Another SMD prototype

[Jay C]

SMD pads are .254mm in this photo.

Jay

[harryn]

Nice work Jay - somehow looks familiar.

[kn6za]

Jay,

Nice! Its great to be able to see what people are working on, keep the pics coming.

How did the other smd sensor proto board work out? I bet you have a new best friend being able to prototype boards like that.

[Jay C]

The sensor was too small for me to see to mount properly. I ordered a 200x USB microscope. They have ordered a bigger SSOP5 device which I milled a circuit for last night. I am trying a DIY soldermask process to see how it goes. Pictures forthcoming.

[kn6za]

Jay,


I hear what your saying about parts being to small. About 10 years ago I tried to make a signal generator, and the main component was a ad9850brs ssop 28lead buger. I mangled the whole project trying to get the thing soldered in.

Hope you have better success next time.

[Jay C]

Here is a photo of my failed attempt .. .I tried 8 times (6 popped out of sight). What made it frustrating was the flux would wick on top of the sensor and obscure the "dot" that marked pin 1. My magnifier lamp was no help.

I scrubbed the board (and chip) before this shot. Ignore the "blobs" of solder. I tried to use an old tube of paste and it just beaded up on me. Oh well.

Just ordered a new batch of end mills from Drewtronics. I'll be a lot more careful with the tips on these as I'm loosening the collet

[Jay C]

As promised, here is the replacement circuit milled for the SSOP5 (similar to the SOT23-5) hall sensor. I am trying a DIY soldermask I read about on the diyaudio.com forum. Using paint made to paint on glass (Vitrea 160) I painted a layer on using a fine tipped (low grade) brush to paint a mask on. Another guy had used Technics PNP blue to mask the pads first, but my attempt failed so I just did it by hand. Some places it was thicker than others so in my ignorance, I tried some 600grit wet dry to smooth the lumps. It only dulled the gloss which is the mottled gray you see. Won't do that again. I baked it this AM for 20 mins at 300 (bottle says 325 but I didn't want to ruin the copper adhesion) the 10 at 325. The paint comes in a rainbow of colors and is $4.99 a bottle. Comes in gloss and frosted, and comes in paint pens.

Once I get the sensors I'll show a completed circuit.

Jay

[kn6za]

Jay,

That one looks like it will be easier to work with. Good luck

Look out for a package in the next few days.

[Jay C]

Ok, this is how it turned out. Soldering was very easy with this mask in place. The part was much bigger and easy to hold. The cap is 805, the open pads are if the circuit needs any additional filtering.

I already have a new circuit to layout and mill. I really need to get some sort of easy masking for the paint so I can get a nice finish this royal purple color is going to last a very long time, but the paint comes in a rainbow of colors (3 shelves worth at Michaels)

Jay

[kn6za]

Jay,

Solder job looks like it went very nicely. Gota love it when a plan comes together

[Zig]

JayC,

great find

Zig

[Jay C]

Update: I played with the Press-N-Peel blue last night after reading a blog about the right technique. I like the results. The paint is still "uneven" despite my using a bigger brush. I may have to try an airbrush next After I let it dry, I baked it this AM at 325F for 30 mins. Then using pure acetone I was able to remove the PNP blue. The acetone does remove the Vitrea 160, but much slower ... I had to scrub very hard to remove the paint in the bottom right corner of the test area where as the masked portions came off easily.

Anyone have any other suggestions for a more even coat before I go buy an airbrush kit

UPDATE: Nevermind. Airbrushing is a whole new hobby ... no thanks :P

Jay