Citation
Ellis, B. (2005), "Internet commentary", Soldering & Surface Mount Technology, Vol. 17 No. 3. https://doi.org/10.1108/ssmt.2005.21917cag.001
Publisher
:Emerald Group Publishing Limited
Copyright © 2005, Emerald Group Publishing Limited
Internet commentary
Thou hast caused printing to be used...[1]
You’ll remember that in the last issue I commented on Mozilla Firefox, as a first class browser with many distinct advantages over Microsoft’s Internet Explorer. Today, I’ll chat with you about another new Mozilla product, Thunderbird. This is their latest e-mail client, which has equally distinct advantages over Outlook and Outlook Express. What is perhaps not very well known is that Microsoft has not been devoting much energy to the development of improvements to these softwares for several years, perhaps a little cosmetic touch here and there. This is probably one of the reasons why these e-mail clients are not very good in terms of internet security. Thunderbird is a horse of a different colour!
Let me be very frank from the start; Thunderbird is not perfect, but what software is? Whatever, it is a whole host better than anything else I have tried and the cost is attractive – free-of-charge, because it is an open source software, costing only the time to download it. If you wish to do so, it can be found at www.mozilla.org.
If we have a look at Figure 1, we can see that the Window has three boxes, by default (other configurations are possible). The left hand one gives a folder tree. In this case, I have mailboxes at different levels, all of which are filled automatically by my POPFile automatic classification system. In this example, I have one new message in the IPC TechNet mailbox and 26 spam messages that have gone into the Trash box (these can be viewed for checking before mass-deleting them).
Figure 1
Typical Mozilla Thunderbird layout, as an e-mail client reader. To send e-mails,
the left-hand box displays the address book, the top right one handles the
addressing and the bottom one is the space for typing the message
The top right-hand box shows the listing of messages in the selected mailbox. This may be organised in several different ways; here I have chosen to show it by thread. Underneath this, is the box displaying a selected message. So far, there is nothing outstanding in this. The only thing that can be seen which is perhaps not visible in most other clients is the icon entitled Junk in the toolbar. Thunderbird has its own spam filter, working on the Bayesian principle. I don’t use this feature, preferring POPFile to do my filtering. However, it is probably very useful for those who wish a simple Go/No Go classification of spam. If you highlight every message that is spam, and press the Junk icon, the system will learn and subsequently automatically classify the spam which you receive. This can be automatically filtered into the Trash box. If you wish an independent review of my set-up, please visit the web site http://channels.lockergnome.com/it/archives/ 20050315_bayesian_filtering_at_its_ best.phtml.
Where Thunderbird excels is more behind the scenes. In particular, the authors have taken extreme measures to ensure maximum security. For example, it would be very difficult for anybody to hack into the application. Above all, the Address Book is encrypted to prevent illicit use of the contents, to propagate viruses for example.
From the Options menu, there are several tens of ways you can configure Thunderbird to your liking. For example, the Message Filter system is probably the most powerful that I’ve come across and is even customisable so that you can filter from header lines and automatically give colour-coded priorities to e-mails from your boss or wife. You can also automatically set-up filters from an incoming message. All the features are far too numerous to catalogue here, though. However, that is not all, there are script files that the knowledgeable user may modify, with hundreds of parameters, to change how Thunderbird reacts to specific situations.
One negative point I found is that, although it is blindingly fast when you start with it, if your mailbox contains many thousands of messages, it does begin to slow down. It is easy to mitigate this problem by moving the old messages to be archived to a different ad hoc mailbox. I use a different profile for this.
Now, is it easy to move to Thunderbird from other e-mail clients? The answer is yes. It can be done in two phases: moving existing messages and address lists and going along the learning curve. I have a friend who is totally computer-illiterate and she asked my advice about some e-mail security problems she was having. With some trepidation, I moved her from Outlook Express to Thunderbird (amongst some other things). I was very surprised to find that her learning curve lasted only a couple of hours, to the extent that she expressed the view that the new client was much superior and more “user-friendly” compared to her old one, just the following day. With this in mind, I recommend Mozilla Thunderbird very strongly, no matter which e-mail client you are used to.
Regular readers are used to my security rants. Please allow me to revisit the problem of “phishing”. The last time I wrote about this, it was still called “fishing” and was in its infancy. Let me remind you what it is. You receive an e-mail purporting to come from your bank or another trusted person, asking for a confirmation of some details through an https page on their web site, with a link to it. This may be relatively banal, such as to obtain details for targeted advertising but, more often than not, it seeks bank account numbers, user IDs, passwords, credit card details and so on. “Phishers” have become very astute at their métier and it may be almost excusable to be tempted to fall into the trap set by these criminals, under some circumstances. They make the “419 Nigerian scammers” look primitive in comparison, and we all know that even they are sometimes successful in extorting money from the gullible. For example, the “phishers” clearly show in their message that the hyperlink to their web site is that of the URL you are familiar with, but if you look at the Hyperlink Properties (how many people would?), you will probably see that it goes to an IP number. If you click on this, it is a pixel-by-pixel reproduction of the page you would normally see. However, there is worse to come. The original e-mail message asking you to co-operate will contain a tiny HTML sequence that will contain the QHosts Trojan. If you then type the real URL of, say, your bank, the internal DNS Hosts file in your PC will cause it to be shunted to the “phisher’s” site. This is a terrible security flaw in Windows that has not been widely publicised and is certainly valid for all versions of Windows up to XP SP1. I do not know whether it is the case for the relatively recent SP2. To mitigate the danger, many firewalls and anti-malware utilities lock the Hosts file against unauthorised changes so, if you have taken my past advice and installed these, the risk is minimised.
Finally, before we get down to business and look at some web sites, let me mention that the new(ish) SP2 for Windows XP has a “Security Center” that can lull you into a false sense of security. (By the way, in the last issue, I mentioned that Microsoft withdrew their offer of a free CD for SP2; and downloading was the only way to upgrade. No doubt under pressure, it is now possible to order a free CD-ROM again. My apologies if I misled anyone.) Well, this “Security Center” will not show whether some third-party firewalls or anti-virus utilities are up-to-date and working. Worse, this is because the authors of these utilities have disabled the feature inasmuch as it is claimed that it may interfere with how they work. This is not a Microsoft error. Nevertheless, if it is so easy for the utility authors to disable a feature designed to show whether you are at risk or not, how easy would it be for a malware author to design a Trojan Horse to do the same thing – and do something worse to your machine while you believe that you are safe?
What do you think about having a look at what is possibly one of the most contentious issues in our industry? If I use a search engine to look for stencil “solder paste”, it comes up with over 15,000 results from suppliers of the paste itself, the stencils, squeegees and the machines themselves. This is quite a mixture of subjects, but they are all closely inter-related. So let’s go for it!
http://www.efdsolder.com/app_printing.htm
The first reference that comes up is a page from a solder paste manufacturer. It gives a very brief précis of the stencilling process, without going into much detail. It is really there as a commercial support for the company’s paste range, which is offered with a wide choice of alloys and four flux types. The site generally is, itself, adequate but no more. However, there is a wealth of downloadable information, including – hooray! – MSDSs.
http://www.dek.com/web.nsf/dek/stencils_vectorguard
This is a description of a method allowing stencils to be stored out of their frames – a great space saver, no doubt. The stencils are laser cut with a good level of precision with a choice of thicknesses ranging from 100 to 200 μm, and the overall thickness is a mere 5 mm. They are available to fit Dek’s own standard frames, but the manufacturer claims that they can be made to be compatible with other makes. A good idea! However, Dek’s web site, generally, is not the most “user-friendly”, with pop-ups and an over-heavy Home Page, so be prepared to spend some time if you are on a dial-up connection and you wish to see their range of machines and other products.
http://www.zblob.com/solder_paste_stencil.html
Thought of making your own stencils? This is a description of how to make polyester stencils – and how to use them, even if you don’t happen to have the preferred laser cutter. Somehow, I’m a little sceptical of the instructions, even with a laser, let alone by hand, but maybe that’s just old cynical me!
http://www.stencilsunlimited.com/stencil_products.php
This manufacturer provides a range of stencil products, including frameless ones, much as I have described for Dek, but with a greater assortment of thicknesses and sizes. The first time this page came up, the products were displayed to the side of the page and not in it. This corrected itself on the second viewing, but I suspect that, as the page was written with a PHP scripting tool, there may be a small HTML error between the in-page header and the body. This is not too serious because everything is still readable. What is more serious is that the company’s Home Page is horrendously graphics-heavy with very long download times.
http://www.empf.org/empfasis/oct04/correct1004.htm
The EMPF needs no introduction in the USA. It started as an offshoot of the Naval Avionics Center in Indianapolis and is now a semi-academic service for the Department of Defense and US Navy, in particular, and the electronics manufacturing industry, in general. This page gives a guideline covering most of the aspects of stencilling solder paste. I recommend it as mandatory reading for someone just starting out with this process, and interesting for others.
http://www.iupui.edu/ ∼ eet360/m200/printing.ppt
From Indian University, this is a 60-slide PowerPoint presentation of many aspects of stencilling and screening solder paste, including troubleshooting. Very obviously the background for a lecture, it is written in a telegraphic style. This makes it somewhat incomplete, but is otherwise an excellent aide-mémoire. It is worth the bother of going through it and it would make an extremely good training device for employees, as editing it to suit one’s own needs is easy.
http://www.teknek.com/cleanmachines/smt/solder_paste_applications.htm
This page describes a machine, which is claimed to remove particulate contamination from the bare boards immediately before stencilling the solder paste. It works by elastomer rollers picking up the particles and transferring them to an adhesive roller, without transferring the adhesive back to the board. Of course, good cleanliness is a must for stencilling, especially where there are ultra-fine apertures and it is possible that this could be a useful tool for companies with problems in this sector.
Have you ever wondered how often the bottom of your stencil needed cleaning? This is a magazine article that describes a series of experiments to determine the cost-effective optimum for a given set of conditions. Using ANOVA analysis, the same method could be applied to any other set of conditions. My personal opinion is that the determination may have been less onerous using Taguchi analysis and optimisation, with a possibility of more variables in the design of experiment.
http://www.indium.com/documents/pds/97721.pdf
From one of the major solder paste producers, this is a data sheet for one specific low-temperature paste, with an excellent amount of technical information on how to use it, for essentially a commercial document. The URL for the MSDS is included on it, full marks!
http://www.aqueoustech.com/Artical_Stencil_Cleaning_ Choices.htm
This is a “reprint” of another magazine article describing aqueous cleaning of screens. It is unfortunately not very well written, because it tends to be repetitive. However, it does contain some useful information, particularly on water treatment. On the other hand, I’m not keen on the use of evaporators for water recycling because of the very high energy overheads (and greenhouse gas emissions if the local electricity comes from fossil fuel sources).
http://www.clarydon.com/services/solder.html
A UK stencil manufacturer, making both etched and laser-cut products, offers them in nickel silver, as well as the ubiquitous stainless steel, with a wide range of thicknesses up to 0.4 mm. It would seem from the relatively short page that these are only in full frames. However, if you are within easy reach of the West Midlands, they will offer a “while-you-wait” service for urgent jobs (I hope they have a large coffee pot in their waiting room!!!).
http://ieeexplore.ieee.org/xpl/abs_free.jsp?arNumber=1366496
It is not often that I can quote an IEEE document here. Unfortunately, this one is only an abstract of a paper, which can be purchased. But the abstract alone is interesting reading and it may inspire you to make the expenditure for the full paper. It provides a mathematical analysis and subsequent modelling from experimental results of various component configurations to determine the optimum stencil thickness for any given set of conditions. The correlation between the model and the results appears to be high.
http://www.tkb-4u.com/articles/printing/metalstenciloverview/metalstenciloverview.php
This is the first time I’ve come across the Technical Knowledge Base for You. In this case, it is an article comparing the different methods of stencil production, written by a person who appears to be in the chemical etching side of the business. Don’t let this put you off, though. It seems reasonably impartial, although the section on laser cutting is shorter than the other methods and even suggests chemical etching for run-of-the-mill holes, laser for fine-pitch ones and electropolishing the lot!
http://www.tkb-4u.com/articles/printing/stencildesignguide/stencildesignguide.php
From the same source, this anonymous article is useful and provides a lot of information on designing stencils. In particular, there is a section on glue printing, as well as solder paste and a whole host of useful tips.
http://www.aimsolder.com/tds/ NC%20254%20SAC305%20Solder %20Paste.pdf
From another paste manufacturer, this is a four-page technical data sheet of impeccable pedigree for a specific paste and should be a model for competitive products. The only fault I could find was that it mentioned the “accompanying Material Safety Data Sheet”, which wasn’t accompanying! However, it took me only 20 s to find the corresponding MSDS on the company’s web site, and what an MSDS! It is easy-to-read and gives all the details possible for international use over its seven pages, also exemplary. If the quality of this firm’s products is as good as their documentation, then it must be a serious contender for any paste user!
http://www.finelinestencil.com/Products/SqueegeeBlade.htm
So far, we have considered the paste and the stencil itself, but we have not touched a great deal on another essential component of the process, the squeegee. This manufacturer offers squeegees with electroformed nickel blades that can be re-honed, with cost savings. This page is quite eloquent about the technique’s virtues, compared with other blade materials. It is not possible to judge how long this product has been on the market, but the page goes extensively into the results of beta testing it, without any mention of full-scale production use. It is impossible to say whether this is because the page has not been updated or whether the blade has only just been introduced to the world.
http://www.electronics.ca/cbt/vt34.html
Want a training video on the process of printing solder paste? Well, you can order a DVD from this Canadian site for some USD 350 for 29 min of viewing. There is a postage-stamp size preview, lasting about 8 min, on the page, although the download is very long. Judging from this, the video is very professionally produced, albeit with perhaps too many varied transitions.
http://www.speedlinetech.com/docs/StudyofSolderPaste ReleasefromSmallStencil Apertures.pdf
This is a paper entitled “A Study of Solder Paste Release from Small Stencil Apertures of Different Geometries with Constant Volumes”. The experiments were carried out with square and circular apertures in three thicknesses of laser-cut and electropolished stencils. The quantity of paste laid down was determined and compared with the volume calculated from the measured aperture sizes. The paper concludes, not unsurprisingly, that, after statistical analyses, the release from circular apertures is better than from square ones.
There is obviously a wealth of information available on the internet about these related techniques. What I’ve cited here is only the tip of the iceberg and varies between the technical papers and the articles, commercial (both useful and “hyped”) information and some miscellaneous sites. Hopefully, some of these will be useful.
Brian EllisCyprusb_ellis@protonique.com
Note
1 …thou hast caused printing to be used…William Shakespeare, Henry VI, Part 2 (1592) act 4, sc. 7.