190 11 Praha 9 Běchovice GPS Loc:
50°5'21.95"N
14°36'45.78"E tel.: +420 242 413 030
fax.: +420 257 951 245
mobil: +420 603 477 901
Shouldering requirements
To be able to execute your order quickly, in the highest quality, and as cheep as possible it is necessary to keep following requirements.
The perimeter board size (blank):
- Width
- 50 - 350 mm
- Length
- 50 - 450 mm
- Depth
- 0,4 - 2,6 mm (it is necessary to consult the possibility of shouldering of thinner desks)
At PCB it is necessary that its longitudinal borders are parallel and the width tolerance in one production set is max. 0,5mm! Otherwise, the risk of board (blank) damage during the production or the delay of production is increasing.
Regarding the rigidity, actually the flexure of the board, we recommend, especially at problematic boards (thin boards, narrow blank bridges, too deep milled slots, Teflon boards, etc.), consultation for each specific case.
Minimal distance of soldering flap edges from the PCB border is 3 mm. If the soldering flaps are closer to the PCB border, the board must have technological border. If this requirement is not fulfilled, it is necessary to mount additionally the parts at the border of the board and the board mounted in this way is more expensive.
Technological openings:
It is appropriate the board to have two openings of diameter 2 - 3 mm (see picture 1) optimally 5 mm (possibly 4 - 8 mm) from its lower border for PCB gripping in the automatic mounting machine. If it is not so, the risk of inexact shouldering is increasing.
pic. 1
Technological signs:
It is appropriate the board to have at least two bearing signs for exact bearing of the PCB before the printing or before mounting. These can be for example circles of diameter approx. 1 - 2 mm located on the board diagonally and as far from each other as possible with the same surface as soldering flaps' surface. These signs must be located at least 5 mm from the longitudinal border of the board (see picture 2). Other shape of the bearing flaps then circular must be consulted in advance. It is necessary not to have any soldering flaps, printmaking, etc. at least 3mm round the bearing point on the board. If there are not signs on the board (blank) or they are not visible, the risk of inexact shouldering is increasing.
pic. 2
Wave soldering:
Parts:
- Part must be delivered in belts, bars or pallets
- The belts with parts should be in one piece, they should have pilot partition at least 5 cm long and separate covering strip at least 15 cm long. It is also necessary to take into account a small technological reserve.
- The parts in bars must all have the same orientation
- It is necessary to secure well the parts in pallets during the transport, so they won't be damaged
- The parts shouldn't be too old because they could have oxidized outlets, which are inappropriate for soldering.
Production documentation:
- The design of the mounting with definite part position assignment and its marking (e.g. R5)
- Sheet of definite identification of each part (e.g. C5 - 100nF, 50V, 10%, X7R, 0805)
- If necessary, list of comments and extra requirements for the way of mounting, shouldering, testing, etc.
Screens for printing:
The printing of the soldering paste or glue for SMD can be executed either by manual device UNIPRINT or by automatic machine DEK.
Screen for DEK should have on the bottom side two stampings (not holes!!) of the circle shape with the same diameter as the bearing flaps on the board in the positions corresponding with bearing points on the board. If there are not the stampings on the screen, the inexact printing or printing time extension can occur.
The depth of the screen or the way of screen production is chosen according to the type of mounted parts.