Hi Guys, I'd like to share this to all of you...you can start playing with the rests...Stated prices, if not indicated, are in Aussie $ or Singapore $.
Stencil Printing Adhesive
Pros
a) Less Capital Equipment Cost (Short Term).
In reality it is far more costly in the long term (min. 3 years) compare to acquiring a dispensing machine when all the Materials (Stencils, Cleaning Materials etc.), Extra Labour, Wastage, Rework Cost etc. are calculated.
b) Less Manufacturing Space.
Using a screen printer for adhesive deposition also enables increased equipment utilisation. No longer does a Solder Paste Printer sit idle waiting for a dispensing machine to complete its task.
c) High Throughput.
Do you really need the above benefit? With Stencil Printing Adhesive, an average tact time of 10 to 15 secs. per board which is roughly 4 to 6 PCB�s per minute against 1 PCB per 4 minutes on Component Placement. This speed is beneficial only with High-end High Speed Chip-shooters.
Cons
a) The chemicals used to clean stencils are generally considered hazardous material (acetone, xylol, etc), this adds a safety concern to manual cleaning. In addition, the safety and prevention of exposure to solvents are paramount to the operator staff. Frequent Stencil Cleaning is required (every 2 � 3 hrs.) to avoid aperture clogging. Manual Cleaning of Adhesive from Stencil is totally �not acceptable�.
- Adhesive Cleaner @ $95.00 / 1 pkt. Of 100 pre-saturated clothe. (Usage of 6 to 8 clothe/cleaning) Or a spray and wipe cleaner @ $80.00 / solution with 200 pcs. Of lint free clothe. - Cleaning Time of 30 mins @ $20.00 / Hr at an interval of 3 hrs. (Manual Cleaning). - Possible Installation of Exhaust for clearing Fumes @ $5,000.00 Est. Material and Labour Cost. - Stencil Cleaner costs between US$12,800 to US$40,000.00 excluding cleaning agent/solutions. Cleaning Time 2 to 3 mins. per stencil.
b) Stencil Cost @ $850.00 per stencil (Laser Cut). Whenever there�s a problem in design layout, stencil is affected and needs to be replaced. Whenever there are new products or revisions that affect PCB layout, the more stencil costs we have to spend. This is not the case with Adhesive Dispensing Machine.
c) Material Wastage. Epoxy is hydroscopic. Unnecessary exposure to the atmosphere can cause problems in reflow and will require process exposure evaluation. Adhesive stencil life is between 3 to 4 hours only. Exposed material should never be "recycled". This increases waste and adds cost to our process.
d) The stencil thickness determines deposition volumes and can not be altered. This limits the range of components (stand-off height) which can be reliably glued with a stencil. (not an issue if chips only).
e) Release characteristics of epoxy differ from solder paste. Aperture dimensions and shape must be considered. The smaller the aperture, the greater the difficulty in release.
f) Longer Set-up time against dispensing equipment when using a semi-auto printer.
g) Higher rework rate compare with using a Dispensing Machine. If there is insufficient volume of deposition, the component will skew or detach during placement and processing. If there is too much volume, the adhesive will intrude on the land patterns, causing opens and increasing cost through rework and wastage.
h) Possibility of Solder Paste contamination during the process if the stencil printer was not properly cleaned. This is if manual cleaning is the chosen method rather than getting a stencil cleaner. With a stencil cleaner, is it right to use the same solutions/cleaning agent that have been used in cleaning stencil adhesive or do you need to replace it for solder paste cleaning ? This you need to ask from supplier.
i) Need constant working of paste printer to avoid aperture clogging. Adhesive stencil life is 4 hrs. in a good environment...3 hrs. is average.
j) The more the products with bottomside components for adhesive printing, the higher the ongoing costs (eg. Consumption etc.).
Adhesive Dispensing Machine
Pros
a) Less Cleaning Required and cleaning cost is remarkably cheaper than stencil printing. b) Flexibility. Can handle various standoff height and adhesive dispensing volume can be controlled. c) Less Adhesive Wastage. d) No need for exhaust installation to extract cleaning solution fumes. e) Quicker to set-up than semi-auto stencil printer. f) Less rework rate.
Cons
a) Initially Costly. Between $85,000 (second hand) to $150,000.00 (Brand New). b) Slower than Stencil printing but this depends on how fast the line is.
Dreamsniper
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Had cheacked the archives but I didn't see much about their...
- Oct 03, 2000
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Hi
This is what i think:
1. Screen printing is fast and dis...
- Oct 03, 2000
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