A Tour of The
CSM Electronics Prototyping Facility

Christopher G. Braun



About the Electronics Prototyping Facility

The CSM Electronics Prototyping Facility brings together an integrated set of tools to allow users the ability to design, simulate, fabricate and test electronics systems. This facility was developed to better prepare students to enter the workforce by allowing them to gain experience in the basic skills they need in electronics system fabrication.


Figure 1. Shown is a outside view of the CSM Electronics Prototyping Facility.

Students in our Junior level electronics laboratories are taught how to use this facility as well it is available for our Senior level classes, each with a class sizes of about 40-50 students. In order to achieve our educational goals, each student team is required to design and fabricate their own unique circuit board for each of several projects. This results in a high mix, low volume prototyping environment, quite different from typical manufacturing needs. Over the past several years, our students have designed well over 300 different printed circuit boards (PCBs) and fabricated more than 600 boards.

The development of this vertical integration of hardware and software tools has required a substantial effort over several years. There are many methods to accomplish each of the tasks for electronics system fabrication. For each method there are a number of competing considerations including cost, safety, space requirements and feasibility in a university setting.


Figure 2. A photograph of the first project, an adjustable
power supply, students fabricate using the Electronics Prototyping Facility.
The left photograph is a completed system, the right is the bottom side PCB.
Link to more project information on slide show.



Electronic System Production Steps

Listed below are the main steps in fabricating an electronic system using the prototyping facility. The Junior level laboratory projects start from simple and very well defined and increase in difficulty and level of design effort. Since there we have only one PCB fabrication machine, students must allocate time outside of the scheduled laboratory hours to fabricate their designs. While it is tempting to assign exciting real-world projects with both significant design and fabrication effort, the objective at this level is to develop a good background in using these tools. Later, in their Senior year laboratories and Capstone design projects, students have the opportunity, and the skills, to design and fabricate more advanced projects.

Total time for entire project: Typical for laboratory projects is about 9-12 hours using the Electronic Prototyping Facility. Link to more information on slide show.

There are a number of methods to produce a printed circuit boards including using commercial board shops, various chemical means and mill/drill. Shown on Table 1 is a list of the standard methods with tradeoffs and costs for a school environment.



Method



Pros



Cons



Comments / Cost

Commercial production of PCBs

- High quality
- Plate through holes, vias
- Multi-layer
- Lowest cost for many PCBs
- High cost for 1 to few of many different projects
- Longer turn around than in-house
- No startup costs
- Direct cost per boards:
=> 1-sided, small PCB: $75-200
=>2-sided, medium PCB: $150-400
- No indirect costs

In-house facilities for photo-exposure, chemical etching and automated drilling

- Industry standard methods
- Good for production of many of the same PCBs
- Low cost in quantity
- Chemical handling: storage, safety, waste disposal
- Large floor space needed (darkroom, etching tanks, etc.)
- Difficult for students to control production processes ("art")
- Drill alignment issues
- Good for production training
- In use in a number of schools
- Requires substantial maintenance
- Startup cost of $2-10k for facility
- Direct cost per boards:
=> Single sided, small PCB: Few $
=> Double sided, medium PCB: Few $
- Indirect costs of chemical handling and space can be high

Use of pre-sensitized PCBs, photo-
processing, manual drilling

- Low startup cost (~$100)
- Easy to use
- High cost per cm2 of PCB material
- Chemical handling issues
- Production "art"
- Time and alignment issues in manual drilling
- Startup cost from $100-$1,000
- Direct cost per boards:
=> Single sided, small PCB: $10+
=> Double sided, medium PCB: $20+
- Indirect cost per board depends on chemical disposal costs


Mill/drill machine

- Quick
- Low $ per PCB
- Alignment of holes and pads
- Most tasks automated
- Modest space & maintenance requirements
- High initial cost for machine and software
- Must learn/use 2 new CAM programs
- Dust removal
- PCBs differ from industry standard
- Harder to solder
Manual vias
- Best for prototyping, high mix
- Startup cost from $10-20k
- Direct cost per boards:
=> Single sided, small PCB: Few $
=> Double sided, medium PCB: Few $
- Indirect cost per board depends on space and maintenance costs (relatively low)

Table 1. Alternatives for printed circuit board manufacturing in a university environment.
Costs assume PCB design is complete and labor is not included.


Function

CSM Electronics Prototyping Facility Tool


Pros


Cons

Simulation

Microsim Pspice (student version)

Free

Some limits, generally good for student projects

Schematic
capture

Protel Schematic Capture

- Educational Discount
- Full feature
- Coupled to PCB Layout


No connections to circuit simulation, not industry standard

PCB Layout


Protel PCB Layout

- Educational Discount
- Full feature
- Coupled to Sch. Cap.


Not industry standard

Programmable
Logic Devices

Altera MaxPlus2 and Logical Devices CUPL

- Educational grant
- HDLs Industry accepted
- Simplifies prototyping by allowing fewer ICs
- Time to teach
- Cost and maintenance
- Fine pitch ICs are hard to manual solder

Printed Circuit Board (PCB) Manufacture


T-Tech QC-7000 Mill/drill machine

- Local/quick PCB fab.
- Good for single/double sided PCBs
- Low cost per PCB
- Traces/holes aligned
- High initial cost ($10-15k)
- Space, dust issues
- Additional software and board preparation tasks

Part Insertion

Manual
- Cheap/easy/quick
- Time, reliability issues

Soldering

Manual soldering Metcal SMT Stations

- Industry standard
- High quality soldering experience
- High cost limits wide use
- Lower cost stations are adequate for most projects

Inspection

Vision System Mantis optical inspection (stereo, wide view)

- Easy to use
- Needed to see details (esp. surface mount)
- High cost
- Not required
for simple PCBs

Operational Testing

Standard laboratory bench test equipment (scopes, DVMs, etc.)

- Easy to use
- Uses available equipment


Limited ability to test

Table 2. A detailed description of our implementation of the main functions
for the CSM Electronics Prototyping Facility.

Table 2 presents greater detail into the particular methods we use here at CSM to accomplish the various design and production functions previously mentioned. For each function there are many possible methods and tools available on the market. A number of our choices were driven by cost -- some tools are used because we were able to receive substantial educational discounts and grants. Another issue is that all of our computers available for general use are personal computers, not workstations, which constrains the selection of computer-aided design (CAD) software.

The key step in the Electronics Prototyping Facility is the production of printed circuit boards (PCBs). There are a number of issues to consider in this selection process. First, a university environment is much different than a production facility. To get the benefit of hands-on instruction, each student must take their PCB through the production process. As a result, each student must be trained to complete the production steps in a safe and timely manner. Additionally, the student projects tend to be very sporadic with a high demand for PCBs when projects are due. There are a number of methods to produce a printed circuit boards including using commercial board shops, various chemical means, hobbyist kits, and mill/drill machines.

Most PCB fabrication methods use a significant amount of chemicals which leads to very real safety concerns given students are directly involved in handling dangerous chemicals (acids with heavy metals, photoresist, etc.). With appropriate instruction and safety equipment, production of PCBs can be safely accomplished using this standard chemical method in a university setting as demonstrated the facilities at California Polytechnic State University [13] and others [14]. Here at CSM, there is a high direct cost for chemical disposal and this was a major factor in the decision to acquire a mill/drill machine for PCB fabrication.


Electronic Prototyping Facility Components


Figure 3. The dedicated computer and controller with the
QC-7000 Mill/drill machine in the back.

The list below itemizes the major components in the CSM prototyping facility. A number of the vendors for these items offer educational support programs to help sponsor schools to acquire their products.

Space: One enclosed room of size 18 m(200 ft2) with outside venting (Figure 1).

Computers:

Special Software:

Hardware:

Miscellaneous:


Assessment -- How well are we doing?

As part of the assessment process, the students are asked each year for their anonymous open ended comments from "Please give us your comments on the use of the EPF prototyping facility as part of your laboratory projects." While this is not meant to be as thorough assessment, it does provide one level of feedback. The student responses to this type of requests are frank and helpful in pinpointing areas of strengths and weaknesses. The overall response was very favorable and the students especially enjoyed the "hands on" experience. Areas to be improved upon include better documentation, instruction and reducing the time commitment. The summarized survey results are shown in Table 3.

Summarized student comments

Percent of student replies

Great/good experience

45%

Like building circuits
and real-world applications

33%

Fun/cool/neat

21%

Too much time

21%

Need better explanation

18%

Equipment and software
difficult to use

18%

Hard at first

6%

Table 3. The student open ended comments the PCB lab projects 
(total about 150 replies). The total exceeds 100% since the student's
comments may have pertained to more than one item.

The assessment from the faculty members of the introduction of the PCB-based laboratory projects to our Junior year electronics labs is highly positive, but significant work is required to improve the ease of use. Clearly, the documentation requires substantial improvement. The facility also needs a wider range of CAD and hardware tools.

As students have progressed, there have been good indications that they are retaining these fabrication skills and are better at overcoming the "abyss of doubt". Feedback from a wide range of industry representatives and recruiters has also been very positive. Even when their needs are not for circuit fabrication, industry representatives are pleased to see that students are learning to apply their education and working on "real world" projects.



Conclusions

We have developed a new type of electronics prototyping facility to provide our students the tools they need to fabricate electronic systems. This facility is a vertical integration of software design and simulation tools with the means to produce printed circuit boards and then assemble and test the system. This facility is used as a standard part of our electronics laboratories and student projects. Using this facility, students have constructed projects ranging from simple power supplies to RF communication systems to complex data acquisition systems. The students not only learn key skills in electronics production, but also benefit from the satisfaction of designing, building and using working electronic systems. The enthusiastic response from both the students and industry employers indicates this approach may be of interest to other sites.

There are a number of challenges still ahead. One of the drawbacks is the substantial investment in time to train the students. We are looking at developing on-line computer based training aids to help in the instruction process. Also, one very import trend to note is the rapid movement by the electronics industry towards surface mount devices. It is more difficult to manually handle surface mount parts as compared to standard through-hole parts due to the finer track pitch and we are exploring ways to best deal with that issue at CSM.

Based on discussions with industry employers and faculty experience, we believe it is important for students to graduate with the knowledge on how to make their designs become a reality. Without sacrificing other aspects of their education, we are able to improve our students learning experience and make it more relevant to their future needs as working engineers through the use of the CSM Electronics Prototyping Facility.



Vendor List, including some alternative sources:

PCB prototype fabrication:

PCB CAD Tools:

PLD Tools:

Soldering Stations:

Optical inspection stations:

Distributors of PCB and related equipment:


Acknowledgements

Our ability to assemble this facility has only been possible through the support of the electronics industry, the Colorado School of Mines, and the National Science Foundation's Division of Undergraduate Education through grant DUE-#9551502. We would also like to recognize T-Tech, Inc., Altera Corporation, Protel, Inc., Logical Devices and Metcal for their generous support.


References

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  12. Braun, Christopher G. "An Electronics Prototyping Facility for Undergraduate Electronics Laboratories," Proceedings of the 1996 ASEE (CD ROM), 1996
  13. Industrial & Manufacturing Engineering Department, California Polytechnic State University San Luis Obispo, California. CalPoly's Industrial Engineering Program facilities include a chemical PCB facility, sheet metal shop and NC mills for prototyping of electrical/mechanical systems
  14. Cook, Clair "Electronic Design Automation and Fabrication at Ferris State University," Proceedings of the 1996 ASEE Conference (CD ROM), 1996