silver (Ag) was approaching the USD$50/tr.oz. (Troy ounce) level, and threatening to go higher. With 1 Troy ounce being 31.1grams, this makes the cost of pure silver ingot close to USD$1.60/gram.

Image from goldsilveroz.com

Materials costs are therefore a major consideration for anyone using silver in any form. Naturally, we are now seeing a few Power Semiconductor packaging houses evaluating the possibility of moving away from silver-filled epoxies for die-attach. The alternatives they are considering include the adoption of solder paste (or solder in some other form: wire / ribbon / preforms) versus a silver-filled epoxy.

Here are some thoughts on the Power Semiconductor assembly pros and cons, based on using solder paste as an alternative to silver-filled epoxies.

Good news (+)

+   Reduced materials costs
+   Improved pot-life / shelf-life *
+   Improved high temperature thermal-cycling
+   Strong, metallurgical joint formed between leadframe (substrate) / joining material / die
+   Improved thermal conductivity
+   Faster throughput (more units per hour, UPH)**
+   Easy clean-up ***
+   Does not wick onto NiPd surface to cause poor wire bondability

 * Although it is true that solder pastes are stored under refrigerated conditions, they do not require the -40C storage that is typical of silver-filled epoxies. 

 ** The dispense of solder paste is very rapid and can be done using multi-dot dispense heads. It undergoes rapid temperature reflow, versus the slow cure needed for metal-filled epoxies, which can be up to typically 1-3 hours, depending on the volume of silver epoxy.

 *** Because the solder paste flux does not cure like a polymeric material,  tubing and other conduits for the solder paste are easily cleaned out using common solvents, or can be simply purged with flux.


  ==================

Bad news (-)

-   Capital costs #
-   Adoption time / new process learning ##
-   Needs a solderable die surface
-   Voiding increase ####

 # The main cost-drivers here are:

- Reflow: Specialty reflow equipment is required for high temperature solders, such as
Heller or BTU reflow ovens

- Cleaning: If wirebonding is required after the reflow process, standard cleaning equipment and cleaning chemistry (aqueous or solvent-based) will be needed to remove flux residues

- Gas: Forming gas (H2/N2) or simple nitrogen may be needed to assist reflow.

Note that increasingly, for clip-bonding (non-wirebonding) applications using the new ultralow residue solder paste Indium9.32, even cleaning may not be needed, as the residue has been found to be compatible with compatible with a number of molding compounds in the industry.

 ## By partnering with a company like Indium Corporation with many years of experience in die-attach soldering, the ramp-up time can be significantly reduced.

 ### A solderable surface is usually a sequence of Ti / Ni / (Ag or Au) plated layers. The thickness of the silver (Ag) or gold (Au) precious metal layer is usually limited to 100nm (0.1microns). Compare this to a standard silver-epoxy bond line thickness (BLT) of 0.5-2mils (12-50microns).

 #### Acceptable voiding of less than 5% of the total die area is fairly easily achieved with good quality substrates and die-finishes.

  ==================

In closing, I am indebted to my friend and colleague Sehar Samiappan (Indium Corporation Area Technical Manager - South East Asia) for his insights.

Contact me to discuss this further.

Cheers!   Andy

Folks,

It was Wednesday evening and I had just finished a brief pitch on applications of SPC  to a group of twenty. I was followed by Jim Hall,  he spoke of process mapping using SIPOC.  So did these folks have solder paste under their fingernails, or wave solder flux stains on their shirts, or, perhaps, a solder preform or two stuck in their pant leg cuff? None of these souls would have had any of this type of trace evidence of electronic assembly on their person. You see, they were all medical doctors and students at Harvard’s  famed medical school.   (I hope it is OK that the proud dad shares that my daughter Jessica is a colleague of these folks.)

Jim and I were presenting to the doctors, because they are interested in process optimization in the healthcare industry. The event was hosted by Dr. Andy Ellner.  He is a professor and doctor at the medical school and is a focal point for these process improvement efforts. I was introduced to him in the summer of 2009 by Dartmouth’s  new President Jim Kim. 

In November of 2009, Jim Hall, our colleague Larry Parah, and I facilitated Andy’s team in dramatically improving the prescription refill process in Brigham and Women’s Hospital Clinic.  Jim and I plan on working with Andy in similar efforts over the next year or two.

The most striking thing that Jim and I left with on Wednesday evening was how profoundly interested these doctors and students were in healthcare process optimization. The Q&A session lasted nearly an hour.

Ah, yes, would that our many colleagues in electronic assembly were as interested in optimizing their processes!

Integrated® Preforms are connected units of solder that can be placed in an application to provide the sole solder for the joint. They can also be used to add to the volume of solder, when used in conjunction with solder paste - to fortify the joint. Integrated Preforms are available in most alloys that are currently incorporated in common solder pastes.

The only difference between connected preforms and separate preforms is that the Integrated (connected) Preforms are attached to one another and can be placed in the application as one multiple unit of solder. Connecting each individual solder preform is a small strand of solder that is designed so narrow that it will separate during reflow (to prevent bridging).

When manually reworking boards to add additional solder to joints becomes too large of a task, Integrated Preforms can be incorporated prior to reflow so any rework is not necessary. In through-hole applications, the connected preform can be placed on the component and then inserted into the holes of the board that have solder paste placed on top of them. There is no need to flux the Integrated Preform because the flux vehicle in the paste will provide the fluxing.

When used as a stand-alone connected preform, or with solder paste to fortify the joint, Integrated Preforms can be reflowed using the same temperatures and profiles as for the paste by itself.

To learn more about Integrated Preforms and solder fortification, plan to attend the presentation of a paper on this topic at Apex 2011 (Las Vegas, NV, 10-14 April) given by Dr. Ronald C. Lasky (see sidebar →), Indium Corporation Sr. Technologist and Instructional Professor, Thayer School of Engineering, Dartmouth College.

The next post in this series will address the various shapes of Integrated Preforms and how they are packaged.

Low and ultralow alpha-emitting semiconductor assembly materials are now essential for flip-chip packaging and are also becoming increasingly critical for power semiconductor assembly, as smaller active device sizes and thinner wafers increase the devices' sensitivity to ionizing radiation.



An alpha particle is an ionized particle consisting of 2 neutrons and 2 protons emitted spontaneously from the nucleus of specific isotopes of certain high atomic weight  elements. Of particular interest and concern to semiconductor fabricators and packaging houses are the elements uranium (U) and thorium (Th), isotopes of which decay to give stable isotopes of lead (Pb), but which, by decaying, give rise to alpha particles.

For over a year now, we have been supplying low alpha (LA) and ultralow alpha (ULA) emitting solder pastes to Asian customers. During this time, we have faced numerous challenges: most importantly:

-        The absence of standards in the area of measurement and test methodology

-        Metrology at the ultralow alpha level is hampered by a signal to noise ratio of about 1:1, where the “noise” is simple background radiation, present at around the 0.002cph/cm2 level.

Even the definitions of the different levels are not well defined, but we are operating under the working rule that:

-        LA =< 0.020cph/cm2

-        ULA =< 0.0020cph/cm2

I had the opportunity to discuss our work at the latest Second Annual IEEE-SCV Soft Error Rate (SER) Workshop in late October this year - please follow the link to learn more -  and I’d like to thank Peng Su of Cisco for giving me the opportunity to speak at this meeting. Also look for the forthcoming (at time of writing) review paper “Challenges in Supply of Ultralow Alpha-Emitting Solder Materials” by me and Olivier Lauzeral of iROC Technologies in Chip Scale Review magazine for November/December 2010.

In the coming months, Indium Corporation will be providing LA and ULA solder alloy, preform, solder powder, solder paste and flux materials.

Cheers! Andy

Spending back-to-back weeks at two electronics assembly trade shows is a unique experience, to me.

First up was SMTAI in Orlando, FL where I helped present a paper on Solder Fortification Preforms. 

How does one "help" present a paper?  Have you ever listened to a great paper and then, at the end, seen so many people rush around the speaker that no one can get a chance to make a further connection?  My role was to be available as an additional resource for answering questions after the presentation.

The second show was IMAPS 2010 in Raleigh, NC.  This is one of the best showcases for our Engineered Solder Materials.

There are many facets to the trade show experience. 

• There is the booth, which has to have the right message and the right pictures to draw the right people in. Our message is "From One Engineer to Another". Most of our staff IS engineers. Our team is extremely knowledgeable about materials and assembly processes.  We provide the best service when we are talking with Process or Design Engineers that need our soldering or bonding expertise.   
• There are the technical presentations, as mentioned above.
• There is the networking with industry leaders.  Being able to visit a variety of complimentary suppliers and discussing topics we have in common is tremendously valuable.

Even in the face of the myriad technology devices that keep us connected 24 hours a day, there is still nothing like that face-to-face experience.  The IMAPS Global Business Council presented two speakers during the show: one from DuPont and one from Dow.  One of them (I am sorry I can't remember which one) stated the overwhelming importance of getting their Application Engineering staff into the field to work face-to-face with customers.  

So if you want to more about what we know, check out our blogs.  When you see something you like or want to know more about, call us or email us.  We are glad to work with you!

And if you want to hear another viewpoint on trade shows, check out Andy Mackie's blog.

This is my second post on the implications of using aluminum silicon carbide (AlSiC) metal matrix composite materials as the heat spreader, heat sink, or TEC medium for thermal dissipation. Previously, I described how the CTE of an AlSiC substrate could be altered for matching mating surfaces based on the amount of SiC filler used.

These mating surfaces are assumed to be bonded via a solder bond. That begs the question, “Can AlSiC be soldered directly? Is the aluminum metal filler free and in great enough density to provide for metallic surface bonding?”

In order to be sure of this answer, I went to another AlSiC materials expert, Tom Sleasman, business manager at Rogers Corporation. Rogers Corporation offers a new, special AlSiC variety with an aluminum skin (AlSic-D3), which I thought would have the best solderability of any of these materials, if that was even possible.

 Unfortunately, Tom’s response was, “We do not recommend soldering directly to the AlSiC for the same reasons as to aluminum. Our process yields a part with an Aluminum rich skin on the outside of the part and in all cases [where the AlSiC is soldered] I am aware of utilizing a nickel plating or copper coating process to provide a solderable surface.”

I cannot speak directly to soldering these new aluminum skin AlSiC materials, however soldering to aluminum is a difficult process, which cannot be accomplished without the appropriate flux. That flux is typically acid-based and offered only as a stand-alone product, not as a solder paste or preform flux coating. 

Based on Tom’s remarks, I conclude that the best way to solder AlSiC is to have it pre-coated with an oxide-resistant metal, such as nickel or copper. Regular AlSiC substrates cannot be soldered without this surface treatment.   

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

PS: 最近在做某大客戶的生意，其中有一個性格爽朗的活躍女工程師K引起了我的注意。她看樣子就像剛PhD畢業參加工作的女孩子。後來客戶中了解這位工程師的好友L告訴我，K其實已經30多嵗了；18嵗時在某囯嫁給了36嵗的男人，漂亡來美國這個異國它鄉，先後生下兩個孩子。因爲前夫對她不好，K忍無可忍終于離婚了，但是前夫一直以來不讓她有探望孩子的權利，更別説照料了。K在美國，先後讀完了本科，碩士和博士；現在在好公司有份好工作，並且每天都努力地工作著。現在K也有了一個相處4年多的穩定男朋友了……聼完K的故事，讓我肅然起敬。從K開懷的笑聲中，外人全然看不出來她有這種痛苦的過去! 一個不對困境地頭，對生活充滿了熱情，對未來充滿期望並為之奮鬥的可貴靈魂！

In the surface mount technology (SMT) electronics and semiconductor packaging industries, Indium Corporation has a reputation for offering custom solutions.  In the world of solar cell manufacturing, I hope that same status is obvious.  I feel custom solutions are even MORE important in emerging technology fields like CIGS cell manufacturing.  Being the leading global supplier of indium (the metal), and a supplier of unique solder alloy shape/size/tolerance forms, we are well equipped to offer you evaporation sources that are tailored to your application.  Sure, we can supply round shot, teardrop shot, wire, ingot, preforms, and various other bulk forms of solder to keep your evaporation chamber filled.  Did you know we can also make custom solder castings to fit your particular crucible?  The process is easy, let us know if you are interested!

(Just click here to get started)