 Issue Number 48 June/July 1999
Surface Mount '99
International Conference on Electronics Design and Manufacture
The eleventh annual conference organised by the SMCBA has been developed to offer something for everyone - design, production, inspection, test and management issues are all covered in this year's program. The international line up of presenters will include:
- John Sabo, Rockwell/Allen Bradley USA
- John Maxwell, JMA USA
- Peter Biocca, Multicore USA
- Martin Cotton, ViaSystems UK
- Marie Cole, IBM Microelectronics USA
The current program and early bird registration offer is enclosed with this issue of Pick 'N' Place. The full conference registration not only offers a discount on the session fees, it also includes a ticket at the conference dinner which will be at the new Darling Harbour restaurant Zaaffran.
Elenex '99: Australian Exhibition Services (AES) organisers of the Elenex Exhibition offer SMCBA corporate members a discount on their space/stand costs at Elenex. AES has managed to secure an additional hall at Darling Harbour for the exhibition - if you are interested in exhibiting then why not join over 180 other exhibitors and gain exposure to over 12,000 visitors.
Annual General Meeting:
The AGM will be held on Wednesday September 29 at 11.15 am.
All members welcome and details will be mailed to each nominated representative and also posted on the SMCBA website at www.smcba.an.au
SMCBA Executive Committee:
If you are interested in the future of the electronics industry in Australia and NZ why not consider assisting the industry by becoming a member of the SMCBA Executive? Nominations will soon be called for five places on the committee - for further info please contact Andrew on (03) 9568 0599.
Thanks...
To the presenters and SMCBA members who participated in or provided equipment for the
1999 Australasian SMT Academy:
Michael Mahoney and Rich Kopcho
Allen Chia
Terry Clitheroe
Mektronics
Solder Static
Good News....
Following on from his very successful High Speed Design courses Lee Ritchey is looking at dates to return to Australia in 2000. Lee has more info for those who attended his course in April and for those who missed out he will also offer another two day course.
IPC STANDARDS UPDATE:
Amendment 2 (BGAs) for the IPC-SM-782A is now available - contact the SMCBA on (03) 9568 0599, fax (03) 9568 0622 or by email to pollocka@smcba.asn.au for pricing.
ANSI/J-STD-001 is under revision with Revision C expected to be published in the last quarter this year. Revision C of IPC-A-610 is also expected at around the same time.
Congratulations...
To Ken Galvin (CIT) who successfully completed the IPC Certified ANSI/J-STD-001 Instructor course at the MTTC in May. Whilst in the USA Ken also completed recertification as a Class A IPC-A-610 instructor and also recertified in several of his NASA certificates at JPL.
Why not send it out with Pick 'N' Place?
If you'd like to include something with Pick 'N' Place phone (03) 9568 0599 to find out how.
Soldering Iron Calibration
The electronics manufacturing industry directs much of its time and energy toward process control to ensure high quality first time yields. An important aspect of process control and quality procedures is the temperature profiling of the automated soldering process. Temperature profiling is important for many reasons including prevention of damage to the PCBs and components. Another very important reason is to ensure that the correct temperature is used in the alloying of the base metal of the items to be soldered with the tin in the solder. If the temperature is too high or too low, instead of alloying the metals, intermetallic compounds will be formed. These compounds are both physically weak and electrically inferior to the solder alloy.
It is difficult to understand why hand soldering temperatures are taken so much for granted after the automated process has placed so much emphasis on this aspect of the assembly procedure.
When did you last consider the thermal capacity of your soldering iron tip?
It may have been about the same time you considered the recovery rate of your iron or when you last checked your tip to ground resistance. Maybe it was when you last calibrated your favourite soldering iron!
Soldering irons are vital to good workshop practices in the repair and rework of PCBs, yet they are probably the most neglected tool on the bench.
As parts become smaller and more sensitive to ESD and temperature, good work practices and process control are becoming more important.
Soldering iron calibration units are readily available and are an essential item if we are serious about quality standards of hand soldered joints. All soldering iron standards refer to specifications such as temperature, tip to ground resistance, recovery rate etc and yet most workshops and assembly lines do not consider soldering iron calibration from one year to the next.
If you are in the process of attempting to improve your workmanship standards in hand soldering it may be time to consider the condition of your irons and the introduction of a maintenance and calibration plan. Once your soldering irons are of a known quality you can then look toward other aspects of hand soldering process control.
This article was written by Ken Galvin and provided to the SMCBA courtesy of Cooper Tools.
Fine Pitch Stencils - Types
Reproduced from a technical presentation by David Muscat, Arqtek Design phone: (03) 9521 8139
- Chemically manufactured stencils
These are the main types of stencil in use today. They are manufactured as follows:
A thin sheet of brass or, more commonly, stainless steel is taken, and coated on both sides with photosensitive acid-resist. A photopositive (black solder pads) master is sandwiched either side of it, and the assembly is exposed to powerful ultraviolet light. The exposed areas harden, allowing the soft pad areas to be washed away. The board is then placed in an acid etch bath, which eats away the holes from both sides.
The registration of the masters with respect to each other is critical, especially with fine component pitch. If the masters are misregistered, the holes will be sloping, and cause a bad print; this used to be the case with about 1 in 10 stencils, but the problem has been largely overcome in the last couple of years, resulting in about a 1 in 50 reject rate. A successful technique is to make the master as an envelope into which the blank sheet is then placed, giving 2-20 micron accuracy.
The sides of the holes are never perfect, because the acid eats into them as well as through the stencil, leaving a figure-of-eight type section.
However, because the stencil is very thin, this isn't usually a problem.
- Laser-cut stencils
Another technique is to use a computer-controlled CO2 or YAG laser to melt away the holes in the blank from one side only. It can take around half an hour to cut a stencil this way: the more open area there is, the longer it takes, and more expensive it is. The lasers are expensive, so the cost of this process is more than that of etching a typical stencil. The system is very accurate.
- Electroformed Stencils
The manufacturing process is additive, unlike the others, and the stencil is formed with the holes in it as follows: An earthed mandrel (base-plate) is coated with photosensitive insulating emulsion, and is exposed to ultraviolet light through a negative master (pad areas clear, non-printing areas opaque). The pad areas harden, allowing the remainder to be washed away. The mandrel is then placed in a bath of acidic electrolyte solution, and connected to a current source as the cathode, with a sacrificial nickel anode. Over a few hours, nickel is deposited on the conducting (non-pad) areas, and can subsequently be peeled off as a sheet, complete with holes. These stencils have a number of advantages over other types. They are extremely accurate. The internal walls of the holes are very smooth, and can be made trapezoidal - that is, slightly wider at the bottom that the top, with an angle of 1-2 degrees - which helps the solder paste to come out onto the board. They also have a "blip" of 10-20 microns around the bottom of the hole, which forms a gasket around the pad during printing and helps to make sure the solder paste stays accurately on the pad.
In the Next Issue: Cleaning Stencils
Bluegum Technology Pty Ltd - Surplus Equipment Clearance
Due to a recent consolidation of PBA facilities within Bluegum Group, numerous items relevant to the production of Circuit Boards have become surplus. The following list outlines the major items that Bluegum Technology would like to offer for external Tender.
Item #
1. Board Carriers and trays
2. 35 x Bench Inspection Lamps
3. Multiple Fume extraction ducting systems
4. Slautterback LS10H glue dispenser
5. Electrovert H500 Hydro cleaner including DI water processing plant
6. Electrovert Wave Solderer UPK15F
7. Omega Meter - Ionic Contamination Test System
8. Solder Stencil wash
9. Magazine conveyor
10. Nuline adhesive/paste refrigerator
11. 2 Depth microscopes (Hisomet and Hunter)
12. 2 Stereo Microscopes
13. Manual Insertion assembly line
14. 4 Magazine loader/unloaders
15. Component Hot Room approx. 10m3, 45oC, 25% RH
16. Panasert MA Component Placer with many spares
17. Senju 4 zone IR Curing/Reflow oven
18. Seho IR 4735-G reflow oven (Complete but partially disassembled)
19. Universal Multi Mod 6772A
20. Universal VCD 6287A
21. Universal Radial 0.2" 6346A
22. Universal Radial 0.1" 6360A
23. Universal Sequencer 2596A
24. Approx. 150 Panasonic MA/MPA/MPA80 Component Feeders
25. Adola ATC-300 Radial Lead prepper
26. Heller Dip cut and prepper
27. 2 x Heller Axial lead prepper
28. Ebsomat lead prepper
29. Lumonics Lightwriter Spe Laser Etcher complete with chiller unit
30. MPI HG-6000 Hot Air rework station
Interested Parties may enquire or arrange for inspections through Gavin Bergman gbergman@bluegumtech.com.au or Ph. 03 57202592. Tenders will be accepted for each/all lots until July 30th after which the successful bidders will be notified. Goods are to be removed by buyer or through shipment where buyer pays freight. All goods are to be paid for prior to removal. Tenders are to be submitted via email to Tom Caelli tcaelli@bluegumtech.com.au and must include full details of Company Name, Contact Name, Position, Phone/Fax/Email details and ship to address if required. Items may be subject to a reserve.
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