With the increasing integration density of ICs, IC pins are becoming more numerous and denser. However, the vertical hot air solder leveling (HASL) process is difficult to blow the formed pads flat, which brings difficulties to SMT mounting.
With the increasing integration density of ICs, IC pins are becoming more numerous and denser. However, the vertical hot air solder leveling (HASL) process is difficult to blow the formed pads flat, which brings difficulties to SMT mounting.
Gold-plated boards exactly solve these problems. For surface mount technology, especially for small surface mount components such as "0402" and "0201", since the flatness of pads is directly related to the quality of solder paste printing process and plays a decisive role in the subsequent reflow soldering quality, full-board gold plating is commonly used in high-density and ultra-small surface mount processes.
Full-Board Electroplated Hard Gold
Gold Thickness Requirement: ≤1.5μm
Process Flow
Manufacturing Requirements
① Dry film shall use GPM-220 anti-electrolytic gold dry film;
② Secondary dry film is not required for products without solder mask printing on the whole board;
③ For products with solder mask printing, secondary dry film is only applied to the solder mask pad opening positions, not the whole board;
④ The secondary dry film film is equivalent to the solder mask film, only retaining the pads, but cannot be shared with the solder mask film, and shall be 2mil larger overall than the solder mask film.
Gold Thickness Requirement: 1.5μm < Gold Thickness ≤4.0μm
Process Flow
Manufacturing Requirements
① Dry film shall use GPM-220 anti-electrolytic gold dry film;
② Secondary dry film is not required for products without solder mask printing on the whole board;
③ For products with solder mask printing, secondary dry film is only applied to the solder mask pad opening positions, not the whole board;
④ The secondary dry film film is equivalent to the solder mask film, only retaining the pads, but cannot be shared with the solder mask film, and shall be 2mil larger overall than the solder mask film;
⑤ The spacing of gold-plated areas shall be designed with reference to the circuit capability;
⑥ Adopt hand-tear lead or lead trimming process.
Special Notes
- At present, gold-cobalt alloy is used for thick gold plating, and this process is generally used for PCB plugs or contact pad switches;
- For full-board thick gold plating, it is necessary to evaluate whether there are SMT or BGA surface mount pads at the thick gold positions. If yes, it is necessary to inform the customer of the potential risk of poor solderability, and it is recommended to use pattern plated copper-nickel-gold for these positions;
- If the customer has already made leads to lead out the pads that need hard gold plating, only the hard gold plating process needs to be performed after outer layer etching;
- When the gold thickness exceeds 4μm, it cannot be manufactured;
- For the process using secondary dry film in gold plating + hard gold plating, the corresponding requirements for gold thickness and hard gold pad spacing: minimum 7mil for conventional gold thickness 0.38μm, minimum 8mil for 0.8μm, and 10mil for above 1.0μm.
Full-Board Electroplated Soft Gold
Gold Thickness Requirement: ≤1.5μm
Process Flow
Manufacturing Requirements
① Dry film shall use GPM-220 anti-electrolytic gold dry film;
② Secondary dry film is not required for products without solder mask printing on the whole board;
③ For products with solder mask printing, secondary dry film is only applied to the solder mask pad opening positions, not the whole board;
④ The secondary dry film film is equivalent to the solder mask film, only retaining the pads, but cannot be shared with the solder mask film, and shall be 2mil larger overall than the solder mask film.
Gold Thickness Requirement: 1.5μm < Gold Thickness ≤4.0μm
Process Flow
Manufacturing Requirements
① Dry film shall use GPM-220 anti-electrolytic gold dry film;
② Secondary dry film is not required for products without solder mask printing on the whole board;
③ For products with solder mask printing, secondary dry film is only applied to the solder mask pad opening positions, not the whole board;
④ The secondary dry film film is equivalent to the solder mask film, only retaining the pads, but cannot be shared with the solder mask film, and shall be 2mil larger overall than the solder mask film;
⑤ The spacing of gold-plated areas shall be designed with reference to the circuit capability;
⑥ Adopt hand-tear lead or lead trimming process.
Special Notes
- If the customer has already made leads to lead out the pads that need soft gold plating, only the soft gold plating process needs to be performed after outer layer etching;
- When the gold thickness exceeds 4μm, it cannot be manufactured;
- For the process using secondary dry film in gold plating + soft gold plating, the corresponding requirements for gold thickness and soft gold pad spacing: minimum 7mil for conventional gold thickness 0.38μm, minimum 8mil for 0.8μm, and 10mil for above 1.0μm.
Nickel-Free Electroplated Gold (Including Hard/Soft Gold)
Requirement Description
- For nickel-free gold plating required by customers, whether soft gold or hard gold, the minimum gold thickness shall be controlled at 0.5μm. If it is less than this requirement, nickel-free gold plating cannot be used;
- When the gold thickness exceeds 4μm, it cannot be manufactured;
- For nickel-plated hard gold and soft gold, they shall also be manufactured according to the above requirements. The only difference is that the requirement of "only gold plating without nickel plating" cannot be noted in the MI, and the corresponding nickel thickness shall be filled in as required;
- For the process using secondary dry film in gold plating + hard gold plating, the corresponding requirements for gold thickness and hard gold pad spacing: minimum 7mil for conventional gold thickness 0.38μm, minimum 8mil for 0.8μm, and 10mil for above 1.0μm.
Gold Plating Process Capability Design Requirements
With Leads
Add a 12mil wide wire at the end of the gold fingers (for finished copper thickness ≤2OZ). For leads with copper thickness greater than 2OZ, the width shall not be less than the minimum line width in the board. Add a dummy gold finger at each of the nearest routing empty positions on both sides of the gold fingers to distribute current and prevent uneven thickness of the middle gold fingers.
Without Leads (Local Electroplated Thick Gold)
① Drilling: Only drill PTH holes in the board, and NPTH holes are processed by secondary drilling;
② Solder Mask 1: Note in MI to use electroplated gold film;
③ Silkscreen 1: Note in MI no silkscreen, only bake the board;
④ Solder Mask 2: Note in MI to strip solder mask, and transfer to the next process immediately after stripping to avoid oxidation.
● Notes:
Ⅰ. The circuit film production must cover the electroplated gold positions with film;
Ⅱ. Teardrops must be added to the wires at the connection positions between electroplated gold pads and wires;
Ⅲ. Solder Mask 2: Note in MI that the electroplated gold surface cannot be brushed, and pre-treatment is board cleaning (note only brush the large copper surface for single-sided electroplated gold).
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