The problem lies in placing the part correctly, which is a problem when you have a tinned board and try to place a large device on the bulging tin.Most people do not use hot air to actually solder a board. It is very useful for removing and reworking parts, but not as good for actually soldering. A decent iron with a fine tip is much better at this.
Most people do not use hot air to actually solder a board. It is very useful for removing and reworking parts, but not as good for actually soldering. A decent iron with a fine tip is much better at this.
... soldermask which makes soldering much easier. Unless you apply way too much paste the soldermask will generally keep the solder to the correct places!
2) You really need to check your resolution. I know these are expensive: but they allow you to check resolution. I looked for "photolithography test targets". You can try making your own for the smallest packages you have. Put the pads down and attempt to draw parallel lines from them. There is a cheaper source on the new somewhere.
How many of these boards do you plan to make?
I use a cheap HP laser and toner transfer and don't have any trouble doing QFN's. I'm assuming with photo you should be fine, but that's based on your actual process.
The problem lies in placing the part correctly, which is a problem when you have a tinned board and try to place a large device on the bulging tin.
With passives, it's easy to dab down solder on all the pads, drop the 0603's or 0802's and then hit it with hot air. Easier than tinning a pad and setting the component then soldering the other pad.
I disagree on the usefulness of soldermask. I'm not certain why I don't have a problem with this and others seemingly do, but I have no more bridging with soldermask than without.
I use a cheap HP laser and toner transfer and don't have any trouble doing QFN's. I'm assuming with photo you should be fine, but that's based on your actual process.
What minimum sizes do you recommend for resistors and similar?
With average soldering ability and good eyesight you can easily do 0805. With good soldering technique or a little practise 0603 is also quite reasonable. I've never gone smaller than this but check out any modern PC peripheral for how small some stuff gets!
Hi edaca
I have designed a LED head....and am going to try and assemble this ....by hand..for the time being. Here are the LED's I will be working with...
Please see PDF attachment. Is this possible???
Could you elaborate on the process? What films do you use? I typically printing straight on "over head" films from HP, it's been good so far, but perhaps i need to refine my process?
Just search for toner transfer. It's a process where the board outline is printed on paper and then ironed on the copper clad. If you are using photo transfer and are happy with it, I would stick with that. Toner transfer is much more finicky and can take a good amount of work to get right.
If you decide to try toner transfer, and for those who already use it, you may find this discussion interesting:
**broken link removed**
http://dangerousprototypes.com/2012/09/29/pcb-manufacture-using-oracal-vinyl-film-laser-printer/
In brief, the video describes using vinyl for the backing, instead of paper. The question of whether it will melt on the laser fuser was not fully addressed, but several posters to that group claimed great results.
I use the photo method, make my transparencies on a laser printer, and then darken them with white board marker as described in my blog here at ETO.
John
They will work as is with a few pinholes, but the marker I mentioned makes them quite opaque.
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