![]() |
![]() |
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 |
![]() ![]() ![]() ![]() ![]() |
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 |
![]() ![]() ![]() ![]() ![]() |
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 |
![]() ![]() ![]() ![]() ![]() |
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 |