|
|
IPC-7351 SMD & PTH Reference Calculators |
Post Reply 
|
Page <123 |
| Author | |
Jeff.M 
Admin Group 
Joined: 16 May 2012 Location: San Diego Status: Offline Points: 482 |
 Post Options
 Thanks(0)
 Quote Reply
 Posted: 02 Apr 2014 at 12:44pm |
|
Both are correct. The difference is due to the definitions of the 'Placement' (P) and 'Fabrication' (F) tolerances. IPC-7351 demonstrates them as a single value. For example in their publication they use 0.10 mm for F and 0.20 mm for P (this is your 2nd equation). We use plus-or-minus values where an equivalent F would be +/- 0.05 mm and P would be +/- 0.10 mm so they're doubled before squaring (this is your 1st equation). Either way, the tolerances are the same and the result is the same.
|
|
 |
|
|
|
|
jk-999
New User 
Joined: 12 Dec 2012 Status: Offline Points: 1 |
Post Options
Thanks(0)
Quote Reply
Posted: 02 Apr 2014 at 9:00am |
|
Which equation is correct? Zmax=Lmin +2JT + SQRT((CL)² + (2*F)² + (2*P)²) or
Zmax=Lmin +2JT + SQRT((CL)² + (F)² + (P)²)
IPC 7351A uses the second equation. I believe the calculator is using the first equation.
|
|
|
|
|
Nick B
Admin Group
Joined: 02 Jan 2012 Status: Offline Points: 1960 |
Post Options
Thanks(0)
Quote Reply
Posted: 07 Jan 2013 at 2:35pm |
|
Here are the latest Reference Calculators. Please note there are TWO (2), one is Surface Mount, and the other Plated Through Hole, also referred to as TH. (you need to be logged in, registration is absolutely free!) IPC-7351 SMD Reference Calculator Below is the is the PCB Library Expert PTH Reference Calculator:  |
|
|
|
|
Post Reply
|
Page <123 |
| Tweet |
| Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |
Topic Options