The PCB is prone to bending and warping when it passes through the reflow furnace, which makes people very distressed. So how to prevent PCB board from bending and warping through the reflow furnace? Let’s explain it to you:
1. Reduce the influence of temperature on PCB stress
Since “temperature” is the main source of plate stress, as long as the temperature of the reflow furnace is reduced or the heating and cooling rate of the plate in the reflow furnace is slowed down, the occurrence of plate bending and plate warping can be greatly reduced. However, there may be other side effects, such as solder short circuit.
2. Use high Tg plate
Tg is the glass transition temperature, that is, the temperature at which the material changes from glass to rubber. The lower the Tg value of the material, the faster the plate begins to soften after entering the reflow furnace, and the longer the time to become soft rubber, the more serious the deformation of the plate. The use of plates with higher Tg can increase their ability to withstand stress and deformation, but the price of materials is relatively high.
3. Increase the thickness of the circuit board
In order to achieve the goal of thinner, many electronic products have left 1.0mm, 0.8mm and even 0.6mm thick plates. It is really a bit difficult to keep the plates from deforming after the reflow furnace. It is suggested that if there is no requirement of thinner, the plates can preferably use 1.6mm thick plates, which can greatly reduce the risk of bending and deformation.
4. Reduce the size of circuit board and the number of panels
Since most of the reflow furnaces use chains to drive the circuit board forward, the larger size of the circuit board will be dented and deformed in the reflow furnace because of its own weight, so try to put the long side of the circuit board on the chain of the reflow furnace as far as possible, which can reduce the dented deformation caused by the weight of the circuit board itself. This is also the reason for the reduction of the number of panels, Try to use the narrow edge perpendicular to the direction of furnace passage to achieve the minimum concave deformation.
5. Used reflow carrier
If the above methods are difficult to achieve, the last is to use the reflow carrier/template to reduce the deformation. The reason why the reflow carrier can reduce the bending and warping of the plate is that the template is expected to hold the circuit board until the temperature of the circuit board is lower than the Tg value and begins to harden again, and can maintain the original size..
If the single-layer template cannot reduce the deformation of the circuit board, it is necessary to add another layer of cover to clamp the circuit board with the upper and lower layers of templates, which can greatly reduce the deformation of the circuit board through the reflow furnace. However, the template is very expensive, and it has to be placed and recycled manually.
6. Use Router instead of V-Cut
Since V-Cut will destroy the structural strength of the panels between the circuit boards, try not to use the sub-panels of V-Cut or reduce the depth of V-Cut.
Kingtronics Components to use on your board:
GKT-Aluminum Electrolytic Capacitors, radial, axial, SMD, snap-in, Lug, screw types
Bridge Rectifiers: MB1S-MB10S, KBPC6005-KBPC610, KBP2005-KBP210
Diodes & Transistors: M7, 1N4007, LL4148, BZV55C, Fast Recovery Diodes
DKT-Super Capacitors: 2.7V, 3V Radial, Snap-in, Screw Type and 5.5V Coin Type
MLCC and Tancap: Multilayer Ceramic Capacitors and Tantalum Capacitors
KKT-Ceramic Capacitors: SMD 3mm Trimmer Capacitor 3pF, 6pF,10pF, 20pF, 30pF
RKT-Trimming Potentiometers: Rectangular, SMD, Square 3006, 3362, 3386, 3590
QKT-Crystals: Crystals and Oscillators size 1612 to 7050,Tuning Fork 32.768KHz
SKT-Surge Arresters: Axial and SMD Gas 2-Electrode and 3-Electrode Arresters
NKT-NTC Thermistors: NTC Negative Temperature Coefficient Thermistor
XKT-Varistors: Metal Oxide Varistor 05D, 07D, 10D, 14D, 20D
WKT-Switches: DIP and SMD Tact Switches
FKT-Film Capacitors: Metallized Polyester and Polypropylene Film Capacitor