1
\$\begingroup\$

I have designed a circuit with a voltage regulator(ADP7156) from Analog Devices in KiCad. I have chosen the package type as 8-lead SOIC since I am planning to hand solder it to the PCB. While creating the footprint, I found the dimension of datasheet a little confusing. enter image description here

From the picture, I figured out basic footprint as follows(drew in paint for clarification purpose) enter image description here

X=0.41mm,

Y=1.05mm (=(6-3.9)/2 mm), here 6 is median ,

C=4.95mm (=Y+3.9),

E=1.27mm

2.29mmX2.29mm for exposed pad

Am I good to go draw the footprint in KiCad Footprint editor with these information I collected from Data Sheet. I usually find the recommended pcb layout on other manufacturer's datasheet which helped a lot to draw the footprint easily. Please guide me.

\$\endgroup\$
  • \$\begingroup\$ You need to make the pads extend out beyond the leads by 0.5 to 1 mm on each side to leave room for a solder fillet. Likewise they should be wider than the lead width, you currently have the pads 0.41 mm wide while the lead can be up to 0.51 mm. This would be difficult to solder well. \$\endgroup\$ – pericynthion Jun 7 '17 at 21:34
  • \$\begingroup\$ Do you mean Y=1.05+0.5=1.55mm, Rest of them are okay?@pericynthion \$\endgroup\$ – sbz Jun 7 '17 at 21:36
  • \$\begingroup\$ Increase all of C, Y and X. Find a recommended SO-8 footprint from Analog or another manufacturer as reference. \$\endgroup\$ – pericynthion Jun 7 '17 at 21:37
1
\$\begingroup\$

SOIC is SOIC, they're mostly all the same. You can adjust pad dimensions depending on how you want your solder fillet. Making pads a bit longer makes it easier to solder by hand.

When designing a PCB, I usually order the parts first, then print the PCB on a sheet of paper, and place any doubtful parts on the printout to check for errors. This is especially useful with connectors, and often avoids errors.

| improve this answer | |
\$\endgroup\$
  • 2
    \$\begingroup\$ SOIC does come in different widths, so beware of that, but it will be obvious if you look at the dimensions. This one has the exposed pad to deal with too. \$\endgroup\$ – pericynthion Jun 7 '17 at 21:40

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.