Difference between revisions of "Part Procurement"

Revision as of 00:52, 18 February 2016

The miniscope system is consists of a machined plastic housing, custom Printed Circuit Boards (PCBs), and off the shelf components. This guide will take you through the process of ordering everything you need to build a system of your own.

General Note on PCB Fabrication and Assembly

Pricing for small batch PCB fabrication and assembly is usually dominated by the one time cost of the PCB manufacturer setting up their equipment for the specific order. When ordering 1000's of PCBs this cost is negligible but for orders of 1 to 10 PCBs this cost effectively greatly increases the per board cost.

  We have been contacted by a many labs interested in coordinating larger orders of PCBs to decrease the per board price and have set up a forum for those labs to get in touch with each other.

For our own labs we usually aim for the following quantities when ordering:

DAQ PCB

Fabrication: 20 PCBs. The total price for fabrication will likely be the same for quantities of 20 or less of this board so you might as will order the maximum number of boards.

Assembly: 10 PCBs. Assembly is less affected by the one time setup fee so smaller quantities will have a less dramatic per board price change when increasing total quantity. We aim for getting at least 10 PCBs assembled at a time but the cost for doing just 2-4 is still pretty reasonable.

Price quote you can reference from Sierra Circuits: DAQ PCB Quote. The quote for 'Components' is for Sierra Circuits to order all the electrical components for you. The other option would be to order the components yourself and ship them to Sierra Circuits.

CMOS Imaging Sensor PCB

Fabrication: 50 to 100 PCBs. Again, the total price will likely stay the same for quantities under 50 to 100 of these boards.

Assembly: 10 PCBs. Just like with the DAQ PCB, per board assembly cost will change less dramatically with smaller quantity orders.

Price quote you can reference from Sierra Circuits: CMOS Imaging Sensor PCB Quote. The quote for 'Components' is for Sierra Circuits to order all the electrical components for you (except the CMOS imaging sensor). The other option would be to order the components yourself and ship them to Sierra Circuits.

Excitation LED PCB

This board only requires basic fabrication technology which doesn't have a high one time setup fee. We suggest using Silver Circuits PCB Fabricators for this board.

Miniscope Master Parts List

An up-to-date list of all components (besides electrical components listed in the each PCB project's Bill of Materials (BoM)) can be found in our Google Documents parts list. All components on this list should have less than a two week lead time except

• GRIN lenses (see GRIN Lens Information)
• CMOS Imaging Sensor

After running through the procurement details below make sure to double check with the parts list that all components have been ordered.

Head Mounted Scope

Machined Housing Parts

The design files for all parts that need to be machined can be found on the Miniscope Machined Parts Github Repository. We have included both the Solidworks files as well as exported each part as a .stl.

The three housing components (MainBody, FocusingSlider, FilterSetCover) are CNC machined out of Delrin plastic. While the parts themselves are not too complex, their small size and thin walls makes them tricky to machine. Your campus machine shop should be able to machine these parts for you but generally this will take longer and be significantly more expensive than sending the parts out for machining.

Shylo Stiteler is a local machinist that is very familiar with our project. You can contact Shylo by email, shylostiteler@gmail.com, with the parts you need machined. His work is very reasonably priced, quick, and consistent.

We also should mention Protolabs for general machining projects. They are very quick and reliable but will not machine parts with wall thickness under 1mm. This means they won't be able to machine the majority of scope parts without added addition mass.

Machined Aluminum Baseplate

The design file for the Baseplate can also be found on the Miniscope Machined Parts Github Repository. Similar to what is stated above, this part can likely be machined by your local machine shop but we recommend getting the part machined by Shylo Stiteler's company, shylostiteler@gmail.com.

Optical Components

The optical components in the microscope are all off the shelf components which generally have less than a week lead time to arrive.

Diced filter set

We use Chroma filters sets in all our scopes but have also had success with Semrock and Omega Optical filters. All three of these companies will dice their standard filters to what ever size you need. The filter set and dice dimensions we use can be found on our parts list, and you can contact Dick Stewart <dstewart@chroma.com> for a price quote.

Internal lenses

Both the half-ball lens and achromatic lens can be purchased through Edmund Optics. Part numbers can be found on our parts list.

GRIN lenses

Acquiring GRIN lenses may prove a bit more complicated than acquiring the rest of the components in our system. For this reason we have a dedicated GRIN lens page on this topic.

CMOS Imaging Sensor PCB

IMPORTANT: If you downloaded the CMOS Imaging Sensor PCB files before January 27, 2015 please update them with the current version on GitHub.

Design, fabrication, and assembly files can be found that the Miniscope CMOS imaging sensor PCB Github repository.

The 'Fabrication Files' folder contains all the information needed to get the PCB fabricated. PCB fabrication means the PCB is printed but not assembled. The PCB is a 4 layer, 0.031" thick FR4 circuit board with In Pad Vias.

• 'CMOS_Imaging_Sensor_PCB_Fab_Info.docx' has all the relevant specs for PCB fabrication.

The 'Assembly Files' filder contains all the information needed to get the fabricated circuit board assembled with electrical components.

• 'Serializer_System2_MT9V032_BOM.xlsx' lists all electrical components needed for assembly along with each components PCB designator. A PCB assembly house can likely offer a turn-key assembly solution where they will hand the ordering of all these components for a small markup. You can also order them yourself and ship them as a kit to the assembler.
• 'CMOS_Imaging_Sensor_PCB_Assy_Info.docx' has all the relevant information for PCB assembly.

While it is possible to assemble this PCB yourself, we suggest most labs send it out to a professional assembly house. For both fabrication and assembly we recommend using Sierra Circuits. The gerber files and board information document are needed for fabrication. The BOM (Bill of Materials) file and PnP (Pick and Place) file are needed for assembly. Generally PCB assembly houses can provide turnkey services which means they will not only assembly the PCB but also handle ordering all the individual components for a small markup.

In order to minimize the size of this PCB, buried vias and two sided assembly are used which results in a higher production costs than more standard boards. When getting a price quote we suggest asking for pricing at a few different quantities (5, 10, 20 boards). At these small quantities there is usually a range of quantities where the overall price remains practically the same for fabricating and assembly more boards.

IMPORTANT: Ordering the Imaging Sensor: All electrical components can be easily purchased through Digikey except for the imaging sensor. You should order the imaging sensor yourself and send it in to be assembled. The CMOS imaging sensor used is the Aptina (or OnSemiconductor) MT9V032C12STM and can be found through Arrow Electronics or Aliexpress.

Excitation LED PCB

Design and fabrication files can be found at the Miniscope Excitation LED PCB GitHub Repository.

The technology needed to fabrication this board is much simpler than what is needed for the CMOS imaging sensor PCB and DAQ PCB. For this reason we suggest using the 'PCB Production' option through [Silver Circuits]. You can upload the gerber files directly to their site for a price quote but we suggest emailing them to get a better deal.

Fabrication Properties:

• Number of layers: 2
• Substrate: 0.031” FR4
• Board width: 5mm
• Board height: 7.5mm
• Copper weight: 1oz (not important)
• Surface: HASL or ENIG (not important)
• Board shape: Custom
• Cutouts: None
• Solder mask color: Black
• Sinkscreen layers: Bottom
• Sinkscreen color: White
• Electrical Test: Not required
• Routing: Either individual or panalized with v-scores
• Ask to get them panelized on 4"x5" PCBs

You can reference Order #6364 in your price quote request.

Miscellaneous Parts

Data Acquisition System

The DAQ system is composed of a DAQ PCB and 3D printed housing. The DAQ PCB needs to be fabricated and assembled by a PCB Fab and Assembly House capable of handling prototype and low volume orders (we suggest Sierra Circuits). In general you will mainly be paying for the setup cost when getting low volumes of PCBs fabricated and assembled. For this reason it is cost effective to ask for a price quote at multiple quantities (1, 5, 10, 20) to get an idea of price breakdown. For these DAQ PCBs it will cost around the same amount to get 1, 5, 10 produced.

Data Acquisition PCB

Design, fabrication, and assembly files can be found at the Miniscope DAQ PCB Github repository.

The 'Fabrication Files' folder contains all the information needed to get the PCB fabricated. PCB fabrication means the PCB is printed but not assembled. The PCB is a 4 layer, 0.062" thick FR4 circuit board with controlled impedance and tented vias. The DAQ board contains a 0.8mm pitch BGA component so the surface finish needs to be ENIG.

• 'Miniscope_DAQ_PCB_Fab_Info.docx' has all the relevant specs for PCB fabrication.

The 'Assembly Files' filder contains all the information needed to get the fabricated circuit board assembled with electrical components. I usually have all components except the through-hole components assembly by an Assembly House but you can have the through-hole components assembled by them as well. You will need to modify the Bill of Materials (BOM) depending on which components you want assembled.

• 'USB_Control_FPD_Linkv2_BOM.xlsx' lists all electrical components needed for assembly along with each components PCB designator. A PCB assembly house can likely offer a turn-key assembly solution where they will hand the ordering of all these components for a small markup. You can also order them yourself and ship them as a kit to the assembler.
• 'Miniscope_DAQ_PCB_Assy_Info.docx' has all the relevant information for PCB assembly.

DAQ PCB Case

We have designed a simple case to enclose and protect the DAQ PCB which can be 3D printed here.

Miscellaneous Parts

Cabling

On the 'Head Mounted Scope' page of the parts list you will find part numbers for 2 coaxial cable options as well as the suggested SMA coaxial connector. Even if you are experienced with soldering, we suggest using the Coax_2_SMA PCB along with an edge mounted SMA connector to connectorize the coax cables.

Tools

There is a dedicated page of the parts list outlining the tools you will need for assembly of the Miniscope system.